31/08/2025
Case Discussion: -
Pronator Teres Syndrome
Title: A Case of Wrist Pain and Weakness: Looking Beyond the Carpal Tunnel
Chief Complaint: "Aching pain in my right forearm and numbness in my thumb that's getting worse, along with weakness in my grip."
History of Present Illness:
A 45-year-old, right-handed female administrative assistant presents with a 6-month history of progressive right forearm discomfort. She describes the pain as a deep, aching sensation in the proximal volar (front) aspect of her forearm, exacerbated by repetitive pronation and supination motions (e.g., using a screwdriver, pouring from a heavy pot). She also reports numbness and paresthesia (tingling) in her thumb, index finger, and middle finger.
Recently, she has noticed significant difficulty with tasks requiring fine motor skills, such as buttoning her shirt and writing. She has dropped her coffee cup on several occasions due to a loss of grip strength. She denies neck pain, recent trauma, or similar symptoms in the contralateral hand.
Relevant Risk Factors:
Repetitive Pronation/Supination: Her job involves extensive data entry and frequent filing of heavy, bound manuals, which requires a forceful pronation motion.
Anatomical Variants:
(Theoretical, but a common RF) Potential fibrous bands or a tight tendinous arch of the Flexor Digitorum Superficialis muscle.
Muscular Hypertrophy: Possible hypertrophy of the Pronator Teres muscle itself from repetitive use.
Physical Examination:
Inspection: Mild, but noticeable atrophy of the thenar eminence is observed on the right hand compared to the left.
Palpation: Tenderness to deep palpation over the Pronator Teres muscle belly in the proximal forearm. No tenderness at the volar wrist crease (over the carpal tunnel).
Sensory Exam: Diminished light touch and pinprick sensation in the thumb, index, and middle fingers (the median nerve distribution). Crucially, sensation is also diminished over the thenar eminence.
Motor Exam:
4/5 strength in thumb abduction and opposition.
4/5 strength in flexion of the index finger DIP joint (Flexor Digitorum Profundus) and IP joint of the thumb (Flexor Pollicis Longus).
Provocative Tests:
Tinel's Sign: Negative at the wrist. Positive when percussed over the Pronator Teres muscle in the forearm.
Phalen's Test: Negative.
Pronator Compression Test (PCT): Positive. Resistance to forced pronation and flexion of the elbow against resistance for 30 seconds reproduces her pain and paresthesia.
Resisted Flexion of the Superficialis to the Middle Finger: Positive. Reproduction of symptoms.
Electrodiagnostic Studies (EMG/NCS):
Nerve Conduction Studies (NCS): Showed slowed sensory and motor conduction across the forearm segment (through the Pronator Teres). Distal motor and sensory latencies across the wrist (carpal tunnel) were within normal limits.
Electromyography (EMG): Revealed active denervation (fibrillation potentials, positive sharp waves) and chronic reinnervation changes in the Pronator Teres muscle itself, the Flexor Pollicis Longus, and the Abductor Pollicis Brevis.
Diagnosis: Pronator Teres Syndrome (Median Nerve Entrapment at the Elbow/Forearm)
Discussion: PTS vs. CTS - Atrophy, Numbness, and Key Differentiators
This case exemplifies the classic presentation of Pronator Teres Syndrome (PTS) and highlights its critical distinctions from the more common Carpal Tunnel Syndrome (CTS). The confusion arises because both conditions involve compression of the median nerve, but at different locations.
1. The Critical Anatomical Difference:
CTS: Compression occurs at the wrist, within the rigid carpal tunnel.
PTS: Compression occurs in the proximal forearm, typically under the Pronator Teres muscle or the fibrous arch of the Flexor Digitorum Superficialis.
2. The "Thenar Atrophy AND Thenar Numbness" Paradox (The Key Differentiator):
This is the most reliable clinical feature to distinguish PTS from CTS.
In Carpal Tunnel Syndrome (CTS):
The palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel and travels over it. Therefore, it is not compressed in CTS.
Result: Patients with CTS have thenar muscle atrophy and weakness (due to compression of the motor branch within the tunnel) but preserved sensation over the thenar eminence itself. They feel numbness in the digits, but not on the palm at the base of the thumb.
In Pronator Teres Syndrome (PTS):
The compression site is proximal to the origin of the palmar cutaneous branch. This branch, along with the main trunk and the anterior interosseous nerve branch, is affected.
Result: Patients with PTS experience BOTH thenar muscle atrophy/weakness AND sensory loss over the thenar eminence. This is a hallmark sign that the lesion is proximal to the wrist.
3. Nature of Pain and Provocative Maneuvers:
CTS Pain: Typically nocturnal, burning, tingling, centered at the wrist and hand, often relieved by shaking the hand.
PTS Pain: Aching, exertional pain localized to the proximal forearm, exacerbated by repetitive pronation/supination. Provocative tests like the Pronator Compression Test are positive, while Phalen's and Tinel's at the wrist are negative.
4. Motor Involvement:
CTS: Only affects muscles distal to the wrist (Abductor Pollicis Brevis, Opponens Pollicis, superficial head of Flexor Pollicis Brevis).
PTS: Can also affect the Pronator Teres (though weakness may be masked by the Pronator Quadratus), Flexor Carpi Radialis, Flexor Digitorum Superficialis, and the anterior interosseous nerve-innervated muscles (Flexor Pollicis Longus, Flexor Digitorum Profundus for index/middle, Pronator Quadratus). This explains the weakness in thumb and index finger flexion seen in our case.
A. Conservative (First-Line) Management
Activity Modification & Rest: Avoid repetitive pronation, gripping, and elbow flexion; workplace ergonomics.
Splinting: Long-arm splint (elbow 90°, forearm neutral), especially at night or during aggravating tasks.
Physical/Occupational Therapy:
Modalities: ultrasound, iontophoresis, soft tissue mobilization.
Stretching: Pronator Teres and forearm flexors.
Strengthening: Shoulder/scapular stabilizers after pain subsides.
Pharmacological:
NSAIDs for pain/inflammation.
Corticosteroid injection (diagnostic + therapeutic).
B. Surgical Management
Indications:
Failed conservative treatment (≥3–6 months).
Progressive/severe weakness or atrophy.
Procedure: Median nerve decompression:
Release lacertus fibrosus.
Free fibrous bands in Pronator Teres.
Possibly divide superficial head of Pronator Teres or FDS tendinous arch.
Outcome: Good pain/paresthesia relief; motor recovery may be incomplete if longstanding.
S.D Physiotherapy and rehabilitation center.
Physio Syed Didar.
