oculomotoriusparese

Oculomotor nerve palsy, or oculomotoriusparese, is a disorder of the third cranial nerve that affects most of the eye muscles and, via parasympathetic fibers, the pupil and the lens. The oculomotor nerve innervates the levator palpebrae superioris (lifting the upper eyelid) and four extraocular muscles, allowing most eye movements, as well as the sphincter pupillae and ciliary muscle for pupil constriction and accommodation. When the nerve is impaired, both motor and sometimes autonomic functions can be affected.

Clinically, the typical finding is ptosis with a “down and out” position of the affected eye due to unopposed lateral rectus and superior oblique activity, accompanied by diplopia that worsens on gaze toward the affected side. If the parasympathetic fibers are involved, the pupil becomes dilated and unreactive to light. Pupil-sparing third nerve palsy (no pupillary involvement) is common in microvascular conditions such as diabetes or hypertension, whereas pupil-involving palsy raises concern for compressive lesions, including aneurysms of the posterior communicating artery or other space-occupying processes.

Causes of oculomotor nerve palsy are diverse and include microvascular ischemia, compressive lesions, head trauma, inflammatory or demyelinating diseases, and congenital abnormalities. Evaluation typically starts with a thorough neurological and ocular examination, focusing on pupil status. Imaging (usually MRI with MRA or CT angiography) is guided by the presence of pupil involvement, age, vascular risk factors, and sudden onset. Urgent assessment is required if an aneurysm or mass is suspected.

Management targets the underlying cause. Ischemic, pupil-sparing palsies may be observed with rehabilitation for diplopia; pupil-involving palsies or suspected aneurysm require urgent neurosurgical or endovascular intervention. Prognosis varies, with many ischemic cases improving over weeks to months, while decompression or tumor-related cases depend on specific treatment.