Case report
A 53-year-old woman, who had been suffering from serous rhinorrhea for several years, with no specific medical conditions except for obesity with a body mass index of 41 kg/m2, presented emergently to the neurological department with high fever and impaired consciousness. Cerebrospinal fluid (CSF) examination by lumbar puncture revealed a diagnosis of bacterial meningitis. Only an accumulation of fluid with air was noted in the right sphenoid sinus through brain computed tomography (CT) taken at 4-mm slice thickness (Figure 1A) and magnetic resonance imaging (MRI) (Figure 1B). There were no other findings that could be considered a focus of inflammation. She was referred to the otorhinolaryngological department to investigate whether the right sphenoid sinus was the focus of the meningitis. High-resolution (HR) CT images were taken with 0.5-mm slice thickness, and coronal and sagittal sections were reconstructed (Figure 2A1-3). HRCT revealed a skull base fistula at the lateral wall of the right sphenoid sinus and arachnoid pits at the middle cranial fossa. In addition, the fluid in the right sphenoid sinus, draining into the nasal cavity via the natural ostium of the right sphenoid sinus (Figure 3A), was collected and measured for glucose, and was found to be similar to the CSF from the lumbar region. Therefore, we diagnosed the patient with spontaneous CSF leakage due to fistula of the middle cranial fossa and an ascending bacterial infection spilled over into the cranium via the fistula. After improvement of the meningitis by medical treatment, an interdisciplinary team of otorhinolaryngologists and neurosurgeons performed reconstruction of the skull base.
An otolaryngologist and a neurosurgeon performed the reconstruction surgery. First, right endoscopic sinus surgery was performed to open the sphenoid sinus via the ethmoid sinus (Figure 4A). The base of the right sphenoid sinus was observed with a 70-degree telescope, and a fistula was identified on the lateral wall of the right sphenoid sinus (Figure 4B, 4C). Subsequently, bilateral sphenoid sinuses were opened using a transseptal approach (Figure 4D, 4E). To secure a wide surgical field and sufficient field of view, a rescue incision was made to the natural ostium of the right sphenoid sinus, parallel to the nasal floor, at the area where the olfactory epithelium did not exist (Figure 4F). The sphenoid crest was removed, and the surgical field was developed laterally so that the floor of the right sphenoid sinus could be fully manipulated (Figure 4G, 4H). The blood vessels and nerves in the right palatovaginal and Vidian canals were cauterized, and the surgical field was further expanded laterally to enable manipulation of the lateral wall of the right sphenoid sinus. The arachnoid mater was identified in the fistula after removal of the right sphenoid sinus mucosa (Figure 5A). A collagen matrix (DuraGenTM Dural Graft Matrix [Integra Life Sciences, Plainsboro, NJ, USA]) was inserted into the fistula and laid against the dura mater (Figure 5B, 5C, 5D). The vomer bone was shaped into a pile and fitted into the fistula for rigid reconstruction of the skull base (Figure 5E, 5F, 5G). A multilayer reconstruction was performed by covering the outermost layer with a pedicle nasoseptal mucosal flap (Figure 5H).
At 6-month follow-up, no recurrence of CSF leakage or resorption of the inserted bone pile was observed (Figure 2B1-3, 3 B). There were no complications, such as olfactory disturbances or nasal septal perforation, due to surgical invasion. There were no findings of intracranial infection or sinusitis.