From the Guidelines
The median nerve plays a crucial role in hand motor function, controlling muscles responsible for thumb opposition, abduction, and flexion, as well as the first and second lumbrical muscles, enabling precise movements like pinching and gripping objects. The median nerve's motor function is essential for the thenar eminence, which is the muscle group at the base of the thumb, and it also provides sensation to the thumb, index, middle, and half of the ring finger 1. Damage to the median nerve can result in characteristic deficits such as weakness in thumb opposition, difficulty making an "OK" sign, and the classic "ape hand" deformity in severe cases. This deformity features a flattened thenar eminence and the thumb aligned with other fingers rather than opposed. Some of the key conditions that can affect median nerve function include:
- Carpal tunnel syndrome
- Pronator teres syndrome
- Anterior interosseous syndrome Treatment for these conditions depends on the cause but may include rest, splinting, anti-inflammatory medications, corticosteroid injections, or surgery in severe cases, as noted in the evaluation of chronic hand and wrist pain 1. Early intervention is crucial to prevent permanent muscle atrophy and loss of hand function. Ultrasound (US) can be used to evaluate tendon and soft tissue pathology of the wrist and to assess for entrapment of the median or ulnar nerves, providing valuable diagnostic information 1.
From the Research
Hand Motor Function Associated with the Median Nerve
The median nerve is responsible for controlling several important hand motor functions, including:
- Pronation of the forearm 2
- Flexion of the wrist, thumb, index finger, and middle finger 2
- Antepulsion and opposition of the thumb 2
- Sensation for the palmar aspect of the first three fingers 2
Motor Impairments Associated with Median Nerve Damage
Damage to the median nerve can result in severe impairment of hand functions, including:
- Weakness or paralysis of the thenar muscles, leading to loss of thumb opposition and flexion 3, 4
- Impaired sensation in the hand, particularly in the palmar aspect of the first three fingers 2
- Reduced grip strength and dexterity 3, 4
Diagnostic and Treatment Approaches
Diagnostic methods for median nerve damage include:
- Clinical evaluation 4
- Electrophysiological testing, such as nerve conduction studies and electromyography 4, 5
- High-resolution ultrasound imaging 4 Treatment approaches may involve:
- Reconstructive surgery to restore motor and sensory function 3, 6
- Nerve transfers, such as distal median to ulnar nerve transfer 6
- Occupational therapy to improve hand function and dexterity 5