Median Neuropathy Clinical Presentation

Patients typically complain of pain, tingling, and numbness in the dominant hand and affecting digits 1-3 in particular, and awakening them from sleep.

• In early carpal tunnel syndrome (CTS), paresthesias are intermittent, and the hand is reported as falling asleep, with pins and needles sensation.
• Most often, the symptoms are in the thumb, index, and middle finger. Classic CTS includes symptoms affecting at least 2 of the first 3 digits, but not the palm of dorsum of the hand.
• Many patients report that the entire hand falls asleep. Detailed questioning sometimes reveals that the digit 5 is not affected. Others, if asked to observe whether the little finger is involved, often note subsequently that it is spared.
• A diagram of symptoms in the hand can help patients to localize symptoms. In a clinic-based sample, a diagram of symptoms (Katz hand diagram of classic or probable CTS) had a sensitivity of 61% and a specificity of 71% for the diagnosis of CTS.^{[18, 19]}
• Patients with CTS may describe rather diffuse, poorly localized aching that involves the entire hand and radiates to the forearm and elbow and even the shoulder region, but not to the neck.
• Patients may report coldness, swelling, dry skin, and/or color changes in the hand. Raynaud phenomenom is more common in patients with CTS.
• Nocturnal pain and paresthesias may awaken the patient from sleep when prolonged wrist flexion or extension leads to increased pressure in the carpal tunnel. In a study of patients with brachialgia paraesthetica nocturna, about 40% were diagnosed with CTS.^[11] A history of nocturnal symptoms has moderate sensitivity (51-77%) and specificity (27-68%).^[19]
• Motor involvement may be reported as clumsiness, difficulty buttoning the shirt or opening jars, dropping objects, and weakness.
• Provocative factors: Symptoms are worsened by excessive use of the hand, including repetitive wrist motion and during a flexed or extended wrist posture. Discomfort may be provoked by driving or by holding the phone, a book, or a newspaper.
• Alleviating factors: Patients often report that they shake the hand to lessen the symptoms, the so-called flick sign, with sensitivity and specificity reported as high (>90% for both)^[20] to moderate (50% and 77%, respectively).^[21]
• CTS is unlikely if no symptoms are present in any of the first 3 digits, and in particular if the complaint is wrist pain without pain or paresthesias in the fingers.
• Inquire about a trauma to the hand or wrist, occupational or habitual hazards involving repetitive wrist movements, excessive hand use or exposure to vibratory forces, and associated medical conditions (see Causes below).

Although patients often have difficulty isolating the sensory complaints to the median-innervated digits, sensory findings on examination are typically limited to the distribution of the median nerve. Motor examination often reveals slight weakness of thumb abduction. Thenar muscle atrophy indicates axonal nerve injury in more advanced CTS. The classic motor and sensory signs of CTS including the provocative bedside tests, but do not reliably distinguish among patients with suggestive CTS symptoms between focal median nerve neuropathy as confirmed by electrophysiological testing and other conditions with similar complaints and negative electrophysiological results.

Inspection

• Atrophy of the thenar muscle group is a late sign (see Motor examination below).
• Trophic changes: Dry skin may be noted over digits 1-3. Many patients report subjective hand swelling^[22] , but usually no edema is noted on examination. Raynaud's phenomenon and blanching of the hands may be present.
• Square-shaped wrist: A correlation of wrist dimensions with CTS was first reported in 1983.^[23] Measured at the distal wrist crease, a ratio of greater than 0.7 for the anterior-posterior dimension divided by the mediolateral dimension had a sensitivity of 69% for electrophysiologically confirmed CTS.^[24] An increasing wrist ratio correlates with prolongation of the median nerve sensory latencies and distal motor latencies.^{[23, 25]}
• Scars may be noted related to prior injuries or surgeries including prior carpal tunnel release surgery.Scars from carpal tunnel release surgery.

Sensory findings

• In early CTS, the examination may be normal or limited to abnormal sensation to light touch or pinprick over the fingertips of digits 2 and/or 3.
• Sensory deficits are noted within the median-innervated hand area that includes the palmar aspects of the medial thumb, the index and middle fingers, and the lateral ring finger.
• The sensation over the thenar eminence is spared, as it is innervated by the palmar cutaneous branch of the median nerve that arises proximal to the carpal tunnel.
• Rubbing the patient's fingertips with the examiner's own and comparing the sensation in the first 3 digits to the digit 5 is the easiest way to determine sensory loss. Patients may report tingling, pins and needles, a feeling like sandpaper, or as if their fingertips are covered by a thin glove.
• Testing with pinprick may document decreased sensation (hypalgesia) in median innervated fingers versus digit 5, and may be particularly useful in comparing the affected lateral aspect of the ring finger from the nonaffected medial (ulnar) aspect. Occasionally, the patients report hyperalgesia instead of numbness.
• Decreased 2-point discrimination is less useful due to low sensitivity, but fairly specific. Testing of vibration is of uncertain value.

Motor examination

• Inspect the hand for thenar muscle atrophy suggestive of CTS that may be noted only by comparing both hands. Assess the hypothenar and first dorsal interosseus muscles for comparison that should be normal in isolated focal median neuropathy, but may show atrophy in patients with C8 radiculopathy or polyneuropathy.
• Test the abductor pollicis brevis (APB) muscle strength:

  • Isolating the muscle action of abductor pollicis brevis is difficult. Typically, the muscle strength is tested for a movement perpendicular to the palm against the examiner's fingers. The abductor pollicis longus (radial nerve) contributes to thumb abduction function, and the combination of the flexor pollicis brevis, deep head (ulnar nerve) and the flexor pollicis longus (anterior interosseous nerve of the median nerve) contribute to opposition movement.
  • In many patients with CTS, no clear weakness of the APB or thenar atrophy is present.
  • The intact function of the long finger flexors of the forearm as tested by the Ok-sign (Flexor pollicis longus, Flexor digitorum profundus innervated by the anterior interosseus branch) differentiates CTS from more proximal lesions affecting the median nerve.
  • Severe atrophy of the APB muscle is more often noted in elderly patients with long-standing symptoms who present with hand clumsiness and relatively minor pain.

Diagnostic bedside tests

Provocative tests (symptom replication tests) may assist in the clinical diagnosis of CTS by exacerbating or reproducing the symptoms reported by the patient. However, the tests have low validity. In 1 study of patients with CTS symptoms and subsequent neurophysiological testing, the probability of CTS ranged from 35-70% for positive test results and from 41-62% for negative test results.^[26]

• Tinel sign: Radiating paresthesias into the hand and the median innervated fingers are provoked by tapping over the palmar wrist region overlying the carpal tunnel. The sensitivity varies greatly and is estimated as 50%; the specificity is estimated at 73%.^[21]
• Phalen test: Holding the hand in maximally flexed position at the wrist for 60-120 seconds may elicit paresthesia distally within the median nerve distribution. Phalen performed the test by having the patient rest the elbows on a table, hold the forearms vertically, and then allow the hands to drop with complete wrist flexion for 1 minute. The sensitivity is reported as 68% (greater than for the Tinel sign), and the specificity as 73%.^[21] Time to onset of symptoms may be documented in the chart with earlier onset, indicating greater CTS severity; advanced CTS is suggested by onset within 20 seconds.
• Carpal compression test (median nerve compression test): Pressure is applied by the examiner with both thumbs on the palmar aspect of the patient's wrist.^[27] Estimates are 64% for sensitivity and 83% for specificity according to one study^[21] , but vary widely.^[16]
• Reverse Phalen test: Holding the hand in hyperextension position at the wrist may similarly worsen or reproduce the complaints within one minute. This test is less commonly used than the Phalen test.
• Tethered median nerve stress test: Tension of the median nerve is produced by simultaneous extension of the supinated wrist and the distal interphalangeal joint of the index finger for 1 minute. Patients with chronic CTS report pain over the volar aspect of the proximal forearm.^[28] A sensitivity of 43% was reported compared with 56% with Phalen and 42% with Tinel sign. In spite of his low sensitivity, in some cases this test is the only clinical positive sign.^[29]
• Tourniquet test: Application of a tourniquet or inflated blood pressure cuff at the upper arm results in paresthesias in median-innervated digits.

Symptom relief test

With the affected hand facing upward, the distal metacarpal heads are gently squeezed. Stretching of digits 3 and 4 may also be used. These maneuvers may diminish the paresthesias in patients with CTS.

Most cases are idiopathic. In up to 50% of cases, an underlying condition may be identified that causes a locally reduced space in the carpal tunnel or increased susceptibility to nerve damage. Many metabolic or endocrine conditions are associated with increased risk of CTS, and several risk factors may coexist. Some cases may be attributed to excessive or repetitive hand movements.

Local causes with reduced space in the carpal tunnel

• Congenital - Congenital small carpal tunnel, anomalous muscles and tendons, vascular anomalies including persistent median artery
• Thickened transverse ligament
• Tumor - Ganglion, hemangioma, cysts, lipoma, neuroma
• Trauma, acute or chronic manifestation due to associated degenerative changes - Distal radius fracture (Colles fracture), dislocation or fracture of one of the carpal bones
• Exostosis, osteophytes
• Hematoma
• Local infection - Septic arthritis, histoplasmosis

Regional or systemic conditions with reduced space

• Osteoarthritis
• Rheumatoid arthritis
• Mucopolysaccharidoses and mucolipidoses
• Amyloidosis
• Gout
• Spasticity with persistent wrist flexion

Systemic conditions with increased susceptibility of nerves to pressure

• Hereditary neuropathy with liability to pressure palsies (HNPP)
• Diabetes mellitus
• Other polyneuropathies

Other associated systemic conditions

• Obesity
• Hypothyroidism, hyperthyroidism
• Alcoholism
• Pregnancy (third trimester, usually bilateral), lactation
• Menopause
• Connective tissue disorders - Systemic lupus erythematodes, scleroderma, dermatomyositis
• Rheumatoid arthritis
• Sarcoidosis
• Renal failure, hemodialysis
• Acromegaly
• Leukemia, multiple myeloma
• Infections - Lyme disease, histoplasmosis

Familial carpal tunnel syndrome

• X-linked dominant (females), autosomal dominant, and recessive (childhood) forms
• Bilateral presentation
• Anatomical abnormalities include a narrow carpal tunnel and thick transverse carpal ligaments

Work/activity-related causes

• Highly repetitive wrist and finger use is a greater risk factor than forceful hand use.
• The combination of finger flexion with repetitive wrist motion is probably the most provocative stressor.
• The classic concept of repetitive motion-induced chronic tenosynovitis resulting in CTS has been questioned.
• Keyboard data entry has not been established as a cause of CTS.