Late Recurrence of Intractable Epilepsy Associated with MRI-occult Pilocytic Astrocytoma in the Temporal Lobe Nine Years after Initial Removal : A case report with surgical and late-seizure recurrence observations

A 28-year-old male who presented a relapse of intractable epilepsy consisting of complex partial seizures with occasional secondary generalizations at the age of 26, had undergone removal of a left mesial temporal lobe tumor at another hospital at 18 years old. Pathological examination at that time revealed a low-grade astrocytoma, and the tumor was further treated by complementary adjuvant irradiation therapy. Magnetic resonance imaging (MRI) findings on admission portrayed a post-operative cavity anterior to the atrophied hippocampus on the left side with hyperintense in fluid-attenuated inversion recovery (FLAIR) images. There were no enhanced lesions in T1-weighted gadolinium images. As it was diagnosed as left mesial temporal lobe epilepsy with preoperative evaluations, the patient underwent left anterior temporal lobe resection (TLR). Intraoperative findings revealed that a small lump of grey tissue was attached to the anteromesial side of the sclerotic hippocampus. We surgically removed this and the tissue was a pilocytic astrocytoma. The patient has since remained seizure-free for 2.5 years. Seizure outcomes at postoperative 1-2 years are highly predictive of long-term outcomes after TLR for temporal lobe epilepsy (TLE). Late-seizure recurrence (> postoperative 2 years) with an initially successful outcome rarely occurs in TLR patients. This case report suggests that recurrence of even benign pilocytic astrocytomas may occur when seizure recurs in long-term follow-up.