Trigeminal Nerve.txt

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Svetik
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53398
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Trigeminal Nerve.txt
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2010-12-05 01:14:04
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  1. Trigeminal Nerve
    • Sensory stimuli: touch, vibration, pressure, pain, temperature, proprioception
    • Sensory receptors: as previously discussed
  2. Trigeminal nerve major divisions
    • Opthalmic
    • Maxillary
    • Mandibular
  3. Trigeminal nerve provides sensory information to
    face, cornea, oral cavity including tongue (general somatic afferents), teeth, dura, external ear, tympanic membrane
  4. Nuclei of CN V
    • 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
  5. trigeminal Tactile sensation Neuron Cell body - Axon locations
    • 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
  6. trigeminal Pain and temperature sensation Neuron Cell body - Axon locations
    • 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
  7. Cortical localization of trigeminal pain and temp
    • 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:
  8. Somatotopic orientations
    perioral regions project to more rostral regions of the spinal trigeminal nucleus
  9. Proprioception: locations of cell body and axon
    • 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
  10. Proprioception of Trigeminal nerve
    • 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
  11. Reflex Pathways of Clinical Importance of Trigeminal nerve
    • 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
  12. Trigeminal Neuralgia
    • 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

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