Block 5 Neuro Atlas Ch 6 W Expl Part 1

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Questions and Answers
  • 1. 

    A 16-year-old boy is brought to the emergency department following a diving accident at a local quarry. The examination reveals a bilateral loss of motor and sensory function in the trunk and lower extremities. At 36 hours after the accident the boy is able to dorsiflex his toes, barely move his right lower extremity at the knee, and is able to perceive pinprick stimulation of the perianal skin (sacral sparing).Which of the following most specifically describes the spinal cord lesion in this patient?

    • A.

      Central cord

    • B.

      Complete

    • C.

      Hemisection

    • D.

      Incomplete

    • E.

      Large syringomyelia

    Correct Answer
    D. Incomplete
    Explanation
    Although this patient initially presented with complete motor and sensory losses, some function had returned by36 hours; in this case the lesion is classified as an incomplete lesion of the spinal cord. Patients with no return of function at 24hours and no sacral sparing have suffered a lesion classified as complete and it is unlikely that they will recover useful neurological function. In a central cord and a large syringomyelia there is sparing of posterior column sensations and in a hemi section the loss of motor function is unilateral.(p.96–97)

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  • 2. 

    A 54-year-old morbidly obese and hypertensive man is brought to the emergency department after experiencing sudden onset of weakness of his left upper and lower extremities. CT shows an infarcted area in the medulla. Damage to which of the following tracts or fiber bundles of the medulla would most likely explain this deficit?

    • A.

      Anterolateral system

    • B.

      Corticospinal fibers

    • C.

      Medial lemniscus

    • D.

      Rubrospinal tract

    • E.

      Vestibulospinal fibers

    Correct Answer
    B. Corticospinal fibers
    Explanation
    A medullary lesion that results in weakness of the extremities on one side indicates involvement of the corti-cospinal fibers located in the pyramid on the contralateral side; these fibers largely cross in the pyramidal (motor) decussation. Rubrospinal and vestibulospinal fibers influence the activity of spinal motor neurons, but isolated lesions of these fibers would not result in a unilateral weakness of upper and lower extremities. The anterolateral system and the medial lemniscus are sensory tracts.(p.103–109,112)

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  • 3. 

    A 78-year-old healthy, active woman experiences a sudden weakness of her right upper extremity during an angiogram to determine the patency of her carotid bifurcation. The immediate examination reveals weakness of both extremities on the right and a partial loss of vision in both eyes (homonymoushemianopsia).These observations suggest an embolic stroke resulting in a lesion involving motor and visual structures. The infarcted area in CT points to the occlusion of one vessel. Which of the following vessels is most likely occluded?

    • A.

      Anterior cerebral artery

    • B.

      Anterior choroidal artery

    • C.

      Ophthalmic artery

    • D.

      Lateral posterior choroidal artery

    • E.

      Posterior cerebral artery (P3 and P4 segments)

    Correct Answer
    B. Anterior choroidal artery
    Explanation
    The anterior choroidal artery serves the optic tract(homonymous hemianopsia) and the inferior portions of the posterior limb of the internal capsule (weakness of the extremities).The ophthalmic artery, via its central retinal branch, serves the retina; the anterior cerebral artery serves the lower extremity areas of the motor and sensory cortices; and distal segments of the posterior cerebral artery serve the medial temporal cortex and the visual cortex. The lateral posteriorchoroidal artery serves the choroid plexus in the lateral ventricle and some adjacent structures.(p.148–152,160)

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  • 4. 

    .A 69-year-old man is brought to the emergency department by his wife after complaining of a severe headache and becoming stuporous. CT shows a hemorrhage into the head of the caudate nucleus that has ruptured into the anterior horn of the lateral ventricle. This hemorrhage has most likely originated from which of the following vessels?

    • A.

      Anterior choroidal artery (branch of internal carotid)

    • B.

      Lenticulostriate branches (of M1 )

    • C.

      Medial posterior choroidal artery (branch of P2)

    • D.

      Medial striate artery (branch of proximal A2)

    • E.

      Thalamoperforating artery(ies)

    Correct Answer
    D. Medial striate artery (branch of proximal A2)
    Explanation
    The head of the caudate nucleus is located in the lateral wall of the anterior horn of the lateral ventricle and receives its blood supply from the medial striate artery (also called the artery of Heubner).This vessel also serves much of the anterior limb of the internal capsule. The lenticulostriate arteries serve a large part of the lenticular nucleus and portions of the surrounding internal capsule, and thalamo perforating arteries serve anterior portions of the dorsal thalamus. The anterior choroidal artery provides blood supply to inferior portions of the internal capsule, optic tract, and structures in the medial portions of the temporal lobe. The medial posteriorchoroidal artery serves choroid plexus in the lateral and third ventricles and adjacent areas of the lateral midbrain and caudomedial thalamus.(p.154–159,160)

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  • 5. 

    A 23-year-old man is brought to the emergency department from the site of an automobile collision. The neurological examination reveals weakness of the right lower extremity and a loss of pain and thermal sensations on the left side beginning at the level of the umbilicus. CT shows a fracture of the vertebral column with dis-placement of bone fragments into the vertebral canal. Damage to which of the following tracts would correlate with weakness of the lower extremity in this man?

    • A.

      Left lateral corticospinal tract

    • B.

      Reticulospinal fibers on the right

    • C.

      Right lateral corticospinal tract

    • D.

      Right rubrospinal tract

    • E.

      Vestibulospinal fibers on the right

    Correct Answer
    C. Right lateral corticospinal tract
    Explanation
    In this patient the weakness of the right lower extremity is related to a lesion of lateral corticospinal tract fibers on the right side of the spinal cord. The left corticospinal tract serves the left side of the spinal cord and the left lower extremity. Rubrospinal, reticulospinal, and vestibulospinal fibers influence the activity of spinal motor neurons; however, the deficits related to corticospinal tract damage (significant weakness) will dominate over the lack of excitation to flexor or extensor motor neurons in the spinal cord via these tracts.(p.90–93,96–97)

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  • 6. 

    A 23-year-old man is brought to the emergency department from the site of an automobile collision. The neurological examination reveals weakness of the right lower extremity and a loss of pain and thermal sensations on the left side beginning at the level of the umbilicus. CT shows a fracture of the vertebral column with dis-placement of bone fragments into the vertebral canal. Which of the following represents the most likely level of dam-age to the spinal cord resulting from the fracture to the vertebral column in this man?

    • A.

      T6 on the left

    • B.

      T8 on the left

    • C.

      T8 on the right

    • D.

      T10 on the left

    • E.

      T10 on the right

    Correct Answer
    C. T8 on the right
    Explanation
    The loss of pain and thermal sensations beginning at the level of the umbilicus (T10 dermatome) on the left side results from damage to fibers of the anterolateral system at about the T8 level on the right. These fibers ascend one to two levels as they cross the midline. Damage at the T6 level would result in a loss beginning at the T8 level on the contralateral side and damage at the T10 level would result in a loss beginning at about the T12 level.(p.90–93,96–97)

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  • 7. 

    The artery of Adamkiewicz is an especially large spinal medullary artery supplementing the arterial blood supply to the spinal cord. Which of the following represents the most consistent location of this vessel?

    • A.

      At C7–C8 on the left

    • B.

      At L5–S1 on the left

    • C.

      At L5–S1 on the right

    • D.

      At T6–T7 on the right

    • E.

      At T12–L1 on the left

    Correct Answer
    E. At T12–L1 on the left
    Explanation
    The artery of Adamkiewicz is usually located at theT12–L1 spinal cord levels and is more frequently (about 65% of the time) seen on the left side. The other cord levels listed may have small spinal medullary arteries but not the large diameter vessel characteristic of Adamkiewicz.(p.88–89,96–97)

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  • 8. 

    The CT of a 73-year-old woman shows an infarcted area in the rostral portions of the dorsomedial nucleus, the anterior nucleus,and the ventral anterior nucleus. Which of the following arteries supply blood to this area of the brain?

    • A.

      Anterior choroidal

    • B.

      Lateral striate (lenticulostriate)

    • C.

      Medial striate

    • D.

      Thalamogeniculate

    • E.

      Thalamoperforating

    Correct Answer
    E. Thalamoperforating
    Explanation
    The thalamoperforating arteries serve the more rostral portions of the dorsal thalamus. These vessels may originate as a single trunk or as several vessels from the P1 segment of the posterior cerebral artery. The anterior choroidal artery serves the optic tract, inferior portions of the internal capsule, choroidplexus in the temporal horn, and structures in the medial region of the temporal lobe. The thalamogeniculate artery sup-plies blood to the caudal thalamus, the medial striate arteries to the head of the caudate nucleus, and the lateral striate arteries to much of the lenticular nucleus.(p.146–150,160)

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  • 9. 

    Which of the following structures is insinuated between the external and extreme capsules and is functionally related to the insular cortex?

    • A.

      Claustrum

    • B.

      External medullary lamina

    • C.

      Lamina terminalis

    • D.

      Putamen

    • E.

      Stria terminalis

    Correct Answer
    A. Claustrum
    Explanation
    The claustrum is the thin layer of grey matter that is located between the extreme and external capsules. It is generally regarded as being functionally related to the insular cortex. The external medullary lamina is found at the interface of the lateral portions of the thalamus with the internal capsule and the lamina terminalis is the thin structure forming the rostral wall of the third ventricle. The putamen is located medial to the external capsule and lateral to the globus pallidus and the stria terminalis is a fiber bundle in the groove between the body of the caudate nucleus and the dorsal thalamus.(p.146–154)

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  • 10. 

    An 83-year-old man is brought to the emergency department by his daughter, who explains that her father started having “fits.” The examination reveals an alert, otherwise healthy, man who frequently has uncontrollable flailing movements of his left arm. Which of the following structures is most likely involved in this lesion?

    • A.

      Cerebellar cortex plus nuclei

    • B.

      Lenticular nucleus

    • C.

      Subthalamic nucleus

    • D.

      Ventral lateral nucleus

    • E.

      Ventral posterolateral nucleus

    Correct Answer
    C. Subthalamic nucleus
    Explanation
    Wild flailing movements of the extremities, especially the upper, are hemiballistic movements (hemiballismus);these are characteristic of a lesion in the subthalamic nucleus. Damage to the cerebellar cortex and nuclei and the lenticularnucleus will result in motor deficits, but these are usually described as involving tremor, ataxia, and related motor problems. The ventral lateral nucleus is a thalamic relay center for motor information and the ventral posterolateral nucleus is a sensory relay nucleus. Lesions of these nuclei will result in motor (but not hemiballismus) and sensory deficits.(p.145–149,160)

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  • 11. 

    A 17-year-old girl presents with a bilateral loss of pain and thermal sensations at the base of the neck (C3 dermatome) and extending over the upper extremity and down to the level of the nipple (C4 to T4 dermatomes). MRI shows a cavitation in the spinal cord at these levels. Damage to which of the following structures would most likely explain this deficit?

    • A.

      Anterior white commissure

    • B.

      Left anterolateral system

    • C.

      Medial longitudinal fasciculus

    • D.

      Posterior columns

    • E.

      Right anterolateral system

    Correct Answer
    A. Anterior white commissure
    Explanation
    Fibers conveying pain and thermal sensations cross the midline in the anterior white commissure. Consequently, a lesion of this structure, as in syringomyelia, would result in a bilateral loss of these sensations, reflecting the levels of the syrinx. Damage to fibers of the anterolateral system results in a loss of these sensations on the contralateral side and the posterior columns convey proprioception, discriminative touch, and vibratory sense. The medial longitudinal fasciculus does not contain fibers conveying sensory input.(p.92–93,96–97)

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  • 12. 

    Which of the following structures is located within the territory of the medulla that is served by the anterior spinal artery?

    • A.

      Anterolateral system

    • B.

      Gracile fasciculus

    • C.

      Medial lemniscus

    • D.

      Rubrospinal tract

    • E.

      Spinal trigeminal tract

    Correct Answer
    C. Medial lemniscus
    Explanation
    The anterior spinal artery serves the medial portion of the medulla, an area that encompasses the medial lemniscus, exiting roots of the hypoglossal nerve, and the corticospinal fibers in the pyramid. The anterolateral system, spinal trigeminal tract, and rubrospinal tract are in the territory of the posterior inferior cerebellar artery (commonly called PICA by clinicians).The posterior spinal artery in the caudal medulla and spinal cord serves the gracile fasciculus.(p.104–109,112)

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  • 13. 

    A 59-year-old man complains to his family physician that he has trouble chewing. The examination reveals a weakness of masticatory muscles on the left side. Which of the following nuclei is specifically related to the deficit seen in this man?

    • A.

      Left facial motor

    • B.

      Left hypoglossal

    • C.

      Left trigeminal motor

    • D.

      Right facial motor

    • E.

      Right trigeminal motor

    Correct Answer
    C. Left trigeminal motor
    Explanation
    The masticatory muscles receive their motor innervation via the motor neurons located in the trigeminal motornucleus on the ipsilateral side; this excludes the right trigeminal nucleus. Facial motor neurons innervate the muscles offacial expression on the ipsilateral side and the hypoglossal nucleus innervates the ipsilateral side of the tongue.(p.122–123,126)

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  • 14. 

    A 15-year-old boy with signs of increased intracranial pressure(stupor, vomiting, and headache) is referred to a neurologist. The examination reveals a paralysis of upward gaze, and MRI shows a large tumor of the pineal gland. Damage to which of the following structures would be most specifically related to the gaze deficit?

    • A.

      Exit of the trochlear nerve

    • B.

      Inferior colliculus

    • C.

      Occlusion of the great cerebral vein

    • D.

      Posterior commissur

    • E.

      Superior colliculus

    Correct Answer
    E. Superior colliculus
    Explanation
    A pineal tumor impinging on the superior colliculus may result in a paralysis of upward gaze (Parinaud syndrome).The inferior colliculus is related to the auditory system, trochlear fibers innervate the ipsilateral superior oblique muscle, and the posterior commissure contains fibers related to the pupillary light pathway. Occlusion of the great cerebral vein may cause serious neurological deficits but not specifically a paralysis of upward gaze.(p.138,144–145)

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  • 15. 

    A 61-year-old man is brought to the emergency department after a fall from his garage roof. The examination reveals a hemiplegia on the left, a loss of vibratory sense on the left, and a loss of pain and thermal sensation on the right side involving the upper and lower extremities. These deficits are characteristically seen in which of the following syndromes?

    • A.

      Benedikt

    • B.

      Brown-Séquard

    • C.

      Claude

    • D.

      Wallenberg

    • E.

      Weber

    Correct Answer
    B. Brown-Séquard
    Explanation
    Alternating sensory losses accompanied by a motor deficit on the same side as the loss of vibratory sensation are characteristics of the Brown-Séquard syndrome (also commonly called a spinal cord hemi section).The Wallenberg syndrome is seen in lesions of the medulla, and the Benedikt, Claude, and Weber syndromes are seen in lesions of the midbrain. In these brainstem syndromes there are usually characteristic cranial nerve and long tract signs and symptoms.(p.50,88–93,96–97)

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  • 16. 

    .Based on their relative locations in the spinal cord, which of the following tracts or fiber bundles would most likely be involved in a lesion located in the immediate vicinity of the lateral corticospinal tract?

    • A.

      Anterolateral system

    • B.

      Anterior spinocerebellar tract

    • C.

      Gracile fasciculus

    • D.

      Medial longitudinal fasciculus

    • E.

      Rubrospinal tract

    Correct Answer
    E. Rubrospinal tract
    Explanation
    The rubrospinal tract lies immediately anterior (ventral) to, and partially overlaps with, the lateral corticospinal tract. The anterolateral system is in the anterolateral area of the spinal cord and is spatially separated from the lateral corti-cospinal tract. The gracile fasciculus is in the posterior columns, the medial longitudinal fasciculus is in the ventral funiculus, and the anterior spinocerebellar tract is located on the antero-lateral surface of the spinal cord.(p.88–93)

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  • 17. 

    A 92-year-old woman is brought to the emergency department by her caregiver. The woman had suddenly become drowsy and confused. The examination revealed no cranial nerve deficits and age-normal motor function, but a loss of pain, thermal,  vibratory, and discriminative touch sensations on one side of the body excluding the head. CT shows a small infarcted area. Which of the following structures is the most likely location of this lesion?

    • A.

      Anterolateral system

    • B.

      Medial geniculate nucleus

    • C.

      Subthalamic nucleus

    • D.

      Ventral posterolateral nucleus

    • E.

      Ventral posteromedial nucleus

    Correct Answer
    D. Ventral posterolateral nucleus
    Explanation
    The ventral posterolateral nucleus of the thalamus receives the pathways (medial lemniscus and anterolateral sys-tem) that relay the information lost as a result of the lesion in this woman. The ventral posteromedial nucleus relays comparable information from the face and the medial geniculate nucleus is related to the auditory system. Lesions in the subthalamic nucleus result in hemiballismus. The anterolateral system relays pain and thermal sense; this is only part of the sensory deficits experienced by this woman.(p.144–145,160)

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  • 18. 

    In its location immediately internal to the anterior spinocere-bellar tract, which of the following fiber bundles would most likely be damaged in a lesion to this area of the spinal cord?

    • A.

      Anterolateral system

    • B.

      Anterior corticospinal tract

    • C.

      Anterior white commissure

    • D.

      Cuneate fasciculus

    • E.

      Lateral corticospinal tract

    Correct Answer
    A. Anterolateral system
    Explanation
    The anterolateral system is located internal to the position of the anterior spinocerebellar tract; damage to this area of the spinal cord would most likely result in a loss of pain and thermal sensations on the contralateral side of the body below the lesion. The lateral corticospinal tract is located internal to the posterior spinocerebellar tract, the anterior white commissure and the anterior corticospinal tract are located in the anterior funiculus of the cord, and the cuneate fasciculus is in the posterior column medial to the posterior horn at upper thoracic and cervical levels.(p.88–93)

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  • 19. 

    A 37-year-old man is brought to the emergency department with a severe head injury. Within a few hours he is decerebrate (upper and lower extremities extended) and comatose. The extension of his extremities indicates a dominant input to extensor motor neurons through reticulo spinal fibers/track Which of the following most specifically describes the position of these activated fibers within the spinal cord?

    • A.

      Anterolateral area (area of anterolateral system)

    • B.

      Posterolateral area (area of lateral corticospinal tract)

    • C.

      Posterior columns

    • D.

      Posterolateral (dorsolateral) tract

    • E.

      Intermediate zone

    Correct Answer
    A. Anterolateral area (area of anterolateral system)
    Explanation
    Reticulospinal fibers (medial and lateral) and later-al vestibulospinal fibers are found predominantly in the anterolateral area of the spinal cord; medial vestibulospinal fibers are located in the medial longitudinal fasciculus. In the decerebrate patient, the descending influence of rubrospinal fibers on spinal flexor motor neurons is removed, and descending influence on extensor motor neurons is predominant. The posterior columns, posterolateral area of the cord, and the posterolateral tract do not contain vestibulospinal or reticulospinalfibers. The intermediate zone, a part of the spinal cord grey matter, contains some of the terminals of these fibers but not the descending tracts in toto.(p.88–93,210–211)

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  • 20. 

    71-year-old woman presents to her family physician with the complaint that “food dribbles out of my mouth when I eat. “the examination reveals a unilateral weakness of muscles around the eye (palpebral fissure) and the opening of the mouth (oral fissure).She also has a loss of pain and thermal sensations on the opposite side of the body excluding the head. CT shows an infarcted area in the lateral portion of the pontine tegmentum. Damage to which of the following nuclei would most likely explain the muscle weakness experienced by this woman?

    • A.

      Abducens

    • B.

      Arcuate

    • C.

      Facial motor

    • D.

      Hypoglossal

    • E.

      Trigeminal motor

    Correct Answer
    C. Facial motor
    Explanation
    Weakness of the muscles of the face, particularly when upper and lower portions of the face are involved, indicate a lesion of either the facial motor nucleus or the exiting fibers of the facial nerve; both are located in the lateral pontinetegmentum at caudal levels. The hypoglossal nucleus innervates muscles of the tongue, the trigeminal nucleus innervates masticatory muscles, and the abducens nucleus innervates the lateral rectus muscle, all on the ipsilateral side. The arcuatenucleus is a group of cells located on the surface of the pyramid.(p.118–121,126)

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  • 21. 

    71-year-old woman presents to her family physician with the complaint that “food dribbles out of my mouth when I eat. “the examination reveals a unilateral weakness of muscles around the eye (palpebral fissure) and the opening of the mouth (oral fissure).She also has a loss of pain and thermal sensations on the opposite side of the body excluding the head. CT shows an infarcted area in the lateral portion of the pontine tegmentum. The loss of pain and thermal sensations experienced by this woman would most likely correlate with a lesion involving which of the following structures?

    • A.

      Anterior (ventral) trigeminothalamic tract

    • B.

      Anterolateral system

    • C.

      Lateral lemniscus

    • D.

      Medial lemniscus

    • E.

      Spinal trigeminal tract

    Correct Answer
    B. Anterolateral system
    Explanation
    The fibers of the anterolateral system are located in the lateral portion of the pontine tegmentum anterior (ventral) to the facial motor nucleus; these fibers convey pain and thermal inputs. The spinal trigeminal tract and the anteriortrigeminothalamic tract also convey pain and thermal input but from the ipsilateral and contralateral sides of the face, respectively. The lateral lemniscus is auditory in function and the medial lemniscus conveys proprioception, vibratory sense, and discriminative touch.(p.50,118–121,126)

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  • 22. 

    A 77-year-old woman is discovered slumped on the floor in the grocery store; emergency medical personnel transport her to a local hospital. The examination reveals a drowsy somewhat stuporous woman who is difficult to arouse. CT shows a large hemorrhage within the brain medial to the internal medullary lamina. Which of the following structures is most likely involved in this lesion?

    • A.

      Anterior thalamic nucleus

    • B.

      Dorsomedial nucleus

    • C.

      Globus pallidus

    • D.

      Ventral lateral and anterior nuclei

    • E.

      Ventral posterolateral nucleus

    Correct Answer
    B. Dorsomedial nucleus
    Explanation
    The dorsomedial nucleus is located medial to the internal medullary lamina and, through its connections, one if its functions is to participate in arousal of the cerebral cortex. The other choices are in (anterior nucleus) or lateral to the internal medullary lamina, or, in the case of the globus pallidus, lateral to the internal capsule.(p.148–151,160)

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  • 23. 

    A 78-year-old man presents with deficits suggesting an occlusion of the posterior spinal artery at spinal cord levels C4–T2.Which of the following structures are in the territory served by this vessel at these levels?

    • A.

      Anterolateral system

    • B.

      Cuneate fasciculus

    • C.

      Gracile nucleus

    • D.

      Lateral corticospinal tract

    • E.

      Medial longitudinal fasciculus

    Correct Answer
    B. Cuneate fasciculus
    Explanation
    Penetrating branches of the posterior spinal artery serve the posterior columns (gracile and cuneate fasciculi) of the spinal cord at all levels. Branches of the posterior spinal artery also serve the gracile nucleus, but this structure is in the medulla, not in the spinal cord. The lateral corticospinal tract and the anterolateral system are served by the arterial vasocorona on the surface of the cord and the internal branches of the anterior spinal artery. The medial longitudinal fasciculus is in the territory of the anterior spinal artery.(p.90–94,96–97)

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  • 24. 

    Based partially on their embryological origin from a common group of cells, which of the following combinations of structures appear to be the same shade of grey in a T1-weightedMRI?

    • A.

      Dorsomedial nucleus and globus pallidus

    • B.

      Globus pallidus and caudate

    • C.

      Globus pallidus and putamen

    • D.

      Putamen and caudate nucleus

    • E.

      Putamen and pulvinar

    Correct Answer
    D. Putamen and caudate nucleus
    Explanation
    The putamen and the caudate nucleus originate from the same group of developing neurons, are collectively referred to as the neostriatum, and appear in the same shade of grey in a T1-weighted MRI. In general, the globus pallidus and pulvinar are distinctly lighter than the putamen and the dorsomedial nucleus frequently appears dark in a shade of grey distinctly different from that of the globus pallidus.(p.146–155)

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  • 25. 

    Which of the following portions of the trigeminal nuclear complex is found in lateral areas of the brainstem between the level of the obex and the spinal cord-medulla junction and is the source of trigeminothalamic fibers conveying pain and thermal information originating from the face and oral cavity?

    • A.

      Mesencephalic nucleus

    • B.

      Principal sensory nucleus

    • C.

      Spinal trigeminal nucleus, pars caudalis

    • D.

      Spinal trigeminal nucleus, pars interpolaris

    • E.

      Spinal trigeminal nucleus, pars oralis

    Correct Answer
    C. Spinal trigeminal nucleus, pars caudalis
    Explanation
    The pars caudalis portion of the spinal trigeminal nucleus is located in the lateral medulla adjacent to the spinal trigeminal tract in cross-sectional levels between the obex and the C1 level of the spinal cord. This portion of the spinal trigeminal nucleus is responsible for relaying pain and thermal information originating from the face and oral cavity on one side to the ventral posteromedial nucleus on the contralateral side. The pars interpolaris is found at levels between the obex and the rostral end of the hypoglossal nucleus and the parsoralis between the interpolaris and the principal sensory nucleus. The principal sensory nucleus is in the pons and the mesencephalic nucleus is in the midbrain.(p.100–105)

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  • 26. 

    Which of the following structures is located within the territory served by branches of the posterior inferior cerebellar artery(commonly called PICA by clinicians)?

    • A.

      Corticospinal fibers

    • B.

      Hypoglossal root

    • C.

      Medial lemniscus

    • D.

      Nucleus raphe magnus

    • E.

      Solitary nucleus

    Correct Answer
    E. Solitary nucleus
    Explanation
    The solitary nucleus receives general visceral afferent(GVA) and special visceral afferent information (SVA, this input is taste) and is located in the region of the medulla served byposterior inferior cerebellar artery. All of the other choices are in the territory served by the anterior spinal artery.(p.112–113)

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  • 27. 

    Space-occupying lesions within the posterior cranial fossa, or events that increase pressure within this infratentorial region, may result in herniation of a portion of the cerebellum through the foramen magnum. Which of the following parts of the cerebellum is most likely involved in this event?

    • A.

      Anterior lobe

    • B.

      Flocculus

    • C.

      Nodulus

    • D.

      Simple lobule

    • E.

      Tonsil

    Correct Answer
    E. Tonsil
    Explanation
    The tonsil of the cerebellum is located close to the midline and immediately above the medulla. Its position relative to the cerebellum is caudal, medial, and inferior. Tonsillarherniation may compress the medulla, and if sudden, may result in death. The other portions of the cerebellum usually do not herniate.(p.114–115)

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  • 28. 

    A 67-year-old woman is brought to the emergency department. She is stuporous and has signs that suggest a lesion in the brain-stem; CT confirms this. Her right pupil is constricted (small)when compared with the left. Damage to which of the following tracts or fiber bundles in the pons or medulla would most likely explain this observation?

    • A.

      Anterolateral system

    • B.

      Hypothalamo spinal fibers

    • C.

      Medial longitudinal fasciculus

    • D.

      Reticulospinal fibers

    • E.

      Vestibulospinal fibers

    Correct Answer
    B. Hypothalamo spinal fibers
    Explanation
    In addition to other signs or symptoms, lesions in lateral areas of the brainstem may also interrupt hypothalamo-spinal fibers descending from the hypothalamus to the inter-mediolateral cell column in upper thoracic levels of the spinal cord. In this case the patient may present with a Horner syndrome, part of which is a small (constricted) pupil. In addition, the affected pupil may react slowly to reduced light. The antero-lateral system conveys somatosensory input and fibers of the medial longitudinal fasciculus (originating from the medulla)are primarily descending to spinal cord levels. Reticulospinal and vestibulospinal tracts influence spinal motor neurons.(p.49,112)

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  • 29. 

    In addition to the medial and lateral geniculate nuclei, which of the following structures is also served by the thalamogeniculate artery, a branch of P2 ?

    • A.

      Anterior thalamic nucleus

    • B.

      Globus pallidus

    • C.

      Pulvinar nucleus(i)

    • D.

      Substantia nigra

    • E.

      Ventral anterior thalamic nucleus

    Correct Answer
    C. Pulvinar nucleus(i)
    Explanation
    The pulvinar, geniculate nuclei, ventral posterome-dial and posterolateral nuclei, centromedian, and some other adjacent nuclei are served by the thalamogeniculate artery. The anterior and ventral anterior thalamic nuclei receive their blood supply from thalamoperforating arteries, the substantianigra via branches of P1 and P2 ,and globus pallidus from the lenticulostriate branches of M1.(p.160)

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  • 30. 

    A 71-year-old man is brought to the emergency department by his wife. She explains that he suddenly became weak in his left lower extremity. She immediately rushed him to the hospital, a trip of about 20 minutes. The examination reveals an alert man who is obese and hypertensive. He has no cranial nerve deficits, is slightly weak on his left side, and has no sensory deficits. Within 2 hours the weakness has disappeared. An MRI obtained the following day shows no lesions. Which of the following most specifically describes this man’s medical experience?

    • A.

      Central cord syndrome

    • B.

      Small embolic stroke

    • C.

      Small hemorrhagic stroke

    • D.

      Syringobulbia

    • E.

      Transient ischemic attack

    Correct Answer
    E. Transient ischemic attack
    Explanation
    The short-term loss of function, frequently involving a specific part of the body, is characteristic of a transient ischemic attack (commonly called a TIA).The follow-up MRI shows no lesion because there has been no permanent damage. TIAs are caused by a brief period of inadequate perfusion of a localized region of the nervous system; recovery is usually rapid and complete. However, TIAs, especially if repeated, maybe indicative of an impending stroke. Hemorrhagic strokes frequently result in some type of permanent deficit, and the central cord syndrome has bilateral deficits. A small embolic stroke would be visible on the follow-up MRI, and in this patient would have resulted in a persistent deficit. Syringobulbia may include long tract signs as well as cranial nerve signs.(p.160)

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