Clinical application of an EEG-based brain–computer interface: a case study in a patient with severe motor impairment

Objective: This case study describes how a completely paralyzed patient, diagnosed with severe cerebral palsy, was trained over a period of several months to use an electroencephalography (EEG)-based brain–computer interface (BCI) for verbal communication. Methods: EEG feedback training was performed in the patient's home (clinic), supervised from a distant laboratory with the help of a ‘telemonitoring system’. Online feedback computation was based on single-trial analysis and classification of specific band power features of the spontaneous EEG. Task-related changes in brain oscillations over the course of training steps was investigated by quantifying time–frequency maps of event-related (de-)synchronization (ERD/ERS). Results: The patient learned to ‘produce’ two distinct EEG patterns, beta band ERD during movement imagery vs. no ERD during relaxing, and to use this for BCI-controlled spelling. Significant learning progress was found as a function of training session, resulting in an average accuracy level of 70% (correct responses) for letter selection. ‘Copy spelling’ was performed with a rate of approximately one letter per min. Conclusions: The proposed BCI training procedure, based on electroencephalogram (EEG) biofeedback and concomitant adaptation of feature extraction and classification, may improve actual levels of communication ability in locked-in patients. ‘Telemonitoring-assisted’ BCI training facilitates clinical application in a larger number of patients.