Spontaneous cerebrospinal fluid (CSF) leak through the posterior fossa (PF) aspect
of the petrous bone is exceedingly rare. A case series allows analysis of etiologies
and how they may differ from the more common middle fossa (MF) route of leakage. The
design was a retrospective case series. The setting was a tertiary care institution.
A series of three patients with PF spontaneous CSF leaks was identified. High-resolution
imaging (CT and MRI) and intraoperative observations were evaluated. Both in this
series and in previously reported cases, patients share the demographics typically
found in the MF leak population. In our series, two patterns of PF CSF leak were identified:
(1) large unilateral with cerebellar encephalocele and (2) small punctate defects
just lateral to the endolymphatic sac. Two presented with simultaneous MF and PF leaks
suggesting a shared etiology, at least in some cases, with a role for increased intracranial
pressure. In spontaneous CSF leaks, it is important to evaluate the posterior petrous
bone along with the tegmen. The concomitant appearance of MF with PF leaks points
out the risk that repair via MF craniotomy could fail to identify a leakage site in
the vicinity of the endolymphatic sac.
Keywords
cerebrospinal fluid leak - arachnoid granulation - petrous bone - posterior fossa
