Carpal Tunnel Syndrome (CTS) frequently affects both hands, a condition known as bilateral CTS. This simultaneous or sequential compression of the median nerve in both wrists is common, occurring in over half of all cases. CTS is fundamentally a nerve entrapment issue where the median nerve is compressed as it passes through a narrow passageway in the wrist.
The Mechanism of Carpal Tunnel Syndrome
The carpal tunnel is a tight space in the wrist formed by the small carpal bones and the transverse carpal ligament, which acts as the roof. This tunnel houses the median nerve and nine flexor tendons that control finger movement. Normal pressure within this tunnel is quite low.
Compression occurs when pressure inside this space rises, interrupting the blood flow and nerve signaling of the median nerve. This pressure increase is often caused by swelling of the synovial tissue surrounding the tendons or by fluid retention. Systemic health conditions are a major factor in bilateral presentation because they affect the entire body simultaneously.
Conditions like diabetes and thyroid disorders, particularly hypothyroidism, are strongly associated with CTS in both wrists. Inflammatory conditions such as rheumatoid arthritis cause the tissue around the tendons to swell, increasing pressure on the nerve. Pregnancy is another common cause of temporary bilateral CTS due to hormonal changes leading to generalized fluid retention.
Recognizing Bilateral Symptoms
Symptoms manifest when the compressed median nerve can no longer transmit sensory information. This results in the characteristic feeling of numbness, tingling, and pain. These sensations are felt in the thumb, index finger, middle finger, and the thumb-side half of the ring finger, which are the areas supplied by the median nerve.
The symptoms often follow a recognizable pattern, frequently worsening at night or upon waking. Many people unconsciously sleep with their wrists bent, which increases pressure on the nerve. Patients often report the need to “shake out” their hands to find temporary relief from the numbness or tingling.
When the condition is caused by systemic issues, both median nerves are stressed by the same underlying pathology, leading to bilateral symptoms. Symptoms may begin gradually and often present more severely in the dominant hand, but the non-dominant hand is likely to develop symptoms as well. As the condition progresses, a weakened grip, clumsiness, and difficulty with fine motor tasks, like buttoning a shirt, can occur in both hands.
Diagnosis and Treatment Pathways
Diagnosis of Carpal Tunnel Syndrome begins with a detailed physical examination that includes specific provocative tests. These maneuvers attempt to temporarily increase pressure on the median nerve to reproduce the characteristic symptoms. Two common examples are Tinel’s sign, where tapping over the median nerve at the wrist elicits tingling, and Phalen’s maneuver, where holding the wrist in a flexed position brings on symptoms.
For moderate or severe cases, electrodiagnostic studies are used for treatment planning. Nerve conduction studies measure how quickly electrical signals travel down the median nerve, revealing slowing that indicates compression. Electromyography (EMG) may also be performed to assess the health of the muscles controlled by the nerve.
Initial management for mild to moderate CTS is conservative, focusing on reducing pressure and inflammation. Nighttime wrist splinting is a common first step, preventing the wrist from flexing during sleep and relieving pressure. Corticosteroid injections delivered into the carpal tunnel can reduce localized swelling and provide months of relief, often delaying the need for surgery.
Surgical intervention, known as carpal tunnel release, is considered when conservative treatments fail or when nerve damage is severe. The procedure involves cutting the transverse carpal ligament to increase the space within the tunnel and permanently relieve pressure on the median nerve. This surgery can be performed using an open technique or an endoscopic, minimally invasive approach, with both methods providing similarly effective long-term results.