Chapter 10 : Trigeminal System (3) Flashcards
- 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 n midpontine level
I-D. The afferent limb of the jaw jerk re’lex, 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.
- All of the following statements concerning the ventral trigeminothalamic tract arc correct EXCEPT
(A) it transmits pain and temperature information
(B) it consists ofaxons from the spinal trigeminal nucleus .;
(C) it receives axons from the principal sen¬sory 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 mes¬encephalic nucleus
2-E. The mesencephalic nucleus does not contribute to the ventral trigeminothalamic tract. The ventral trigeminothalamic tract consists ofaxons 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 nu·
cleus of eN v to the VPM nucleus.
- 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
3-B. An aneurysm of the cavernous sinus wc.-uld 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 (CNIII), if complete, would result in internal ophthalmoplegia because of interruption of preganglionic parasympathetic fibers (a fixed, dilated, unresponsive pupil).
- All of the following statements concerning trigeminal neuralgia are correct EXCEP’l’
(A) it is charaeterized by recurrent paroxysmsofsharp lancinatinpain
(B) it occurs in any of the three divisions of posteromedial 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
4-D. Trigeminal neuralgia is more common in women than in men. and it occurs most often Oil
the right side of the face. A redundant loop of the superior cerebellar artery may impinge on the
trigeminal nerve, causin~ electric “chatter,” which is felt as pain. This type of trigeminal neuralgia has been successfully treated by placing a smull sponge between the artery and the nerve. Classic idiopathic trigeminal neuralgia is treated with carbama zepine, an anticonvulsant drug.
- All of the following statements concerning¬the trigeminal ganglion are correct EXCEPT
(A) it lies in the Meckel cave
(B) it lies in the middle cranial fossa
(C) it contains bipolar ganglion cells
(D) it contains first-order neurons of the dor¬ sal trigeminothalamic tract
(E) its destruction. results in abolition of the corneal reflex and the jaw jerk reflex
5-C. The trigeminal (gasserian) ganglion lies within a dural duplication, the Meckel 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-I) and jaw jerk (CN V-a) reflexes. The motor root of CN V lies between the ganglion and the petroul’l hone.
- All of the following statements concerning the maxillary nerve are correct EXCEPT
(A) it runs in the lateral wall ofthe cavernous
(B) it exits the cranial vault via the foramen rotundum
(C) it contains only general somatic afferent(GSA) fibers
(D) it innervates the skin of the dorsum of the nose
(E) it innervates the palate
6-D. The maxillary nerve (CN V-2) contains only general somatic afferent (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 in·
nervated by the ophthalmic nerve (CN V-I).
- All of the following statements concerning the mesencephalic nucleus are correct EX CEPT ¬
(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
7-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.
(8) 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(VPM) nucleus of the thalamus
(E) its first-order neurons are found in the trigeminal ganglion
8-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 dorlial trigeminothulamic tract does not mediate the corneal reflex.
- All of the following statements concerning principal sensory nucleus of CN V are cor¬rect EXCEPT
(A) it projects to the ipsilateral ventral pos¬ teromedial (VPM) nucleus of the thalamus
(B) it projects to the contralateral VPM nucleus of the thalamus
(C) it receives input from Meissner and Pacini corpuscles
(D) it is located in the medulla and pons
(E) it is a homolog to the dorsal column nuclei
9-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 and Pacini corpuscles. It projects to the ipsilateral ventral posteromedial (VPM) nucleus of the thalamus via the dorsal trigeminothalamic tract and to the contralateral VPM nucleus of the thalamus via the ventral trigeminothalamic tract. The principal sensory nucleus is homologous to the dorsal column nuclei (gracile and cuneate nuclei).
- 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 general somatic afferent (GSA) and somatic visceral efferent (SVE)
(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
10.C. The trigeminal nerve (CN V) is the nerve of the first branchial arch (mandibular nerve) and contains only general somatic afferent (GSA) and special visceral efferent (SVE) fibers. It innervates
the supratentorial dur!l 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 CS), which hitchhike with the hypoglossal nerve (CN XII). The tensor tympani muscleus innervated by the trigeminal nerve; the stapedius muscle is innervated by the facial nerve (CN VII). The ophthalmic nerve (CN V-I) mediates the afferent limb oCthe corneal reflex; the facial nerve (CN VII) mediates the efferent limb of the corneal reflex (orbicularis oculi muscle).
- All of the following lesions could interrupt the corneal reflex EXCEPT
(A) occlusion of the anterior inferior cerebel¬lar artery
(B) occlusion of the posterior inferior cerebel¬lar artery
¬(C) an acoustic neuroma
(D) an aneurysm of the cavernous sinus
(E) destruction of the principal sensory nu¬cleus ofCNV
ll-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 both interrupt the afferent corneal pathway as mayan aneurysm of the cavernou’s sinus. An acoustic neuroma interrupts the efferent limb of the corneal reflex (CN VII).
- All 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 fibers
(D) it is mediated via axons found in the spinal trigeminal tract
(E) it is mediated via axons arising from the spinal trigeminal nucleus
12-C. The afferent corneal reflex pathway is as follows: First-order neurons of the ophthalmic
nerve (CN V-I) 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.
