Imaging description

Cerebrospinal fluid (CSF) leak from the skull base is most commonly secondary to bony defects occurring after blunt head trauma or surgery. The most common location for post-traumatic CSF leak is the cribriform plate. Patients presenting with CSF leak who have no history of prior trauma or surgery are said to have spontaneous CSF leak. The most common site for spontaneous CSF leak at the skull base is the sphenoid sinus, more specifically the lateral wall of the sphenoid sinus, which may be weaker than the other sites due the incomplete fusion of the greater wings of the sphenoid bone with the basisphenoid, a.k.a. the Sternberg’s canal [1,2]. The second most common site is the ethmoid roof and cribriform plate. Multiple sites of leak may be seen in up to 30% of patients.

Unenhanced high-resolution CT is usually performed first, and this shows the defect in the majority of cases. Well-defined soft tissue and fluid attenuation structures can be seen in the sinuses adjacent to the bone defect and represent meningoceles or encephaloceles (collectively known as cephaloceles). Cephaloceles mimic inflammatory sinus disease such as mucoceles or lytic bone lesions on CT (Figs. 70.1, 70.3). High-resolution MRI is helpful in identifying cephaloces, revealing their content and differentiating them from inflammatory mucosal changes (Figs. 70.2, 70.4). CT cisternogram is performed in cases where non-invasive methods are equivocal or show multiple potential sites of leak to pinpoint the exact location of the skull-base defect.