Meningocele and Meningoencephalocele of the Lateral Wall of the Sphenoid Sinus.

The article by Zoli and colleagues 1 highlights the vagaries of bony skull base anatomy, as demonstrated by the occurrence of meningoceles and meningoencephaloceles that extend through apertures in the skull base and through the lateral wall of the sphenoid sinus (LWSS). Although many of these lesions present with cerebrospinal fluid (CSF) rhinorrhea, and occasionally with meningitis, the diagnosis and management are different from those of patients with posttraumatic CSF leaks. The large series of cases that Zoli and colleagues present, their expertise in diagnosing them, and their successful surgical management using skillfully applied endonasal endoscopic techniques are admirable. Among the 23 patients there were 11 meningoencephaloceles and 12 meningoceles, all of which extended into the sphenoid sinus and none of which was associated with known or suspected previous trauma. Most had presented with CSF leakage, and 2 of the meningoencephalocele cases had epilepsy. Their technique of endoscopic sphenoidotomy and repair of the lesions was successful in treating all the patients. In 1985, we reviewed the Mayo Clinic experience with surgery for nontraumatically associated CSF rhinorrhea. 2 At that time, there were 28 spontaneous cases of rhinorrhea, with the remainder of our 200 cases being posttraumatic. Imaging diagnosis depended primarily on computed tomography (CT), tomograms, and cisternograms. Fluorescein was rarely used, and radioactive isotope studies were occasionally used to confirm the diagnosis, and, it was hoped, to lateralize the leak. We had begun then to use an endonasal microscopic approach for repair, with the help of our colleagues from otorhinolaryngology. However, many of the patients had craniotomies for visual localization of the leak site and for definitive repair. In that series, 17 were repaired by 1 surgical procedure, 5 had multiple operations, and 5 remained failures, with persistent CSF leaks. Among our 28 patients, 3 had LWSS leaks, none of which was adequately repaired by an endonasal approach. They were visualized and repaired by craniotomy. The presence of the LWSS aperture was a surprise but is now recognized as a more common anatomically based problem. Subsequent to our report, the transnasal microscopic approach was effective in treating 2 meningoencephaloceles not associated with epilepsy and not presenting laterally in the sphenoid sinus. Modern diagnostic imaging with thin-slice CT, magnetic resonance imaging and the occasional CT cisternogram is usually effective in delineating the defect in the skull base. We no longer use radioisotope cisternal and CSF studies but occasionally use fluorescein to visualize the leak. In most cases, the site of the lesion is visible and can be treatable endoscopically through the endonasal approach. A wide endoscopic view of the entire anterior skull base is essential and the use of intraoperative navigation can be helpful. The addition of a nasoseptal flap adds to the security of the repair. 3 Two of the patients of Zoli and colleagues had meningoencephaloceles associated with epilepsy. They postulate that, in some similar cases, resection of the abnormal brain in the encephalocele might result in long-lasting seizure control. This