A 35-year-old woman presents to the clinic with complaints of numbness in her thumb, index finger, and part of the ring finger. On physical examination, there is wasting of the thenar eminence (base of the thumb), and she reports weakness in gripping objects. There is no significant joint pain or systemic symptoms. What is the most likely diagnosis?
A. Rheumatoid arthritis
B. Guillain-Barré syndrome
C. Amyotrophic lateral sclerosis
D. Carpal tunnel syndrome
E. Cervical spondylosis
Correct Answer: D. Carpal tunnel syndrome
Explanation:
The most likely diagnosis is carpal tunnel syndrome (CTS). The condition arises from compression of the median nerve as it passes through the carpal tunnel in the wrist. It commonly affects individuals performing repetitive hand or wrist motions and is often associated with occupations requiring sustained hand movements.
The median nerve supplies sensation to the thumb, index finger, middle finger, and half of the ring finger, which corresponds to the patient’s reported numbness. Motor innervation to the thenar muscles explains the wasting observed in this area.
Key features pointing to carpal tunnel syndrome:
- Numbness/tingling in the median nerve distribution.
- Wasting of the thenar eminence, indicating chronic nerve compression.
- Symptoms may worsen at night or during activities involving wrist flexion or repetitive hand movements.
Why Other Options Are Incorrect:
A. Rheumatoid arthritis:
While RA can affect the wrist, it typically causes joint swelling, pain, and deformity rather than isolated nerve compression. RA is not known to directly cause thenar muscle wasting or sensory deficits in the distribution of the median nerve without other systemic or joint symptoms.
B. Guillain-Barré syndrome:
GBS usually presents as an ascending paralysis with symmetric muscle weakness starting in the legs. Sensory involvement is minimal, and it does not typically cause localized symptoms like thenar wasting or isolated median nerve symptoms.
C. Amyotrophic lateral sclerosis (ALS):
ALS is a progressive neurodegenerative disease causing upper and lower motor neuron symptoms, such as generalized muscle weakness, fasciculations, and spasticity. The presentation in this case is focal, affecting only the median nerve, which makes ALS less likely.
E. Cervical spondylosis:
Cervical spondylosis can cause radiculopathy due to nerve root compression, but the symptoms follow a dermatomal pattern. It would more commonly involve the entire arm or shoulder and not isolate the median nerve distribution or lead to thenar wasting without affecting other areas.
Clinical Features of Carpal Tunnel Syndrome:
- Sensory Symptoms:
- Numbness or tingling in the thumb, index, middle, and half of the ring fingers.
- Symptoms are often worse at night or with activities like typing or gripping.
- Motor Symptoms:
- Weakness in thumb opposition, leading to difficulty gripping or pinching.
- Wasting of the thenar muscles in severe cases.
- Provocative Tests:
- Phalen’s maneuver: Flexing the wrist for 60 seconds reproduces symptoms.
- Tinel’s sign: Tapping over the carpal tunnel elicits tingling.
- Advanced Cases:
- Persistent numbness and irreversible thenar muscle atrophy.
Diagnostic Workup:
- Clinical Examination: Provocative tests like Phalen’s and Tinel’s signs.
- Nerve Conduction Studies: Confirm median nerve compression.
- Ultrasound or MRI: Evaluate structural abnormalities of the carpal tunnel.
Management of Carpal Tunnel Syndrome:
- Conservative Treatment:
- Wrist splinting: Maintains the wrist in a neutral position, especially during sleep.
- Activity modification: Reducing repetitive wrist movements.
- NSAIDs: For pain relief in mild cases.
- Steroid Injections:
- Local corticosteroid injections can reduce inflammation and relieve symptoms temporarily.
- Surgical Intervention:
- Carpal tunnel release surgery is indicated for severe or refractory cases, where the transverse carpal ligament is cut to relieve pressure on the median nerve.
Key Takeaway:
Carpal tunnel syndrome should be suspected in patients with numbness in the median nerve distribution and thenar wasting, especially if symptoms are worsened by wrist movements. Early diagnosis and intervention can prevent permanent nerve damage and functional loss. Differentiating CTS from systemic diseases or other neurological conditions is crucial for effective management.