Noninvasive Localization of Language Cortex in an Awake 4-Year-Old Child with Rasmussen Encephalitis: A Case Report

BACKGROUND AND IMPORTANCE: Presurgical mapping of eloquent cortex in young patients undergoing neurosurgery is critical for timely intervention, surgical planning, and minimizing postoperative deficits. However, invasive direct cortical stimulation has limited success in young children and noninvasive modalities, such as magnetoencephalography and functional MRI, require sedation, often precluding localization of critical language cortices. Transcranial magnetic stimulation (TMS), a noninvasive brain stimulation technique, is well suited to evaluate language areas in young children because it does not require the patient to remain still during mapping. CLINICAL PRESENTATION: A 4-yr and 11-mo-old female patient diagnosed with epilepsia partialis continua of the right arm and face and right-sided weakness was evaluated at our institution. MRI findings and clinical examination led to the diagnosis of Rasmussen encephalitis involving left frontal lobe and insula. Language cortices were successfully identified in both hemispheres using TMS. The TMS findings aided in discussing with the family the risks of postsurgical deficits of left functional hemispherectomy, the definitive treatment for Rasmussen encephalitis. Postoperatively, the patient had intact speech and was seizure free. CONCLUSION: We illustrate the feasibility and utility of TMS as a noninvasive functional mapping tool in this young child. The preoperative demonstration of bilateral language organization indicated a greater likelihood of preserved language functions postsurgery. We demonstrate that TMS is a safe and noninvasive tool to map language cortices in young children with serious epilepsy syndromes.