Abstracts

Rationale: OBJECTIVE: We report a case of a patient with drug-resistant, localization-related epilepsy who underwent intracranial EEG monitoring without resection and later developed encephaloceles at the sites of her burr holes.Methods: BACKGROUND: Invasive EEG recording is a key element of surgical evaluation for patients with drug-resistant localization-related epilepsy. The most commonly cited surgical complications are infection and subdural hemorrhage. Other prominent considerations include increased intracranial pressure and cerebrospinal fluid leakage (Anya et al, 2013). Twenty to thirty percent of patients who undergo invasive EEG monitoring are explanted without resection (van Gompel et al, 2008). There is a paucity of literature on long term outcomes in these patients. We report an uncommon but important potential sequel of invasive EEG recording.Results: CASE: A 45 year old right handed woman was referred for evaluation of localization-related epilepsy. Seizures occurred 3 times weekly with rightward gaze, lip smacking, left hand automatisms and occasional secondary generalization. Medications included gabapentin, tiagabine and lacosamide. Magnetic resonance imaging (MRI) showed volume loss of the right hippocampus and right temporal horn enlargement. Positron emission tomography showed left temporal hypometabolism. Complex partial seizures were recorded with predominantly left temporal onset, however one seizure began with bitemporal rhythmic delta. In 1/2010 the patient underwent bilateral craniotomy for intracranial electrode placement. See table for details of the electrode locations. Seizures were recorded with onset in the left frontal, left mesial temporal and right mesial temporal regions independently. The patient was explanted, and no resection was offered. The patient declined vagal nerve stimulator and continued medical management until 12/2014 when she underwent re-evaluation for consideration of responsive neurostimulator therapy. Seizure frequency had increased to twice daily. MRI demonstrated cystic encephalomalacia of the temporal lobes bilaterally with ex vacuo dilatation of the temporal horns and encephaloceles at the sites of the patient’s residual skull defects. The risk/benefit profile of repeat surgical intervention was considered high, and a conservative management approach was adopted.Conclusions: DISCUSSION: To the authors’ knowledge this is the first report of encephalocele as a complication of invasive EEG monitoring. Although encephalocele can cause epilepsy, it is not clear that this patient’s increased seizure frequency was attributable to her encephaloceles. Alternative explanations include gliotic changes, antiepileptic tolerance, and hormonal changes associated with menopause. Overall, invasive EEG recording is a safe and effective procedure that is an important contribution to the preoperative evaluation of well-selected patients with localization-related epilepsy. Physicians should be aware of the potential risks of the procedure, and increased seizure frequency post-procedure should prompt repeat imaging to rule out unexpected sequelae.