PENS vs TENS for Hand Function in Multiple Sclerosis

Multiple sclerosis frequently affects upper-limb function due to sensorimotor impairments, leading to reduced manual dexterity, impaired coordination, decreased pinch strength, and altered tactile sensitivity. These deficits may limit performance in activities of daily living and reduce functional independence. Peripheral neuromodulation techniques have been increasingly used in neurorehabilitation as complementary interventions to improve sensorimotor function. However, direct comparative evidence between transcutaneous electrical nerve stimulation (TENS) and percutaneous electrical nerve stimulation (PENS) for hand function in people with multiple sclerosis remains limited.

This study is a randomized, parallel, single-blind clinical trial designed to compare the immediate and short-term effects of TENS and PENS applied simultaneously to the median, radial, and ulnar nerves in individuals with multiple sclerosis. Participants are allocated in a 1:1 ratio to one of two intervention groups. The assessor is blinded to group assignment. Assessments are performed at baseline, immediately after the intervention, and 72 hours after treatment.

The PENS intervention is delivered using sterile 0.25 × 25 mm needles connected to an electrical stimulation device, with low-frequency stimulation (2-4 Hz), sensory intensity with mild motor response, and a treatment duration of 15 minutes. The TENS intervention is applied using surface electrodes placed over the anatomical pathways of the median, radial, and ulnar nerves, with a frequency of 35-50 Hz, pulse duration of 200-350 microseconds, intensity increased gradually until a visible painless muscle contraction is achieved, and a treatment duration of 15 minutes. Both interventions are applied according to standardized anatomical landmarks.

The primary outcome is fine manual dexterity measured with the Nine Hole Peg Test (NHPT). Secondary outcomes include gross manual dexterity measured with the Box and Block Test (BBT), pinch strength measured with a pinch dynamometer, and tactile sensitivity assessed with Semmes-Weinstein monofilaments. The objective is to determine whether PENS provides additional benefit over TENS in improving hand function in people with multiple sclerosis.

Inclusion criteria

• Diagnosis of multiple sclerosis according to McDonald criteria.
• Age between 18 and 80 years.
• Clinically stable for at least 2 months before enrollment.
• No recent corticosteroid treatment.
• Functional ability to complete the study assessments, defined as a Nine Hole -Peg Test time of less than 300 seconds and the ability to transfer at least 1 block in the Box and Block Test.
• Ability to understand the study procedures and provide written informed consent.

Exclusion criteria

• Musculoskeletal disorders or injuries affecting the upper limb.
• Implanted electrical devices.
• Skin lesions or dermatological conditions at the stimulation sites.
• Cognitive impairment that interferes with understanding or performing the assessments.
• Recent relapse or any concomitant neurological condition that could interfere with study participation or evaluation.