Causes of Spontaneous Cerebrospinal Fluid (CSF) Leaks
The three main causes of spontaneous cerebrospinal fluid leaks are dural defects, leaking meningeal diverticula, and CSF-venous fistulas. 1
Primary Etiologies
- Dural defects: Small, circumscribed longitudinal slits typically located at the ventral aspect of the dura mater, most commonly at the cervicothoracic or thoracolumbar junction 2
- Leaking meningeal diverticula: Outpouchings of the dura that can rupture or leak CSF 1
- CSF-venous fistulas: Abnormal connections between the CSF space and venous structures 1
Predisposing Conditions and Risk Factors
- Spinal osteophytes: Can perforate the dura, creating a pathway for CSF leakage 1
- Collagen vascular disease: Associated with weakened ectatic dura and meningeal cysts 1
- History of bariatric surgery: Rapid loss of epidural fat may weaken the dura and predispose to CSF leakage 1
- Idiopathic intracranial hypertension: Many spontaneous CSF leaks are seen in patients with this condition 1
- Congenital malformations: Can create potential pathways for CSF leakage 3
Anatomical Considerations
- Location: Most symptomatic CSF leaks occur in the spine rather than intracranially 1
- Pressure dynamics: In the upright position, intracranial hydrostatic pressure is slightly negative relative to atmosphere, whereas spinal hydrostatic pressure is positive, contributing to the predominance of spinal leaks 1
- Dural defect characteristics:
Special Considerations
- Medication-induced CSF leaks: In patients with prolactinomas treated with dopamine agonists like cabergoline, medication-induced shrinkage of tumors that have invaded sphenoid bone can cause CSF rhinorrhea 5
- Multiple leak sites: Some patients may have multiple simultaneous CSF leak sites, complicating diagnosis and treatment 4
- Complex dural defects: The configuration of dural defects can be complex and not always amenable to primary closure 6
Clinical Implications
- Diagnostic challenges: Even when extradural CSF leakage is discovered preoperatively by imaging studies, it may not always be possible to identify the exact site of leakage intraoperatively 6
- Treatment considerations: Surgical repair may be technically challenging due to regional attenuation of the dura preventing primary repair 6
- Unusual manifestations: CSF leaks at the thoracolumbar junction have been associated with altered mental status 2
Understanding the specific cause of spontaneous CSF leaks is crucial for appropriate management, as treatment approaches may differ based on the underlying etiology and anatomical considerations.