Cranial Nerve 5

Aka: Cranial Nerve 5, Cranial Nerve V, Trigeminal Nerve, CN 5, Trigeminal Lemniscus

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II. Anatomy

  1. Central CN 5
    1. neuroCn5central.png
  2. Facial Distribution
    1. neuroCn5V123.jpg
  3. Trigeminal Nerve
    1. neuroTrigeminalNerveGrayBB778.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  4. Alveolar Nerve (V3)
    1. entAlveolarNerveGrayBB779.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

III. Physiology: General

  1. Largest Cranial Nerve
  2. Sensory root innervates head and face
  3. Motor Root innervates mastication Muscles
  4. Fibers cross the midline in the Brainstem (at the level of the motor or sensory nucleii)
    1. Cortical or thalamic CVA involving the trigeminal signals
      1. Affects the contralateral face
    2. Brainstem CVA involving the trigeminal signals
      1. Injures the trigeminal nucleii or crossing fibers, affecting the ipsilateral face
      2. May injure the Trigeminal Lemniscus affecting the contralateral face

IV. Anatomy

  1. Trigeminal Lemniscus
    1. Fibers from the Trigeminal nucleii cross the midline and combine to form the Trigeminal Lemniscus
    2. Trigeminal Lemniscus courses up to the contralateral Thalamus
    3. Signals are ultimately transmitted to the contralateral cerebral cortex
  2. Nucleii (fibers originate in two nuclei)
    1. Motor Nucleus
      1. Small and localized to the Pons
    2. Sensory Nucleus
      1. Very long nucleus (extends from Midbrain to spinal cord)
      2. Mesencephalic nucleus of CN 5 (proprioception) is most superior, in the Midbrain
      3. Main sensory nucleus of CN 5 (light touch) is within the pons
      4. Spinal nucleus of CN 5 (pain and Temperature sense) is in the lower Medulla and upper spinal cord
  3. Course
    1. Course from pons to trigeminal Ganglion at petrous apex

V. Anatomy: Innervation (Divides into three branches)

  1. Ophthalmic Branch (Sensory)
    1. Cornea
    2. Ciliary body
    3. Conjunctiva
    4. Nasal cavity
    5. Sinuses
    6. Skin of eyebrows, forehead, and nose
  2. Maxillary Branch (Sensory)
    1. Side of nose
    2. Lower Eyelid
    3. Upper lip
  3. Mandibular Branch (Sensory and Motor)
    1. Sensory
      1. Temporal
      2. Auricular
      3. Lower face
      4. Lower lip,
      5. Oral Mucosa
        1. Anterior two thirds of Tongue
        2. Mandibular gums and teeth
    2. Motor (Mastication Muscles):
      1. Masseter Muscle
      2. Temporalis Muscle
      3. Pterygoid Muscle

VI. Exam

  1. Motor
    1. Normal
      1. No Tremor, Involuntary chewing, or Trismus
      2. Symmetrically, and tightly clenches teeth
    2. Paralysis
      1. On mouth opening, Mandible deviates to weak side
      2. Vertical misalignment of central medial incisors
  2. Sensory
    1. Oral Mucosa
    2. Jaw
    3. Cheek
    4. Forehead
  3. Reflexes
    1. Jaw Jerk Reflex
      1. Tests both sensory and motor Trigeminal Nerve
    2. Corneal Reflex (Cornea touched with cotton whisp)
      1. Tests both Sensory CN 5 and Motor CN 7
      2. Consensual reflex results in bilateral blinking

VII. Associated Conditions

  1. Trigeminal Neuralgia

VIII. References

  1. Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 87-113
  2. Goldberg (2014) Clinical Neuroanatomy, p. 24-39
  3. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 110-129

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