Background: Chronic subdural hematoma (cSDH) is a type of intracranial bleeding, predominantly affecting the elderly and males, with an estimated incidence of 8/100.000. The collection of subdural fluid expands slowly, leading eventually to brain tissue compression that results in neurological impairment such as seizures, cognitive decline, and paresis. Most patients need neurosurgical evacuation of the blood to improve and to prevent further, possibly permanent deterioration. Evidently, the cause of such a bleeding must be investigated and if possible treated, or preventive strategies need to be installed if possible. Spinal cerebrospinal fluid (CSF) leaks are a known cause of cSDH but are widely underdiagnosed in this population. The spinal CSF leak causes CSF loss that leads to intracranial hypotension, expansion of intracerebral veins, and traction to the brain and the surrounding tissues. A cSDH is a severe complication of such a leak and occurs in about 30% of all cases with a predominance among the elderly. It is crucial to identify these patients with a spinal leak as treatment pathways differ essentially from patients without a leak. Some smaller studies indicated a prevalence of spinal CSF leaks among cSDH patients of 30% to 80% depending on selection criteria (age, extend of cSDH). Notably, the entity of the CSF-venous fistula, that has been discovered as recent as 9 years ago, and that by now is accounting for 20-25% of all spinal leaks, has not been considered in previous research on cSDH and spinal CSF leaks. Currently, there is no prospective data on spinal CSF leaks in patients with cSDH. Establishment of such data is crucial to improve diagnostic and therapeutic algorithms for spinal CSF leaks in patients with cSDH.

Objective: To prospectively assess the prevalence of spinal CSF leaks in patients with cSDH

Methods: This is a prospective observational, monocentric study on patients admitted due to cSDH to the Department of Neurosurgery at the Medical Center of the University of Freiburg. Treatment and diagnostic procedures will follow standard protocols. The number of spinal CSF leaks will be assessed to generate the prevalence of spinal CSF leaks in this patient cohort. Furthermore, clinical data, the specific type of the CSF leak, and imaging parameters are assessed systematically to estimate the diagnostic value of these measures.