Pronator syndrome is a relatively rare compression neuropathy of the upper limb that results from entrapment of the median nerve as it traverses the proximal forearm, specifically through or around the pronator teres muscle before the two heads of the muscle merge [1–5]. First described as a distinct clinical entity in the mid-20th century, this syndrome is now part of a broader group of proximal median nerve compressions, which includes anterior interosseous nerve syndrome and compression at the ligament of Struthers. Though less common than carpal tunnel syndrome, pronator syndrome is

clinically relevant due to its similar symptomatology and the diagnostic challenges it poses [1,3,4].

Anatomically, several sites within the proximal forearm can be responsible for the compression of the median nerve. These include the supracondylar process of the humerus with the ligament of Struthers, a thickened bicipital aponeurosis (lacertus fibrosus), the fibrous arch of the flexor digitorum superficialis, and most commonly, hypertrophy or fibrotic changes in the pronator teres muscle itself [2,3,5]. Inflammatory, neoplastic, or iatrogenic factors may also contribute to nerve entrapment, including Schwannomas, scar tissue following trauma, or repetitive microtrauma in high-risk occupations [1,3].

In most cases, the etiology is associated with repetitive movements involving forearm pronation and supination, frequently observed in occupational activities such as construction work, cleaning, carpentry, and assembly line tasks. Athletes—especially tennis players, rowers, and weightlifters—may also be affected due to the repeated mechanical stress exerted on the forearm musculature [1,3,4,6]. Less commonly, pronator syndrome may occur following direct trauma, in the presence of space- occupying lesions, or in dialysis patients undergoing chronic anticoagulant therapy [1].

Epidemiological data suggest a higher prevalence in females, particularly between the ages of 40 and 50 years [2,3,5]. The clinical picture is often non-specific and includes pain or discomfort in the proximal volar forearm, frequently exacerbated by resisted pronation or elbow flexion. A positive Tinel sign at the proximal pronator teres insertion, as well as paresthesia or numbness in the distribution of the median nerve—particularly affecting the thenar eminence, thumb, index, and middle fingers—are commonly reported [1,2,4]. These symptoms frequently mimic carpal tunnel syndrome, making accurate diagnosis more difficult and sometimes delayed [1,3,5].

Diagnosis is primarily clinical, based on history and physical examination. Provocative tests such as the pronator compression test and resisted pronation with elbow flexion are useful for reproducing symptoms [2,4,5]. However, electromyography often yields normal results, with detectable abnormalities in only around 10% of cases, which contributes to underdiagnosis [1–4]. In some cases, the Phalen test, typically used for carpal tunnel syndrome, may also be positive, adding to diagnostic confusion [1,4].

Treatment typically begins with conservative measures, especially in mild to moderate cases. This includes rest, avoidance or modification of aggravating activities, the use of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), physiotherapy aimed at stretching and nerve gliding exercises, and local infiltrations with corticosteroids or anesthetics when appropriate [2–4]. Ergonomic adjustments in occupational settings may also be beneficial. If conservative therapy fails to achieve symptom resolution after a reasonable trial period—typically several weeks—surgical intervention may be indicated. Decompression surgery involves releasing the median nerve at all possible entrapment sites within the proximal forearm [1,2]. Postoperative outcomes are generally favorable, with symptom resolution occurring in most patients within 3 to 6 weeks after decompression [1,6].