Trigeminal Nerve.txt

• Sensory stimuli: touch, vibration, pressure, pain, temperature, proprioception
• Sensory receptors: as previously discussed

• Opthalmic
• Maxillary
• Mandibular

face, cornea, oral cavity including tongue (general somatic afferents), teeth, dura, external ear, tympanic membrane

• Tactile: sensation principle (chief) sensory nucleus of V
• Proprioception: mesencephalic nucleus of V
• Pain and Temperature: spinal trigeminal nucleus
• Jaw movement: motor nucleus of V

• First order neuron: trigeminal ganglion - cranial Nerve V/ascending root of V
• Second order neuron: chief sensory nucleus of V - Ventral trigeminothalamic tract
• Third order neuron: VPM - posterior limb of Internal capsule

• First order neuron: trigeminal ganglion - cranial Nerve V/ascending root of V
• Second order neuron: Spinal trigeminal nucleus - Ventral trigeminothalamic tract
• Third order neuron: VPM - posterior limb of Internal capsule

• similar to distribution of pain and temperature pathway for body.
• There are both direct and indirect routes to thalamus that project to different cortical locations
• 1) postcentral gyrus: face area
• 2) Cingulate Gyrus:
• 3) Orbitofrontal Cortex:
• 4) Insula:

perioral regions project to more rostral regions of the spinal trigeminal nucleus

• ONLY 2 NEURONS!
• First Order Neuron: Mesencephalic nucleus ; Cranial Nerve V/Mesencephalic Root of V
• Second Order Neuron: Motor Nucleus of V ; Motor root of V

• Pathway from mesencephalic nucleus to cortex to conscious perception of proprioception is unknown
• ** proprioceptive reflexes are important: initiated by
• 1) muscle stretch during chewing, eating, talking, etc.
• 2) tooth mechanoreceptors during chewing/eating
• 3) extrinsic muscles of eye during eye movements
• This information arises from tongue, jaw muscles, teeth and orbit and travels in V1, V2, V3 to brainstem

• Jaw Jerk Reflex: stretch reflex involving masseter; initiated by tap on chin - causes a weak contraction of jaw exaggerated/noticeable in some pathological conditions
• Corneal Reflex: 1) testing a patient who had sudden onset of right-sided facial paralysis 2) comatose patient --- Stimulus though CNV via pain pathway to spinal trigeminal nucleus, other neurons to facial motor nucleus and then signal transmitted to CN VII and blink reflex occurs

• tic Doloreux
• causes: microvascular compression of V2 or V3, tumor, aneurysm, infarct, MS, idiopathic
• usually observed in patients older than 50
• therapies: anticonvulsants; surgery ot trigeminal nerve roots or trigeminal ganglion