Stimulation-Based Modulation of Spinal and Cortical Sensory Pathways

Stimulation Evoked Primary Afferent Depolarization to Modulate Sensory Transmission to Spinal Motoneurons and the Sensory Cortex

The goal of this study is to assess cervical (neck) reflexes by intra-operatively stimulating the neck nerve roots to evoke motor responses through their connections to spinal motoneurons. This data is critical to reveal changes to the spinal sensory modulating circuitry in neurological disorders like stroke.

Spinal afferents continuously convey sensory information on limb movements to the central nervous system which not only gives people conscious experience of movement, but also plays a major role in shaping motor output through monosynaptic afferent-motoneuronal connections. Stroke induces changes in the spinal circuitry modulating this sensory input, leading to sensorimotor deficits.

Specifically, the investigators will 1) activate the dorsal root fibers with single and double electrical stimulation pulses at various frequencies using FDA-cleared devices, 2) quantify the stimulation evoked motor potentials in arm and hand muscles recorded with intramuscular EMGs, 3) quantify stimulation evoked sensory potentials in the cortex with intra-op EEGs.

Inclusion Criteria:

• All Subjects: Ages between 21 and 75 years. The minimum age is selected to age match control subjects with stroke subjects. In addition, participants outside this age range may be at an increased medical risk.
• Control subjects: Patients undergoing elective posterior cervical spinal surgery that includes a decompressive laminectomy, and who will have electrophysiological monitoring performed as part of the standard of care for their procedure.
• Stroke subjects: Participants must have a suffered a single, ischemic or hemorrhagic stroke more than 6 months prior to the time of enrollment with hemiparesis as a result, is undergoing a cervical epidural lead implant or undergoing elective posterior cervical spinal surgery that includes a decompressive laminectomy with electrophysiological monitoring performed as part of the standard of care.

Exclusion Criteria:

• Patients will be excluded from the study if they have any known neurological diseases other than stroke, such as amyotrophic lateral sclerosis, spinal muscular atrophy, spinal cord injury, autoimmune neuropathy, or sensory nerve disorders, that may affect the integrity of cervical sensory afferents.
• Only patients that are eligible for surgery will be enrolled. Therefore this automatically include as exclusion criteria: pregnancy and other clinical conditions eligible for surgery.
• Participants must not be on anti-spasticity or anti-epileptic medications.