Pediatric Flashcards
Embryonic precursors of Schwann cells also give rise to which of the following?
Answers:
A. Adrenal Medulla
B. Squamous skin cells
C. Vertebral bodies
D. Red nucleus
E. Vascular endothelium
Adrenal Medulla
The neural crest population emerges from the dorsal neural tube and migrates throughout the embryo to give rise to several important cell populations, including components of the sensory, autonomic and enteric nervous systems, as well as certain glial cell types, including Schwann cells. Chromaffin cells of the adrenal medulla are derivatives of neural crest. The red nucleus comprises central neurons, derived from neuroectoderm. Vertebral bodies arise from the fusion of somites, or paraxial mesoderm. Squamous cells of the skin arise from the ectodermal layer, not neural crest, though the pigmented melanocytes of the skin are derivatives of neural crest. Lastly, vascular endothelium is derived from the endodermal layer of the embryo.
The dura mater of the lumbar region is opened during a dorsal rhizotomy procedure. This meningeal layer is embryologically derived from which of the following structures?
Answers:
A. Cutaneous ectoderm
B. Endoderm
C. Henson’s Node
D. Paraxial Mesoderm
E. Primitive Streak
Paraxial Mesoderm
The meningeal layers are divided into the pachymeninges (dura mater) and leptomeninges (arachnoid and pia mater). Somites that derive from paraxial mesoderm are the embryonic precursors of the vertebrae, ribs, paraspinal muscles and pachymeninges in the spine. The cranial meninges, on the other hand, form from a combination of mesenchymal cells and neural crest cells. Notably, the neural crest cells contribute primarily to the leptomeninges, rather than the pachymeninges. Cutaneous ectoderm is the embryonic precursor of the skin and hair, and endoderm forms most of the internal organs. Henson’s node is the “organizer” of gastrulation and primary neurulation. The primitive streak forms during the blastula stage and directs axis formation of the embryo, as well as gastrulation and early primary neurulation.
A 12-year-old girl is evaluated because of small stature for her age. MR images are shown. The
abnormality seen in the sella turcica is derived from the same embryologic origin as which of the
following structures?
Answers:
A. Smooth muscle cells
B. Cells of the adrenal cortex
C. Skeletal muscle cells
D. Thyroid cells
E. Skin cells
Skin cells
Rathke’s cleft cysts are non-neoplastic epithelium-lined cysts that arise from the embryologic remnants of Rathke’s pouch. Often asymptomatic and incidentally found, larger lesions may cause symptoms by direct compression of the optic chiasm or the pituitary gland. On MR imaging, Rathke’s cleft cysts are variable in appearance, but are generally non-enhancing lesions. A thin rim of enhancement, which represents the compressed pituitary gland, may be seen. Rathke’s pouch—along with skin and other epithelial cells, neurons, and pigment cells—arise from the ectoderm, or external layer. Thyroid cells, digestive cells, and other internal organs largely arise from the endoderm, or internal layer. All types of muscle and blood cells, along with cells of the adrenal cortex, arise from the mesoderm, or middle layer.
Which of the following is the site of the closure of the anterior neuropore?
Answers:
A. The rostral tip of the neural groove
B. The cervical level
C. The prosencephalic-mesencephalic boundary
D. The primitive lamina terminalis
E. The mesencephalic-rhombencephalic boundary
The primitive lamina terminalis
Neural tube formation and closure is a more complex and dynamic process than originally thought. At least three different modes of neural tube closure, driven by various mechanisms, result in the different shapes of the neural tube along its rostral-caudal axis. Furthermore, it is now thought that neural tube closure initiates at multiple sites and proceeds both rostrally and caudally. The prospective cervical region, the mesencephalic-rhombencephalic boundary, and the rostral tip of the neural groove are all thought to be initiation sites for closure. From the rostral tip of the neural groove, closure proceeds caudally until it meets the rostral extension of closure from the mesencephalic-rhombencephalic boundary initiation site. This occurs near the rostral end of the prosencephalon at the anterior neuropore, resulting in a thickening in the dorsal portion of the embryonic lamina terminalis, the future site of the anterior commissure.
Which of the following structures originate from the embryonic metencephalon?
Answers:
A. Hippocampus
B. Pons
C. Basal Ganglia
D. Basal forebrain
E. Medulla
Pons
The metencephalon is the vesicle of origin that eventually forms the pons and cerebellum. The telencephalon is responsible for formation of the cerebral cortex, basal ganglia, basal forebrain and hippocampus. The diencephalon is the origin of the thalamus, hypothalamus, posterior pituitary and retina. The mesencephalon forms the midbrain. The myelencephalon forms the medulla.
A 9-year-old boy presents with behavioral problems. Which of the following surgical skull-based
approaches was most likely used to obtain the diagnostic biopsy specimen shown?
Answers:
A. Kawase
B. Endoscopic transphenoidal
C. Pre-sigmoid transpetrosal
D. Far lateral
E. Orbitozygomatic
Orbitozygomatic
Traditionally, hypothalamic hamartomas were reached through an open orbitozygomatic approach. This affords wide exposure of the suprasellar region and visualization of the interface between the hypothalamus and hamartoma tissue. Endoscopic transsphenoidal is a feasible approach but is limited by the need to mobilize the pituitary gland and potentially disrupt the stalk to fully visualize the hamartoma. The other listed approaches offer inferior visualization of the hamartoma and normal hypothalamus. In the modern era, endoscopic transventricular and stereotactic laser ablative approaches have largely supplanted open resection/disconnection of these lesions. These minimally invasive approaches have excellent seizure outcomes with improved surgical safety profiles.
Which of the following structures is the deepest possible extent of a nasal dermal sinus tract?
Answers:
A. Frontal Sinus
B. Hard Palate
C. Petrous Apex
D. Pituitary Stalk
E. Foramen cecum
Foramen cecum
Nasal dermal sinus tracts are thought to result from an error in naso-frontal fusion, whereby the dural projection extending from the foramen cecum to the superficial ectoderm of the nose fails to involute. This projection can fuse to the skin, leaving a dimple, and a tract that extends a variable depth. The foramen cecum is the site of intracranial entry for these tracts. The frontal sinus is anterior to the base of the dural projection and is part of the frontal bone. The petrous apex is lateral to the midline and a component of the temporal bone and is not involved in nasal dermal sinus development. The pituitary stalk is intracranial and posterior to the typical insertion site of nasal dermal sinus tracts. The hard palate separates the oropharynx from the nasopharynx and is therefore below the typical location of a nasal dermal sinus tract.
A failure of which of the following stages of embryogenesis leads to the malformation visible in the
image shown?
Answers:
A. Secondary neurulation
B. Organogenesis
C. Primary neurulation
D. Organogenesis
E. Gastrulation
Primary neurulation
The formation of the spinal cord involves two main processes: primary neurulation, which begins on postovulatory day (POD) 18, and secondary neurulation, which begins between POD 28 and 48. Primary neurulation begins when the notochord induces the overlying ectoderm to proliferate as neuroectoderm. Initially the neural groove is formed, and with continued elevation and infolding, it fuses to form the neural tube. Cutaneous ectoderm separates from the neuroectoderm and fuses on the midline, forming the overlying skin layer. This process, in which the cutaneous ectoderm separates from the neuroectoderm, is a critical step known as disjunction, and is a part of primary neurulation. Abnormalities during disjunction are responsible for many forms of spinal dysraphism. The most severe form of spinal dysraphism, myelomeningocele, is due to a focal interruption in this step—or nondisjunction—at the level of the lesion. Defects during secondary neurulation lead to abnormalities of the filum terminale and a range of caudal/sacral agenesis syndromes. Gastrulation is the process of cellular movement, occurring between POD 14-19. By the end of gastrulation, the three primary germ layers (endoderm, mesoderm, and ectoderm) are formed. Organogenesis begins during the third to eighth week of development and continues until birth; it is the process by which the organs develop.
Which of the following systems arise(s) from the paleocortex and archicortex rather than the
neocortex?
Answers:
A. Basal Ganglia
B. Motor
C. Limbic
D. Sensory
E. Visual
Limbic
Components of the limbic system, including the hippocampal formation and piriform cortex, arise from the archicortex and paleocortex. Other components of the limbic system, including the amygdala and septal nuclei, are considered corticoid areas. They do not arise from neocortex. Neocortex comprises most of the cerebral cortex, including areas contributing to speech (frontal and temporal cortical areas), vision (occipital cortex), movement (frontal cortex) and sensation (parietal cortex). The basal ganglia are a collection of deep structures that are not cortical.
A 6-month-old girl is evaluated because of a midline dimple on the skin over her lumbar spine.
Neurological examination shows no abnormalities, although she has a history of recurrent bouts of
meningitis. The most likely underlying diagnosis is a defect during which of the following
developmental stages?
Answers:
A. Disjunction
B. Primary Neurulation
C. Gastrulation
D. Blastula
E. Secondary Neurulation
Disjunction
Dermal sinus tracts in the spine are the result of incomplete separation of the neural tube from the skin, a process known as disjunction. This process occurs at the end of primary neurulation and allows the formation of the vertebrae and intervening layers between the spinal cord and skin to continue. This is the most correct answer of the given choices. The close relationship between the ectoderm and neuroectoderm in development explains the common association between skin findings and occult spinal dysraphism. The blastula is the stage prior to gastrulation. The embryo is not yet divided into cell layers at this stage. Errors at this stage are typically not compatible with life. Gastrulation is the stage at which the embryo divides into ectoderm, endoderm, and mesoderm, and occurs just prior to neurulation. Errors at this stage are thought to lead to split cord malformations and some teratomas, neurenteric, dermoid and epidermoid cysts. Primary neurulation results in formation of the neural plate and folding of the neural tube. Errors at this stage can lead to myelomeningocele, anencephaly and cranioraschisis. Secondary neurulation is the condensation and cavitation of the caudal cell mass, leading to formation of the caudal neural tube. Errors of secondary neurulation can result in caudal regression syndrome, sacral agenesis, fatty filum and terminal lipomas.
A 9-year-old boy with Down syndrome is evaluated for frequent falls. CT scan of the cervical spine
is shown. This abnormality is due to which of the following?
Answers:
A. Acute fracture
B. Craniocervical dislocation
C. Incomplete odontoid ossification
D. Recurrent early childhood trauma
E. Rheumatoid arthritis
Recurrent early childhood trauma
Os odontoideum is an odontoid anomaly most seen in children with syndromes that impart ligamentous laxity, such as Down, Morquio and Ehlers Danlos syndromes. Recent evidence has suggested that recurrent early childhood trauma is associated with Os odontoideum. This entity does not indicate an acute fracture, as is clear from the sharp borders and corticated margins of the involved bone. Incomplete ossification of the dens leads to Os terminale, a related but different entity. Craniocervical dislocation is defined most often by the absence of fracture but instead separation of occiput from its articulation on C1. A widened basion-dental interval is seen, and this is often fatal. Rheumatoid arthritis can result in formation of a pannus behind the odontoid, leading to medullary compression.
A 3-year-old boy is involved in a motor vehicle collision; he was belted into his car seat. Neurological examination shows no abnormalities. He undergoes a rapid sequence spiral CT scan in the emergency department. Which of the following radiologic findings in C1 are indicated by the
two lateral arrows in the x-ray film shown?
Answers:
A. Anterior arch fractures
B. Transverse foramen
C. Anatomic variant of congenital non-union
D. Transverse ligament attachments
E. Synchondroses of C1
Synchondroses of C1
C1 is formed by three primary ossification sites: the anterior arch and the two neural arches. This results in three distinct sites of synchondrosis: one on either side of the anterior arch where it meets with the neural arches (as indicated by the arrows in the figure), and a third posterior site where the two neural arches eventually fuse in the midline to form the posterior arch. The neural arches become apparent during the 7 fetal week. The anterior arch is ossified in only 20% of neonates at birth, but becomes visible by 1 year of age. All three synchondroses can be seen in infants and toddlers. The neural arches fuse posteriorly by about 3-5 years of age; the anterior arch does not fuse with the neural arches until about 7-9 years of age, and in nearly half of patients there may be incomplete ossification even up to 10 years of age. Therefore, in a threeyear-old child, it is normal to see synchondroses as bony defects between the anterior arch and the neural arches. Occasionally these synchondroses can be misinterpreted as fractures. The sclerotic margins and knowledge of developmental anatomy are key in differentiating these entities
Preoperative imaging defines the globus pallidus in a patient who is to undergo deep brain
stimulation. This structure is derived from which of the following embryonic brain vesicles?
Answers:
A. Mesencephalon
B. Telencephalon
C. Myelencephalon
D. Diencephalon
E. Metencephalon
Telencephalon
The globus pallidus is part of the basal ganglia, which form from the telencephalon. The telencephalon is also responsible for formation of the cerebral cortex, basal forebrain, and hippocampus. The diencephalon is the origin of the thalamus, hypothalamus, posterior pituitary, and retina. The mesencephalon forms the midbrain. The metencephalon forms the pons and cerebellum, and the myelencephalon forms the medulla. On a more granular level, the neurons forming the globus pallidus are thought to arise from the medial and lateral ganglionic eminences as a result of patterning gene Nkx2.1.
The image shown demonstrates two white matter tracts of the cerebrum, labeled tract 1 and tract
2. Which of the following is the correct representation of either tract 1 or tract 2?
Answers:
A. They both can be injured in anterior temporal approaches to the temporal horn of the
lateral ventricle
B. They both can be injured in posterior interhemispheric approaches to the lateral ventricle
C. They both can be injured in anterior interhemispheric approaches to the lateral ventricle
D. Damage to these tracts can cause Gerstmann syndrome
E. Together these tracts form the corona radiata
They both can be injured in anterior temporal approaches to the temporal horn of the lateral ventricle
Tract 1 is the inferior longitudinal fasciculus, which helps in recognition & identification of visually perceived objects. Disconnection syndrome results in progressive prosopagnosia, visual agnosia, and alexia. Tract 2 is the inferior fronto-occipital fasciculus (IFOF). It functions for lexical-semantic processing and visual-spatial processing. Disconnection syndrome results in semantic paraphasia. The posterior part of the IFOF runs lateral to the temporal horn and the inferior two-thirds of the atrium to reach the occipital lobe. The anterior part of the IFOF courses lateral and superior to cover the anterior two-thirds of the frontal horn. The dorsal external capsule fibers (claustrocortical fibers) run lateral and superior to the posterior one-third of the frontal horn and body of the lateral ventricle and superior one-third of the atrium to form part of the corona radiata. Removing the IFOF and putamen exposes the anterior commissure, internal capsule, and globus pallidus. The internal capsule involves varied fibers connecting the supratentorium structures to the brainstem and joins the external capsule fibers ascending above the level of the upper edge of the putamen to form the corona radiate.
