Anatomy Flashcards
The endosteal layer of the dura mater ends at which of the following anatomical structures?
Answers:
A. Cervical nerve root sleeve
B. Sphenoid wing
C. Foramen magnum
D. Infratentorial space
E. Sacrum
Foramen magnum
Discussion:
The meninges are composed of the dura, the arachnoid, and the pia. Although there is conflicting
data, it is felt that the pia is derived from the neural crest, while the dura mater arises from paraxial
somitic mesoderm. The dura is a thick collagenous membrane with an outer periosteal or
endosteal layer that is simply a layer of periosteum that covers the inner surface of the skull, and
an inner meningeal layer. The two layers are typically fused within the skull except at sites of
venous sinuses. The endosteal layer is highly vascularized and provides vascular supply to the
calvarium. The dura also contains a lymphatic system involved in drainage of CSF. The spinal dura
mater is continuous with the meningeal layer of the cranial dura where they join at the foramen
magnum, and contracts to form the filum distally, and there is no endosteal layer. In the spine,
meningeal development results from the meninx primitiva around days 56-60, which forms internal
and external layers. The external layer is adherent to the developing bone, and gives rise to the
dura, while the internal layer gives rise to the pia and arachnoid. The cranial meninges are derived
from the primary meninx located on the surface of the developing brain and are actively involved in
the development of the calvarium.
References:
Snell RS, ed. Clinical Neuroanatomy. 7th Ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009.
Dasgupta K and Jeong J. Developmental biology of the Meninges. Genesis, 2019. 57(5): e23288
Pubmed Web link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520190/
Sakka L, Gabrillargues J, and Coll G. Anatomy of the spinal meninges. Oper Neurosurg, 2016.
12(2):168-188.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/29506096/
The highlighted subcortical white matter pathway in the figure shown, which connects the frontal
opercular cortical sites with the superior and middle temporal cortex and can cause naming deficits
with stimulation, is which of the following?
Answers:
A. Uncinate fasciculus
B. Arcuate fasciculus
C. Middle longitudinal fasciculus
D. Inferior frontooccipital fasciculus
E. Tapetum
Arcuate fasciculus
Discussion:
The arcuate fasiculus (AF) is involved with lexical, semantic, and phonological language
processing (dominant hemisphere) as well as perception and production of nonlinguistic
communication (nondominant hemisphere). The ventral segment of the AF is associated with
phonological language processing, and the dorsal segment is associated with
lexical and semantic language processing. Damage to the mid and posterior segments of
the ventral part of the AF can result in anomia and phonemic paraphasia, while damage to the
dorsal part of the AF can result in semantic paraphasia.
The superior part of the AF extends from the inferior and middle frontal gyri to the posterior insular
point (junction of the inferior and superior limiting insular sulci) and runs lateral to the superior twothirds of the frontal horn and body of the lateral ventricle. The central part of the AF runs from the
posterior insular point to the angular gyrus and lateral to the anterior two-thirds of the atrium. The
inferior part of the AF runs from the level of the posterior insular point to the anterior tip of the
temporal horn. The AF wraps around the posterior edge of the insula in a horseshoe-like
configuration; connects the mid, posterior, and anterior parts of the middle and superior temporal
gyri to the mid parts of the inferior and middle frontal gyri; and passes deep to the middle and
superior part of the lateral surface of the temporal lobe, anterior part of the occipital lobe, angular
and supramarginal gyri, middle and inferior parts of the pre- and postcentral gyri,
and anterior and middle parts of the middle and inferior frontal gyri.
References:
Güngör A, Baydin S, Middlebrooks EH, Tanriover N, Isler C, Rhoton AL Jr. The white matter tracts
of the cerebrum in ventricular surgery and hydrocephalus. J Neurosurg. 2017 Mar;126(3):945-971.
doi: 10.3171/2016.1.JNS152082. Epub 2016 Jun 3. PMID: 27257832.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/27257832/
Duffau H. Stimulation mapping of white matter tracts to study brain functional connectivity. Nat Rev
Neurol. 2015 May;11(5):255-65. doi: 10.1038/nrneurol.2015.51. Epub 2015 Apr 7. PMID:
25848923.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/25848923/
Muftah Lahirish IA, Middlebrooks EH, Holanda VM, Batista-Quintero R, Maeda FL, Neto MR,
Parraga RG, de Olivieira E. Comparison Between Transcortical and Interhemispheric Approaches
to the Atrium of Lateral Ventricle Using Combined White Matter Fiber Dissections and Magnetic
Resonance Tractography. World Neurosurg. 2020 Jun;138:e478-e485. doi:
10.1016/j.wneu.2020.02.161. Epub 2020 Mar 6. PMID: 32147552.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32147552/
The fornix arises from the _____?
Answers:
A. Amygdala
B. Hippocampus
C. Mammillary bodies
D. Hypothalamus
E. Parahippocampal gyrus
Hippocampus
Discussion:
The fornix is a white matter bundle located in the mesial aspect of the cerebral hemispheres, which
connects various nodes of limbic circuitry and is believed to play a key role in cognition and
episodic memory recall.
The fornix is the major output tract of the hippocampus. Medial to the floor of the temporal horn of
the lateral ventricle, hippocampal fibers collect into a thin lamina known as the alveus. Fibers from
the subiculum join the alveus as it courses posteromedially and bundles into the fimbria of the
fornix. As the fimbria enlarge in cross-sectional area by collecting additional fibers, they become
known as the crura of the fornix. The crura arch superoanteriorly under the splenium of the corpus
callosum and project contralaterally via the thin triangular forniceal commissure. The crura run
paracentrally to form the forniceal body, which arches over the thalamus and under the septum
pellucidum. Rostrally, the fornix body bifurcates into left and right columns that descend into the
basal forebrain anterior to the interventricular foramina. The fornix columns divide at the anterior
commissure—fibers travelling anteriorly form the pre-commissural fornix, while those curving
posteriorly make up the post-commissural fornix. Pre-commissural fibers house the
septohippocampal pathway, also projecting to the forebrain. Post-commissural tracts originate from
the subiculum and project to the thalamus, forming the direct subiculothalamic pathway, and the
indirect subiculothalamic pathway which relays via the mammillary bodies. It does not have any
major direct input from the parahippocampal gyri or amygdala.
References:
Senova, S; Fomenko, A; Gondard, E; Lozano, A.M. (2020). “Anatomy and function of the fornix in
the context of its potential as a therapeutic target”. Journal of Neurology, Neurosurgery &
Psychiatry. 91 (5): 547–559
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32132227
Senova, S; Fomenko, A; Gondard, E; Lozano, A.M. (2020). “Anatomy and function of the fornix in
the context of its potential as a therapeutic target”. Journal of Neurology, Neurosurgery &
Psychiatry. 91 (5): 547–559
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32132227
The cerebellar mossy fibers have an excitatory effect on which of the following cells?
Answers:
A. Granule Cells
B. Stellate cells
C. Basket cells
D. Purkinje cells
E. Vestibular nuclei
Granule Cells
Discussion:
Mossy fibers make excitatory projections onto the cerebellar nuclei and onto granule cells in the
cerebellar cortex, which in turn synapse on Purkinje neurons via their parallel fibers. Mossy fibers
originate in the pontine nuclei, the spinal cord, and the brainstem reticular formation. Each
mossy fiber innervates hundreds of granule cells. Granule cells send axons that bifurcate in the
molecular layer, sending a collateral in opposite directions. These fibers are called parallel fibers,
as they run parallel to the folds of the cerebellar cortex, where they make excitatory synapses with
Purkinje cells along the way. Basket cells and stellate cells are reciprocally connected via
“inhibitory” synapses.
References:
Fore TR, Taylor BN, Brunel N, Hull C. Acetylcholine Modulates Cerebellar Granule Cell Spiking by
Regulating the Balance of Synaptic Excitation and Inhibition. J Neurosci. 2020 Apr
1;40(14):2882-2894. doi: 10.1523/JNEUROSCI.2148-19.2020. Epub 2020 Feb 28. PMID:
32111698; PMCID: PMC7117893.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32111698/
Neuroanatomy Text and Atlas, John H. Martin. The McGraw-Hill Companies – 2012. Chapter 13 –
The Cerebellum
Gaia Bonassi, Elisa Pelosin, Giovanna Lagravinese, Ambra Bisio, Giorgio Grasselli, Marco Bove,
Laura Avanzino, Somatosensory inputs modulate the excitability of cerebellar-cortical interaction,
Clinical Neurophysiology, 10.1016/j.clinph.2021.08.026, 132, 12, (3095-3103), (2021).
The stria terminalis originates in the
Answers:
A. Amygdala
B. Hippocampus
C. Thalamus
D. Pituitary gland
E. Hypothalamus
Amygdala
Discussion:
The stria terminalis connects the amygdala with the hypothalamus and is involved in regulation of
fear and anxiety responses as well as regulation of the hypothalamic-pituitary-adrenal (HPA) axis.
The anteroventral bed nuclei of the stria terminalis, which resides within the central extended
amygdala, is involved in the processing of fear- and anxiety-related information and helps
coordinate restraining influences on the HPA axis.
References:
Radley JJ, Johnson SB. Anteroventral bed nuclei of the stria terminalis neurocircuitry: Towards an
integration of HPA axis modulation with coping behaviors - Curt Richter Award Paper 2017.
Psychoneuroendocrinology. 2018 Mar;89:239-249. doi: 10.1016/j.psyneuen.2017.12.005. Epub
2017 Dec 24. PMID: 29395488; PMCID: PMC5878723.
Pubmed Web link: Anteroventral bed nuclei of the stria terminalis neurocircuitry: Towards an
integration of HPA axis modulation with coping behaviors - Curt Richter Award Paper 2017 -
PubMed (nih.gov)
Stamatakis AM, Sparta DR, Jennings JH, McElligott ZA, Decot H, Stuber GD. Amygdala and bed
nucleus of the stria terminalis circuitry: Implications for addiction-related behaviors.
Neuropharmacology. 2014 Jan;76 Pt B(0 0):320-8. doi: 10.1016/j.neuropharm.2013.05.046. Epub
2013 Jun 7. PMID: 23752096; PMCID: PMC3858407.
Pubmed Web link: Amygdala and bed nucleus of the stria terminalis circuitry: Implications for
addiction-related behaviors - PubMed (nih.gov)
In which of the following areas of the brain is the secondary somatosensory cortex (SII) found?
Answers:
A. Postcentral gyrus
B. Parietal operculum
C. Occipital operculum
D. Temporal operculum
E. Frontal operculum
Parietal operculum
Discussion:
The secondary somatosensory cortex (S2), which is a part of the somatosensory system, is
located in the upper part of the lateral sulcus in the parietal operculum over the insular cortex. It is
situated posterior to the primary somatosensory cortex. The S2 is believed to be associated with
performing higher-order functions of sensorimotor integration, including tactile object recognition
and memory.
The primary somatosensory cortex (S1) is the area of the postcentral gyrus that receives sensory
information from the VPL of the thalamus via the internal capsule and corona radiata. The S2
region helps to process the sensory information delivered to S1. The S2 has connections to the
hippocampus and the amygdala.
References:
Bretas RV, Taoka M, Suzuki H, Iriki A. Secondary somatosensory cortex of primates: beyond body
maps, toward conscious self-in-the-world maps. Exp Brain Res. 2020 Feb;238(2):259-272. doi:
10.1007/s00221-020-05727-9. Epub 2020 Jan 21. PMID: 31960104; PMCID: PMC7007896.
Pubmed Web link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007896/
Klingner CM, Witte OW. Somatosensory deficits. Handb Clin Neurol. 2018;151:185-206. doi:
10.1016/B978-0-444-63622-5.00009-7. PMID: 29519458.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/29519458/
1. Schluppeck, S. Francis, Somatosensory Processing, Editor(s): Arthur W. Toga, Brain
Mapping,
Academic Press, 2015, Pages 549-552, ISBN 9780123973160.
Pubmed Web link: https://doi.org/10.1016/B978-0-12-397025-1.00045-2
Which of the following is the sensory modality mediated by the anterior insula/frontal operculum?
Answers:
A. Visual
B. Olfactory
C. Somatosensory
D. Gustatory
E. Auditory
Gustatory
Discussion:
The primary gustatory cortex is a region of the cerebral cortex responsible for perception of taste
and flavor and is comprised of the anterior insula and the frontal operculum. Third-order fibers
travel ipsilaterally through the posterior limb of the internal capsule to terminate in the frontal
operculum/anterior insular cortex to provide discriminatory taste sensations.
The primary auditory cortex is in the superior temporal gyrus, the primary olfactory cortex is in the
medial temporal lobe, the visual cortex is in the occipital pole, and the somatosensory cortex in the
post-central gyrus of the parietal lobe.
References:
Iannilli E, Gudziol V. Gustatory pathway in humans: A review of models of taste perception and
their potential lateralization. J Neurosci Res. 2019 Mar;97(3):230-240. doi: 10.1002/jnr.24318.
Epub 2018 Aug 31. PMID: 30168865.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/30168865/
Small DM, Bender G, Veldhuizen MG, Rudenga K, Nachtigal D, Felsted J. The role of the human
orbitofrontal cortex in taste and flavor processing. Ann N Y Acad Sci. 2007 Dec;1121:136-51. doi:
10.1196/annals.1401.002. Epub 2007 Sep 10. PMID: 17846155.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/17846155/
Principles of Neural Science. E.R. Kandel, J.H. Schwartz, and T.M. Jessell (Eds.), McGraw Hill,
New York, 2000.
Which of the following structures connects the amygdaloid nuclei?
Answers:
A. Anterior commissure
B. Uncinate fasciculus
C. Arcuate fasciculus
D. Hippocampal commissure
E. Posterior commissure
Anterior commissure
Discussion:
While association fibers connect ipsilateral areas of the cerebral cortex, commissural fibers extend
contralaterally and connect corresponding regions of cerebral cortex interhemispherically.
Functionally, the amygdaloid nuclei regulate autonomic and endocrine components of emotional
states and behavioral responses through various projections to the neocortex, hippocampus, basal
ganglia, and hypothalamus. Efferent fibers from the amygdala include the stria terminalis and
ventral amygdalofugal pathway, both projecting to the hypothalamus. The amygdaloid nuclei are
connected interhemispherically by the anterior commissure, which travels anterior to the columns
of the fornix and adjacent to the posterior aspect of the uncinate fasciculus.
The uncinate fasciculus contains association fibers between antero-inferior frontal lobe gyri and
anterior temporal lobe gyri. Positioned more posteriorly, the arcuate fasciculus connects structures
within the frontal and temporal lobes integral to language function, particularly the posterior
superior temporal gyrus (Wernicke’s area) and the posterior inferior frontal gyrus (Broca’s area).
The hippocampal commissure connects the bilateral fornices, with each fornix representing the
primary outflow tract of the ipsilateral hippocampus. Located within the posterior aspect of the
third ventricle, the posterior commissure interconnects the pretectal nuclei and contributes to the
consensual pupillary light reflex.
References:
Sah, P., E. S. L. Faber, M. Lopez de Armentia, and J. Power. The Amygdaloid Complex: Anatomy
and Physiology. Physiol Rev 83: 803–834, 2003; 10.1152/physrev.00002.2003
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/12843409/
Lavrador JP, Ferreira V, Lourenco M, et al. White-matter commissures: a clinically focused
anatomical review. Surg Radiol Anat. June 2019; 41(6): 613-624. 10.1007/s00276-019-02218-7
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/31119409/
Cerebellar afferents that terminate as climbing fibers originate in the
Answers:
A. Pontine nuclei
B. Reticular formation nuclei
C. Inferior Olivary Nuclei
D. Spinal Cord
E. Vestibular Nuclei
Inferior Olivary Nuclel
Discussion:
There are two principal classes of afferent fibers in the cerebellum. Climbing fibers are axons of
the neurons of inferior olivary nuclei and have monosynaptic connections with the Purkinje fibers.
Mossy fibers are the second afferents which originate from pontine nuclei, reticular formation
nuclei, vestibular nuclei and the spinal cord. They then synapse on granular cells, which in turn
synapse via parallel fibers with Purkinje neurons.
References:
Barmack NH, Yakhnitsa V. Cerebellar climbing fibers modulate simple spikes in Purkinje cells. J
Neurosci. 2003 Aug 27;23(21):7904-16. doi: 10.1523/JNEUROSCI.23-21-07904.2003. PMID:
12944521; PMCID: PMC6740591.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/12944521/DOI:
10.1523/JNEUROSCI.23-21-07904.2003
Neuroanatomy Text and Atlas, John H. Martin. The McGraw-Hill Companies – 2012. Chapter 13 –
The Cerebellum
Melanocytes in the CNS are found in which of the following locations?
Answers:
A. Leptomeninges
B. Gray matter
C. White matter
D. Choroid plexus
E. Periventricular region
Leptomeninges
Discussion:
Melanocytes are derived from the multipotent neural crest cells, with induction dependent on bone
morphogenetic protein (BMP) signaling. Development of the cell into a mature melanocyte typically
occurs in the neural tube and is dependent on Wnt signaling. Melanocytes are found within the
leptomeninges and are primarily located in the brain along with skull base and ventral spinal cord,
with pigmentation of the meninges often grossly apparent intraoperatively or at autopsy. While
relatively uncommon, primary melanin-containing tumors can arise from CNS melanocytes, while
CNS metastasis of a primary melanoma more commonly occurs. Melanomas are commonly
associated with overactivation of BRAF and NRAS through somatic mutation, and loss of the
CDKN2A locus is also commonly observed.
References:
Smith AB, Rushing EJ, and Smirniotopoulos JG. Pigmented lesions of the central nervous system:
radiologic-pathologic correlation. Radiographics. Sept-Oct 2009; 29(5): 1503-24.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/19755608/
Trinh V et al. Primary melanocytic tumors of the central nervous system: Report of two cases and
review of the literature. Surg Neurol Int. 2014. 5:147.
Pubmed Web link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4209706/
Uong A and Zon LI. Melanocytes in development and cancer. J Cell Physiol. 2010. 222(1):38-41.
Pubmed Web link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2783760/
Which of the following is the anatomic landmark that marks the posterior border of the superior
frontal sulcus?
Answers:
A. Postcentral Gyrus
B. Precentral Gyrus
C. Middle Frontal Gyrus
D. Superior Frontal Gyrus
E. Inferior Frontal Gyrus
Precentral Gyrus
Discussion:
The superior frontal gyrus is the most medial gyrus of the superolateral surface of the frontal lobe.
The superior frontal gyrus runs from the frontal pole all the way to the precentral sulcus and
precentral gyrus at its posterior border. The superior frontal sulcus lies laterally, separating it from
the middle frontal gyrus. When feasible, the superior frontal transsulcal transventricular approach
offers a safe and effective corridor to the anterior part of the lateral ventricle.
References:
Briggs RG, Khan AB, Chakraborty AR, Abraham CJ, Anderson CD, Karas PJ, Bonney PA,
Palejwala AH, Conner AK, O’Donoghue DL, Sughrue ME. Anatomy and White Matter Connections
of the Superior Frontal Gyrus. Clin Anat. 2020 Sep;33(6):823-832. doi: 10.1002/ca.23523. Epub
2019 Dec 2. PMID: 31749198.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/31749198/
Catani M. The anatomy of the human frontal lobe. Handb Clin Neurol. 2019;163:95-122. doi:
10.1016/B978-0-12-804281-6.00006-9. PMID: 31590750.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/31590750/
In the illustration, the site of the skin incision and craniectomy is shown in the upper left. Careful
removal of the cross-hatched part of the cerebellum (indicated by the arrow) will expose which of
the following structures?
Answers:
A. Dentate Nucleus
B. Telovelar junction
C. Superior Cerebellar Peduncle
D. Culmen
E. Flocculus
Telovelar junction
Discussion:
The cerebellar tonsils are ovoid structures on the inferomedial surface of each cerebellar
hemisphere. They are attached to the underlying cerebellum by the tonsillar peduncle. In the
paramedian suboccipital approach pictured here, removal or elevation of the tonsil would expose
the obex, telovelar junction and inferior margins of the inferior and middle cerebellar peduncles.
The culmen is a segment of the vermis positioned on the tentorial surface of the cerebellum. The
flocculus is positioned laterally, at the foramen of Luschka, and would be visible from a
cerebellopontine angle approach, or after dividing the telovelar junction during a telovelar
approach. The superior cerebellar peduncle and dentate nuclei would not be visible from this
approach without significant cerebellar resection.
References:
Neuroanatomy Text and Atlas, John H. Martin. The McGraw-Hill Companies – 2012. Chapter 13 –
The Cerebellum. Refer to Figure 13-2 C
Matsushima, K., Yagmurlu, K., Kohno, M., & Rhoton, A. L., Jr. (2016). Anatomy and approaches
along the cerebellar-brainstem fissures, Journal of Neurosurgery JNS, 124(1), 248-263. Retrieved
Mar 17, 2022, from https://thejns.org/view/journals/j-neurosurg/124/1/article-p248.xml
Damage to this white matter structure in the dominant hemisphere has been demonstrated to
result in difficulty naming famous people. The fiber tract highlighted in yellow in the figure shown is
known as which of the following?
Answers:
A. Arcuate fasiculus
B. Uncinate fasiculus
C. Anterior limb of the internal capsule
D. Tapetum
E. Optic radiation
Uncinate fasiculus
Discussion:
The uncinate fasciculus connects the orbitofrontal gyrus to the anterior temporal lobe as shown
above. The arcuate fasciculus connects Wernicke’s area to Broca’s area. The anterior limb of the
internal capsule contains fibers that run between frontal cortex to pons and thalamus to frontal
cortex. The tapetum is the posterior aspect of the corpus callosum that forms the roof of the lateral
ventricle. Optic radiations run from the lateral geniculate nucleus to the primary visual cortex.
References:
Von Der Heide RJ, Skipper LM, Klobusicky E, Olson IR. Dissecting the uncinate fasciculus:
disorders, controversies and a hypothesis. Brain. 2013 Jun;136(Pt 6):1692-707. doi: 10.1093/brain
/awt094. Epub 2013 May 6. PMID: 23649697; PMCID: PMC3673595.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/23649697/
Papagno C, Miracapillo C, Casarotti A, et al. What is the role of the uncinate fasciculus? Surgical
removal and proper name retrieval. Brain. 2011 Feb;134(Pt 2):405-14.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/20959310/
A patient has a lesion in Meyer’s loop in the anterior part of the right temporal lobe. Which of the
following parts of the visual field is most likely involved?
Answers:
A. Left Inferior Quadrant
B. Right Inferior Quadrant
C. Left Hemi-field (Superior and Inferior Quadrants)
D. Left Superior Quadrant
E. Right Superior Quadrant
Left Superior Quadrant
Discussion:
The inferior or temporal portion of the optic radiations extends anteriorly from the lateral geniculate
nucleus of the thalamus for a short, variable distance before turning posteriorly towards the
primary visual cortex. This fascicular tract, known as Meyer’s Loop, contains visual sensory
information regarding the contralateral superior visual field. Therefore, patients with lesions
located in the anterior temporal lobe and those undergoing standard anterior temporal lobectomy
may encounter contralateral superior quadrantanopsia. Accordingly, a lesion in the right anterior
temporal lobe would correspond to a left superior quadrant visual field deficit.
Due to the pattern of visual information received by the nasal and temporal portions of the retina
and the decussation of medial (nasal) optic nerve fibers at the optic chiasm, the optic tracts and
radiations carry visual sensory information from the contralateral visual field. The optic tract
extends from the optic chiasm to the lateral geniculate nucleus of the thalamus. Subsequently,
fibers representing the contralateral superior visual field travel within Meyer’s Loop (temporal optic
radiations) while fibers representing the contralateral inferior visual field travel more superiorly
(parietal optic radiations). The optic radiations travel posteriorly to the primary visual cortex
located along the medial surface of the occipital lobe. Ultimately, the primary visual cortex
receives information from the contralateral visual field. Based on these anatomic relationships, the
other question responses would not reflect a visual field deficit related to a right anterior temporal
lesion.
References:
Gustavo De Moraes C. Anatomy of the visual pathways. J Glaucoma 2013; 22(5): 2-7; doi:
10.1097/IJG.0b013e3182934978
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/23733119/
Pula JH, Yuen CA. Eyes and stroke: the visual aspects of cerebrovascular disease. Stroke and
Vascular Neurology 2017;2: e000079. doi:10.1136/svn2017-000079
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/29507782/
Patel SC, Smith SM, Kessler AT, Bhatt AA. Imaging of the Primary Visual Pathway based on Visual
Deficits. J Clin Imaging Sci. 2021 Apr 7;11:19. doi: 10.25259/JCIS_12_2021. PMID: 33880244;
PMCID: PMC8053434.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/33880244/
The endosteal layer of the dura mater ends at which of the following anatomical structures?
Answers:
A. Cervical nerve root sleeve
B. Sacrum
C. Sphenoid wing
D. Infratentorial space
E. Foramen magnum
Foramen magnum
Discussion:
The meninges are composed of the dura, the arachnoid, and the pia. Although there is conflicting
data, it is felt that the pia is derived from the neural crest, while the dura mater arises from paraxial
somitic mesoderm. The dura is a thick collagenous membrane with an outer periosteal or
endosteal layer that is simply a layer of periosteum that covers the inner surface of the skull, and
an inner meningeal layer. The two layers are typically fused within the skull except at sites of
venous sinuses. The endosteal layer is highly vascularized and provides vascular supply to the
calvarium. The dura also contains a lymphatic system involved in drainage of CSF. The spinal dura
mater is continuous with the meningeal layer of the cranial dura where they join at the foramen
magnum, and contracts to form the filum distally, and there is no endosteal layer. In the spine,
meningeal development results from the meninx primitiva around days 56-60, which forms internal
and external layers. The external layer is adherent to the developing bone, and gives rise to the
dura, while the internal layer gives rise to the pia and arachnoid. The cranial meninges are derived
from the primary meninx located on the surface of the developing brain and are actively involved in
the development of the calvarium.
References:
Snell RS, ed. Clinical Neuroanatomy. 7th Ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009.
Dasgupta K and Jeong J. Developmental biology of the Meninges. Genesis, 2019. 57(5): e23288
Pubmed Web link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520190/
Sakka L, Gabrillargues J, and Coll G. Anatomy of the spinal meninges. Oper Neurosurg, 2016.
12(2):168-188.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/29506096/
A 45-year-old man is evaluated because of right-sided partial seizures. An MR image is shown.
Removal of the lesion is planned. Postoperatively, he is most likely to have which of the following
deficits?
Answers:
A. Receptive aphasia
B. Contralateral paraesthesias
C. Contralateral motor neglect
D. Acalculia
E. Contralateral motor weakness
Contralateral motor neglect
Discussion:
The supplementary motor area (SMA) syndrome is a frequently encountered clinical phenomenon
associated with surgery of the dorsomedial prefrontal lobe. It is a transient disturbance of the
ability to initiate voluntary motor and speech actions that will often occur immediately after
neurosurgical resections in the dorsal superior frontal gyrus, but will typically disappear after 3
months. The inability to initiate is thought to be due to contralateral motor neglect that usually
improves with time. True motor weakness is caused by damage to the motor cortex. Receptive
aphasia is caused by injury to Wernicke’s area. Acalculia is caused by injury to the angular gyrus
of the parietal lobe. Injury to the somatosensory cortex can cause paresthesias. Recent evidence
has also implicated the supplementary motor area in modulating frailty in older patients.
References:
Lammers-Lietz F, Zacharias N, Mörgeli R, Spies CD, Winterer G. Functional connectivity of the
supplementary and presupplementary motor areas in postoperative transition between stages of
frailty. J Gerontol A Biol Sci Med Sci. 2022 Jan 18:glac012. doi: 10.1093/gerona/glac012. Epub
ahead of print. PMID: 35040961.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/35040961/
Sjöberg RL, Stålnacke M, Andersson M, Eriksson J. The supplementary motor area syndrome and
cognitive control. Neuropsychologia. 2019 Jun;129:141-145. doi:
10.1016/j.neuropsychologia.2019.03.013. Epub 2019 Mar 28. PMID: 30930302.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/30930302/
The roof of Dorello’s canal is formed by which of the following?
Answers:
A. Ligamentum petrosphenoidale (Gruber ligament)
B. Lesser wing of the sphenoid
C. Pterygospinous ligament
D. Petroclinoid ligament
E. Interclinoid ligament
Ligamentum petrosphenoidale (Gruber ligament)
Discussion:
The Gruber ligament, or ligamentum petrosphenoidale, forms the roof of Dorello’s canal. It
transmits the abducens nerve (CN VI) and courses laterally along the clivus. It extends from the
superior border of the petrous apex to the lateral border of the dorsum sella and clivus.
The petroclinoid ligaments are folds of the dura the extend from the anterior and posterior clinoid
processes and the petrous part of the temporal bone.
The lesser wing of the sphenoid is part of the sphenoid bone and forms the roof of the superior
orbital fissure.
The interclinoid ligament connects the anterior and posterior clinoid processes.
The pterygospinous ligament is a membranous ligament extending from the spine of the sphenoid
to the upper part of the posterior lateral pterygoid plate.
References:
Kshettry VR, Lee JH, Ammirati M. The Dorello canal: historical development, controversies in
microsurgical anatomy, and clinical implications. Neurosurg Focus. 2013 Mar;34(3):E4.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/23451716/
Umansky F, Elidan J, Valarezo A. Dorello’s canal: a microanatomical study. 1991 J Neurosurg 75:
294-298
Pubmed Web link: https://doi.org/10.3171/jns.1991.75.2.0294
Neurons in the entorhinal cortex project to which of the following structures?
Answers:
A. Locus Coeruleus
B. Hippocampus
C. Hypothalamus
D. Thalamus
E. Angular Gyrus
Hippocampus
Discussion:
The entorhinal cortex is a small but complex region of cortex in the medial temporal lobe which
receives highly processed cortical information and relays this information to the hippocampus. It is
thought to be an important relay station for a broad variety of memory-related functions. Its volume
correlates with memory performance in healthy participants as well as patients with Alzheimer’s
disease. The lateral perforant pathway arises from the lateral entorhinal cortex and extends into
the molecular layer of the hippocampus. The medial perforant pathway arises from the medial
entorhinal cortex, extends through the white matter from the subicular cortex, and enters the
alveus of the hippocampus. Many of these fibers carry olfactory, visual, and auditory information to
the hippocampus.
The Angular Gyrus is involved in language processing.
Locus Coeruleus is involved in neuro-hormonal control.
The Hypothalamus is involved in neurotransmitter synthesis.
The Thalamus is involved in sensorimotor relay.
References:
Canto CB, Wouterlood FG, Witter MP. What does the anatomical organization of the entorhinal
cortex tell us? Neural Plast. 2008;2008:381243. doi: 10.1155/2008/381243. PMID: 18769556;
PMCID: PMC2526269.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/18769556/
Schultz H, Sommer T, Peters J. The Role of the Human Entorhinal Cortex in a Representational
Account of Memory. Front Hum Neurosci. 2015;9:628. Published 2015 Nov 20.
doi:10.3389/fnhum.2015.00628
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4653609/
The dorsal nucleus (Clarke’s nucleus) is located in which of the following?
Answers:
A. The intermediolateral horn from C8-L2
B. The intermediolateral horn from T1-2
C. The ventral horn from C7-T12
D. The ventral from C1-T4
E. The intermediolateral horn from S2-4
The intermediolateral horn from C8-L2
Discussion:
Clarke’s nucleus (the dorsal nucleus) is located in the intermediolateral horn from C8-L2. It is
rarely referred to as the nucleus thoracicus. It is in Rexed lamina of the gray matter. It gives rise
to the posterior spinocerebellar tract and is notable in that it is an uncrossed tract. The neurons
project to the cerebellum via the restiform body, a portion of the inferior cerebellar peduncle.
References:
Felten DL, Jozefowicz RF. Netter’s Atlas of Human Neuroscience. pp 142-143, 2003
Carpenter MB. Core Textbook of Neuroanatomy, 4th Ed. Ch 4: Tracts of the Spinal Cord, pp70,
1991
Haines DE. Neuroanatomy: An Atlas of Structures, Sections, and System. 4th Ed. Ch7: Synopsis
of Functional Components, Tracts, Pathways, and Systems, pp 190-191, 1995
On the medial wall of the cerebral hemisphere, which of the following sulci is immediately posterior
to the central sulcus?
Answers:
A. Postcentral sulcus
B. Intraparietal sulcus
C. Calcarine Sulcus
D. Marginal limb of the cingulate sulcus
E. Parieto-occipital sulcus
Marginal limb of the cingulate sulcus
Discussion:
The marginal limb of the cingulate sulcus is immediately posterior to the central sulcus in the
medial wall of the of the cerebral hemisphere and divides the precuneus from the postcentral
gyrus. The postcentral sulcus is also the sulcus immediately posterior to the central sulcus, but it
is positioned on the convexity of the hemisphere between the postcentral gyrus and the parietal
lobule. The parieto-occipital sulcus separates the cuneus and precuneus on the medial wall. On
the medial wall we also find the calcarine sulcus, but it is more posterior, dividing the cuneus from
the lingual gyrus. The intraparietal sulcus is located in the lateral wall separating the parietal lobule
into superior and inferior portions, and therefore it is posterior to the postcentral sulcus.
References:
Campero et al. Brain Sulci and gyri: a practical anatomical review. J. Clin Neurosci 2014
21(12):2219-25
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/25092274/
The Cerebrum. Anatomy. Rhoton Jr. A. Neurosurgery 2007 61: 37-118
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/18813175
Which of the following statements most accurately describes the anterior corticospinal tract?
Answers:
A. It is composed of lower motor neurons
B. It travels in the anterior funiculus and travels ipsilaterally, descending from the brain.
C. It is present throughout the spinal cord.
D. It travels in the lateral funiculus and travels contralaterally and crosses in the pyramidal decussation
E. It is the primary tract for motor effectors in the body
It travels in the anterior funiculus and travels ipsilaterally, descending from the brain
Discussion:
The anterior corticospinal tract is distinct from the lateral corticospinal tract in two ways: 1) It does
not decussate until much more distally and travels ipsilaterally in the anterior funiculus. 2) It is not
present in all levels of the cord and terminates in the thoracic cord.
Functionally, it acts mostly to coordinate the axial body muscles, to effectively stabilize the trunk. It
is made of the 20-30% of the corticospinal tract fibers that do not cross. They descend in the
ipsilateral anterior funiculus.
Unlike the anterior corticospinal tract, the lateral corticospinal tract travels in the lateral funiculus
and is the primary tract for motor effector neurons of the body.
Like all motor effector tracts, the anterior corticospinal tract is composed of upper motor neurons.
And, like all motor tracts it eventually does decussate.
References:
Van Wittenberghe IC, Peterson DC. Corticospinal Tract Lesion. [Updated 2021 Aug 26]. In:
StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 JanPubmed Web link: https://www.ncbi.nlm.nih.gov/books/NBK542201/
Khan YS, Lui F. Neuroanatomy, Spinal Cord. [Updated 2021 Jul 31]. In: StatPearls [Internet].
Treasure Island (FL): StatPearls Publishing; 2021 JanPubmed Web link: https://www.ncbi.nlm.nih.gov/books/NBK559056
Haines DE. Neuroanatomy: An Atlas of Structures, Sections, and System. 4th Ed. Ch7: Synopsis
of Functional Components, Tracts, Pathways, and Systems, pp 176-177, 1995
Which of the following cell groups is derived embryologically from the alar plate?
Answers:
A. General somatic efferent
B. General somatic afferent
C. Mirror neurons
D. Ependymal cells
E. Purkinje cells
General somatic afferent
Discussion:
The alar plate is the region of the primitive neural tube that lies lateral to the sulcus limitans and
gives rise to the sensory and interneurons of the developing embryo. General somatic afferents
are the sensory neurons from the periphery and originate in the alar plate. The basal plate gives
rise to motor neurons, including general somatic efferents.
Ependymal cells are classified as neuroglia and arise from periventricular radial glial cells. Purkinje
fibers of the cerebellum and mirror neurons in the cortex arise from cells in the subventricular
zone.
References:
Spassky N, Merkle FT, Flames N, Tramontin AD, García-Verdugo JM, Alvarez-Buylla A. Adult
ependymal cells are postmitotic and are derived from radial glial cells during embryogenesis. J
Neurosci. 2005 Jan 5;25(1):10-8. doi: 10.1523/JNEUROSCI.1108-04.2005. PMID: 15634762;
PMCID: PMC6725217.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/15634762/
Which of the following structures passes through the opening at the base of the skull indicated by
the arrow in the image shown?
Answers:
A. Internal Carotid Artery
B. Trigeminal Nerve (V2)
C. Middle Meningeal Artery
D. Trigeminal Nerve (V3)
E. Tensor Veli Palatini
Trigeminal Nerve (V3)
Discussion:
The correct answer is Trigeminal nerve V3 (mandibular branch). The foramen ovale transmits the
third branch of the trigeminal nerve from the trigeminal ganglion in the middle cranial fossa, in the
pocket formed next to the sella turcica (Meckel’s cave), into the infratemporal fossa.
V2 (maxillary branch) exits via the foramen rotundum, an anteriorly angled hiatus in the greater
wing of the sphenoid.
The internal carotid artery enters through the foramen lacerum.
The middle meningeal artery enters the skull via the foramen spinosum. In certain individuals, an
accessory middle meningeal artery may be present.
The tensor veli palatini is a muscle and is in the pterygoid fossa, and therefore does not enter the
skull.
References:
Ginsberg, LE, Pruett SW, Chen MYM, Elster, Allen. Skull-Base Foramina of the Middle Cranial
Fossa: Reassessment of Normal Variation with High-Resolution CT Am J Neuroradio 15:283-291 ,
Feb 1994
Pubmed Web link: http://www.ajnr.org/content/ajnr/15/2/283.full.pdf
Rock, Patrick J. “Foramen Ovale” Radiopedia.org – 14 Dec. 2020
Pubmed Web link
Case courtesy of Dr Pir Abdul Ahad Aziz Qureshi, <a>Radiopaedia.org</a>. From the case <a>rID: 78240</a>
https://radiopaedia.org/articles/foramen-ovale-skull?lang=us
Felten DL, Jozefowicz RF. Netter’s Atlas of Human Neuroscience. Pp 22, 2003
The function of the climbing fiber system of the cerebellum is mediated through which of the
following effects?
Answers:
A. Purkinje cells
B. Sodium influx
C. Magnesium efflux
D. Potassium influx
E. Complex spikes
Complex spikes
Discussion:
Climbing fibers (CFs) generate complex spikes (CS) and Ca2+ transients in cerebellar Purkinje
cells, serving as instructive signals. Neither sodium, potassium nor magnesium play a role.
Adult Purkinje cells each receive input from a single climbing fiber (CF), which makes hundreds of
synapses across its highly branched main dendrite. CF activation produces a distinctive highfrequency burst of spikes: the complex spike. The CS is thought to represent a critical signal for
the operation of the cerebellar cortex, conveying both timing and triggering synaptic plasticity.
References:
Roh SE, Kim SH, Ryu C, Kim CE, Kim YG, Worley PF, Kim SK, Kim SJ. Direct translation of
climbing fiber burst-mediated sensory coding into post-synaptic Purkinje cell dendritic calcium.
Elife. 2020 Sep 28;9:e61593. doi: 10.7554/eLife.61593. PMID: 32985976; PMCID: PMC7581426.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32985976/
Neuroanatomy Text and Atlas, John H. Martin. The McGraw-Hill Companies – 2012. Chapter 13 –
The Cerebellum
Which of the following structures contains the cell bodies of the deep petrosal nerve?
Answers:
A. Geniculate ganglion
B. Superior cervical ganglion
Superior cervical ganglion
Discussion:
The deep petrosal nerve carries postganglionic sympathetic nerve fibers that originate in the
intermediate gray horn of the spinal cord near T1, travel through the sympathetic chain, and then
synapse in the superior cervical ganglion. Following synapse, the nerve fibers then travel in the
carotid plexus and form the deep petrosal nerve, which carries sympathetic innervation to the
blood vessels and secretomotor elements of the lacrimal gland, nasal region, and oral cavity. In the
foramen lacerum, the deep petrosal nerve joins with the greater petrosal nerve to form the vidian
nerve, which carries parasympathetic and sympathetic fibers through the pterygoid canal to the
pterygopalatine (sphenopalatine) ganglion.
References:
Clinical functional anatomy of the pterygopalatine ganglion, cephalgia, and related dysautonomias:
A review. Surg Neurol Int. 2013. Nov 20;4(Suppl6):S422-8.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/24349865/
Goosmann MM, Dalvin M. Anatomy, Head and Neck, Deep Petrosal Nerve. StatPearls [Internet].
2021. Aug 11
Pubmed Web link: https://www.ncbi.nlm.nih.gov/books/NBK534817/
Which of the following fiber bundles contains first-order sensory axons projecting to the
cerebellum?
Answers:
A. Vestibulocerebellar tract
B. Dorsal spinocerebellar tract
C. Superior cerebellar peduncle
D. Cuneocerebellar tract
E. Pontocerebellar trac
Vestibulocerebellar tract
Discussion:
The middle and inferior cerebellar peduncles carry afferent fibers from various pathways to the
cerebellum. The vestibulocerebellar tract carries afferent information from the vestibular nuclei to
the cerebellum via the inferior cerebellar peduncle. Some fibers of the vestibular root continue
directly to the cerebellum without synapsing in the vestibular nuclei first. Purkinje cells in the
cerebellum send efferent fibers back to the vestibular nuclei. These circuits are involved in the
coordination of balance and eye movements.
The dorsal spinocerebellar tract conveys proprioceptive information from the muscle spindles and
golgi tendon organs to the cerebellum. First order neurons synapse in the dorsal horn, where
second order neurons of Clarke’s nucleus project to the cerebellum.
The pontocerebellar tract carries the fibers of second order neurons from the pontine nucleus. This
tract is part of the cortico-ponto-cerebellar pathway – first order neurons from the cerebral cortex
project to the pontine nucleus, where second order neurons cross the midline and travel within the
middle cerebellar peduncle to the contralateral cerebellum.
The cuneocerebellar tract carries sensory information from the head, neck, and upper limbs,
enters the dorsal horn, and ascends ipsilaterally to the medulla, where it synapses with the
accessory cuneate nucleus (also called the external cuneate nucleus). The accessory cuneate
nucleus projects external arcuate fibers through the inferior cerebellar peduncle to the cerebellar
cortex.
The superior cerebellar peduncle is the primary efferent pathway of the cerebellum, carrying the
cerebellothalamic and cerebellorubral tracts. Afferent tracts, including the ventral spinocerebellar
tract, also run within the superior cerebellar peduncle.
References:
Takahashi M, Shinoda Y. Neural Circuits of Inputs and Outputs of the Cerebellar Cortex and
Nuclei. Neuroscience. 2021 May 10;462:70-88. doi: 10.1016/j.neuroscience.2020.07.051. Epub
2020 Aug 6.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/32768619/
Özcan OO, Wang X, Binda F, Dorgans K, De Zeeuw CI, Gao Z, Aertsen A, Kumar A, Isope P.
Differential Coding Strategies in Glutamatergic and GABAergic Neurons in the Medial Cerebellar
Nucleus. J Neurosci. 2020 Jan 2;40(1):159-170. doi: 10.1523/JNEUROSCI.0806-19.2019. Epub
2019 Nov 6. PMID: 31694963; PMCID: PMC6939494.
The majority of the orbital floor is formed by the roof of which of the following sinuses?
Answers:
A. Ethmoid sinus
B. Frontal sinus
C. Cavernous sinus
D. Sphenoid sinus
E. Maxillary sinus
Maxillary sinus
Discussion:
The maxillary sinus is directly beneath the floor of the orbit. It forms the majority of the floor of the
orbit. The sphenoid sinus forms the posteromedial wall, and the ethmoid sinus forms the medial
wall. The frontal sinus is above the orbit and the cavernous sinus does not make any significant
contact to the orbit.
References:
Rhoton AL Jr. The Orbit In Cranial Anatomy and Surgical Approaches. Neurosurgery Supplement.
2003: 331.
Cohen-Gadol, A. “Orbit” The Neurosurgical Atlas Apr. 7 2021.
Pubmed Web link: https://www.neurosurgicalatlas.com/volumes/operative-neuroanatomy
/supratentorial-operative-anatomy/orbit?highlight=orbit
Cohen-Gadol, A. “Neuroanatomy: Sphenoid and Palatine Bones” The Neurosurgical Atlas
In the coronal image of the head shown, which of the following arrows points to the collateral
sulcus?
Answers:
A. C
B. A
C. E
D. D
E. B
A. C
Discussion:
The collateral sulcus lies along the tentorial surface of the temporal pole (extending to the occipital
pole) between the parahippocampal gyrus and the fusiform gyrus. Choice (A) represents the
superior temporal gyrus. Choice (B) represents the middle temporal gyrus. Choice (D) represents
the hippocampus, and (E) represents the sylvian fissure.
References:
Diagnostic Imaging: Brain. Anne G. Osborn, Karen L. Salzman, A. James Barkovich. Amirsys
2010. ISBN 9781931884723, 1931884722.
Atlas of the Human Brain. Juergen K. Mai, Milan Majtanik, George Paxinos. Elsevier 2015. ISBN:
9780128028018
The arrow in the figure shown corresponds to which of the following structures?
Answers:
A. Dentate gyrus
B. Area entorhinalis
C. Cornu Ammonis
D. Subiculum
E. Uncus
Subiculum
Discussion:
The arrow is pointing to the subiculum or the subiculum area, the transition zone between the
hippocampus proper and the entorhinal area.
The hippocampus proper or Cornu Ammonis (CA) 1-4 wraps the dentate gyrus right above the
subiculum area and all 3 together (CA, dentate gyrus and subiculum) constitute the hippocampal
formation. The hippocampus proper and dentate gyrus are situated superior to the subiculum.
The entorhinal area within the parahippocampal gyrus lies next to the collateral sulcus, inferior and
lateral to the arrow. The uncus is ventral to the hippocampal formation.
The subiculum’s functional properties are not well understood, but it is thought to play an important
but ill-defined role in spatial navigation, mnemonic processing and control of the response to
stress.
References:
Anand KS and Dhihav V. Hippocampus in health and disease. An overview. Ann Indian Acad
Neurol. 2012 15(4) 239-246.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/23349586/
O’Mara S. The subiculum: what it does, what it might do, and what neuroanatomy has yet to tell
us. Journal of anatomy. 207 (3): 271-82. doi:10.1111/j.1469-7580.2005.00446.x - Pubmed
Insausti R, Muñoz-López M, Insausti AM, Artacho-Pérula E. The Human Periallocortex: Layer
Pattern in Presubiculum, Parasubiculum and Entorhinal Cortex. A Review. Frontiers in
neuroanatomy. 11: 84. doi:10.3389/fnana.2017.00084 - Pubmed
Which of the following is the single most important biomechanically stabilizing soft tissue structure
at the craniocervical junction?
Answers:
A. The transverse and alar ligaments
B. The tectorial membrane
C. The apical and transverse ligaments
D. The anterior longitudinal ligament and atlantoaxial joint capsules
E. The ligamentum flavum of C1-2 and nuchal ligaments
The transverse and alar ligaments
Discussion:
The importance of the alar and transverse ligaments cannot be overstated. The transverse
ligament holds the dens against the anterior ring of the atlas. It projects across from one side of
the atlas to the other, holding the dens to within 3 mm of the atlas. It prevents folding of the
brainstem into the upper cervical spine during flexion motion. The inferior and superior crura
project perpendicularly to the transverse ligament to form the cruciate ligament.
The alar ligaments project from the anterolateral dens and connect to the medial aspect of the
occipital condyles, forming a Y-shaped structure that secures the C1-C2 complex to the basilar
aspect of the skull, while allowing rotational freedom of the head.
The tectorial membrane is a relatively thin structure and is a projection of the posterior longitudinal
ligament. It attaches to the clivus superiorly and blends into the dura. It is not structurally strong
and can be torn in severe trauma.
The apical ligament extends from the uppermost tip of the dens to the anterior portion of the
foramen magnum. It can be absent in certain instances.
The anterior longitudinal ligament and facet joint capsules do not provide significant structural
integrity to the craniocervical complex, nor do the nuchal ligament or ligamentum flavum.
References:
Menezes AH, Traynelis VC. Anatomy and biomechanics of normal craniovertebral junction (a) and
biomechanics of stabilization (b). Childs Nerv Syst. 2008 Oct;24(10):1091-100.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/18389261/
Lopez AJ, Scheer JK, Leibl KE, Smith ZA, Dlouhy BJ, Dahdaleh NS. Anatomy and biomechanics
of the craniovertebral junction.
Neurosurg Focus. 2015 Apr;38(4):E2. doi: 10.3171/2015.1.FOCUS14807.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/25828496/
On the illustrations shown, in which the right lateral ventricle is exposed using the head position,
scalp incision, bone flap, and cortical incision shown, which of the following is the correct location
of the thalamostriate vein?
Answers:
A. B
B. D
C. E
D. A
E. C
E. C
Discussion:
This right frontal craniotomy and middle frontal gyrus corticotomy provide a transcortical approach
to the frontal horn of the right lateral ventricle. Identifying components of intraventricular anatomy
and critical neurovascular structures helps confirm laterality and should be performed prior to any
surgical manipulation or dissection. The thalamostriate vein (location c) joins the anterior septal
vein (location b) and anterior caudate vein (location a). The thalamostriate vein traverses through
the foramen of Monro and lies along the striothalamic sulcus between the caudate nucleus and the
thalamus. The septum pellucidum (location d) and body of the fornix along the choroidal fissure
(both along location e) are positioned along the medial aspect of the exposure. The thalamus
comprises the floor of the body of the lateral ventricle and lateral wall of the third ventricle (not
shown).
References:
Anderson RC, Ghatan S, Feldstein NA. Surgical approaches to tumors of the lateral ventricle.
Neurosurg Clin N Am. 2003 Oct;14(4):509-25. doi: 10.1016/s1042-3680(03)00054-8. PMID:
15024798.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/15024798/
Mortazavi MM, Adeeb N, Griessenauer CJ, Sheikh H, Shahidi S, Tubbs RI, Tubbs RS. The
ventricular system of the brain: a comprehensive review of its history, anatomy, histology,
embryology, and surgical considerations. Childs Nerv Syst. 2014 Jan;30(1):19-35. doi:
10.1007/s00381-013-2321-3. Epub 2013 Nov 16. PMID: 24240520.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/24240520/
The roof of Dorello’s canal is formed by which of the following?
Answers:
A. Ligamentum petrosphenoidale (Gruber ligament)
B. Interclinoid ligament
C. Lesser wing of the sphenoid
D. Petroclinoid ligament
E. Pterygospinous ligament
Ligamentum petrosphenoidale (Gruber ligament)
Discussion:
The Gruber ligament, or ligamentum petrosphenoidale, forms the roof of Dorello’s canal. It
transmits the abducens nerve (CN VI) and courses laterally along the clivus. It extends from the
superior border of the petrous apex to the lateral border of the dorsum sella and clivus.
The petroclinoid ligaments are folds of the dura the extend from the anterior and posterior clinoid
processes and the petrous part of the temporal bone.
The lesser wing of the sphenoid is part of the sphenoid bone and forms the roof of the superior
orbital fissure.
The interclinoid ligament connects the anterior and posterior clinoid processes.
The pterygospinous ligament is a membranous ligament extending from the spine of the sphenoid
to the upper part of the posterior lateral pterygoid plate.
References:
Kshettry VR, Lee JH, Ammirati M. The Dorello canal: historical development, controversies in
microsurgical anatomy, and clinical implications. Neurosurg Focus. 2013 Mar;34(3):E4.
Pubmed Web link: https://pubmed.ncbi.nlm.nih.gov/23451716/
Umansky F, Elidan J, Valarezo A. Dorello’s canal: a microanatomical study. 1991 J Neurosurg 75:
294-298
Pubmed Web link: https://doi.org/10.3171/jns.1991.75.2.029
