Clinical characteristics and outcomes of non-obese patients with idiopathic intracranial hypertension: a retrospective cohort study

BACKGROUND: Idiopathic intracranial hypertension (IIH) in non-obese patients represents a notable subtype of the condition, and its underlying causes require further investigation. This study aimed to analyse the clinical features and risk factors associated with non-obese IIH patients. METHODS: A retrospective analysis was conducted on 252 adult patients with clinically confirmed IIH between January 2015 and December 2023. Data on epidemiological characteristics, clinical manifestations, and imaging findings were reviewed. The cases were classified into two groups: obese group (body mass index, BMI≥28 kg/m²) and non-obese group(BMI<28 kg/m²). A comparative assessment of clinical data was performed between the groups, including demographic information, clinical findings, medical history, laboratory results, radiological indices, diagnosis, treatment, and prognosis. RESULTS: A total of 96 obese IIH and 82 non-obese IIH cases were included in this observation. Compared to the obese IIH group, non-obese cases were much older (37.94 ± 17.05vs.34.15 ± 8.74 year-old, P = 0.044), exhibited a lower frequency of abnormal radiological signs indicating intracranial hypertension (58.54%vs72.92%; P = 0.043), more severe visual impairment, and a reduced remission rate (60.98% vs. 81.25%%, P = 0.003). Additionally, 71 patients (86.59%) in the non-obese group had identifiable risk factors for IIH, including over-weight (63cases), obstructive sleep apnoea syndrome (OSAS) (36 cases), and weight gain (12cases). The mean duration of final follow-up was 15.02 ± 2.82 months. Univariate analysis showed that BMI, disease duration before treatment, visual field grading, and non-obese were significantly associated with poor best corrected visual acuity(BCVA) outcome (P<0.05). BCVA before treatment and imaging findings showed marginally significant associations (P<0.1). Multivariate logistic regression revealed that non-obese group (OR = 9.16, 95%CI: 1.09-77.18, P = 0.041) and longer disease duration (OR = 1.14, 95%CI: 1.05-1.24, P = 0.002) were independent risk factors for poor BCVA outcome. Poor BCVA before treatment showed a marginally significant trend toward poor prognosis (P = 0.089). CONCLUSIONS: Non-obese patients with IIH tend to exhibit more severe visual impairment and longer disease duration. Close monitoring and early intervention are recommended for non-obese patients with a long disease course.