Quiz 122 · Thalamus

Answers to Quiz 121 · Trigeminal System

1. The first-order sensory neurons of the trigeminal nerve have their cell bodies in the:

   Answer: Semilunar (gasserian) ganglion

   The pseudobipolar cells sit in the trigeminal (semilunar or gasserian) ganglion, and each central axon then splits into an ascending and a descending branch. The spinal nucleus is inside the brainstem and holds second-order cells. Revise trigeminal pathway and trigeminal neuralgia

2. The three divisions of the trigeminal nerve are:

   Answer: Ophthalmic, maxillary and mandibular

   V1 is ophthalmic, V2 maxillary and V3 mandibular, and each covers one horizontal band of the face. The facial and lingual nerves are separate nerves. Revise trigeminal pathway and trigeminal neuralgia

3. Which nucleus of the trigeminal nerve is the homologue of the dorsal column nuclei?

   Answer: Main sensory nucleus

   Main sensory V takes large-diameter fibres from low-threshold mechanoreceptors of face and teeth, just as the dorsal column nuclei do for the body. The spinal nucleus, fed by small pain fibres, is the spinothalamic homologue instead. Revise trigeminal pathway and trigeminal neuralgia

4. Why is the spinal nucleus of the trigeminal nerve regarded as the spinothalamic pathway of the trigeminal system?

   Answer: Its input arrives mainly on small-diameter nociceptive fibres

   Small fibres carrying nociception are what the spinal nucleus mainly receives, so the sensation and the fibre type match the spinothalamic system. Large mechanoreceptor fibres go to main sensory V. Revise trigeminal pathway and trigeminal neuralgia

5. The interpolar subdivision of the spinal nucleus of the trigeminal nerve receives input mainly from:

   Answer: Teeth, gums and the lining of the mouth

   The middle (interpolar) subdivision takes both mechanosensitive and nociceptive input from teeth, gums and oral mucous membrane. The oral subdivision above it is nociceptive, mainly from the oral cavity. Revise trigeminal pathway and trigeminal neuralgia

6. Chronic facial pain that no drug will control may be relieved by a surgical lesion of the:

   Answer: Caudal subdivision of the spinal nucleus

   The caudal subdivision is where most facial nociceptive afferents end, so lesioning it relieves intractable pain. Cutting main sensory V or the lemniscus would take away facial touch instead of, or as well as, the pain. Revise trigeminal pathway and trigeminal neuralgia

7. Trigeminal fibres reach the thalamus by way of the:

   Answer: Trigeminal lemniscus, running alongside the medial lemniscus

   Second-order fibres from both trigeminal nuclei cross and ascend as the trigeminal lemniscus, hugging the medial lemniscus. The spinal tract of V is made of first-order descending branches, and no facial fibres pass through the cuneate nucleus. Revise trigeminal pathway and trigeminal neuralgia

8. The posterior (PO) nucleus of the thalamus receives trigeminal input from the:

   Answer: Caudal subdivisions of the spinal nucleus

   Caudal spinal V, the most nociceptive part, projects to PO. VPL (VPM in most texts) takes the other two sources, main sensory V and the rostral subdivisions of spinal V. Revise trigeminal pathway and trigeminal neuralgia

9. Which statement about the trigger zone in trigeminal neuralgia is NOT true?

   Answer: It must lie inside the area where the pain is felt

   The trigger zone need bear no particular relation to the area in which the pain is perceived: touching the lip can throw the pain into the cheek. The other three statements all describe it correctly. Revise trigeminal pathway and trigeminal neuralgia

10. A woman of 55 has bursts of stabbing pain in the right cheek, each lasting a few seconds and brought on by lightly touching her upper lip. The usual underlying cause of this condition is:

    Answer: Compression of the trigeminal nerve roots

    Most patients with trigeminal neuralgia have compressed trigeminal nerve roots; the irritation or degeneration that follows makes the nerve fire episodic bursts of severe pain. Surgical release of the compression is considered when analgesics fail. Revise trigeminal pathway and trigeminal neuralgia

15 questions on chapter 122. Pick one answer for each, then save. Your answers stay in this browser, and the right ones are shown at the top of the next quiz.

1. The anterior group of thalamic nuclei lies:

In the fork of the internal medullary laminaWithin the internal medullary laminaBeneath the pulvinar, beside the LGBOutside the external medullary lamina

2. Which of these is a specific relay nucleus of the thalamus?

Ventral posterolateral nucleusMidline nucleiReticular nucleusCentromedian nucleus

3. Which thalamic nucleus forms part of the Papez circuit?

Ventral lateral nucleusLateral geniculate bodyPulvinarAnterior nucleus

4. Which pairing of a thalamic nucleus with its cortical target is correct?

Pulvinar → cingulate gyrusMGB → auditory cortexVA → visual cortexLGB → auditory cortex

5. Within the VPL nucleus, cutaneous input ends mainly in the:

Central coreDorsal partAnterior surfacePosterior pole

6. Which thalamic nuclei carry nociceptive input yet have no somatotopic map?

Ventral anterior (VA)Posterior nuclei (PO)Lateral geniculate bodyVentral posterolateral (VPL)

7. The thalamic reticular nucleus differs from the other nonspecific nuclei because it:

Projects only to the visual cortexLies in the fork of the laminaReceives no somatosensory inputSends no fibres to the cortex

8. Low-frequency stimulation of the intralaminar nuclei of the thalamus produces:

Flinging movements of the opposite armEEG synchronization over the same sideEEG desynchronization and arousalPain over the opposite half of the body

9. Which of these is NOT a function of the thalamus?

Relaying smell to the cortexSensory feedback for movementRelaying hearing to the cortexCrude perception of pain

10. After a posterior cerebral artery branch is blocked, a man loses discriminative touch and pressure over the left half of his body. Pain and temperature are only mildly affected, and his face feels normal. The lesion is most likely in the:

Right lateral geniculate bodyLeft VPL nucleusRight VPL nucleusRight VPM nucleus

11. Besides the sensory loss, which motor features occur in thalamic syndrome?

Flinging movements of one armLow tone, marked weakness and ataxiaResting tremor and cogwheel rigiditySpasticity with an extensor plantar

12. An electrical lesion of the intralaminar nuclei of the thalamus:

Abolishes both acute and chronic painAbolishes fine touch but spares painRelieves chronic pain, sparing acute painCauses pain over the opposite side

13. A lesion of the body of Luys produces:

HemiballismusLoss of hearingLoss of recent memoryThalamic pain

14. Which of these belongs to the epithalamus?

Subthalamic nucleusPulvinarMedial geniculate bodyPineal gland

15. The ventral lateral (VL) nucleus relays cerebellar input to:

Motor areas 4 and 6The inferior parietal lobeSensory areas 3, 1 and 2The cingulate gyrus

Save my answers