A 60-year-old female complains of double vision when looking straight ahead

Left CN III

Educational Objective:

Identify the clinical presentation of oculomotor nerve palsy.

Key Point:

Isolated oculomotor nerve palsy may occur in patients at risk for microvascular disease, and presents with diplopia and a somewhat “down-and-out” gaze of the affected eye (intensity of the down-and-out position of the affected pupil varies; it may be nearly midline, but unable to cross the midline).

Explanation:

This patient demonstrates a left cranial nerve III (oculomotor) palsy with the eye in a lateral and down position during frontal gaze and a dilated pupil on the affected side. The oculomotor nerve innervates the medial rectus muscle (adduction), the superior rectus muscle (elevation), inferior rectus muscle (depression), and inferior oblique muscle (excytotorsion and elevation in adduction).

The precipitating event could have been from pressure on the oculomotor nerve from an aneurysm. Often, however, there is no recognized event before the diploplia develops.

Isolated oculomotor nerve palsy typically occurs in older patients with vascular risk factors such as diabetes and hypertension. It usually presents with diplopia and lateral gaze to the affected side, ipsilateral pupillary dilation and ptosis, and a “down and out” appearance on extra-ocular movement testing. It is important to remember that diabetic neuropathies can affect any nerve in the body, and therefore can present as an infinite number of clinical syndromes.