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 |
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