Cranial nerves

Eye movements by extra-ocular muscles and cranial nerve innervation
(A) Schematic diagram of the motor innervation of the facial nerve. (B) Schematic diagram of the parasympathetic innervation of the facial nerve.

Cranial nerves

  • CN I (Olfactory)
    • Anosmia + perceived change in taste of food
    • Deficit caused by shearing of the nerve ending passing through the cribriform plate usually by closed head trauma
  • CN II (Optic)
    • Monocular and binocular visual field defects
    • Monocular: Giant cell arteritis, Anterior ischemic optic neuropathy, glaucoma, optic neuritis, trauma, increased ICP, emboli/arteritis/stenosis leading to retinal ischemia, ophthalmic artery or vein occlusion
    • Binocular - Hemianopsia due to bilateral optic nerve disease.
  • CN III (Oculomotor) –See Third Nerve Palsy
  • CN IV (Trochlear)- See Trochlear nerve palsy
  • CN VI (Abducens)- See Abducens nerve palsy
  • Internuclear ophthalmoplegia - Lesion in medial longitudinal fasciculus, cannot adduct in horizontal lateral gaze, but normal convergence. Caused by multiple sclerosis or stroke
  • CN V (Trigeminal)
    • Jaw weakness and spasm. Jaw closure may be weak and/or asymmetric. +/- Trismus if irritative lesion to motor root.
    • See trigeminal neuralgia
  • CN VII (Facial)
  • CN VIII (Vestibular)
    • Dysfunction may be characterized by: tinnitus, deafness, nausea, vertigo, balance issues
    • See vertigo
  • CN IX (Glossopharyngeal)
    • Dysfunction may be characterized by: dysarthria, dysphagia
  • CN X (Vagus)
    • Dysfunction may be characterized by: hoarseness (unilateral vocal cord paralysis), dyspnea and inspiratory stridor (bilateral). Dysarthria, dysphagia.
  • CN XI (Accessory)
    • Dysfunction may be characterized by: Sternocleidomastoid and trapezius weakness leads to weak head rotation and shoulder shrug
  • CN XII (Hypoglossal)
    • Dysfunction may be characterized by: tongue deviation and wasting

See Also