The correct answer is:

opening pressure on lumbar puncture

Educational Objective:

Recognize idiopathic intracranial hypertension.

Key Point:

The image reveals papilledema. The patient’s presentation is suggestive of idiopathic intracranial hypertension (IIH), also known as benign intracranial hypertension or pseudotumor cerebri. The condition is characterized by increased intracranial pressure (ICP) and papilledema with normal CSF cellularity and chemistry and CT imaging in an alert patient.

Explanation:

Of the tests listed, opening pressure on lumbar puncture is the most useful in confirming this patient’s diagnosis. In cases of IIH, opening pressure on lumbar puncture is elevated above 200 mm H20 in nonobese patients and above 250 mm H20 in obese patients as measured by lumbar puncture in the recumbent position.

The primary role of neuroimaging, such as CT or MRI, is to exclude other causes of elevated CSF pressure such as brain tumor, dural sinus thrombosis, or hydrocephalus. The ESR is not expected to be elevated in IIH. An elevated ESR is a diagnostic criterion for temporal arteritis, which is another condition associated with headache and potential vision loss.

Common symptoms of IIH include headache, nausea, vomiting, and vision disturbance (blurred vision, enlarged blind spot, diplopia, visual field defect). Pulsatile tinnitus, a whooshing sound in the ears synchronous with the pulse, has been reported with IIH.

In addition to a complete neurologic examination, an eye examination is critical and should include ophthalmoscopy, visual field assessment, and an ocular motility examination.

Potential findings include blurred disk margins, venous engorgement, loss of venous pulsations, and elevated optic disk. A palsy of the sixth cranial nerve may be present with resulting diplopia on lateral gaze. Sixth nerve palsy occurs because the elevated intracranial pressure (ICP) displaces the brainstem downward, which in turn stretches CN VI as it crosses over the petrous ridge and enters Dorello’s canal. Approximately 12% of adults with IIH develop sixth nerve palsy.

The primary potential adverse outcome is vision loss. Treatment options include acetazolamide, serial lumbar punctures to drain CSF, CSF shunt, or optic nerve fenestration.

Figure: