Rationale:
Skull base defects with encephalocele are recognized contributors to epilepsy. However, the risk of developing seizures in these patients is not well defined. This study aims to identify the clinical and radiological factors associated with seizure development in patients with skull base defects.
Methods:
We performed a retrospective review of patients aged 18 or older with skull base defects identified radiologically or intraoperatively at our center between 1/1/2010 and 12/31/2019. Patients with inadequate imaging, post-traumatic or iatrogenic cause of skull defects or CSF leak, or spinal CSF leaks were excluded. Patients were categorized into seizure and non-seizure groups. Those with a history of childhood epilepsy were excluded. Demographic, clinical, and radiological features including defect size, location, content, and idiopathic intracranial hypertension (IIH) imaging findings were compared.
Results:
A total of 145 patients were identified (mean age 60.5 years). Seventeen patients (11.7%) had seizures.
In the seizure group (n=17), the mean (SD, range) age was 52.5 years (13.19, 27 – 71years) compared to 62.09 years (13.24, 30 - 99 years) in the non-seizure group (n=123) (t = 2.793, p = 0.003). All patients in the seizure group were female (100%) versus 69.9% (n=86) females in the non-seizure group (χ²=4.4227, p=0.035). The seizure group had a higher representation of African American individuals (n=13, 76.4%) relative to the non-seizure group (n=30, 24.3%) (χ²=16.6366, p = 0.00004). The median (IQR) BMI was higher in the seizure group at 41.8 kg/ m² (34.85 - 48.45 kg/ m²) compared to 35.3 kg/ m² (29.07 - 40.07 kg/ m²) in the non-seizure group (U= 594.5, p=0.004). The median (IQR) bony defect size was also larger in the seizure group at 7.3 mm (6 - 11mm) versus 5.9 mm (3 - 8.7mm) in the non-seizure group (U= 555.5, p=0.017). The seizure group had a higher median (IQR) number of cumulative IIH radiological findings at 3 (3 to 4), compared to 1 (0 to 3) in the non-seizure group (χ² = 25.654, p< 0.001). There was no significant correlation between seizure and extracranial extension of brain tissue, sleep related disorder, presence of CSF leak, location of the skull base defect, recurrent CSF leak.
Extent of extracranial brain herniation positively correlated with bony defect size (ρ = 0.589, p < 0.001). Size of the extracranial extension was higher in the female patients (F= 10.662, p = 0.001).