Cavernous Sinus Encephalocele: Surgeon Beware

Introduction: Encephaloceles occur throughout the brain/skull base interface. The etiology can be congenital, spontaneous, or secondary to trauma. The clinical presentation and treatment of an encephalocele is dependent on its location. While the majority of encephaloceles are incidental findings, the most common presenting symptom is CSF leak. Seizures also occur in 5% of patients with temporal lesions. While encephaloceles commonly occur in the middle fossa, herniation into the cavernous sinus is thus far unreported in the literature.

Setting: A tertiary medical referral center.

Case Report: The patient is a 61-year-old female with a history of migraines and vertigo who presented in 2013 to an outside facility for hypnagogic spells. A seizure workup was negative, but an MRI revealed a large left middle fossa encephalocele. She was observed locally for several years without any signs of CSF leak or meningitis. She was eventually referred to our institution where a CT cisternogram demonstrated CSF pooling in the ipsilateral Eustachian tube and sphenoid sinus. Nasal pledgets were positive for Beta-2 transferrin. Due to an occult CSF leak, she was seen by Neurosurgery and recommended a temporal craniotomy and skull base repair. At the time of bone flap elevation, substantial venous bleeding was encountered. Ligation of the middle meningeal artery and inspection of the brain surface did not elicit a source. Bleeding was traced to the cavernous sinus, and upon inspection, the encephalocele infiltrated the cavernous sinus. Once this was recognized this was easily managed however was quite distressing during surgery. After reduction of the encephalocele and hemostasis, the sphenoid sinus was packed with fat and the skull base repaired. The patient recovered with no deficits and discharged home on postoperative day 2.

Conclusion: The appearance of significant bleeding during surgery for a middle fossa or midline encephalocele may indicate invasion into the local venous sinuses and require quick recognition and change in technique for adequate hemostasis. Awareness of this anatomic possibility may limit intraoperative blood loss and improve patient outcomes.