Low incidence of true Sternberg's canal defects among lateral sphenoid sinus encephaloceles.

BACKGROUND: Spontaneous sphenoid sinus cerebrospinal fluid (CSF) encephaloceles have been postulated to arise from a persistent Sternberg's canal. However, recent evidence has questioned this embryological etiology. We examined the anatomic location of a series of lateral sphenoid sinus encephaloceles to determine if they corresponded with the location of Sternberg's canal. METHODS: We queried a prospectively acquired database of surgically treated spontaneous CSF leaks and identified those arising from the sphenoidal sinus. Images were reviewed to characterize the leaks with respect to the foramen rotundum (FR) and the vidian canal (VC). Four leak types were classified of which Type I (medial to FR and VC entering nasopharynx) was theoretically located in the precise location of Sternberg's canal. Type II was medial to FR; Type III was lateral to FR; Type IV passed through an enlarged FR into sphenoid sinus. Demographic data were analyzed. RESULTS: Of 103 repaired CSF leaks, 17 arose from the lateral sphenoid sinus. There were no true Type I leaks, 3 Type II leaks, 12 Type III leaks, and 2 Type IV leaks. No differences were found with respect to sphenoid pneumatization, BMI, age, sex, arachnoid pits, or postoperative leak between different types. CONCLUSIONS: No evidence was found to support the existence of a classic Sternberg canal CSF leak, supporting the hypothesis that most sphenoid spontaneous leaks likely occur secondary to chronically elevated ICP. Rare cases may be related to a weakness in the sphenoid wall in the region of Sternberg's canal.