Electromyographic and Morphological Evaluation of the Palmaris Longus Muscle Variant and Its Association with Median Nerve Compression

International Journal of Anatomy and Physiology | Vol. 15, No. 11, November 2026 | pp. 244–252

DOI: 10.46882/2026/IJAP/001028

Research Article

Title: Electromyographic and Morphological Evaluation of the Palmaris Longus Muscle Variant and Its Association with Median Nerve Compression

Names of Authors: R. E. Dubois¹, S. M. Patel², O. A. Sanusi³*

Authors’ Affiliations:
¹ Department of Anatomy, Faculty of Medicine, Sorbonne University, Paris, France.
² Department of Radiology, All India Institute of Medical Sciences, New Delhi, India.
³ Department of Anatomy, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Ibadan, Nigeria.

Abstract:
The palmaris longus muscle is a superficial flexor of the forearm known for its high rate of evolutionary agenesis and structural variations, including duplicated, reversed, or hypertrophied muscle bellies. These muscular anomalies can reduce the available space within the proximal forearm and carpal tunnel, compressing the median nerve. This study combined cadaveric dissection and surface electromyography (sEMG) to examine the morphological variations of the palmaris longus and evaluate their functional association with median nerve compression. Dissection of 100 formalin-fixed upper limbs revealed palmaris longus variants in 6 extremities (6.0%). A reversed palmaris longus (muscle belly located distally near the wrist) was identified in 2 limbs (2.0%). In the clinical phase, eight symptomatic patients diagnosed with a reversed or hypertrophied palmaris longus via musculoskeletal ultrasound underwent sEMG and nerve conduction velocity (NCV) testing. The sEMG evaluation during sustained grip tasks demonstrated a high root-mean-square (RMS) voltage over the anomalous muscle distal belly, which correlated with a significant reduction in median nerve sensory conduction velocity across the wrist joint (38.5 ± 3.4 m/s vs. 54.2 ± 4.1 m/s in normal controls; p < 0.01). These anatomical and neurophysiological findings demonstrate that structural palmaris longus variants can cause mechanical median nerve entrapment, and should be considered in the differential diagnosis of atypical carpal tunnel syndrome.

Keywords: Palmaris longus muscle, Anatomical variant, Median nerve compression, Carpal tunnel syndrome, Electromyography.

Manuscript Timeline: Received: September 02, 2026; Revised: October 18, 2026; Accepted: November 05, 2026; Published: November 26, 2026.

Citation: Dubois RE, Patel SM, Sanusi OA. Electromyographic and Morphological Evaluation of the Palmaris Longus Muscle Variant and Its Association with Median Nerve Compression. International Journal of Anatomy and Physiology. 2026; 15(11): 244–252. doi:10.46882/2026/IJAP/001028

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