The efficacy of median nerve electrical stimulation in rehabilitating post-stroke cognitive impairment and its mechanism

Objective To test the effectiveness of electrical stimulation of the median nerve (MNES) for relieving post-stroke cognitive impairment (PSCI) and explore the possible mechanism. Methods Thirty patients with PSCI were randomly divided into a routine treatment group (the control group) and an MNES group, each of 15. Both groups were given routine rehabilitation treatment, including cognitive rehabilitation training, medications and acupuncture. The MNES group additionally received 30 minutes of MNES on their right hands every day, five times a week for six weeks. One electrode was positioned over the median nerve 2cm up from the rasceta of the right wrist. The other was on the muscles of the thenar eminence. Forty seconds of stimulation were applied with intervals of 20 seconds, for 30 min daily. Before and after 3 and 6 weeks of treatment, both groups were evaluated using the mini-mental state examination (MMSE), the Montreal cognitive assessment (MoCA), the modified Barthel index (MBI) and the Fugl-Meyer assessment (FMA). In another 15 patients oxyhemoglobin levels in the brain before and during the MNES were observed using near-infrared spectroscopy. Results After 3 weeks of treatment, a significant improvement was observed in the average MMSE, FMA and MBI scores of both groups, and the average MoCA score of the observation group. Three weeks later, the average MMSE, FMA, MBI and MoCA scores of both groups had improved significantly compared with before the treatment, with the average MMSE and MoCA improvements in the MNES group significantly greater than the control group′s averages. After 6 weeks of treatment the significant improvements persisted in both groups. Both group′s average FMA scores had also improved significantly, as had the average MBI score of the control group. After 6 weeks of treatment, the observation group′s average time orientation, location orientation, language instant memory, attention, calculation and short-term memory in MMSE had all improved significantly along with visual space capacity, executive capacity, attention, language, orientation and memory in MoCA. The spectroscopic results showed significantly improved oxyhemoglobin concentration in the bilateral frontal lobes after the MNES. Conclusions Electrical stimulation of the median nerve can help to improve cognition after a stroke. It increases oxyhemoglobin concentration in the bilateral frontal lobes. Key words: Median nerves; Electrical stimulation; Stroke; Cognitive impairment; Rehabilitation