Emma Foster¹, Mastura Monif^{1, 2}, Kylie Mason³, Anneke van der Walt^{1, 4}

A 56 year old man presented with several months of new onset headaches and blurred vision. Lumbar puncture revealed elevated intracranial pressure, but multiple cerebral imaging studies failed to identify a secondary cause. Eventually a formal venogram revealed a transverse venous sinus thrombosis, and an occult malignancy screen led to a diagnosis of non-Langerhans histiocytosis, or Erdheim-Chester Disease. This case highlights two important learning points: 1) secondary causes for raised intracranial pressure should be vigorously sought in atypical cases of idiopathic intracranial hypertension; 2) ECD is a rare but important cause of ophthalmologic and neurologic presentations, and should be a differential for orbital infiltration, intra- and extracranial disease.

Papilloedema, Erdheim-Chester Disease, histiocytosis, optic nerve fenestration, elevated intracranial pressure, proto-oncogene protein B-raf