Child Neurology: Presurgical Evaluation of Dominant Hemisphere Function in a Child With Rasmussen Encephalitis Using Magnetoencephalography.

Rasmussen's encephalitis (RE) is a devastating progressive inflammatory disorder that leads to debilitating neurological deficits and intractable epilepsy. Surgical treatment of the dominant hemisphere has been attempted with hesitation given the lack of effective diagnostic tools to determine the potential functional deficits from disconnection procedures.We present the case of a 15-year-old male with RE, right hemiparesis, profound aphasia, and recurrent status epilepticus, who underwent language assessment using magnetoencephalography (MEG) prior to urgent hemispherectomy for epilepsia partialis continua. Cortical responses in the passive auditory task were localized to the left and right hemispheres at latencies of 200 and 380 ms, respectively from the stimulation onset. The current density reconstruction analysis showed the sources at 380 and 200 ms in the right and left temporal-parietal junctions, respectively. These findings confirmed that the patient's language was represented bilaterally. Other tests conventionally used to assess cortical language function were not attempted given his poor functional status and ongoing seizures. The left functional hemispherectomy has resulted in seizure freedom and significantly improved language function.The MEG-based evaluation of the language function could provide valuable information regarding cortical language organization prior to hemispherectomy in patients with RE. Such approach of mapping the eloquent cortical functions can be used in other structural and autoinflammatory disorders of the brain, especially in patients who cannot participate in the conventional diagnostic modalities designed to assess critical brain functions like language and memory.