Ross Davis

Therapeutic Effectiveness of Electric Stimulation of the Upper-Limb Poststroke Using Implanted Microstimulators

OBJECTIVE To investigate the therapeutic effect of functional exercise augmented by programmable implanted microstimulators on arm and hand function. DESIGN Before and after study. SETTING Implantation was performed in a neurosurgery unit, systems were programmed, and tests were conducted in a university laboratory and subjects exercised at home. PARTICIPANTS Hemiparetic subjects (N=7) with reduced upper-limb function who were at least 12 months poststroke were recruited from the community. No subjects withdrew. INTERVENTION Microstimulators were implanted into the arms and forearms to activate elbow, wrist, and finger extension, and thumb abduction. After training and programming of the system, subjects underwent 12 weeks of functional home-based exercise with stimulation. MAIN OUTCOME MEASURES The primary functional measure was the Action Research Arm Test (ARAT). Impairment measures included upper-limb Fugl-Meyer Assessment (FMA) and tests of motor control (tracking index), spasticity (electromyography stretch index) strength, and active range of motion (AROM). The assessor was not blinded, but scores were validated by an independent blinded observer. RESULTS All subjects were able to perform functional activities at home by using the system. Compliance was excellent, and there were no serious adverse events. Statistically significant improvements were measured (P<.05) in the tracking index (57.3 degrees(2)+/-48.65 degrees(2)), FMA score (6.3+/-3.59), wrist-extensor strength (5.5+/-4.37 N), and wrist AROM (19.3 degrees +/-18.96 degrees). The mean improvement in ARAT score +/- SD of 4.9+/-7.89 was not statistically significant. CONCLUSIONS This study has shown the feasibility of a programmable implanted microstimulator system used at home to perform functional exercises and a reduction in impairment after 12 weeks.

Control of Spasticity and Involuntary Movements – Cerebellar Stimulation

By stimulating the medial aspect of the superior surface of the cerebellum with relatively short, low current stimulating pulses, spasticity and some involuntary movements have been reduced. Voluntary movements, as a result, are able to come through better; however, if the child has little voluntary ability, he is at least more relaxed, thus allowing the parents to care for him more easily. The children and adults with cerebral palsy have not been transformed from their previous status, although CCS has allowed them to become more independent, more ambulatory, and more communicative.

A Personalized Sensor‐Controlled Microstimulator System for Arm Rehabilitation Poststroke. Part 1: System Architecture

Objectives:  For rehabilitation of the poststroke upper limb in seven subjects, an external sensor‐based system controls the timing of five to seven microstimulators implanted near radial nerve branches or their motor points to sequentially extend the elbow, wrist, and fingers with thumb extension and abduction, enabled at the subjects own pace. We hypothesize this system will support sequential activation of affected upper limb muscles intended to improve functional recovery.

Cerebellar stimulation for spastic cerebral palsy: preliminary report; on-going double blind study.

To date, June 1, 1986, 33 spastic cerebral palsy (CP) patients have taken part in a double blind study testing the safety and efficacy of chronic cerebellar stimulation (CCS) for reduction of spasticity and improvement in function. Seven U.S. surgical centers involving ten neurosurgeons have implanted the Neurolith 601 cerebellar stimulator supplied by Pacesetter Systems Inc. (Sylmar, CA). A pilot study was run with three patients at Stanford University (Stanford, CA) using taped‐on real (strong) and dummy (weak) magnets to control the ON‐OFF status. Following the pilot study, a magnetically controllable switch was placed in line between the Neurolith stimulator and the cerebellar lead to allow more reliable switching sequences for the study. The test battery included joint angle measurements (passive and active), motor performance testing, reaction time, hand dynamometry, grooved peg board placement, hand/foot tapping, and rotary pursuit testing. Testing only was done at presurgery. Testing and ON‐OFF switching was performed following recovery from surgery and at one, two, and four months. After four months, the switch was left turned ON. Of the 30 patients using the implanted switch, 11 were dropped from the study and seven are still in progress. Of the 11 dropped from the study, four were due to switch problems and three were due to double blind protocol violations, i.e., the participants discovered the stimulus status. The remaining four were removed because of a broken lead, infection, or unrelated medical problems, or refusal to participate after implant. A preliminary analysis indicated that three‐quarters of the patients have a demonstrable quantitative improvement during the time the stimulation was “ON.” Three patients showed no significant change.

Bioengineering changes in spastic cerebral palsy groups following cerebellar stimulation.

Quantitative bioengineering tests were performed on 30 spastic cerebral palsy (CP) patients who underwent chronic cerebellar stimulation (CCS) using the fully implantable pulse generator (Neurolith 601, 1.1-1.8 microC/cm2/phase). Using respiratory inductive plethysmography to measure 8 patients with paroxysmal and/or ataxic breathing patterns, 5 were shown to revert to normal with 3 others markedly improved within 5 months of CCS. Compliance testing of the ankle was performed on 4 patients who showed improvement in 9 of the 16 tests performed. Motor performance ability was evaluated with 9 comprehensive tests in 17 patients. Following 1-2 weeks of CCS, 52% showed performance increases greater than 10%, increasing to 62% during the first year.