Chapter 10 : Trigeminal System (2) Flashcards Preview

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Flashcards in Chapter 10 : Trigeminal System (2) Deck (14):
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1. A facial sensory loss in an onion-skin distribution around the mouth would most likely
be associated with which of the following lesions?
(A) Cavernous sinus thrombosis
(B) Cerebellopontine angle tumor
(C) Tumor of the orbital apex
(D) Glioma of the lateral medulla
(E) Peripheral neuropathy including CN V-2 and CN V-3

l-D. A glioma of the lateral medulla could destroy part of the spinal trigeminal nucleus and result in a facial sensory loss in an onion-skin distribution around the mouth. Lesions involving the peripheral divisions of CN V would correspond to the derma tomes shown in Figure 10-1.

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2. All of the following statements concerning the spinal trigeminal tract are correct EXCEPT
(A) it contains axons from the trigeminal ganglion
(B) it mediates pain and temperature sensation
(C) it is equivalent to the dorsolateral tract of Lissauer
(D) it is the afferent limb of the jaw jerk reflex
(E) it extends from C3 to a midpontine level

2-D. The afferent limb of the jaw jerk reflex, a myotatic (muscle stretch) reflex, is mediated by
the pseudounipolar neurons of the mesencephalic nucleus; the efferent limb is mediated by the motor neurons of the trigeminal motor nucleus.

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3. All of the following statements concerning the ventral trigeminothalamic tract are correct
EXCEPT
(A) it transmits pain and temperature information
(B) it consists of axons from the spinal trigeminal nucleus
(C) it receives axons from the principal sensory nucleus of CN V
(D) it projects to the contralateral ventral posteromedial (VPM) nucleus of the thalamus
(E) first-order neurons are located in the mesencephalic nucleus

3-E. The mesencephalic nucleus does not contribute to the ventral trigeminothalamic tract.
The ventral trigeminothalamic tract consists of axons from the spinal trigeminal nucleus that
transmit pain and temperature information to the contralateral ventral posteromedial (VPM) nucleus. In addition, it receives and transmits tactile discriminatory input from the principal sensory nucleus of CN V to the VPM nucleus

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4. The trigeminal motor nucleus innervates all of the following muscles EXCEPT
(A) the tensor tympani muscle
(B) the posterior belly of the digastric muscle
(C) the mylohyoid muscle
(D) the temporalis muscle
(E) the lateral and medial pterygoid muscles

4-B. The posterior belly of the digastric muscle is innervated by the facial nerve (CN VII); the anterior belly of the digastric muscle is innervated by the trigeminal nerve (CN V).

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5. An aneurysm of the cavernous sinus could result in all of the following EXCEPT
(A) ptosis
(B) anesthesia of the tongue
(C) paralysis of the superior oblique muscle
(D) complete internal ophthalmoplegia
(E) diplopia

5-B. An aneurysm of the cavernous sinus would not involve the mandibular nerve (CN V-3),
which does not pass through the wall of the sinus. The mandibular nerve provides the sensory innervation of the anterior two-thirds of the tongue. Involvement of the oculomotor nerve (CN III), if complete, would result in internal ophthalmoplegia because of interruption of preganglionic para sympathetic fibers (a fixed, dilated, unresponsive pupil).

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6. All of the following statements concerning trigeminal neuralgia are correct EXCEPT
(A) it is characterized by recurrent paroxysms of sharp, lancinating pain
(B) it occurs in any of the three divisions of the trigeminal nerve
(C) it usually occurs in people over 50 years of age
(D) it is more common in men than in women
(E) it may result from pressure on the nerve from a nearby artery

6-D. Trigeminal neuralgia is more common in women than in men, and it occurs most often
on the right side of the face. A redundant loop of the anterior inferior cerebellar artery may impinge on the trigeminal nerve, causing electric "chatter," which is felt as pain. This type of trigeminal neuralgia has been successfully treated by placing a small sponge between the artery and the nerve. Classic idiopathic trigeminal neuralgia is treated with carbamazepine, an anticonvulsant drug.

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7. All of the following statements concerning the trigeminal ganglion are correct EXCEPT
(A) it lies in Meckel's cave
(B) it lies in the middle cranial fossa
(C) it contains bipolar ganglion cells
(D) it contains first-order neurons of the dorsal trigeminothalamic tract
(E) its destruction results in abolition of the corneal reflex and the jaw jerk reflex

7-C. The trigeminal (gasserian) ganglion lies within a dural duplication, Meckel's cave, located in the trigeminal fossa of the petrous portion of the temporal bone in the middle cranial fossa. It contains pseudounipolar ganglion cells similar to those found in the dorsal root ganglia. These first-order neurons give rise to the ventral and dorsal trigeminothalamic tracts. Destruction of the trigeminal ganglion interrupts the afferent limbs of the corneal (CN V-l) and jaw jerk (CN V-3) reflexes. The motor root of CN V lies between the ganglion and the petrous bone.

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8. All of the following statements concerning the maxillary nerve are correct EXCEPT
(A) it runs in the lateral wall of the cavernous sinus
(B) it exits the cranial vault via the foramen rotundum
(C) it contains only GSA fibers
(D) it innervates the skin of the dorsum of the nose
(E) it innervates the palate

8-D. The maxillary nerve (CN V-2) contains only GSA fibers, runs in the lateral wall of the cavernous sinus, and exits the cranial vault via the foramen rotundum and canalis rotundus. It innervates the palate via the palatine nerves. The dorsum of the nose is innervated by the ophthalmic nerve (CN V-l).

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9. All of the following statements concerning the mesencephalic nucleus are correct EXCEPT
(A) it projects to the cerebellum
(B) it is located in the pons
(C) it mediates the afferent limb of the jaw jerk reflex
(D) it contains bipolar neurons
(E) it receives input from muscle spindles

9-D. The mesencephalic nucleus of CN V contains pseudounipolar neurons that mediate the afferent limb of the jaw jerk reflex. It is located in the rostral pons and in the mesencephalon and gives rise to collaterals that project to the cerebellum via the superior cerebellar peduncle. It receives input from muscle spindles and pressure and joint receptors

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10. All of the following statements concerning the dorsal trigeminothalamic tract are correct EXCEPT
(A) it is an uncrossed tract
(B) it mediates two-point tactile discrimination
(C) it mediates the corneal reflex
(D) it projects to the ventral posteromedial (VPM) nucleus of the thalamus
(E) its first-order neurons are found in the trigeminal ganglion

10-C. The dorsal trigeminothalamic tract mediates discriminative tactile and pressure sensation
(including two-point discrimination), is an uncrossed tract, and projects to the ventral posteromedial (VPM) nucleus. First-order neurons are in the trigeminal ganglion, second-order
neurons lie in the principal sensory nucleus of the rostral pons, and third-order neurons are located in the VPM nucleus of the thalamus. This tract corresponds in function to the dorsal column-medial lemniscus system. The dorsal trigemino thalamic tract does not mediate the corneal reflex.

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11. All of the following statements concerning the principal sensory nucleus of CN V are correct EXCEPT
(A) it projects to the ipsilateral ventral posteromedial (VPM) nucleus of the thalamus
(B) it projects to the contralateral VPM nucleus of the thalamus
(C) it receives input from Meissner's and Pacini's corpuscles
(D) it is located in the medulla and pons
(E) it is a homolog to the dorsal column nuclei

11-D. The principal sensory nucleus of CN V is located in the rostral pons at the level of the
motor trigeminal nucleus; it receives input from Meissner's and Pacini's corpuscles. It projects
to the ipsilateral ventral posteromedial (VPM) nucleus of the thalamus via the dorsal trigemino thalamic tract and to the contralateral VPM nucleus of the thalamus via the ventral trigemino thalamic tract. The principal sensory nucleus is homologous to the dorsal column nuclei (gracile and cuneate nuclei).

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12. All of the following statements concerning the trigeminal nerve are correct EXCEPT
(A) it is the nerve of the first branchial arch (mandibular nerve)
(B) it contains only GSA and SVE fibers
(C) it innervates the stapedius muscle
(D) it innervates the dura of the anterior and middle cranial fossae
(E) it mediates the afferent limb of the corneal reflex

12-C. The trigeminal nerve (CN V) is the nerve of the first branchial arch (mandibular nerve) and contains only GSA and SVE fibers. It innervates the supratentorial dura of the anterior and middle cranial fossae. The dura of the posterior cranial fossa is innervated by the vagal nerve (CN X) and the second and third spinal nerves (C2 and C3), which hitchhike with the hypoglossal nerve (CN XII). The tensor tympani muscle is innervated by the trigeminal nerve; the stapedius muscle is innervated by the facial nerve (CN VII). The ophthalmic nerve (CN V-l) mediates the afferent limb of the corneal reflex; the facial nerve (CN VII) mediates the efferent limb of the corneal reflex (orbicularis oculi muscle).

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13. All of the following lesions could interrupt the corneal reflex EXCEPT
(A) occlusion of the anterior inferior cerebellar artery (AICA)
(B) occlusion of the posterior inferior cerebellar artery (PICA)
(C) an acoustic neuroma
(D) an aneurysm of the cavernous sinus
(E) destruction of the principal sensory nucleus of CN V

13-E. The principal sensory nucleus of CN V mediates tactile discriminatory sense and position
sense, homologous to the gracile and cuneate nuclei. The anterior and posterior inferior cerebellar arteries (AICA and PICA, respectively) both interrupt the afferent corneal pathway as may an aneurysm of the cavernous sinus. An acoustic neuroma interrupts the efferent limb of the corneal reflex (CN VII).

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14. All of the following statements concerning the corneal reflex are correct EXCEPT
(A) it is a bisynaptic reflex
(B) it is abolished ipsilaterally by transection of the facial nerve
(C) it is abolished by a transection of the spinal trigeminal tract made within its caudal medullary extent
(D) it is mediated via axons found in the spinal trigeminal tract
(E) it is mediated via axons arising from the spinal trigeminal nucleus

14-C. The afferent corneal reflex pathway is as follows: First-order neurons of the ophthalmic
nerve (CN V-l) are found in the trigeminal ganglion. Their axons enter the pons and descend in the spinal trigeminal tract. They enter the spinal trigeminal nucleus in its rostral portion and synapse on second-order neurons, which project to the ipsilateral and contralateral facial nuclei. Axons from third-order neurons in the facial nuclei innervate the orbicularis oculi muscles bilaterally (directly and consensually). Trigeminal tractotomy at caudal levels produces facial anesthesia without interruption of the corneal reflex.