case_images: PMC8422469_01
case_images: (a) Preoperative electroencephalogram recorded at the start of the habitual seizure (sensitivity: 10 microV, time constant: 0.1 s, high cut filter: 30 Hz, reference: average). Ictal activities begin with rhythmic alpha activity at T3 and T5 (red line). (b) Coronal view of preoperative magnetic resonance image (MRI) with fluid-attenuated inversion recovery (FLAIR) sequence demonstrates that protrusion of a part of the left temporal lobe is confirmed in the lateral fossa of the sphenoid sinus, indicating sphenoidal encephalocele (Red arrow). (c) Coronal computed tomography (CT) at a comparable level with (b) confirms the bone defect on the left lateral wall of the sphenoid sinus (white arrow). (d and e) Coronal view of 18-F fluorodeoxyglucose (FDG)-positron emission tomography (PET) image at the hippocampus (d) and a few centimeters behind the sphenoidal encephalocele and at the sphenoidal encephalocele (e). Decreased accumulation of FDG is observed around the left medial and basal temporal area (white arrows). (f) The fusion image of FDG-PET (e) and FLAIR-MRI (b) clearly shows that markedly decreased accumulation of FDG is observed at the tip of the encephalocele (white arrow).
case_images: SNI-12-379-g001.jpg
case_images: PMC8422469_01_SNI-12-379-g001.jpg
case_images: F1
case_images: Long-term video electroencephalogram (EEG) demonstrated ictal discharges with low-amplitude, rhythmic, irregular alpha waves appearing in T3 and T5; these waves demonstrated increasing amplitude, with frequency changing from delta to delta, when the patient experienced a dull sensation that lasted several seconds [Figure 1a]. Magnetic resonance imaging (MRI) revealed a protrusion of the left medial temporal lobe from the middle cranial fossa to the lateral fossa of the sphenoid sinus [Figure 1b]. At that site, a bony defect was also detected on bone-targeted computed tomography (CT) [Figure 1c]. Although 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) demonstrated decreased FDG accumulation in the left medial temporal area and temporal base area around the lesion [Figure 1d and e], the fusion image of FDG-PET and MRI with fluid-attenuated inversion recovery sequence clearly depicted markedly decreased FDG accumulation in the temporal lobe encephalocele [Figure 1f]. 123I-Iomazenil (IMZ) single-photon emission tomography in the delayed phase demonstrated a decreased IMZ accumulation in the basal area of the left temporal lobe.
case_images: (a) Posterior wall of the left maxillary sinus is drilled, and the pterygopalatine sacs are exposed, after opening the sphenoid sinus (Sp.S), posterior ethmoid sinus (P.E.S.), and left maxillary sinus (Lt.M.S.) from both nasal cavities. (b) While flipping the pterygopalatine sac (Pt. Sac) outwards, the base of the pterygoid plate (Pt.P.) and the sphenoid sinus septum connected to it is being removed, and encephalocele is confirmed (white arrow). (c) A depth electrode (white arrow heads) is inserted into the encephalocele (white arrows). (d) Intraoperative EEG reveals frequent spikes in the encephalocele (bipolar recording, sensitivity: 20 muV, time constant: 0.1 s, high cut filter: 60 Hz). (e) Time-frequency analysis reveals high-frequency oscillations ranging from 50 Hz to 150 Hz, superimposing to the spikes. (f) The tip of encephalocele is successfully resected (in the white dotted line).
case_images: SNI-12-379-g002.jpg
case_images: PMC8422469_01_SNI-12-379-g002.jpg
case_images: F2
case_images: After opening the sphenoid sinus, posterior ethmoid sinus, and left maxillary sinus from both the nasal cavities, the posterior wall of the left maxillary sinus was drilled, and the pterygopalatine sac was exposed [Figure 2a]. While flipping the pterygopalatine sac outward, the base of the pterygoid plate and the sphenoid sinus septum connected to it was removed, and the encephalocele divided into two components in the lateral fossa of the left sphenoid sinus was confirmed [Figure 2b]. A depth electrode with three electrode contacts was inserted 1.0 cm into the lateral component of the encephalocele [Figure 2c]. Frequent spikes were recorded [Figure 2d], and the time-frequency analysis revealed superimposing HFOs ranging from 50 Hz to 150 Hz on each spike [Figure 2e]. Piecemeal resection was performed for the encephalocele protruding into the sphenoid sinus [Figure 2f], and subsequent reconstruction was performed with the femoral fascia, fat, nasal septum, and nasal mucosa flap.
case_images: (a) Postoperative MRI confirms that the sphenoidal encephalocele was resected 8 mm from the tip. (b) Postoperative CT shows successful repair of the temporal base with nasal septum cartilage. (c) Histopathological examination shows cerebral cortical tissue with several reactive astrocytes.
case_images: SNI-12-379-g003.jpg
case_images: PMC8422469_01_SNI-12-379-g003.jpg
case_images: F3
case_images: Postoperative MRI confirmed that the sphenoidal encephalocele was resected 8 mm from the tip [Figure 3a]. On postoperative CT, successful repair of the temporal base with nasal septum cartilage was confirmed [Figure 3b]. Histopathological examination of the resected specimen showed cerebral cortical tissue with several reactive astrocytes [Figure 3c].