Inpatient and emergency service utilization in patients with idiopathic intracranial hypertension

BACKGROUND:: Many patients with idiopathic intracranial hypertension (IIH) are diagnosed in the emergency department (ED) or visit the ED during the course of their illness. We studied the use of inpatient and emergency services, determined what procedures and tests were provided at those encounters, evaluated how these variables changed over the study period and examined the coding validity of the International Classification of Diseases (ICD)-9 code for IIH (348.2) for adult patients seen in our affiliated EDs and inpatient services. METHODS:: Retrospective review of medical records over a 11-year period (2000-2011). RESULTS:: We were able to analyze 137 encounters from 51 patients. Sixty-eight percent of encounters were to the ED and 40% of those patients were subsequently admitted to the hospital. The most common symptoms were headaches (96%), vision change (53%), and photophobia (27%). Recurrent symptoms accounted for 43% of encounters, followed by surgical complications (26%) and initial presentation (12%). Four patients (25% of the patients who received a diagnosis in the ED) were misdiagnosed at their initial presentation and correctly diagnosed on a subsequent ED visit. The number of ED visits more than doubled over the study period. The ICD-9 code had a low positive predictive value (55%) for identifying patients with IIH. CONCLUSIONS:: The ED was commonly used by patients with IIH, with a mean of 2.7 visits per patient. The rate of a missed diagnosis was similar to another published series and is concerning for potentially permanent visual loss in undiagnosed patients. In our experience, the ICD-9 code vastly overestimated the number of ED and inpatient encounters attributable to IIH. This has important implications for research studies, particularly those relying on national inpatient databases.