Incidence of idiopathic intracranial hypertension in Southern Tasmania, Australia

INTRODUCTION: Anecdotally, the incidence of idiopathic intracranial hypertension (IIH) is increasing, linked to an increase in the obesity rate in Australian society. However, formal incidence and prevalence studies are rare. We therefore sought to determine the incidence and clinical features of IIH in Southern Tasmania, Australia. METHOD: Neurology discharge summaries and lumbar puncture referrals from the single tertiary referral centre in this region were screened for an IIH diagnosis. All regional neurologists were surveyed to capture patients diagnosed through private neurology clinics. A retrospective review of medical records was conducted to confirm the diagnosis and determine whether patients met the Modified Dandy Criteria (MDC). Patients were included if they were above the age of 18 years and received a new diagnosis of IIH between June 2016 and June 2018. Population statistics were obtained from the Australian Bureau of Statistics. RESULTS: IIH incidence was 5.4/100 000. All patients were females, aged between 18 and 45 years. Headache was the most commonly reported symptom, with high rates of pre-existing or concurrent migraine diagnoses. Weight loss and commencement of oral acetazolamide were the most common treatment approaches. Four patients were medically refractory and required surgical intervention. CONCLUSION: The incidence of IIH in Southern Tasmania is comparable with the incidence reported in subgroups of females of childbearing age in recent prior studies. The demographic, diagnostic and therapeutic data presented can inform future local health service provision and serve as a baseline for ongoing assessment of change in incidence and treatment of IIH at a community level.