BACKGROUND: Idiopathic intracranial hypertension (IIH) typically affects young, obese women. We examined 2 groups of atypical patients with IIH: those with a normal body mass index (BMI) and those at least 50 years of age. METHODS: A retrospective cohort study of 407 consecutive adult patients with IIH with known BMI from 3 centers was undertaken. Demographics, associated factors, visual acuity, and visual fields were collected at presentation and follow-up. RESULTS: We identified 18 IIH patients (4%) with normal BMI and 19 (5%) aged 50 years or older at the time of diagnosis who were compared with the remainder of the cohort. Medication-induced IIH was more frequent in patients with IIH with normal BMI (28 vs 7%, p = 0.008). No patient with IIH with a normal BMI had severe visual loss in either eye (0 vs 17%, p = 0.09). Older patients with IIH had a lower BMI, but were still generally obese (33 vs 38, p = 0.04). Older patients were less likely to report headache as initial symptom (37 vs 76%, p < 0.001) and more likely to complain of visual changes (42 vs 21%, p = 0.03). Treatment of any type was less likely in older patients (significant for medications: 74 vs 91%, p = 0.004), and they were more likely to have persistent disc edema at last follow-up (median Frisén grade: 1 vs 0, p = 0.002), but had similar, if not better, visual outcomes compared with younger patients. A case-control study did not identify any new medication or risk factor associations. CONCLUSIONS: Patients with normal body mass index and those 50 years or older make up a small proportion of patients with idiopathic intracranial hypertension (IIH), but appear to have better visual outcomes than more typical patients with IIH.