Use of a Tonometer to Identify Epileptogenic Lesions During Pediatric Epilepsy Surgery

Refractory epilepsy, meaning epilepsy that no longer responds to medication, is a common neurosurgical indication in children. In such cases, surgery is the treatment of choice. Complete resection of affected brain tissue is associated with highest probability of seizure freedom. However, epileptogenic brain tissue is visually identical to normal brain tissue, complicating complete resection. Modern investigative methods are of limited use. An important subjective assessment during surgery is that affected brain tissue feels stiffer, however there is presently no way to determine this without committing to resecting the affected area. It is hypothesized that intra-operative use of a tonometer (Diaton) will identify abnormal brain tissue stiffness in affected brain relative to normal brain. This will help identify stiffer brain regions without having to resect them. The objective is to determine if intra-operative use of a tonometer to measure brain tissue stiffness will offer additional precision in identifying epileptogenic lesions. In participants with refractory epilepsy, various locations on the cerebral cortex will be identified using standard pre-operative investigations like magnetic resonance imagin (MRI) and positron emission tomography (PET). These are areas of presumed normal and abnormal brain where the tonometer will be used during surgery to measure brain tissue stiffness. Brain tissue stiffness measurements will then be compared with results of routine pre-operative and intra-operative tests. Such comparisons will help determine if and to what extent intra-operative brain tissue stiffness measurements correlate with other tests and help identify epileptogenic brain tissue. 24 participants have already undergone intra-operative brain tonometry. Results in these participants are encouraging: abnormally high brain tissue stiffness measurements have consistently been identified and significantly associated with abnormal brain tissue. If the tonometer adequately identifies epileptogenic brain tissue through brain tissue stiffness measurements, it is possible that resection of identified tissue could lead to better post-operative outcomes, lowering seizure recurrences and neurological deficits.