Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a common entrapment neuropathy resulting from compression of the median nerve at the wrist. It affects hand function and can significantly impair daily activities, particularly in individuals engaged in repetitive manual tasks. Early recognition and management are essential to prevent permanent nerve damage.

Anatomy of the Carpal Tunnel

Bones and Ligaments

The carpal tunnel is a narrow, rigid passage in the wrist formed by the carpal bones and the transverse carpal ligament. The carpal bones create the floor and sides of the tunnel, while the transverse carpal ligament forms the roof, maintaining stability and protecting the contents of the tunnel.

Median Nerve

The median nerve passes through the carpal tunnel, providing motor and sensory innervation to the thenar muscles and the lateral three and a half fingers. Compression of this nerve is the primary pathological mechanism in CTS.

Tendons and Muscles Passing Through the Tunnel

The carpal tunnel contains nine flexor tendons of the fingers and thumb. These include the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus tendons. The tendons are enclosed in synovial sheaths that facilitate smooth movement. Swelling or inflammation of these structures can increase pressure within the tunnel, contributing to nerve compression.

Definition and Classification

Primary vs Secondary CTS

Primary CTS occurs idiopathically without an identifiable external cause, often associated with anatomical predispositions or age-related changes. Secondary CTS results from identifiable conditions that increase pressure within the carpal tunnel, such as trauma, arthritis, pregnancy, or space-occupying lesions.

Acute vs Chronic CTS

Acute CTS develops rapidly, often following injury or inflammation, and presents with sudden onset of symptoms. Chronic CTS progresses slowly over months to years and is characterized by gradual onset of numbness, tingling, and weakness in the affected hand.

Severity Grading

CTS can be classified based on clinical and electrodiagnostic findings:

• Mild: Intermittent symptoms with minimal functional impairment.
• Moderate: Persistent symptoms with measurable sensory deficits or mild motor weakness.
• Severe: Constant symptoms with significant sensory loss, marked thenar atrophy, and severe motor dysfunction.

Etiology and Risk Factors

Occupational and Repetitive Activities

Repetitive hand and wrist movements, prolonged use of vibrating tools, and tasks requiring sustained wrist flexion or extension can increase the risk of CTS. Occupations such as assembly line work, typing, and manual labor are commonly associated with higher prevalence.

Medical Conditions

• Diabetes Mellitus: Peripheral neuropathy and microvascular changes can predispose to median nerve compression.
• Hypothyroidism: Accumulation of mucopolysaccharides may lead to swelling within the carpal tunnel.
• Rheumatoid Arthritis: Inflammatory synovitis can increase pressure within the tunnel.
• Pregnancy: Fluid retention during pregnancy can contribute to transient CTS symptoms.

Anatomical Predispositions

Variations in carpal tunnel size, wrist bone alignment, or median nerve course can predispose individuals to CTS. Women generally have smaller carpal tunnels, which may explain higher incidence compared to men.

Other Risk Factors

Additional risk factors include obesity, previous wrist fractures, kidney disease requiring dialysis, and genetic factors that may influence connective tissue structure and nerve susceptibility.

Pathophysiology

Median Nerve Compression

CTS occurs primarily due to increased pressure within the carpal tunnel, compressing the median nerve. This compression impairs nerve conduction, leading to sensory and motor disturbances in the hand.

Ischemia and Nerve Damage

Prolonged compression reduces blood flow to the median nerve, causing ischemia. Ischemic nerve fibers exhibit demyelination and eventual axonal degeneration, resulting in persistent numbness, weakness, and muscle atrophy if left untreated.

Inflammatory and Edematous Changes

Inflammation of flexor tendons or synovial sheaths within the carpal tunnel can exacerbate nerve compression. Edema and swelling increase intratunnel pressure, further compromising nerve function and contributing to symptom progression.

Clinical Presentation

Symptoms

• Paresthesia and Numbness: Tingling or numbness in the thumb, index, middle, and radial half of the ring finger, often worse at night.
• Pain and Burning Sensation: Pain may radiate from the wrist to the forearm or shoulder, with burning or aching sensations.
• Weakness and Clumsiness: Difficulty gripping objects, dropping items, or performing fine motor tasks due to thenar muscle involvement.

Signs

• Tinel Sign: Tingling in the median nerve distribution when tapping over the carpal tunnel.
• Phalen Maneuver: Symptom reproduction when the wrist is fully flexed for 60 seconds.
• Thenar Muscle Atrophy: Visible wasting of the thenar eminence in chronic or severe cases.

Impact on Daily Life

CTS can significantly impair activities such as typing, writing, gripping tools, and household chores. Persistent symptoms may lead to sleep disturbances, decreased work productivity, and reduced overall quality of life.

Diagnostic Evaluation

Clinical Examination

Diagnosis begins with a thorough history and physical examination. Key aspects include symptom distribution, duration, aggravating and relieving factors, and assessment of motor and sensory function in the hand.

Electrodiagnostic Studies

• Nerve Conduction Studies: Measure conduction velocity and latency of the median nerve to confirm compression and assess severity.
• Electromyography: Evaluates electrical activity of muscles innervated by the median nerve, detecting denervation or chronic neuropathic changes.

Imaging

• Ultrasound: Visualizes median nerve swelling and structural abnormalities within the carpal tunnel.
• MRI: Provides detailed assessment of soft tissues and can identify space-occupying lesions contributing to compression.

Differential Diagnosis

Conditions that can mimic CTS include cervical radiculopathy, pronator teres syndrome, peripheral neuropathy, thoracic outlet syndrome, and arthritis affecting the wrist or hand joints. Accurate diagnosis is essential for appropriate management.

Management and Treatment

Conservative Management

Initial treatment for mild to moderate CTS often involves non-invasive strategies aimed at reducing nerve compression and relieving symptoms.

• Activity Modification: Avoid repetitive wrist movements and positions that exacerbate symptoms.
• Splinting: Wrist splints, especially worn at night, maintain a neutral position to decrease pressure on the median nerve.
• Physical Therapy: Exercises to improve wrist flexibility, strengthen forearm muscles, and enhance nerve gliding.
• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroid injections can reduce inflammation and relieve pain.

Minimally Invasive Procedures

For patients not responding to conservative therapy, procedures such as percutaneous or ultrasound-guided corticosteroid injections may provide temporary symptom relief by reducing inflammation within the carpal tunnel.

Surgical Intervention

Surgery is indicated in severe or refractory CTS cases to decompress the median nerve.

• Open Carpal Tunnel Release: Traditional procedure involving incision over the wrist to cut the transverse carpal ligament.
• Endoscopic Carpal Tunnel Release: Less invasive technique using small incisions and a camera to release the ligament, often resulting in faster recovery.

Postoperative Care and Rehabilitation

Post-surgery, patients are advised on wound care, gradual mobilization of the wrist and fingers, and hand therapy exercises to restore strength and function. Recovery time varies depending on the severity and surgical approach.

Psychological and Supportive Care

Addressing the impact of CTS on daily life and mental well-being is important. Patient education, reassurance, ergonomic advice, and support for returning to work or activities can improve adherence to therapy and overall outcomes.

Complications

• Persistent Symptoms: Some patients may continue to experience numbness, tingling, or weakness even after treatment.
• Nerve Injury: Rare complications during surgery can cause additional sensory or motor deficits.
• Recurrence: Symptoms may return if underlying risk factors are not addressed or if scar tissue forms around the median nerve.
• Infection or Scar Formation: Surgical sites may develop infection or hypertrophic scarring, requiring additional care.

Prevention and Patient Education

Ergonomic Strategies

Proper workstation and tool ergonomics are essential to reduce strain on the wrist and prevent CTS. Recommendations include keeping the wrist in a neutral position, using adjustable chairs and desks, positioning keyboards and tools to minimize bending or twisting, and taking regular breaks during repetitive tasks.

Exercise and Stretching

Regular stretching of the fingers, wrists, and forearms can help maintain flexibility and reduce intratunnel pressure. Nerve gliding and tendon mobility exercises may also prevent symptom progression in at-risk individuals.

Awareness of Early Symptoms

Educating patients about early signs of CTS, such as nocturnal tingling, numbness, or hand weakness, promotes prompt evaluation and management. Early intervention can prevent progression to severe nerve damage and the need for surgical intervention.

Future Directions and Research

Novel Therapies

Emerging treatments for CTS include regenerative approaches such as stem cell therapy and platelet-rich plasma injections, which aim to repair nerve damage and improve function. Pharmacological research is also exploring agents that reduce fibrosis and inflammation within the carpal tunnel.

Advances in Surgical Techniques

Minimally invasive and endoscopic techniques continue to evolve, offering reduced recovery times, smaller incisions, and decreased postoperative pain. Innovations in surgical instrumentation and visualization are enhancing precision and safety during carpal tunnel release procedures.

Emerging Diagnostic Technologies

Advancements in imaging, such as high-resolution ultrasound and diffusion tensor MRI, allow more accurate visualization of median nerve pathology. Wearable devices and digital assessment tools are also being developed to monitor hand function and symptom progression in real time.

References

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