Longevity of a Brain-Computer Interface for Amyotrophic Lateral Sclerosis

Abstract

The durability of communication with the use of brain-computer interfaces in persons with progressive neurodegenerative disease has not been extensively examined. We report on 7 years of independent at-home use of an implanted brain-computer interface for communication by a person with advanced amyotrophic lateral sclerosis (ALS), the inception of which was reported in 2016. The frequency of at-home use increased over time to compensate for gradual loss of control of an eye-gaze-tracking device, followed by a progressive decrease in use starting 6 years after implantation. At-home use ended when control of the brain-computer interface became unreliable. No signs of technical malfunction were found. Instead, the amplitude of neural signals declined, and computed tomographic imaging revealed progressive atrophy, which suggested that ALS-related neurodegeneration ultimately rendered the brain-computer interface ineffective after years of successful use, although alternative explanations are plausible. (Funded by the National Institute on Deafness and Other Communication Disorders and others; ClinicalTrials.gov number, NCT02224469.).

Figure 1.

At-home use of the implanted BCI. A) Methods of communication other than the BCI used by the participant in the course of time since implantation in October 2015. B) Frequency of at-home use of the BCI. For every month, the mean number of hours per day of at-home use of the BCI is indicated. Numbers 1–4 refer to noteworthy periods/instances, namely 1) predominantly outdoor use of the BCI system, 2) increasing (indoor) use of the BCI system, related to progressive inability to use the eye gaze device, 3) implementation of the night-mode feature, and 4) gradual decline in BCI use, initially during the night, later also during the day. C) Accuracy (%) of click-commands during research visits (mean ± standard deviation over all click-command-tasks per year). The horizontal lines denote the mean (solid line) ± standard deviation (dashed lines) chance level over all click-command-tasks.

Figure 2.

A) Impedance of electrode pairs E2-E3 (black) and E10–12 (grey), with trend lines for E2-E3 on data after 6 months, and for E10-E12 for data after the replacement surgery, which is indicated by the solid vertical line. The dashed vertical line indicates the change of the at-home use BCI control features from a combination of LFB and HFB power of E2-E3 to a combination of LFB power of E2-E3 and HFB power of E10-E12. B and C) Exemplar slices with the brain tissue (red) and CSF (blue) transparently superimposed on the first (B) and second (C) CT scan. The slices of the two CT scans are exactly matched as a result of the alignment procedure. R and L mark Right and Left hemisphere for all slices. The green box indicates an area that is rich in artefacts due to the implanted electrodes, and a consequently less reliable distinction between brain tissue and CSF.

Figure 2.

A) Impedance of electrode pairs E2-E3 (black) and E10–12 (grey), with trend lines for E2-E3 on data after 6 months, and for E10-E12 for data after the replacement surgery, which is indicated by the solid vertical line. The dashed vertical line indicates the change of the at-home use BCI control features from a combination of LFB and HFB power of E2-E3 to a combination of LFB power of E2-E3 and HFB power of E10-E12. B and C) Exemplar slices with the brain tissue (red) and CSF (blue) transparently superimposed on the first (B) and second (C) CT scan. The slices of the two CT scans are exactly matched as a result of the alignment procedure. R and L mark Right and Left hemisphere for all slices. The green box indicates an area that is rich in artefacts due to the implanted electrodes, and a consequently less reliable distinction between brain tissue and CSF.