Functional Flashcards
Cessation of parkinsonian tremor most typically occurs with occlusion of which of the following
arteries?
Answers:
A. Pericallosal artery
B. Anterior choroidal
C. Recurrent artery of Heubner
D. Capsular artery of McConnell
E. Posterior choroidal
Anterior choroidal
iscussion:
Before the advent of effective pharmacotherapy, ligation of the anterior choroidal artery was a
procedure used to alleviate contralateral tremor and rigidity in Parkinson’s patients. This effect is
thought to derive from infarction of the globus pallidus, and it was discovered serendipitously after
ligation of the artery following an inadvertent intraoperative injury. Although effective, the procedure
carried a high risk of morbidity from infarctions of other anterior choroidal territory structures
including the internal capsule, optic tract, and thalamus.
The recurrent artery of Heubner supplies the head of the caudate and medial globus pallidus in
addition to other deep structures, however there is no evidence to support improvement in
Parkinsonian symptoms following Heubner infarcts, which most commonly cause weakness,
abulia, dysarthria, and choreoathetosis.
The posterior choroidal arteries usually arise from the P2 segment of the posterior cerebral artery,
and supply the posterior thalamus, tegmentum, midbrain, hippocampus, and parahippocampal
gyrus. Posterior choroidal infarction most commonly causes visual field defects and sensory loss
due to involvement of the lateral geniculate and posterior thalamus, but infarction can also cause
neuropsychological or eye movement dysfunction with involvement of the hippocampus or tectum.
The capsular arteries of McConnell arise from the cavernous ICA distal to the
meningohypophyseal trunk and the inferolateral trunk and supply blood to the sella. Ligation of
these arteries does not improve Parkinsonian symptoms.
The pericallosal artery is a distal branch of the anterior cerebral artery that courses over the dorsal
surface of the corpus callosum. The most common symptom of infarction is plegia of the
contralateral lower extremity.
References:
COOPER IS. Surgical alleviation of Parkinsonism; effects of occlusion of the anterior choroidal
artery. J Am Geriatr Soc. 1954 Nov;2(11):691-718. doi: 10.1111/j.1532-5415.1954.tb02479.x.
PMID: 13211192.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/13211192/
Speelman JD, Bosch DA. Resurgence of functional neurosurgery for Parkinson’s disease: a
historical perspective. Mov Disord. 1998 May;13(3):582-8. doi: 10.1002/mds.870130336. PMID:
9613759.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/9613759/
Toyoda K. Anterior cerebral artery and Heubner’s artery territory infarction. Front Neurol Neurosci.
2012;30:120-2. doi: 10.1159/000333607. Epub 2012 Feb 14. PMID: 22377877.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/22377877/
During the stretch reflex, the antagonist muscle groups are inhibited. The inhibitory interneuron
that facilitates this action is located at which of the following sites?
Answers:
A. Rexed laminae IV
B. The dorsal horn of the spinal cord
C. The lateral horn of the spinal cord
D. The ventral horn of the spinal cord
E. The dorsal root ganglion
The ventral horn of the spinal cord
Discussion:
A stretch reflex is mediated by a monosynaptic pathway. The stimulated muscle spindle fiber
transmits information to the spinal cord via a Ia afferent fiber. The afferent fiber synapses on a
homonymous alpha motor neuron and to an interneuron that inhibits the antagonist muscle alpha
motor neuron. Alpha motor neurons are located in the ventral horn of the spinal cord, also known
as the anterior grey column.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
Haines, D. E. (2012). Neuroanatomy: An Atlas of Structures, Sections, and Systems. United
Kingdom: Wolters Kluwer/ Lippincott Williams & Wilkins Health.
Which of the following best describes the action of Renshaw cells?
Answers:
A. Inhibitory interneuron
B. Excitatory interneuron
C. An intrafusal motor neuron
D. Mechanoreceptor
E. Nociceptor
Inhibitory interneuron
Discussion:
Renshaw cells act as part of a negative feedback system to regulate motor neuron excitability.
Renshaw cells are located in ventral horn spinal interneurons that produce recurrent inhibition of
motor neurons and Ia interneurons. They act by releasing the neurotransmitter glycine. Renshaw
cells receive input from collateral axions of motor neurons and descending pathways. Tetanus
toxin acts upon Renshaw cells, removing the inhibition, leading to hyperactive motor neurons and
muscles that constantly contract.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
Boakye, M., Vaccaro, A. R. (2012). Essentials of Spinal Cord Injury: Basic Research to Clinical
Practice. Germany: Thieme.
Schiavo G, Benfenati F, Poulain B, Rossetto O, Polverino de Laureto P, DasGupta BR,
Montecucco C. Tetanus and botulinum-B neurotoxins block neurotransmitter release by proteolytic
cleavage of synaptobrevin. Nature. 1992 Oct 29;359(6398):832-5. doi: 10.1038/359832a0. PMID:
1331807.
Each somatic muscle fiber is innervated by?
Answers:
A. Dynamic beta motor neuron
B. Static beta motor neuron
C. Alpha motor neuron
D. Gamma motor neuron
E. Delta motor neurons
Alpha motor neuron
Discussion:
Each somatic muscle fiber is innervated by an alpha motor neuron which has a cell body in either
the spinal cord or brain stem. A motor neuron and muscle fibers it innervates is called a motor unit.
The number of fibers innervated by one motor neuron can vary. A smaller innervation number
leads to finer motor control. Gamma motor neurons adjust the sensitivity of muscle spindle fibers.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
J. Cuevas. The Somatic Nervous System. Reference Module in Biomedical Sciences, Elsevier,
2015. ISBN 9780128012383, https://doi.org/10.1016/B978-0-12-801238-3.05364-2.
Question:
Which of the following best describes the function of group Ib fibers?
Answers:
A. Transmits information related to muscle length
B. Transmits information related to muscle contraction
C. Transmits information related to muscle stretch
D. Transmits information related to joint angle
E. Transmits information related to vibration
Transmits information related to muscle contraction
Discussion:
Ib fibers are afferent fibers coming from Golgi tendon organs are located at the junction between
skeletal muscle and its tendons. One fiber is associated with one Golgi tendon organ. The nerve
ending splits into a multitude of fiber endings that are intertwined in a collagen matrix within the
tendon organ. When the muscle contracts, the tendon organ stretches resulting in the collagen
fibers within to straighten. As the collagen fibers straighten, the nerve endings are compressed
leading to activation and thus an afferent signal. Consequently, the Ib fibers convey information
related to muscle contraction and active throughout normal movement. Ib fibers synapse with Ib
inhibitory interneurons leading to inhibitory connections to the homonymous motor neurons, part of
the Golgi tendon reflex.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
HUNT CC. Relation of function to diameter in afferent fibers of muscle nerves. J Gen Physiol. 1954
Sep 20;38(1):117-31. doi: 10.1085/jgp.38.1.117. PMID: 13192320; PMCID: PMC2147477.
Ganguly J, Kulshreshtha D, Almotiri M, Jog M. Muscle Tone Physiology and Abnormalities. Toxins
(Basel). 2021 Apr 16;13(4):282. doi: 10.3390/toxins13040282. PMID: 33923397; PMCID:
PMC8071570.
Houk J, Henneman E (1967) Responses of Golgi tendon organs to active contractions of the
soleus muscle of the cat. J Neurophysiol 30(3):466–481
Hemiballismus is most likely caused by a lesion at which of the following sites?
Answers:
A. Contralateral subthalamic nucleus
B. Ipsilateral cerebellar hemisphere
C. Ipsilateral caudate head
D. Contralateral dentate nucleus
E. Ipsilateral thalamus
Contralateral subthalamic nucleus
Discussion:
Hemiballismus is a movement disorder characterized by irregular, involuntary, unilateral large
amplitude movements. Classically hemiballismus is associated with lesions of the contralateral
subthalamic (STN). However, modern studies attempting to confirm this correlation have found that
only a minority of cases of hemiballismus are associated with STN lesions, and that this syndrome
may be more commonly due to lesions of the striatum or putamen.
Although case reports suggest that STN lesions may rarely produce ipsilateral hemiballismus, the
physiology of this is poorly understood. Because the basal ganglia and STN are proximal to the
medullary decussation, hemiballismus is more likely to be caused by a contralateral lesion.
Lesions of the cerebellar cortex or deep nuclei most commonly cause ataxia, and they are not
associated with hemiballismus.
References:
Postuma RB, Lang AE. Hemiballism: revisiting a classic disorder. Lancet Neurol. 2003
Nov;2(11):661-8. doi: 10.1016/s1474-4422(03)00554-4. PMID: 14572734.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/14572734/
Hawley JS, Weiner WJ. Hemiballismus: current concepts and review. Parkinsonism Relat Disord.
2012 Feb;18(2):125-9. doi: 10.1016/j.parkreldis.2011.08.015. Epub 2011 Sep 17. PMID: 21930415.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/21930415/
Which of the following best describes the Achilles reflex?
Answers:
A. A polysynaptic flexor reflex
B. A monosynaptic stretch reflex
C. A polysynaptic stretch reflex
D. A monosynaptic crossed extensor reflex
E. A polysynaptic crossed extensor reflex
A monosynaptic stretch reflex
Discussion:
The Achilles reflex is an example of a stretch reflex, which is mediated by a monosynaptic
pathway. It is innervated by the S1 nerve root resulting in contraction of the gastrocnemius and
soleus. The stimulated muscle spindle fiber transmits information to the spinal cord via a Ia afferent
fiber. The afferent fiber synapses on the homonymous muscle alpha motor neuron and to an
interneuron that inhibits the antagonist muscle alpha motor neuron. The result is a contraction of
the same muscle associated with the muscle spindle fiber with relaxation of the antagonist muscle.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
Louis E. D. (2002). Erb and Westphal: simultaneous discovery of the deep tendon reflexes.
Seminars in neurology, 22(4), 385–390. https://doi.org/10.1055/s-2002-36760
A middle-aged patient had a cerebrovascular accident and developed violent flailing movements of
his right arm. The lesion is most likely located in which of the following?
Answers:
A. Right thalamus
B. Left dentate nucleu
C. Left subthalamic nucleus
D. Right cerebellar hemisphere
E. Right caudate head
Left subthalamic nucleus
Discussion:
The description of the patient’s symptoms is consistent with hemiballismus, a movement disorder
characterized by irregular, involuntary, unilateral large amplitude movements. Classically
hemiballismus is associated with lesions of the contralateral subthalamic nucleus (STN). However,
modern studies attempting to confirm this correlation have found that only a minority of cases of
hemiballismus are associated with STN lesions, and that this syndrome may be more commonly
due to lesions of the striatum or putamen.
Although case reports suggest that STN lesions may rarely produce ipsilateral hemiballismus, the
physiology of this is poorly understood. Because the basal ganglia and STN are proximal to the
medullary decussation, right hemiballismus is more likely to be caused by a left-sided lesion.
Lesions of the cerebellar cortex or deep nuclei most commonly cause ataxia, and these are not
associated with hemiballismus.
References:
Postuma RB, Lang AE. Hemiballism: revisiting a classic disorder. Lancet Neurol. 2003
Nov;2(11):661-8. doi: 10.1016/s1474-4422(03)00554-4. PMID: 14572734.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/14572734/
Hawley JS, Weiner WJ. Hemiballismus: current concepts and review. Parkinsonism Relat Disord.
2012 Feb;18(2):125-9. doi: 10.1016/j.parkreldis.2011.08.015. Epub 2011 Sep 17. PMID: 21930415.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/21930415/
In the neurosurgical management of Parkinson disease, lesioning of the ventrolateral nucleus of
the thalamus has proved especially beneficial in controlling which of the following signs and
symptoms of the disease?
Answers:
A. Tremor
B. Postural instability
C. Rigidity
D. Bradykinesia
E. Dyskinesias
Tremor
Discussion:
Ventrolateral thalamotomy, either via focused ultrasound or thermoelectric coagulation, is most
effective at treating tremor. Dyskinesias are involuntary writhing movements that occur following
levodopa therapy and are not symptoms of Parkinson’s itself. They are not significantly affected by
thalamotomy.
References:
Linhares MN, Tasker RR. Microelectrode-guided thalamotomy for Parkinson’s disease.
Neurosurgery. 2000 Feb;46(2):390-5; discussion 395-8. doi:
10.1097/00006123-200002000-00024. PMID: 10690728.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/10690728/
Bond AE, Shah BB, Huss DS, Dallapiazza RF, Warren A, Harrison MB, Sperling SA, Wang XQ,
Gwinn R, Witt J, Ro S, Elias WJ. Safety and Efficacy of Focused Ultrasound Thalamotomy for
Patients With Medication-Refractory, Tremor-Dominant Parkinson Disease: A Randomized Clinical
Trial. JAMA Neurol. 2017 Dec 1;74(12):1412-1418. doi: 10.1001/jamaneurol.2017.3098. PMID:
29084313; PMCID: PMC5822192.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/29084313/
Which of the following processes activates ion channels in hair cells?
Answers:
A. Phototransduction
B. Mechanoelectrical transduction
C. Action potentials
D. Osmoreception
E. Ligand gated transduction
Mechanoelectrical transduction
Discussion:
Hair cells in the cochlea are stimulated when the basilar membrane oscillates by differences in
pressure between the scala vestibuli and scala tympani. This results in shearing between the
tectorial membrane and organ of Corti resulting in deflection in the hair cell bundles. This
deflection increases tension in a gates spring which opens the molecular gates of hair cell ion
channels, depolarizing the cell through a potassium influx. This depolarization then opens voltagegated calcium channels which further depolarizes the cell.
References:
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Education.
Zheng, W., & Holt, J. R. (2021). The Mechanosensory Transduction Machinery in Inner Ear Hair
Cells. Annual review of biophysics, 50, 31–51. https://doi.org/10.1146/annurev-biophys062420-081842
Which of the following is the most effective pharmacotherapy for long-term management of
essential tremor?
Answers:
A. Alprazolam
B. Clonidine
C. Levetiracetam
D. Primidone
E. Pindolol
Primidone
Discussion:
Evidence supports the efficacy of both anticonvulsants and beta-blockers as long-term treatments
for essential tremor (ET). Of the anticonvulsants, primidone is supported by the most evidence,
and was found to reduce tremor by approximately 50%. Of the beta-blockers, propranolol is
supported by the most evidence, with demonstration of similar efficacy.
Pindolol is a non-selective beta-blocker but a randomize clinical trial failed to demonstrate its
efficacy for improving ET symptoms.
Alprazolam is a benzodiazepine which may reduce tremor exacerbated by anxiety. However,
tolerance and withdrawal (which may worsen tremor) render it inappropriate for long-term
management.
Levetiracetam is an anticonvulsant but has been shown to probably not be effective at treating ET.
Clonidine is an alpha-adrenergic agonist, and it is not effective at treating ET.
References:
Deuschl G, Raethjen J, Hellriegel H, Elble R. Treatment of patients with essential tremor. Lancet
Neurol. 2011 Feb;10(2):148-61. doi: 10.1016/S1474-4422(10)70322-7. PMID: 21256454.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/21256454/
Elias WJ, Shah BB. Tremor. JAMA. 2014 Mar 5;311(9):948-54. doi: 10.1001/jama.2014.1397.
PMID: 24595779.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/24595779/
Which of the following structures is most responsible for control of extensor posturing?
Answers:
A. Tectospinal tract
B. The red nucleus
C. Rubrospinal tract
D. Superior colliculus
E. Medullary reticulospinal tract
Medullary reticulospinal tract
Discussion:
The medullary reticulospinal tract is under cortical control and maintains balance between extensor
and flexor tone. The vestibulospinal and pontine reticular spinal tracts maintain extensor tone
whereas the rubrospinal tract maintains flexor tone. Injury to the midbrain below the level of the red
nucleus injures both the rubrospinal tract which facilitates flexor tone and damages the medullary
reticulospinal tract which inhibits the vestibulospinal and pontine reticular spinal tracts. This leaves
extensor tone unopposed.
References:
Alberstone, C. D., Alberstone, C. (2009). Anatomic Basis of Neurologic Diagnosis. Ukraine:
Thieme.
Kandel, E. R. (2012). Principles of Neural Science, Fifth Edition. United Kingdom: McGraw-Hill
Educat
Parkinsonism is seen most commonly following toxic exposure to which of the following agents?
Answers:
A. Manganese
B. Mercury
C. Ondansetron
D. Zinc
E. Arsenic
Manganese
Discussion:
Parkinsonism can be produced by toxic insults to the dopamine neurons of the substantia nigra,
which of the choices given is most commonly produced by manganese. Parkinsonism can also be
produced by carbon disulfide, carbon monoxide, cyanide, MPTP, and organic solvents.
Arsenic poisoning most commonly causes a sensorimotor polyneuropathy, but it is not associated
with Parkinsonism. Mercury and zinc poisoning may cause non-specific neuropsychiatric
symptoms, but they are not consistently found to be associated with Parkinsonism.
Ondansetron is a selective serotonin receptor agonist that does not block dopamine receptors and
is not associated with Parkinsonism. However, other antiemetics including metoclopramide and
prochlorperazine have significant antidopaminergic activity and can cause drug-induced
Parkinsonism.
References:
Gorell JM, Rybicki BA, Cole Johnson C, Peterson EL. Occupational metal exposures and the risk
of Parkinson’s disease. Neuroepidemiology. 1999;18(6):303-8. doi: 10.1159/000026225. PMID:
10545782.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/10545782/
Caudle WM. Occupational Metal Exposure and Parkinsonism. Adv Neurobiol. 2017;18:143-158.
doi: 10.1007/978-3-319-60189-2_7. PMID: 28889266.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/28889266/
Caudle WM. Occupational exposures and parkinsonism. Handb Clin Neurol. 2015;131:225-39. doi:
10.1016/B978-0-444-62627-1.00013-5. PMID: 26563792.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/26563792/
In most children with acquired torticollis, which of the following is the most likely underlying cause?
Answers:
A. Posterior fossa tumor
B. Muscle injury
C. Cervical fracture or subluxation
D. Epidural hematoma
E. Retropharyngeal abscess
Muscle injury
Discussion:
Torticollis is the involuntary twisting of the neck and tilting of the head, and it may be congenital or
acquired. In children, the most common cause of acquired torticollis is inflammation of the
sternocleidomastoid or trapezius muscles, which may be due to trauma or viral myositis.
Infection is the next most common etiology, with retropharyngeal abscess representing a lifethreatening cause.
Torticollis can rarely be caused by compression of the accessory nerve from an epidural
hematoma or posterior fossa tumor, but muscle injury is more common.
Cervical fracture or subluxation can cause torticollis, but these injuries are uncommon in young
children.
References:
Pharisa C, Lutz N, Roback MG, Gehri M. Neck complaints in the pediatric emergency department:
a consecutive case series of 170 children. Pediatr Emerg Care. 2009 Dec;25(12):823-6. doi:
10.1097/PEC.0b013e3181c06062. PMID: 19952976.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/19952976/
Per H, Canpolat M, Tümtürk A, Gumuş H, Gokoglu A, Yikilmaz A, Özmen S, Kaçar Bayram A,
Poyrazoğlu HG, Kumandas S, Kurtsoy A. Different etiologies of acquired torticollis in childhood.
Childs Nerv Syst. 2014 Mar;30(3):431-40. doi: 10.1007/s00381-013-2302-6. Epub 2013 Nov 6.
PMID: 24196698.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/24196698/
Focal midbrain atrophy is most commonly seen on MR imaging of the brain in a patient with which
of the following neurological disorders?
Answers:
A. Creutzfeldt-Jakob disease (CJD)
B. Corticobasal degeneration (CBD)
C. Normal pressure hydrocephalus (NPH)
D. Progressive supranuclear palsy (PSP)
E. Multiple systems atrophy (MSA)
Progressive supranuclear palsy (PSP)
Discussion:
Focal midbrain atrophy with relative sparing of the pons, sometimes referred to as the
“Hummingbird sign” or “Penguin sign” is characteristic of progressive supranuclear palsy (PSP).
PSP is a neurodegenerative disease characterized by Parkinsonian features, postural instability,
and supranuclear vertical gaze palsy. Pathologic specimens exhibit neurofibrillary tangles
composed of misfolded tau protein. Midbrain atrophy is specific to PSP and can be diagnostically
useful in distinguishing PSP from idiopathic Parkinson’s disease and multiple systems atrophy,
which may have overlapping symptoms.
Multiple systems atrophy (MSA) is a synucleinopathy characterized by Parkinsonian features,
cerebellar ataxia, and autonomic dysfunction. The classic radiographic feature is the “hot cross
bun” sign, formed by T2 hyperintense degeneration of the transverse pontocerebellar tracts and
median pontine raphe nuclei. The midbrain is relatively spared.
Creutzfeldt-Jakob disease (CJD) is a spongiform encephalopathy characterized by rapidly
progressive dementia and death. Variant CJD characteristically shows the “hockey stick sign”
involving the pulvinar and dorsomedial thalamic nuclei.
Corticobasal degeneration (CBD) is a tauopathy characterized radiographically by cortical
degeneration while the brainstem is relatively spared.
Normal pressure hydrocephalus (NPH) is characterized radiographically by ventriculomegaly,
upward bowing of the corpus callosum, and the relative crowding of sulci at the vertex.
References:
Mueller C, Hussl A, Krismer F, Heim B, Mahlknecht P, Nocker M, Scherfler C, Mair K,
Esterhammer R, Schocke M, Wenning GK, Poewe W, Seppi K. The diagnostic accuracy of the
hummingbird and morning glory sign in patients with neurodegenerative parkinsonism.
Parkinsonism Relat Disord. 2018 Sep;54:90-94. doi: 10.1016/j.parkreldis.2018.04.005. Epub 2018
Apr 3. PMID: 29643007.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/29643007/
Williams DR, Lees AJ. Progressive supranuclear palsy: clinicopathological concepts and
diagnostic challenges. Lancet Neurol. 2009 Mar;8(3):270-9. doi: 10.1016/S1474-4422(09)70042-0.
PMID: 19233037.
Pubmed Web link
https://pubmed.ncbi.nlm.nih.gov/19233037/
