Excavating meningoencephaloceles: A newly recognized entity

Spontaneous cerebrospinal fluid (CSF) leaks are largely attributed to idiopathic intracranial hypertension and typically present as skull base defects with or without prolapse of intracranial contents. However, in our practice, we have encountered a distinct type of spontaneous CSF leak that presents in a different manner.

To discuss a newly-classified, difficult to treat, subset of spontaneous CSF leaks that present as excavation of the bone of the skull base in a tunnel- or canal-like fashion by a meningocele or meningoencephalocele instead of as a localized area of bony dehiscence.

A retrospective review was performed at a tertiary care rhinology practice to identify a subset of CSF leak patients with an excavating/canal-like skull base defect visualized radiographically on computed tomography (CT) scan or magnetic resonance imaging and/or endoscopically in the operating room.

The cohort of patients consisted of 7 females and 1 male with an average age of 53.6 years and a self-reported race of 4:3:1 African-American:Caucasian:Indian. All patients presented with CSF rhinorrhea. The most common leak site was the cribriform and upper septum. Six of the 8 patients had multiple defects and/or progression of their skull base defects, and 5 patients required multiple and/or repeat repairs in the operating room. Seven of the 8 patients underwent a cisternogram because the excavating nature of the leaks made it difficult to identify the specific leak site on high-resolution CT scan alone.

In spontaneous CSF leaks that are difficult to identify or recur soon after a proper repair, an excavating pattern should be considered. Failure to recognize this type of leak and all of its tributaries, to fully unroof the excavated bone to completely resect the meningocele, and to visualize and close the site of origin will likely result in failure and recurrence of CSF leak.