Introduction: Functional hemispherotomy (FH) is one of the most effective and durable surgical options for appropriate candidates with medically-refractory epilepsy (MRE) in whom most or all seizures are thought to arise from diffuse areas within a single hemisphere. While there are a number of well-accepted indications for FH (e.g. perinatal MCA syndrome, Rasmussen’s encephalitis, Sturge-Weber Syndrome, hemimegancephaly), there are other patients who may benefit from surgery without fitting neatly into one of these categories. An algorithmic approach to the presurgical evaluation will help guide the appropriate implementation of FH for either cure or palliation of severe MRE.
Methods: We performed a literature review using PubMed to select articles on various imaging modalities and tests which have been used for the presurgical evaluation of patients with MRE who are being considered for FH. Search terms included the following: functional hemispherotomy, hemispherectomy, hemidecortication, epilepsy, epilepsy surgery, medically-refractory epilepsy (MRE), seizure semiology, ictal EEG, interictal EEG, video EEG, brain MRI, PET, SPECT, MEG/MSI, ESI, and neuropsychological evaluation.
Results: Based on a systematic review of the literature, we propose an algorithm that incorporates various elements of the clinical presentation, electroencephalographic analysis, and imaging characteristics to guide the selection of appropriate candidates for FH. While this algorithm still requires prospective validation, we feel it is grounded on a synthesis of the best available evidence in the literature and informed by the expert opinion of the authors.
Conclusions: FH is a powerful tool in the armamentarium of experienced multi-disciplinary epilepsy centers to treat patients with severe MRE arising from diffuse areas throughout one hemisphere. The global crisis of underutilization of epilepsy surgery can be in part remedied by establishing evidence-based pathways for presurgical analyses to determine surgical candidacy.
Patient Care: For a large subset of patients with epilepsy, surgery remains an underutilized and often overlooked option. By providing evidence for the utility of various imaging studies in obtaining a better understanding of underlying pathology, patients should be given the option for an adequate surgical evaluation.
Learning Objectives: To explore the value of emerging technology in the fields of diagnostic and functional imaging and its role in epilepsy surgery, and to provide a framework for exploration of tools that could guide the surgeon in patient selection for surgery.