Recovery of vision in fulminant idiopathic intracranial hypertension

I thank Drs Micieli for their report on fulminant idiopathic intracranial hypertension (IIH) which highlighted the importance of promptly considering interventions like optic nerve sheath fenestration or shunting in the setting of vision loss, rather than just standard medical therapy with acetazolamide.[1] However, a key caveat in the diagnostic process for IIH that is worth noting is the need to rule out secondary causes of intracranial hypertension, the most important one being cerebral venous sinus thrombosis (CVST) which can exactly mimic the clinical symptoms and exam findings of IIH. There are critical implications for management, as patients with CVST require anticoagulation. Consequently, the diagnostic criteria for IIH require normal neuroimaging including venography with no evidence of abnormal meningeal enhancement or venous thrombosis.[2] This can be accomplished using CT or MRI with venography, but the latter has the added advantage of also potentially demonstrating supportive features of IIH like flattening of the posterior globes, tortuous optic nerves, enlargement of the pre-optic optic subarachnoid space, empty sella turcica, or narrowing of the transverse venous sinuses. In the presence of three or more of these findings is required to make the diagnosis of suspected IIH in the absence of papilledema or sixth nerve palsy, although IIH without papilledema (IIHWOP) is a controversial entity.[3]

References
1. Micieli A, Micieli JA. Recovery of vision in fulminant idiopathic intracranial hypertension. CMAJ 2019;191(23):E639.
2. Friedman DI, Liu GT, Digre KB. Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology 2013;81(13):1159–1165.
3. Markey KA, Mollan SP, Jensen RH, Sinclair AJ. Understanding idiopathic intracranial hypertension: mechanisms, management, and future directions. Lancet Neurol 2016;15(1):78-91.