Electrophysiological and Functional Recovery After Carpal Tunnel Release

Carpal tunnel syndrome is the most common peripheral nerve entrapment neuropathy of the upper extremity and results from compression of the median nerve within the carpal tunnel. Patients may experience numbness, tingling, nocturnal paresthesia, pain, sensory loss, reduced grip strength, and, in advanced cases, thenar muscle weakness or atrophy. These impairments may negatively affect sleep, occupational performance, daily activities, and overall upper-extremity function.

Carpal tunnel release surgery aims to decompress the median nerve and is generally performed in patients who do not obtain adequate benefit from conservative treatment or who have progressive neurological or electrophysiological abnormalities. Although improvements in pain, paresthesia, and hand function are commonly observed after surgery, the rate and extent of recovery may vary between patients. Clinical improvement may also occur at a different rate from electrophysiological recovery of the median nerve.

This is a single-center, prospective observational cohort study involving adults with clinically and electrophysiologically confirmed carpal tunnel syndrome who are scheduled to undergo primary carpal tunnel release surgery as part of routine clinical care. The decision to perform surgery and the selection of the surgical technique will be made by the treating physician independently of participation in the study. Participation will not influence the surgical decision or the participant's routine treatment. No experimental intervention or additional treatment will be assigned by the investigators.

Only the surgically treated hand will be included in the analysis. For participants with bilateral carpal tunnel syndrome who undergo unilateral surgery during the study period, the operated hand will be evaluated. Two hands from the same participant will not be analyzed as independent observations.

Clinical and functional evaluations will be performed at baseline before surgery and at postoperative week 8. The evaluations will include the Boston Carpal Tunnel Questionnaire, Quick Disabilities of the Arm, Shoulder and Hand questionnaire, Numeric Rating Scale for pain, grip strength, pinch strength, Semmes-Weinstein monofilament testing, static two-point discrimination, and Tinel and Phalen tests.

Standard nerve conduction study findings obtained during routine clinical evaluation will be recorded at baseline and postoperative month 3. Electrophysiological variables will include median nerve distal motor latency, compound muscle action potential amplitude, sensory distal latency, sensory nerve action potential amplitude, and sensory nerve conduction velocity. Electrophysiological severity will be classified using the Bland neurophysiological grading scale. Needle electromyography will not be mandatory for study participation and will only be performed when clinically indicated as part of routine care.

The primary objective is to determine whether electrophysiological changes in the median nerve between baseline and postoperative month 6 are associated with changes in carpal tunnel symptoms and upper-extremity function. Particular emphasis will be placed on changes in distal motor latency and sensory nerve conduction velocity and their relationships with changes in the Boston Carpal Tunnel Questionnaire and QuickDASH scores.

Secondary analyses will examine the relationships between electrophysiological recovery and changes in pain severity, grip strength, pinch strength, monofilament sensation, and two-point discrimination. The study will also investigate whether demographic and clinical factors, including age, sex, body mass index, symptom duration, hand dominance, operated side, occupational hand use, diabetes mellitus, and preoperative electrophysiological severity, are associated with postoperative clinical, functional, or electrophysiological recovery.

The planned enrollment is approximately 70 to 100 participants. Findings from this study may help clarify the extent to which objective nerve conduction recovery reflects patient-reported and performance-based recovery after carpal tunnel release surgery.

• Primary Carpal Tunnel Release Surgery (Procedure): Participants will undergo primary carpal tunnel release surgery as part of their routine clinical care. The procedure aims to decompress the median nerve by releasing the transverse carpal ligament. The decision to perform surgery, the timing of surgery, and the surgical technique will be determined by the treating physician independently of study participation. The study will not require an experimental surgical technique or any modification of the participant's standard treatment. Participants will undergo clinical and functional follow-up assessments, and median nerve conduction findings will be evaluated before surgery and at postoperative month 6.

Primary outcomes

• Change in Median Nerve Distal Motor Latency [Baseline and postoperative week 8]: Median nerve distal motor latency will be measured by a standardized nerve conduction study and recorded in milliseconds (ms). Change will be calculated as the postoperative month 6 value minus the preoperative value. A reduction in distal motor latency indicates electrophysiological improvement.

Secondary outcomes

• Change in Median Nerve Sensory Nerve Conduction Velocity [Baseline and postoperative week 8]: Median nerve sensory nerve conduction velocity will be measured by a standardized nerve conduction study and recorded in meters per second (m/s). Change will be calculated as the postoperative month 6 value minus the preoperative value. An increase in sensory nerve conduction velocity indicates electrophysiological improvement.
• The Boston Carpal Tunnel Questionnaire consists of the Symptom Severity Scale and the Functional Status Scale. Each item is scored from 1 to 5, and the mean score is calculated separately for each subscale. Higher scores indicate greater symptom severity [Baseline, postoperative week 8]: The Boston Carpal Tunnel Questionnaire consists of the Symptom Severity Scale and the Functional Status Scale. Each item is scored from 1 to 5, and the mean score is calculated separately for each subscale. Higher scores indicate greater symptom severity or functional limitation. Change will be calculated relative to the baseline score. A reduction in score indicates clinical and functional improvement.
• Change in Quick Disabilities of the Arm, Shoulder and Hand Score [Baseline, postoperative week 8]: Upper-extremity disability will be assessed using the Quick Disabilities of the Arm, Shoulder and Hand questionnaire. The total score ranges from 0 to 100, with higher scores indicating greater disability. Change will be calculated relative to the baseline score. A reduction in score indicates improvement in upper-extremity function.
• Change in Median Nerve Sensory Nerve Action Potential Amplitude [Time Frame: Baseline and postoperative month 3]: Description: Median nerve sensory nerve action potential amplitude will be measured by nerve conduction study and recorded in microvolts (µV). Change will be calculated as the postoperative month 3 value minus the baseline value. A higher amplitude generally indicates better sensory nerve function.
• Change in Median Nerve Compound Muscle Action Potential Amplitude [Time Frame: Baseline and postoperative month 3]: Description: Median nerve compound muscle action potential amplitude will be measured by nerve conduction study and recorded in millivolts (mV). Change will be calculated as the postoperative month 3 value minus the baseline value. A higher amplitude generally indicates better motor nerve function.
• Change in Numeric Rating Scale Pain Score [Baseline, postoperative week 8, month 3,]: Description: Hand and wrist pain intensity will be evaluated using an 11-point Numeric Rating Scale ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst imaginable pain. A reduction in score indicates improvement.
• Change in Semmes-Weinstein Monofilament Sensory Threshold [Baseline, postoperative week 8, month 3,]: Description: Touch-pressure sensation will be evaluated using Semmes-Weinstein monofilaments at the thumb, index finger, and middle finger of the operated hand. The lowest monofilament level perceived at each location will be recorded. A lower sensory threshold indicates better touch-pressure sensitivity.
• Change in Static Two-Point Discrimination Distance [Time Frame: Baseline, postoperative week 8, month 3,]: Description: Static two-point discrimination will be evaluated at the index and middle fingertips of the operated hand. The shortest distance at which two separate points can be distinguished will be recorded in millimeters (mm). A reduction in distance indicates improved sensory discrimination. Time Frame: Baseline, postoperative week 6, month 3,

Sex: All, ages: 18 Years to 75 Years

Inclusion Criteria:

* Age between 18 and 75 years.
* Clinical and electrophysiological diagnosis of carpal tunnel syndrome.
* Scheduled to undergo primary carpal tunnel release surgery based on routine clinical evaluation.
* Availability of a preoperative nerve conduction study.
* Ability to understand and complete the study assessments and questionnaires.
* Ability to read and understand Turkish.
* Willingness to participate and provide written informed consent.
* Ability and willingness to attend the planned postoperative follow-up assessments.

For participants with bilateral carpal tunnel syndrome who undergo unilateral surgery during the study period, only the operated hand will be included in the study. Two hands from the same participant will not be analyzed as independent observations.

Exclusion Criteria:

* Previous carpal tunnel release surgery on the study hand.
* Planned revision carpal tunnel surgery.
* Electrophysiological evidence of generalized polyneuropathy.
* Another peripheral neuropathy affecting the median nerve or function of the study hand.
* Active cervical radiculopathy or brachial plexopathy.
* A central or peripheral neurological disorder that substantially affects upper-extremity function.
* History of major trauma or surgery involving the study hand or wrist that may affect outcome assessments.
* Active inflammatory rheumatologic disease.
* Pregnancy.
* Uncontrolled systemic disease that may interfere with surgery, assessment, or follow-up.
* Cognitive or communication impairment that prevents completion of the study assessments.
* Inability to complete the planned postoperative follow-up assessments.

Participants with controlled diabetes mellitus will not be excluded solely because of diabetes. However, participants with electrophysiologically confirmed generalized polyneuropathy will be excluded. Diabetes status will be recorded and considered as a potential confounding variable in the analyses.