Block 5 Neuro Atlas Ch 6 W Expl Part 2
Questions and Answers
- 1.
A 41-year-old man is brought to the emergency department after an accident at a construction site. The examination reveals a weakness(hemiplegia) and a loss of vibratory sensation and discriminative touch all on the left lower extremity, and a loss of pain and thermal sensations on the right lower extremity. CT shows a fracture of the vertebral column adjacent to the T8 level of the spinal cord. Damage to which of the following fiber bundles or tracts would most likely explain the loss of vibratory sensation in this man?
- A.
Anterolateral system on the right
- B.
Cuneate fasciculus on the left
- C.
Cuneate fasciculus on the right
- D.
Gracile fasciculus on the left
- E.
Gracile fasciculus on the right
Correct Answer
D. Gracile fasciculus on the leftExplanation
Damage to the gracile fasciculus on the left (at theT8 level this is the only part of the posterior columns present)accounts for the loss of vibratory sensation (and discriminative touch).Injury to the gracile fasciculus on the right would result in this type of deficit on the right side. The level of the cord damage is caudal to the cuneate fasciculi and the anterolateral system conveys pain and thermal sensations.(p.90–93,96–97)Rate this question:
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- 2.
A 41-year-old man is brought to the emergency department after an accident at a construction site. The examination reveals a weakness(hemiplegia) and a loss of vibratory sensation and discriminative touch all on the left lower extremity, and a loss of pain and thermal sensations on the right lower extremity. CT shows a fracture of the vertebral column adjacent to the T8 level of the spinal cord. The loss of pain and thermal sensation in this man reflects damage to which of the following fiber bundles or tracts?
- A.
Anterolateral system on the left
- B.
Anterolateral system on the right
- C.
Cuneate fasciculus on the left
- D.
Gracile fasciculus on the left
- E.
Posterior spinocerebellar tract on the left
Correct Answer
A. Anterolateral system on the leftExplanation
The loss of pain and thermal sensations on the right side of the body correlates with a lesion involving the antero-lateral system on the left side of the spinal cord. A lesion of the right anterolateral system would result in a left-sided deficit. The gracile and cuneate fasciculi convey discriminative touch, vibratory sensation, and proprioception. The posterior spinocerebellar tract conveys similar information, but it is not perceived/recognized as such (consciously) by the brain.(p.90–93,96–97)Rate this question:
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- 3.
Which of the following is the prominent population of melanin-containing cells located immediately internal to the crus cerebri?
- A.
Locus ceruleus
- B.
Pontine nuclei
- C.
Red nucleus
- D.
Reticular formation
- E.
Substantia nigra
Correct Answer
E. Substantia nigraExplanation
The substantia nigra contains a large population of melanin-containing cells, is located in the midbrain just internal to the crus cerebri, and the loss of these cells gives rise to the motor deficits characteristic of Parkinson disease. The neurotransmitter associated with these cells is dopamine. The reticular formation is in the core of the brainstem and the pontinenuclei are in the basilar pons; neither of these contains cells with melanin. The red nucleus is in the midbrain, but its red-dish tone is related to a rich vascular supply, not to cells containing a pigment.(p.133–135)Rate this question:
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- 4.
Which of the following structures receives visceral sensory input and is located immediately inferior to the medial and spinal vestibular nuclei at medullary levels?
- A.
Cochlear nuclei
- B.
Inferior salivatory nucleus
- C.
Nucleus ambiguus
- D.
Spinal trigeminal nucleus
- E.
Solitary nucleus
Correct Answer
E. Solitary nucleusExplanation
The solitary nucleus is located immediately inferior(ventral) to the medial and spinal vestibular nuclei and is the only nucleus in the choices to receive a general visceral afferent(GVA) and special visceral afferent (SVA-taste) input. The inferior salivatory nucleus and the nucleus ambiguus are visceromotor (general visceral efferent [GVE] and special visceral efferent [SVE],respectively) and the spinal trigeminal and cochlear nuclei are sensory (general somatic afferent [GSA]and special somatic afferent [SSA],respectively).(p.104–109)Rate this question:
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- 5.
Which of the following groups of visceromotor (autonomic)cell bodies is located lateral to the abducens nucleus, directly adjacent to the exiting fibers of the facial nerve, and sends its axons out of the brainstem via this cranial nerve?
- A.
Dorsal motor nucleus
- B.
Edinger-Westphal nucleus
- C.
Inferior salivatory nucleus
- D.
Intermediolateral cell column
- E.
Superior salivatory nucleus
Correct Answer
E. Superior salivatory nucleusExplanation
The superior salivatory nucleus lies adjacent to the exiting fibers of the facial nerve in a position just lateral to the abducens nucleus in caudal levels of the pons. The preganglionic axons originating from these cells distribute on peripheral branches of the facial nerve. The dorsal motor and inferior salivatory nuclei are in the medulla and associated, respectively, with the vagus and glossopharyngeal nerves. The Edinger-Westphal nucleus is related to the oculomotor nucleus and the intermediolateral cell column is located primarily in thoracic levels of the spinal cord.(p.188–119)Rate this question:
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- 6.
A 56-year-old woman presents to her family physician with persistent headache and nausea. MRI shows a tumor in the fourth ventricle impinging on the facial colliculus. Which of the following nuclei is found immediately internal to this elevation?
- A.
Abducens
- B.
Facial
- C.
Hypoglossal
- D.
Trigeminal
- E.
Vestibular
Correct Answer
A. AbducensExplanation
The facial colliculus is an elevation in the floor of the fourth ventricle located medial to the sulcus limitans and formed by the underlying abducens nucleus and fibers (internal genu) originating from the facial nucleus. The vestibular
area, indicating the position of the vestibular nuclei, is lateral to the sulcus limitans and the hypoglossal nucleus is internal to the hypoglossal trigone in the medial floor of the ventricle in the medulla. The trigeminal and facial nuclei are located in the pontine tegmentum and do not border on the ventricular space.(p.118–119)Rate this question:
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- 7.
An 88-year-old man is brought to the emergency department by his daughter. She indicates that he complained of weakness of his “arm “and “leg”(upper and lower extremities) on the right side and of “seeing two of everything”(double vision—diplopia).CT shows an infarcted area in the medial area of the pons at the pons-medulla junction. The infarcted area is consistent with the vascular territory served by paramecia branches of the basilar artery. Weakness of the extremities on the right can be explained by damage to which of the following structures?
- A.
Corticospinal fibers on the left
- B.
Corticospinal fibers on the right
- C.
Middle cerebellar peduncle on the left
- D.
Rubrospinal fibers on the left
- E.
Rubrospinal fibers on the right
Correct Answer
A. Corticospinal fibers on the leftExplanation
In this case the weakness of the upper and lower extremities on the right reflects damage to corticospinal fibers on the left side of the basilar pons. A lesion of these fibers on the right side of the pons would produce a left-sided weakness. Rubrospinal fibers are not located in the territory of paramedian branches of the basilar artery. Also, lesions of rubrospinal fibers and of the middle cerebellar peduncle do not cause weakness but may cause other types of motor deficits.(p.118–121,126)Rate this question:
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- 8.
An 88-year-old man is brought to the emergency department by his daughter. She indicates that he complained of weakness of his “arm “and “leg”(upper and lower extremities) on the right side and of “seeing two of everything”(double vision—diplopia).CT shows an infarcted area in the medial area of the pons at the pons-medulla junction. The infarcted area is consistent with the vascular territory served by paramecia branches of the basilar artery. The diplopia (double vision) this man is having is most likely the result of damage to which of the following structures?
- A.
Abducens nerve root
- B.
Facial nerve root
- C.
Oculomotor nerve root
- D.
Optic nerve
- E.
Trochlear nerve or root
Correct Answer
A. Abducens nerve rootExplanation
The exiting fibers of the abducens nerve (on the left)are in the territory of the paramedian branches of the basil artery and are laterally adjacent to corticospinal fibers in the basilar pons. Diplopia may result from lesions of the oculomotor and trochlear nerves, but these structures are not in the domain of the paramedian basilar branches. A lesion of the optic nerve results in blindness in that eye and damage to the facial root does not affect eye movement but may cause a loss of view of the external world if the palpebral fissure is closed due to facial muscle weakness.(p.50,118–121,126)Rate this question:
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- 9.
An 88-year-old man is brought to the emergency department by his daughter. She indicates that he complained of weakness of his “arm “and “leg”(upper and lower extremities) on the right side and of “seeing two of everything”(double vision—diplopia).CT shows an infarcted area in the medial area of the pons at the pons-medulla junction. The infarcted area is consistent with the vascular territory served by paramecia branches of the basilar artery. Recognizing that this patient’s lesion involves the territory served by paramedian branches of the basilar artery, which of the following structures is also most likely included in the area of infarction?
- A.
Anterolateral system
- B.
Facial motor nucleus
- C.
Hypoglossal nucleus
- D.
Medial lemniscus
- E.
Spinal trigeminal tract
Correct Answer
D. Medial lemniscusExplanation
At caudal pontine levels most, if not all, of the medial lemniscus is located within the territory served by paramedian branches of the basilar artery. Penetrating branches of the anterior spinal artery serve the hypoglossal nucleus. The other choices are generally in the territories of short or long circumferential branches of the basilar artery.(p.50,118–121,126)Rate this question:
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- 10.
A 77-year-old man presents with a weakness of his right upper and lower extremities and he is unable to abduct his left eye on attempted gaze to the left. Which of the following most specifically describes this deficit?
- A.
Alternating hemianesthesia
- B.
Hemihypesthesia
- C.
Inferior alternating hemiplegia
- D.
Middle alternating hemiplegia
- E.
Superior alternating hemiplegia
Correct Answer
D. Middle alternating hemiplegiaExplanation
Weakness of the extremities accompanied by paralysis of the lateral rectus muscle (innervated by the abducens nerve) on the contralateral side indicates a lesion in the caudal and medial pons involving the abducens nerve root and corti-cospinal fibers. This is a middle alternating hemiplegia. Inferior alternating hemiplegia specifies involvement of the hypoglossal root and the pyramid, and superior alternating hemiplegia indicates damage to the oculomotor root and the crus cerebri. Alternating (or alternate) hemianesthesia and hemihypesthesia are sensory losses.(p.49–50,126)Rate this question:
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- 11.
In axial MRI which of the following structures is an important landmark that separates the third ventricle (rostral to this point) from the quadrigeminal cistern (caudal to this point)?
- A.
Lamina terminalis
- B.
Habenular nucleus
- C.
Massa intermedia
- D.
Pulvinar
- E.
Superior colliculu
Correct Answer
B. Habenular nucleusExplanation
The prominent elevation formed on the caudal and medial wall of the third ventricle, at the general level of the posterior commissure, represents the location of the habenularnucleus. This is an excellent landmark to use in axial MRI when designating the separation between the third ventricle(rostral to this point on the midline) and the quadrigeminalcistern (caudal to this point).The pulvinar is lateral to the quadrigeminal cistern, the lamina terminalis forms the rostral wall of the third ventricle, and the massa intermedia bridges the space of the third ventricle. When present (in about 80% of patients) the Massa intermedia appears as a shadow in T2-weighted MRI bridging the third ventricle. The superior colliculus is a mesencephalic structure found in the quadrigeminal cistern.(p.30–31,136–137)Rate this question:
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- 12.
A 77-year-old woman presents with deficits that suggest a lesion involving long tracts and a cranial nerve. CT shows an infarct in the region served by the penetrating branches of the basilar bifurcation. Which of the following structures is most likely located in this vascular territory?
- A.
Abducens nerve
- B.
Anterolateral system
- C.
Corticospinal fibers in pyramid
- D.
Medial lemniscus
- E.
Red nucleus
Correct Answer
E. Red nucleusExplanation
The red nucleus, exiting fibers of the oculomotor nerve, portions of the corticospinal fibers in the crus cerebri, and a number of other medially located structures are found in the territory of the penetrating branches of the basilar bifurcation. The paramedian branches of the basilar artery and the corticospinal fibers in the pyramid serve the abducens nerve by branches of the anterior spinal artery. The anterolateral system and the medial lemniscus are mainly, if not entirely, in the region of the midbrain served by branches of the quadrigeminal and posterior medial choroidal arteries.(p.49–50,132–135,138)Rate this question:
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- 13.
A 69-year-old man is brought to the emergency department with the complaint of a sudden loss of sensation. The history reveals that the man is overweight, hypertensive ,and does not regularly take medication. When the man speaks his voice is gravely and hoarse. The examination further reveals a loss of pain and thermal sensations on the right side of his body and on the left side of his face. CT shows an infarcted area in the medulla. Damage to which of the following structures would most likely explain the man’s hoarse, gravelly voice?
- A.
Facial nucleus
- B.
Gracile nucleus
- C.
Hypoglossal nucleus
- D.
Nucleus ambiguus
- E.
Spinal trigeminal nucleus
Correct Answer
D. Nucleus ambiguusExplanation
The vocalis muscle (this muscle is actually the medial portion of the thyroarytenoid muscle) is innervated, via the vagus nerve, by motor neurons located in the nucleus ambiguus. The gracile nucleus conveys sensory input from the body and the spinal trigeminal nucleus relays sensory input from the face. The hypoglossal nucleus is motor to the tongue and the facial nucleus is motor to the muscles of facial expression.(p.104–109,112)Rate this question:
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- 14.
A 69-year-old man is brought to the emergency department with the complaint of a sudden loss of sensation. The history reveals that the man is overweight, hypertensive ,and does not regularly take medication. When the man speaks his voice is gravely and hoarse. The examination further reveals a loss of pain and thermal sensations on the right side of his body and on the left side of his face. CT shows an infarcted area in the medulla. Injury to which of the following structures in this man is most specifically related to the loss of pain and thermal sensations on the body below the neck?
- A.
Anterolateral system
- B.
Cuneate fasciculus
- C.
Gracile fasciculus
- D.
Medial lemniscus
- E.
Spinal trigeminal tract
Correct Answer
A. Anterolateral systemExplanation
Fibers comprising the anterolateral system convey pain and thermal sensations from the body, excluding the face. These fibers are located in lateral portions of the medulla adjacent to the spinal trigeminal tract; this latter tract relays pain and thermal sensations from the face. The gracile and cuneatefasciculi convey proprioception, discriminative touch, and vibratory sense in the spinal cord and the medial lemniscus conveys this same information from the medulla to the dorsal thalamus.(p.104–109,112)Rate this question:
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- 15.
A 69-year-old man is brought to the emergency department with the complaint of a sudden loss of sensation. The history reveals that the man is overweight, hypertensive ,and does not regularly take medication. When the man speaks his voice is gravely and hoarse. The examination further reveals a loss of pain and thermal sensations on the right side of his body and on the left side of his face. CT shows an infarcted area in the medulla. Damage to which of the following structures would most specifically explain the loss of pain and thermal sensations on the man’s face?
- A.
Anterolateral system
- B.
Medial lemniscus
- C.
Medial longitudinal fasciculus
- D.
Solitary tract
- E.
Spinal trigeminal tract
Correct Answer
E. Spinal trigeminal tractExplanation
The loss of pain and thermal sensations on one side of the face correlates with damage to the spinal trigeminal tract; in this case the loss is ipsilateral to the lesion. The anterolateral system relays pain and thermal sensations from the contralateral side of the body, the solitary tract conveys visceral sensory input (especially taste),and the medial lemniscus contains fibers relaying information related to position sense and dis-criminative touch. The medial longitudinal fasciculus does not contain sensory fibers.(p.104–109,112)Rate this question:
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- 16.
A 69-year-old man is brought to the emergency department with the complaint of a sudden loss of sensation. The history reveals that the man is overweight, hypertensive ,and does not regularly take medication. When the man speaks his voice is gravely and hoarse. The examination further reveals a loss of pain and thermal sensations on the right side of his body and on the left side of his face. CT shows an infarcted area in the medulla. The CT shows an infarcted area in the medulla in this man. Based on the deficits described, and the corresponding structures involved, which of the following vessels is most likely occluded?
- A.
Anterior spinal artery
- B.
Posterior spinal artery
- C.
Posterior inferior cerebellar artery
- D.
Anterior inferior cerebellar artery
- E.
Penetrating branches of the vertebral artery
Correct Answer
C. Posterior inferior cerebellar arteryExplanation
The posterior inferior cerebellar artery (commonly called PICA by clinicians) serves the posterolateral portion of the medulla, which encompasses the anterolateral system, spinal trigeminal tract, and nucleus ambiguus. The anterior and medial areas of the medulla (containing the pyramid, medial lemniscus, and hypoglossal nucleus/nerve) are served by the anterior spinal artery and the anterolateral area of the medulla (the region of the olivary nuclei) is served by penetrating branches of the vertebral artery. The posterior spinal artery serves the posterior column nuclei in the medulla and the anterior inferior cerebellar artery (commonly called AICA) serves caudal portions of the pons and cerebellum.(p.104–109,112)Rate this question:
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- 17.
A 77-year-old man presents with an ataxic gait. There are no other deficits. CT shows an infarcted area in the medulla in the territory served by the posterior inferior cerebellar artery. Damage to which of the following structures would most likely explain the symptoms experienced by this man?
- A.
Anterolateral system
- B.
Corticospinal tract
- C.
Nucleus ambiguus
- D.
Rest form body
- E.
Vestibular nuclei
Correct Answer
D. Rest form bodyExplanation
The restiform body is a large fiber bundle located in the posterolateral area of the medulla in the region served byposterior inferior cerebellar artery (PICA).This structure contains a variety of cerebellar afferent fibers including those of the posterior spinocerebellar tract. Damage to the vestibular nuclei will result in a tendency to fall to the ipsilateral side but will also produce diplopia (double vision) and nausea; symptoms not experienced by this patient. The anterolateral system is sensory, the nucleus ambiguus is motor to muscles of the throat (including the vocalis),and the corticospinal tract is not in the PICA territory.(p.104–109,112)Rate this question:
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- 18.
Which of the following cranial nerve nuclei is located in the anterior (ventral or inferior) and medial portion of the periaqueductal grey at the cross-sectional level of the superior colliculus?
- A.
Abducens
- B.
Mesencephalic
- C.
Oculomotor
- D.
Trigeminal motor
- E.
Trochlear
Correct Answer
C. OculomotorExplanation
The oculomotor nucleus (containing general somatic efferent [GSE] cell bodies),along with the Edinger-Westphal(containing general visceral efferent [GVE] cell bodies) nucleus, is found in the most anterior and medial portion of the periaqueductal grey at the superior colliculus level. The trochlear nucleus is found at a comparable position, but at the cross-sectional level of the inferior colliculus. The mesencephalic nucleus is found in the lateral area of the periaqueductal grey, and the trigeminal and abducens nuclei are located in the pons.(p.132–133)Rate this question:
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- 19.
A 53-year-old woman presents with motor deficits that the examining neurologist describes as a superior alternating hemiplegia. Which of the following cranial nerve roots is most likely involved in this lesion?
- A.
Abducens
- B.
Hypoglossal
- C.
Oculomotor
- D.
Trigeminal
- E.
Trochlear
Correct Answer
C. OculomotorExplanation
A superior alternating (or alternate) hemiplegia is characterized by a loss of most eye movement (damage to oculomotor nerve fibers) on the ipsilateral side and weakness of the upper and lower extremities (damage to corticospinal fibers in the crus cerebri) on the contralateral side. The abducens nerve is the cranial nerve involved in a middle alternating hemiplegia and the hypoglossal is that nerve involved in an inferior alternating hemiplegia. The trigeminal nerve innervates the muscles of mastication and the trochlear nerve innervates the superior oblique muscle.(p.132–133,138)Rate this question:
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- 20.
An 82-year-old woman presents to the emergency department with difficulty swallowing (dysphagia).Which of the following nuclei of the medulla contain motor neurons that innervate muscles involved in swallowing?
- A.
Dorsal motor vagal
- B.
Hypoglossal
- C.
Inferior salivatory
- D.
Medial vestibular
- E.
Nucleus ambiguus
Correct Answer
E. Nucleus ambiguusExplanation
Motor neurons in the nucleus ambiguus innervate, primarily through the vagus nerve, the muscles of the throat that move a bolus of food from the oral cavity to the esophagus. The tongue, via the hypoglossal nucleus and nerve, may move food around in the mouth and toward the back of the oral cavity, but the actual act of swallowing is through the action of pharyngeal and laryngeal musculature. The dorsal motor vagal and inferior salivatory nuclei are both visceromotor (autonomic) nuclei, and the medial vestibular nucleus is involved in the regulation of eye movement and balance and equilibrium.(p.50,104–107,112)Rate this question:
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- 21.
A 73-year-old man is brought to the emergency department after losing consciousness at his home. CT shows a hemorrhage into the right hemisphere. The man regains consciousness, but is not fully alert. After 3 to 4 days the man begins to rapidly deteriorate. His pupils are large (dilated) and respond slowly to light, eye movement becomes restricted, there is weakness in the extremities on the left side, and the man becomes comatose. Repeat CT shows an uncalherniation. Based on its location, which of the following parts of the brain-stem is most likely to be directly affected by uncal herniation, especially in the early stages?
- A.
Diencephalon/thalamus
- B.
Mesencephalon/midbrain
- C.
Myelencephalon/medulla
- D.
Pons and cerebellum
- E.
Pons only
Correct Answer
B. MesencepHalon/midbrainExplanation
The uncus is at the rostral and medial aspect of the parahippocampal gyrus, and, in this position, is directly adjacent to the anterolateral aspect of the midbrain. The diencephalon is rostral to this point and the medulla, the most caudal part of the brainstem, is located in the posterior fossa. Late stages of uncal herniation may, but not always, result in damage to the rostral pons; this is especially so if the patient becomes decerebrate. The cerebellum is not involved in uncal herniation.(p.20,22,24,152–153)Rate this question:
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- 22.
A 73-year-old man is brought to the emergency department after losing consciousness at his home. CT shows a hemorrhage into the right hemisphere. The man regains consciousness, but is not fully alert. After 3 to 4 days the man begins to rapidly deteriorate. His pupils are large (dilated) and respond slowly to light, eye movement becomes restricted, there is weakness in the extremities on the left side, and the man becomes comatose. Repeat CT shows an uncalherniation. Damage to corticospinal fibers in which of the following locations would most likely explain the weakness in his extremities?
- A.
Left basilar pons
- B.
Left crus cerebri
- C.
Right basilar pons
- D.
Right crus cerebri
- E.
Right posterior limb of the internal capsule
Correct Answer
D. Right crus cerebriExplanation
Uncal herniation compresses the lateral portion of the brainstem, eventually resulting in compression of the corti-cospinal fibers in the crus cerebri. Weakness on the patient’s left side indicates damage to corticospinal fibers in the right crus. In situations of significant shift of the midbrain due to the herniation, the contralateral crus also may be damaged, resulting in bilateral weakness. Although all other choices contain corticospinal fibers, none of these areas are directly involved inuncal herniation.(p.138)Rate this question:
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- 23.
A 73-year-old man is brought to the emergency department after losing consciousness at his home. CT shows a hemorrhage into the right hemisphere. The man regains consciousness, but is not fully alert. After 3 to 4 days the man begins to rapidly deteriorate. His pupils are large (dilated) and respond slowly to light, eye movement becomes restricted, there is weakness in the extremities on the left side, and the man becomes comatose. Repeat CT shows an uncalherniation. The dilated, and slowly responsive, pupils in this man are most likely explained by damage to fibers in which of the following?
- A.
Abducens nerve
- B.
Corticonuclear fibers in the crus
- C.
Oculomotor nerve
- D.
Optic nerve
- E.
Sympathetic fibers on cerebral vessels
Correct Answer
C. Oculomotor nerveExplanation
The root of the oculomotor nerve conveys GSE fibers to four of the six major extra ocular muscles and GVE parasympathetic preganglionic fibers to the ciliary ganglion from which postganglionic fibers travel to the sphincter muscle of the iris. Pressure on the oculomotor root, as in uncal herniation, will usually compress the smaller diameter, and more superficially located GVE fibers first. Optic nerve damage results in blindness in that eye, injury to sympathetic fibers to the eye results in constriction of the pupil, and an abducens root injury results in an inability to abduct that eye. A lesion of corticonuclear fibers in the crus results primarily in motor deficits related to the facial, hypoglossal, and accessory nerves.(p.138)Rate this question:
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- 24.
The sagittal MRI of a 26-year-old man shows a dark shadow in the midbrain tegmentum on the midline at the cross-sectional level of the inferior colliculus. Which of the following structures does this dark area represent?
- A.
Central portions of the red nucleus
- B.
Compact and reticular parts of the substantia nigra
- C.
Decussation of the superior cerebellar peduncle
- D.
Decussation of trigeminothalamic fibers
- E.
Motor (pyramidal) decussation
Correct Answer
C. Decussation of the superior cerebellar peduncleExplanation
The decussation of the superior cerebellar peduncle is a prominent fiber bundle located in the tegmentum of the midbrain directly on the midline at the level of the inferior colliculus. This bundle is made up of cerebellar efferent fibers. Thered nucleus is located in the midbrain tegmentum, but not on the midline. Decussating trigeminothalamic fibers are found in the medulla and do not form a visible structure on the midline. The motor decussation is a compact bundle on the midline, but it is in the medulla, not the midbrain. The main parts of the substantia nigra are in the midbrain, are seen in sagittal MRI, but they are definitely not on the midline.(p.130–1Rate this question:
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- 25.
The CT of a 39-year-old man with untreated hypertension shows a small hemorrhage in the brainstem. This lesion encompasses the brachium of the inferior colliculus and the brain sub-stance immediately internal to this structure. Which of the following structures is also most likely involved in this lesion?
- A.
Anterolateral system
- B.
Central tegmental tract
- C.
Corticospinal fibers
- D.
Mesencephalic tract
- E.
Oculomotor nerve
Correct Answer
A. Anterolateral systemExplanation
The anterolateral system is located just internal to the brachium of the inferior colliculus in the lateral portions of the midbrain tegmentum. This tract conveys pain and thermal sensations from the contralateral side of the body excluding the face. Corticospinal fibers are located in the crus cerebri, the mesencephalic tract at the lateral edge of the periaqueductal(central) grey, and the central tegmental tract is, as its name indicates, in the central part of the tegmentum. Oculomotorfibers within the midbrain leave the nucleus, arch through the tegmentum, and exit on the medial surface of the basis pedunculi into the interpeduncular cistern.(p.130–133)Rate this question:
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- 26.
A 69-year-old man complains of difficulty walking. The examination reveals no weakness, but does reveal a loss of discriminative touch and vibratory sense on the left lower extremity. MRI shows a small infarcted area in the midbrain. Which of the following structures is most likely involved in the infarcted area?
- A.
Anterolateral system
- B.
Corticospinal fibers
- C.
Lateral part of the medial lemniscus
- D.
Medial part of the medial lemniscus
- E.
Rubrospinal fibers
Correct Answer
C. Lateral part of the medial lemniscusExplanation
Fibers conveying discriminative touch, vibratory sensations, and proprioception are located in the lateral lemniscus; those from the contralateral upper extremity are medial, whereas those from the contralateral lower extremity are lateral. This man has difficulty walking due to a lesion of fibers conveying position sense from the lower extremity, not due to a lesion influencing descending fibers passing to spinal motorneurons. Fibers of the anterolateral system convey pain and thermal sensation. Rubrospinal and corticospinal are motor infunction; however this man has no weakness.(p.130–133)Rate this question:
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- 27.
Which of the following nuclei containing visceromotor (auto-nomic) cell bodies is located immediately inferior to the medial vestibular nucleus, medial to the solitary tract and nucleus, and has axons that exit the brainstem on the glossopharyngeal nerve?
- A.
Dorsal motor nucleus
- B.
Edinger-Westphal nucleus
- C.
Inferior salivatory nucleus
- D.
Intermediolateral cell column
- E.
Superior salivatory nucleus
Correct Answer
C. Inferior salivatory nucleusExplanation
The inferior salivatory nucleus is located in the rostral medulla, medial to the solitary tract and nuclei and inferior to the medial vestibular nucleus. Preganglionic axons that originate from these cells distribute on branches of the glossopharyngeal nerve. The dorsal motor nucleus is in the medulla, its axons travel on the vagus nerve. The superior salivatory nucleus is in the caudal pons and is associated with the facial nerve. Cells of the Edinger-Westphal nucleus are associated with the oculomotor nucleus of the midbrain and the intermediolateral cell column is located primarily in thoracic levels of the spinal cord.(p.104–107)Rate this question:
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- 28.
An 81-year-old woman is brought to the emergency department by her adult grandson. He explains that during dinner she slumped off of her chair, did not lose consciousness, but had trouble speaking. The examination reveals weakness of the upper and lower extremities on the left and deviation of the tongue to the right on protrusion. Which of the following most specifically describes this deficit in this elderly patient?
- A.
Alternating hemianesthesia
- B.
Hemihypesthesia
- C.
Inferior alternating hemiplegia
- D.
Middle alternating hemiplegia
- E.
Superior alternating hemiplegia
Correct Answer
C. Inferior alternating hemiplegiaExplanation
Weakness of the extremities accompanied by paralysis of muscles on the contralateral side of the tongue (seen as a deviation of the tongue to that side on protrusion) indicates a lesion in the medulla involving the corticospinal fibers in the pyramid and the exiting hypoglossal roots. This is an inferior alternating hemiplegia. Middle alternating hemiplegia refers to a lesion of the pontine corticospinal fibers and the root of the abducens nerve, and superior alternating hemiplegia specifies damage to the oculomotor root and crus cerebri. Alternating(alternate) hemianesthesia and hemihypesthesia are sensory losses.(p.112)Rate this question:
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- 29.
A 79-year-old woman is brought to the emergency department after a fall in her home from which she was unable to get up. The examination reveals a deviation of the tongue to the left on protrusion, pronounced weakness of the right upper and lower extremities, and a loss of position and vibratory sense and discriminative touch on the right side of the body below the neck. CT shows an infarcted area in the medulla. Which of the following represents the best localizing sign in this patient?
- A.
Deviation of the tongue
- B.
Motor loss on lower extremity
- C.
Motor loss on upper extremity
- D.
Sensory loss on lower extremity
- E.
Sensory loss on upper extremity
Correct Answer
A. Deviation of the tongueExplanation
The deviation of the tongue to the left on attempted protrusion is the best localizing sign in this woman. This is especially the case when the deviation of the tongue is seen in concert with the motor and sensory losses described for this patient. This clearly indicates a lesion in the medial medulla encompassing the corticospinal fibers, medial lemniscus, and exiting fibers on the hypoglossal nerve. Motor and sensory losses, without the cranial nerve sign, could suggest a lesion at several different levels of the neuraxis.(p.112)Rate this question:
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- 30.
A 79-year-old woman is brought to the emergency department after a fall in her home from which she was unable to get up. The examination reveals a deviation of the tongue to the left on protrusion, pronounced weakness of the right upper and lower extremities, and a loss of position and vibratory sense and discriminative touch on the right side of the body below the neck. CT shows an infarcted area in the medulla. Damage to which of the following tracts or fiber bundles would most likely give rise to the sensory deficits experienced by this patient?
- A.
Anterolateral system
- B.
Medial lemniscus
- C.
Medial longitudinal fasciculus
- D.
Solitary tract
- E.
Spinal trigeminal tract
Correct Answer
B. Medial lemniscusExplanation
All of the sensory deficits seen in this woman reflecta lesion in the medial lemniscus, which is located in the medial medulla in the territory of the anterior spinal artery. The anterolateral system and the spinal trigeminal tract convey pain and thermal sensations from the body (sans face) and face, respectively. The solitary tract is made up of the central processes of viscerosensory fibers and the medial longitudinal fasciculus at this level contains descending fibers that influence spinal motor neurons.(p.106–109,112)Rate this question:
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- 31.
The MRI of a 12-year-old boy reveals a cavity within the medulla. Which of the following terms most specifically describes this condition?
- A.
Brown-Séquard syndrome
- B.
Central cord syndrome
- C.
Hydromyelia
- D.
Syringobulbia
- E.
Syringomyelia
Correct Answer
D. SyringobulbiaExplanation
Syringobulbia is a cavitation within the medulla. Cavitation in this location may communicate with a cavity in cervical levels of the spinal cord (syringomyelia).Hydromyelia refers to a cavity of the spinal cord that is lined with ependymal cells. The central cord and Brown-Séquard syndromes are lesions of the spinal cord that give rise to characteristic motor and sensory losses.(p.112)Rate this question:
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- 32.
Which of the following cell groups within the white matter of the cerebellum characteristically appears as a long undulating line, looking somewhat like the principal olivary nucleus in the medulla?
- A.
Dentate nucleus
- B.
Emboliform nucleus
- C.
Fastigial nucleu
- D.
Globose nucleus
- E.
Red nucleus
Correct Answer
A. Dentate nucleusExplanation
The dentate nucleus appears as a long thin undulating line within the white matter core of the cerebellar hemi-sphere. It is frequently described as having the three-dimensional shape of a crumpled bag with its hilus (the opening of the bag) directed rostromedially. The other cerebellar nuclei(fastigial, globose, emboli form) are small clumps of cells, and the red nucleus is found in the midbrain, not in the cerebellum.(p.114–115)Rate this question:
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