5 - Trigeminal Sensory Systems: Sensation from the Face

Question 1

The trigeminal ganglion is analogous to what other structure?

Answer 1

The dorsal root ganglion.

Question 2

For touch, vibration, and proprioception: where is the cell body of the first neuron in the trigeminal sensory system? What is the first neuron’s central process and where does it synapse?

Answer 2

Cell body in the trigeminal ganglion

Central process are central trigeminal nerve fibers that travel to the principle/chief/main sensory nucleus.

Question 3

For touch, vibration, and proprioception: where is the cell body of the second neuron in the trigeminal sensory system? What is the neuron’s fiber tract and where does it go to synapse? What is the significance of this neuron?

Answer 3

In the principal/chief/main sensory nucleus.

Fibers travel through the trigeminal lemniscus and dorsal trigeminothalamic tract (parts of the medial lemniscus) and synapse in the VPM.

DECUSSATING NEURON

Question 4

For touch, vibration, and proprioception: where is the cell body of the third neuron in the trigeminal sensory system? Where do it’s fibers go?

Answer 4

Cell bodies in the VPM and the tract goes through the internal capsule to the somatosensory cortex.

Question 5

For touch, vibration, and proprioception: where is the cell body of the first neuron in the DC/ML sensory system from the body? Where does it’s central process go to synapse?

Answer 5

Cell bodies in the DRG.

Central processes through the dorsal column to synapse at the dorsal column nucleus.

Question 6

For touch, vibration, and proprioception: where is the cell body of the second neuron in the DC/ML sensory system frrom the body? What is it’s fiber tract and where does it go to synapse?

Answer 6

Cell body in the dorsal column nuclei.

Fiber tract is the medial lemniscus.

Synapses at the VPL.

DECUSSATING NEURON.

Question 7

For touch, vibration, and proprioception: where is the cell body of the 3rd neuron in the DC/ML sensory system from the body? Where does it’s fiber tract go?

Answer 7

Cell bodies in the VPL.

Fibers travel through the internal capsule to the somatosensory cortex.

Question 8

For pain and temperature: what is the location of the 1st neuron cell body for the sensory from the body? What is its central process and where does it synapse?

Answer 8

Cell body in the DRG

Travels via Lissauer’s tract.

Synapses in the posterior horn.

Question 9

For pain and temperature: what is the location of the 2nd neuron cell body for the sensory from the body? What is it’s path and where does it synapse?

Answer 9

Cell body in the posterior horn.

Travels via the spinothalamic tract (and others)

Synapses in the VPL.

Question 10

For pain and temperature: what is the location of the 3rd neuron cell body for the sensory from the body? Where does its tract go?

Answer 10

Cell body in the VPL.

Travels through the internal capsule to the somatosensory cortex.

Question 11

For pain and temperature: where is the cell body of the 1st neuron of the trigeminal sensory system? What is it’s path and where does it synapse?

Answer 11

Cell body in the trigeminal ganglion.

Travels via the spinal tract of V.

Synapses at the spinal nucleus of V.

Question 12

For pain and temperature: where is the cell body of the 2nd neuron of the trigeminal sensory system? What is it’s path and where does it synapse?

Answer 12

Cell body in the spinal nucleus of V.

Travels via the trigeminothalamic tract (ventral) and others.

Synapses in the VPM.

Question 13

For pain and temperature: where is the cell body of the 3rd neuron of the trigeminal sensory system? Where does it go?

Answer 13

Cell body in the VPM.

Travels through the internal capsule to the somatosensory cortex.

Question 14

What order neurons are in the trigeminal lemniscus? Where does it go? What does it carry?

Answer 14

Portion of the medial meniscus.

2nd degree sensory neurons ascend from the principal sensory nucleus of V to the contralateral VPM.

Carries touch, pressure, and proprioception information from the face.

Question 15

What type of neurons are in the spinal tract of V? Where does this go? What does it carry?

Answer 15

First order neurons that descend from the trigeminal ganglion to the ipsilater spinal nucleus of V.

Carries pain and temp sensation from the face. (analogous to lissauer’s tract in the spinothalamic pathway).

Question 16

Describe the homonculus of the cerebral cortex?

Answer 16

Legs and feet are more medial.

Arm, hand, fingers, thumb are less medial.

Face and lips more lateral.

Teeth, gums, jaw, tongue, throat, and intestines even more lateral.

Question 17

Where is the main/chief/principle sensory nucleus located? What type of sensation is it associated with?

Answer 17

In the lateral pons.

Fine touch and pressure from the face and teeth.

Question 18

Where is the spinal trigeminal nucleus? What type of sensation is it associated with?

Answer 18

Lateral pons, medulla, and cervical spinal cord.

Pain and temperature.

Question 19

Where is the mesencephalic nucleus located? What type of sensation is it associated with?

Answer 19

Pseudounipolar neurons located in the midbrain along the lateral edge of the periaqueductal gray matter.

Proprioception from muscles of mastication and mechanoreceptors in the gums, teeth, and hard palate.

Question 20

What is the dorsal to ventral somatotopy in the spinal trigeminal nucleus?

Answer 20

Mandibular division - dorsal
Maxillary in middle
Ophthalmic division - ventral

Question 21

What is the rostral to caudal somatotopy in the spinal trigeminal nucleus?

Answer 21

Pain and temp fibers from the perioral region are more rostral and the occipital regions are more caudal.

Question 22

What is the clinical significance of the somatotopy of the spinal trigeminal nucleus?

Answer 22

Capitating lesions such as a hole in syringomyelia can cause patients to lose peripheral sensation first and as it progresses upwards it will become more central until it finally effects the perioral region.

Question 23

What are the symptoms of lateral medullary syndrome?

Answer 23

A lateral lesion of the pons or medulla resulting in loss of pain and temp from the CONTRALATERAL side of the body and pain and temp from the IPSILATERAL side of the face.

Question 24

What are the effects of a spinal cord lesion on the sensory systems?

Answer 24

Loss of fine touch on the side of the body ipsilateral to the lesion.

Loss of pain and temp from the side of the body contralateral to the lesion.

Question 25

What are the effects of a lateral lesion of the pons or medulla?

Answer 25

Loss of pain and temperature from the body on the contralateral side from the lesion.

Loss of pain and temp on the ipsilateral side of the face.

Called lateral medullary syndrome.

Question 26

What occurs with a lesion of the cerebral cortex, internal capsule, of thalamus?

Answer 26

Loss of ALL sensation from the CONTRALATERAL side of the body AND face.

Question 27

When testing a corneal reflex, what detects the stimulus? Describe this pathway and the response?

Answer 27

Detected by the trigeminal nerve, carried into the pons to synapse at the chief sensory nucleus, which sends info to the thalamus.

Sensory nucleus also sends axons to the facial motor nucleus in the pons and to the muscles of facial expression to cause blinking.