Idiopathic intracranial hypertension; incidence, presenting features and outcome in Northern Ireland (1991-1995).

OBJECTIVES: To determine the age and sex specific incidence rates, presenting features, and visual outcome of idiopathic intracranial hypertension in Northern Ireland. METHODS: A case-note review of all patients with idiopathic intracranial hypertension, diagnosed at the Royal Victoria Hospital, Belfast between 1991 and 1995. RESULTS: Forty-two patients were identified corresponding to an average annual incidence rate per 100,000 persons of 0.5 for the total and 0.9 for the female population. The commonest presenting symptoms were headache (84%), transient visual obscurations (61%) and sustained visual loss (34%). Impaired Snellen visual acuity and visual field loss were documented in 21% and 62% of patients respectively at presentation, and in 24% and 39% at last follow-up. One patient suffered deterioration in visual functioning sufficient to interfere with normal daily activities. CONCLUSIONS: The age and sex specific incidence rates of IIH in Northern Ireland are lower than have been reported in previous population-based series. Disabling visual loss occurs in a small number of patients despite all interventions.