Neural Prostheses and Gait Performance: Model-Based Strategies

Inclusion Criteria:

This study includes stroke survivors greater than 18 years of age, >180 days from first clinical hemorrhagic or nonhemorrhagic stroke with:

• Unilateral hemiparesis with sufficient endurance and motor ability to ambulate >30 feet continuously without an AFO requiring no more than 25% physical help
• Berg Balance Scale score >23 without assistive devices
• Standing ankle dorsiflexion strength of <4/5
• Foot-drop during ambulation with gait instability or inefficient gait defined as supervision need
• Possible use of physical assistance or assistive device (cane, walker)
• Evidence of foot-drop as seen by "dragging" or "catching" of affected toes during limb swing or circumducting affected limb
• Vaulting of the unaffected limb or hiking the affected hip to clear toes.
• Intact and electrically ex-citable lower motor neurons
• Ankle dorsiflexion to at least neutral while standing with electrical stimulation of common peroneal and tibial nerves without painful hypersensitivity to stimulation
• Adequate social support and stability
• Medically stable with intact skin in affected lower limb
• Willingness to comply during research procedures
• No systemic co-morbidities
• No history of potentially fatal cardiac arrhythmias i.e. ventricular tachycardia, supraventricular tachycardia and rapid ventricular response atrial fibrillation with hemodynamic instability
• No psychological problems or chemical dependency
• No acute medical complications such as depression or chronic anxiety requiring long term pharmacological therapy. Able-bodied controls must be of similar age, body mass and stature as those with hemiparesis and must be free of any medical and disabling orthopedic problems.

Exclusion Criteria:

In addition to failure to meet the inclusion criteria, participants will be excluded from the study for the following:

• Requires an AFO to prevent knee flexion collapse in stance
• Excessive edema of affected extremity
• Absent sensation in affected limb
• History of potentially fatal cardiac arrhythmias such as ventricular tachycardia, supraventricular tachycardia, and rapid ventricular response, atrial fibrillation with hemodynamic instability
• Demand pacemakers or any implanted electronic systems
• Pregnancy
• Uncontrolled seizure disorder
• Ipsilateral lower limb lower motor neuron lesion
• Parkinson's disease
• Spinal cord injury
• Traumatic brain injury
• Multiple sclerosis
• Ankle plantar flexor contraction
• Severely impaired cognition and communication
• Painful hypersensitivity to neuromuscular stimulation of common peroneal nerve
• Knee hyperextension (genu recurvatum) that cannot be adequately corrected with peroneal nerve stimulation
• History of botulinum toxin to the lower extremity within the prior three months.