In general, encephaloceles are congenital (present at birth) and caused by failure of the neural tube to close completely in a developing fetus. This results in sac-like bulges of nerve tissue that come through gaps in the skull. Encephaloceles of the temporal bone are typically acquired rather than congenital and caused by head trauma, erosion of temporal bone by chronic suppurative otitis media/cholesteatoma, iatrogenic due to mastoid surgery or sometimes are idiopathic (form spontaneously). Temporal bone encephaloceles may be asymptomatic for years but eventually produce conductive hearing loss, meningitis, cerebrospinal fluid (CSF) leaks, facial nerve weakness or (rarely) seizures.
Diagnosis of a temporal bone encephalocele is made after obtaining a thorough medical history, performing a microscope exam of the ears and evaluating temporal bone imaging (CT scans of the temporal bones or MRI scans with internal auditory canal protocol). Surgery is the only treatment option. Several surgical techniques including transmastoid and middle cranial fossa approaches are available to address these skull base defects, and the method recommended depends on the size and location of the encephalocele. The primary goal of surgery is to stop CSF leaks and prevent brain herniation, with preservation of hearing and middle ear function whenever possible.