Syringomyelia persistence after Chiari decompression as a result of pseudomeningocele formation: implications for syrinx pathogenesis: report of three cases.

OBJECTIVE AND IMPORTANCE: We present the cases of three patients in whom pseudomeningocele (PSM) formations after posterior fossa decompression of hindbrain herniations (Chiari I malformations) were associated with persistence of syringomyelia. The physiological importance of correcting this complication has not been previously described. CLINICAL
PRESENTATION: We identified three patients who developed suboccipital PSMs after undergoing posterior fossa decompression for hindbrain herniations and syringomyelia. All three patients experienced persistence of their symptoms and their syringomyelia, despite adequate posterior fossa decompression. TECHNIQUE: Subsequent exploration revealed cerebrospinal fluid leaking either from the dural suture line (one patient) or from perforations found within the bed of a polyglactin mesh dural graft (two patients). Correction of the PSM resulted in resolution of both the syringomyelia and the symptoms in all three patients. DISCUSSION: The persistence of syringomyelia in the presence of a PSM may be the result of dissipation of the cerebrospinal fluid systolic pressure wave into the distensible PSM cavity. This phenomenon suggests that the cerebrospinal fluid pressure exerted on the spinal cord surface favors resolution of the syrinx cavity.