Anatomic localization | Specific cause | Common associated clinical features |
Midbrain (nuclear/fascicular) | Aplasia of the nucleus | Hemisensory loss, hemiparesis, central Horner syndrome, other brainstem cranial neuropathies. |
Vascular lesions (eg, brainstem arteriovenous malformations) |
Demyelination (multiple sclerosis) |
Brainstem hemorrhage, ischemia, or infarction |
Trauma (including surgical) |
Neoplasm (eg, glioma, metastasis) |
Subarachnoid space | Aneurysms (eg, superior cerebellar artery) | Headache, stiff neck, and other cranial nerve abnormalities. Focal lesions (aneurysms, schwannomas) may produce isolated fourth nerve palsies. |
Increased intracranial pressure and hydrocephalus |
Infections (eg, mastoiditis, encephalitis meningitis) |
Postlumbar puncture or spinal anesthesia |
Trauma |
Neoplasm (eg, carcinomatous meningitis, cerebellar hemangioblastoma, ependymoma, meningioma, metastasis, neurilemmoma, pineal tumors, or trochlear nerve sheath tumors) |
Cavernous sinus | Neoplasm (eg, meningioma, metastasis) | Third, fifth, or sixth nerve dysfunction, or Horner syndrome. |
Infection (eg, syphilis, tuberculosis, herpes zoster) |
Inflammation (eg, sarcoid, granulomatosis with polyangiitis [Wegener], or the Tolosa-Hunt syndrome) |
Vascular lesions (eg, carotid-cavernous fistulas, internal carotid artery aneurysm) |
Orbital | Neoplasm (eg, hemangioma, metastasis) | Third, fifth, and sixth cranial nerves as well as the optic nerve. Orbital involvement may also produce such signs as proptosis, chemosis, and orbital or conjunctival edema. |
Infection (orbital cellulitis) |
Infiltration (eg, sarcoid) |
Inflammation (eg, orbital inflammatory pseudotumor) |
Trauma |