The goal of this clinical trial is to determine if non-invasive electrical stimulation, using an electric stimulator placed on the skin of the patients back and abdomen for 30 minutes can reduce muscle spasms (spasticity) and improve walking function in patients with primary lateral sclerosis. Participants will attend one in-person clinic visit and participate in one telephone interview 24 hours after the treatment. The clinic visit will include pre-intervention, treatment and post-intervention assessments. The assessments will consist of a complete physical exam by the clinic neurologist followed by assessments and scoring of spasticity, deep tendon reflexes, gait quality, gait speed, gait endurance and balance. Patient's will rate their perceived spasticity pre, immediately post and 24 hours post treatment.

The treatment involves one 30-minute electrical stimulation session, which includes application of electrode pads to the patients back and abdomen. The patient will lay supine (on their back) with a pillow placed under their knees for comfort. The pads will then be connected to an FDA approved electrical stimulator. The electrical stimulator will be turned on and current adjusted to the individual patient based on small muscle contractions in their legs. Once the current is set, the patient will lay supine for 30 minutes. After 30 minutes, the device will be turned off and electrode pads removed.

Objective: The primary aim of this preliminary pilot study is to assess the clinical effects of transcutaneous electrical stimulation (tES) in reducing spasticity in the lower extremities and increasing mobility in patients with Primary Lateral Sclerosis (PLS).

Study population: 6 patients with a confirmed diagnosis of PLS aged 18-90

Design:

Each enrolled participant will attend one in-person clinic visit and participate in one telephone interview 24 hours post-treatment.

The clinic visit will include pre-intervention, treatment and post-intervention assessments. The assessments will consist of a complete physical exam by the clinic neurologist followed by assessments and scoring of spasticity, deep tendon reflexes, gait quality, gait speed, gait endurance and balance. The patients will rate their perceived spasticity pre, immediately post and 24 hours post treatment.

Treatment will include a 30-minute transcutaneous electrical stimulation (tES) session where tES will be applied through two sets of electrodes positioned adjacent to the T11/T12 spinous processes and a second pair of electrodes placed para-umbilically on the lower abdomen. A current-controlled electrical stimulator will be used to deliver charge-balanced symmetrical, biphasic rectangular pulses to the paraspinal electrodes as the anode for the first phase and as the cathode for the second phase of the stimulation phase.

Electrode placement will be verified by applying electrical stimulation to elicit mild posterior root-muscle (PRM) contractions in the L2-S2 innervated rectus femoris, biceps femoris, tibialis anterior, and triceps surae muscle group bilaterally with the participants relaxed in the supine position. This will be determined by palpation at the patellar and achilles tendons of both sides. While the participants remain supine, the stimulator will be set to continuous mode to deliver stimulation at a frequency of 50 Hz and pulse width of 400 microseconds, then the stimulation amplitude will be slowly increased from 0 milliamp (mA) to an amplitude that may generate minor paraesthesias (slight tingling sensations) in some individuals in the bilateral L2-S2 lower extremity dermatomes but below the level that elicited posterior motor root (PMR) contraction responses. The stimulation amplitude will be individually assessed and set for each participant, and the stimulation amplitude upper limit will be no more than 90% of the lowest PRM response for each participant. After this 30-minute tES session, the tES unit will be turned off, the electrodes removed, and the participants assessed.

Inclusion Criteria:

• Diagnosis of primary lateral sclerosis by the treating neurologist
• Ambulatory with or without a assistive device or orthotic

Exclusion Criteria:

• History of cancer in the lumbar or thoracic spine
• History of surgery with hardware in the lumbar or thoracic spine
• Acute lower back pathology
• Current pregnancy
• History of implantable cardiac device
• Diagnosis of significant cognitive impairment by the treating physician
• History of seizures or diagnosis of epilepsy
• Open wound at location of electrodes
• Complete loss of sensation at the area of electrode placement

This study will provide pilot data to establish a larger, more robust study. The data will be kept internally.