Background Based on expert opinion, abducens nerve palsy and a neuroimaging criterion (≥3 neuroimaging signs suggestive of elevated intracranial pressure) were added to the diagnostic criteria for idiopathic intracranial hypertension. Our objective was to validate this. Methods This prospective study included patients with new-onset idiopathic intracranial hypertension for a standardized work-up: interview, neuro-ophthalmological exam, lumbar puncture, neuroimaging. Neuroimaging was evaluated by a blinded neuroradiologist. Results We included 157 patients classified as idiopathic intracranial hypertension (56.7%), probable idiopathic intracranial hypertension (1.9%), idiopathic intracranial hypertension without papilledema (idiopathic intracranial hypertension-without papill edema; 0%), suggested idiopathic intracranial hypertension-without papill edema (4.5%), or non-idiopathic intracranial hypertension (36.9%). Moderate suprasellar herniation was more common in idiopathic intracranial hypertension than non-idiopathic intracranial hypertension (71.4% versus 47.4%, p < 0.01), as was perioptic nerve sheath distension (69.8% versus 29.3%, p < 0.001), flattening of the globe (67.1% versus 11.1%, p < 0.001) and transverse sinus stenosis (60.2% versus 18.9%, p < 0.001). Abducens nerve palsy was of no diagnostic significance. Sensitivity of ≥3 neuroimaging signs was 59.5% and specificity was 93.5%. Conclusion Moderate suprasellar herniation, distension of the perioptic nerve sheath, flattening of the globe and transverse sinus stenosis were associated with idiopathic intracranial hypertension. We propose that idiopathic intracranial hypertension can be defined by two out of three objective findings (papilledema, opening pressure ≥25 cm cerebrospinal fluid and ≥3 neuroimaging signs).

Objective To identify the most frequent causes of secondary pseudotumor cerebri syndrome and compare phenotype, clinical presentation, and symptoms of secondary pseudotumor cerebri syndrome to the primary form of pseudotumor cerebri syndrome, idiopathic intracranial hypertension. Methods The study was a prospective cohort study including patients with new-onset pseudotumor cerebri syndrome. Diagnostic work up was standardized. Patients were diagnosed with secondary pseudotumor cerebri syndrome or idiopathic intracranial hypertension according to the revised Friedman criteria. Secondary pseudotumor cerebri syndrome patients were categorized into five causes: medication, systemic causes, sleep apnea, cerebrovascular causes, and several competing causes. Phenotype, clinical presentation, symptoms and neuroimaging were compared between groups. Results Out of 278 cases, 28 secondary pseudotumor cerebri syndrome and 120 idiopathic intracranial hypertension patients were included. The most frequent causes of secondary pseudotumor cerebri syndrome were medication (n  =  8, 28.6%) and systemic causes (n = 8, 28.6%), followed by sleep apnea (n = 5, 17.9%), cerebrovascular causes (n = 4, 14.3%) and several competing causes (n = 3, 10.7%). Secondary pseudotumor cerebri syndrome and idiopathic intracranial hypertension patients were phenotypically alike and predominately female, premenopausal, and obese. Symptoms and objective findings at disease onset were similar between groups. Conclusion Secondary pseudotumor cerebri syndrome should be considered in all patients with suspected pseudotumor cerebri syndrome as secondary pseudotumor cerebri syndrome and idiopathic intracranial hypertension patients are phenotypically and clinically alike. A thorough diagnostic workup is needed as treatment of idiopathic intracranial hypertension and secondary pseudotumor cerebri syndrome is markedly different.

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A 44 year old man presented to the emergency department with a sudden onset headache. He had no medical history of note and took no drugs. Urgent computed tomography of the head was performed (fig 1). A repeat scan (eight minutes later) was performed after administration of intravenous contrast (OptiRay) (fig 2). Upon return from the radiology department, he developed left sided hemiplegia. His blood pressure was 179/90 mm Hg. After another 46 minutes, computed tomography ( fig 3) with angiography (not shown) was performed; no abnormal vessels were seen. Blood tests did not show an underlying coagulopathy. He subsequently deteriorated to localising to pain and making incomprehensible sounds to pain without opening his eyes (Glasgow coma score 8). His pupils remained equal and reactive to light.