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Updated: Aug 9, 2026
Anteromesial Temporal Lobectomy for Medically Intractable Temporal Lobe Epilepsy: An Operative Study
Published on: August 15, 2025
Temporal lobe epilepsy caused by dermoid cyst
Hidenori Sugano1, Hiroyuki Shimizu, Shigeki Sunaga
1Department of Neurosurgery, Tokyo Metropolitan Neurological Hospital, Japan. debo@med.juntendo.ac.jp
Abstract:
A 15-year-old boy presented with a dermoid cyst in the left temporal lobe manifesting as complex partial seizures. Magnetic resonance imaging demonstrated a tumor with mixed signal intensity in the left anterior temporal subdural area, but no evidence of rupture. Intraoperatively, the tumor was located mainly in the deep sylvian fissure, adjacent to the amygdala, and had compressed the hippocampus. Intraoperative electrocorticography (ECoG) showed sporadic interictal spikes in both the adjacent areas of the tumor and over the anterior segment of the hippocampus. Total removal of the tumor and gliotic area of the surrounding tissue including the amygdala was performed. The hippocampal epileptic region was treated by transection of the pyramidal layer to preserve verbal memory function. Histological examination showed the dermoid tumor was closely attached to the brain parenchyma. The complex partial seizures ceased completely after surgery. Intraoperative recording of ECoG from the hippocampus and other limbic structures was very important to determine the epileptogenic area even if the tumor did not directly invade the hippocampus.
Insights
A temporal lobe dermoid cyst caused complex partial seizures in a teen. Surgical removal and hippocampal treatment resolved seizures, highlighting electrocorticography
Area of Science:
- Neurosurgery
- Neurology
- Pediatric Epilepsy
Background:
- Dermoid cysts, a type of germ cell tumor, can occur in the brain.
- Temporal lobe epilepsy is often associated with complex partial seizures.
- Surgical intervention is a key treatment for intractable epilepsy.
Observation:
- A 15-year-old boy presented with complex partial seizures due to a left temporal lobe dermoid cyst.
- MRI revealed a subdural tumor compressing the hippocampus and amygdala.
- Intraoperative electrocorticography (ECoG) identified epileptogenic activity in adjacent brain regions.
Findings:
- Complete surgical resection of the dermoid cyst and surrounding gliotic tissue was achieved.
- Transection of the hippocampal pyramidal layer preserved verbal memory function.
- Post-operative seizure cessation confirmed the efficacy of the surgical approach.
Implications:
- This case underscores the importance of ECoG in localizing epileptogenic zones, even with non-invasive tumors.
- Surgical management of temporal lobe dermoid cysts can effectively treat associated epilepsy.
- Preservation of hippocampal function during surgery is crucial for cognitive outcomes in pediatric epilepsy patients.
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