Spontaneous vs. Secondary Cerebrospinal Fluid Leaks: A Single-center Retrospective Analysis

Introduction: In the lateral skull base, spontaneous cerebrospinal fluid (CSF) leaks are described as mechanistically distinct from CSF leaks secondary to other ear or cranial pathology. This study aims to characterize the differences between patients experiencing spontaneous versus secondary CSF leaks.

Methods: A retrospective chart review of 153 patients from a single institution from July 2004 to December 2024 was performed. 86 spontaneous and 23 secondary leak patients were analyzed for demographics, comorbidities, workup and treatment of idiopathic intracranial hypertension (IIH), type of repair, presentation, and outcomes. Continuous variables are summarized as mean ± SD or median (IQR) as appropriate. Data was analyzed using Welch’s two-sample t-test, Wilcoxon rank-sum test, and Fisher’s exact test. All tests were two-sided with α=0.05.

Results: On average, spontaneous leak patients were older (56.22 ± 14.88) and had a higher body mass index (35.68 ± 8.86) than secondary leak patients (47.26 ± 14.69, p=0.015; 32.39 ± 5.91, p=0.0397). In both groups, most patients presented with nonspecific symptoms such as hearing loss, otorrhea, and headache. Spontaneous leaks were more likely to present with meningitis. Two spontaneous leak patients had recurrent leaks. Spontaneous leak patients were more likely to have an IIH workup (50/86, 58.14% versus 3/23, 13.04%, p=0.0001). 30 spontaneous leak patients received a ventriculoperitoneal (VP) shunt compared to 2 in the secondary cohort (p=0.0187). Spontaneous leaks had a smaller post-operative air-bone gap (7.58 versus 16.73, p=0.0059). 6/86 spontaneous leak repairs were complicated by wound infection, as opposed to 1/23 secondary leak repairs.

Conclusions: CSF leak repairs in the lateral skull base are usually successful, regardless of the underlying cause. Patients with spontaneous CSF leaks had higher rates of infection, including meningitis, and were more likely to receive an IIH workup and a VP shunt. Spontaneous leak patients had a higher rate of all complications. The role of IIH in secondary CSF leaks is not clearly defined.