Etiology and mechanism of development
The condition belongs to the group of entrapment syndromes in which a peripheral nerve suffers from mechanical compression and secondary ischemia within an osseofibrous canal.
- Anatomical substrate: the median nerve passes inside the carpal tunnel (canalis carpi) directly beneath the transverse carpal ligament (flexor retinaculum — retinaculum flexorum).
- Direct cause of compression: edema or marked thickening of the ligamentous apparatus, leading to a critical narrowing of the canal lumen.
- Role of autonomic innervation: the trunk of the median nerve is rich in autonomic fibers. Their involvement in the pathological process explains the early development of trophic disorders and a high probability of developing complex regional pain syndrome (formerly known as reflex sympathetic dystrophy or Sudeck's atrophy).
Clinical presentation: from paresthesias to atrophy
The course of the pathology is undulating: spontaneous remissions typically alternate with new exacerbations. The severity of clinical symptoms depends on the duration and severity of nerve fiber compression.
Initial manifestations
- Nocturnal brachialgia (brachialgia parestetica nocturna): excruciating pain and tingling occurring in the middle of the night and toward morning. Patients wake up with a sensation of fullness in the wrist or the entire hand.
- Area of disturbance: numbness predominantly affects the 1st, 2nd, and 3rd digits, although symptoms may subjectively spread more widely.
- Positional triggers: raising the hands upward noticeably exacerbates complaints, while lowering the limb brings relief. A decrease in discomfort after vigorously shaking the hand is characteristic.
Late stages and neurological deficit
- Sensory deficits: persistent hypesthesia on the palmar surface of the 1st digit, as well as on the palmar and dorsal surfaces of the 1st–4th digits.
- Motor deficit: weakness of the abductor pollicis brevis muscle and the opponens pollicis muscle. The patient loses the ability to fully abduct and oppose the 1st digit.
- Trophic changes: marked wasting of the thenar eminence (thenar), the palm loses its natural relief and flattens, forming a pathological "ape hand".
Diagnostic tests and instrumental methods
Diagnosis is based on a clinical examination with provocative tests and confirmatory instrumental studies.
- Specific provocative tests:
- Phalen's test: maximal passive or active wrist flexion for 1 minute provokes paresthesias and numbness in the median nerve distribution area (1st–4th digits).
- Tinel's sign: light tapping (percussion) with a neurological hammer over the projection of the carpal tunnel causes shooting pain radiating to the fingertips.
- Electromyography (EMG): records a local drop in nerve conduction velocity along the median nerve fibers within the carpal tunnel.
- Wrist ultrasound: visualizes mechanical compression of the nerve and the state of the flexor retinaculum.
- Differential diagnosis: examination of individual muscle groups must be correlated with segmental (radicular) and peripheral innervation patterns. This allows radicular radiculopathies to be reliably differentiated from peripheral nerve trunk compression.
Conservative and surgical treatment tactics
Treatment strategy is structured in a stepwise manner — from a gentle protective regimen to surgical decompression.
| Direction | Applied methods and drugs |
|---|---|
| Protective regimen | Elimination of flexion and extension movements in the radiocarpal joint, elimination of occupational vibration |
| Immobilization | Application of a stabilizing bandage (wrapping) for the night; in severe symptoms — joint splinting for 2–4 weeks |
| Drug therapy | Pain relievers and NSAIDs to relieve pain |
| Local injections | Blockades with glucocorticosteroids (isolated or in combination with novocaine) directly into the canal cavity |
| Surgical treatment | Surgical nerve decompression; indicated when conservative measures fail or when muscle atrophy appears |
Remember the letter "Ph" in the word Phalen — it resembles two palms bent toward each other: it is flexion of the wrist for one minute that causes paresthesias in this symptom. And Tinel's sign sounds similar to the word "tap" (or knock) — it is percussion over the canal.
Class and exam questions
How to clinically distinguish carpal tunnel syndrome from ulnar nerve entrapment?
In carpal tunnel syndrome, the median nerve is affected with numbness of the palmar surface of the 1st–4th digits and subsequent formation of an "ape hand". In ulnar nerve injury, the ulnar border of the hand suffers (the 5th and half of the 4th digit), adduction of the thumb weakens, the hypothenar wastes, and a "claw hand" forms.
Why does complex regional pain syndrome often develop in carpal tunnel syndrome?
This is due to the anatomical feature of the median nerve: it contains an exceptionally large proportion of autonomic fibers, the damage to which triggers sympathetic dystrophy of the hand tissues.
In what cases is conservative treatment considered ineffective and surgery required?
Surgical intervention (median nerve decompression) is performed if the standard conservative complex does not relieve compression, or if the patient begins to develop worsening motor impairments and thenar muscle atrophy.
What else to study on this topic
- Ulnar tunnel syndrome (compression neuropathy of the n. ulnaris in the cubital canal)
- Formation of a "claw hand" and hypothenar muscle atrophy in ulnar nerve injury
- Other compression entrapment syndromes of the upper extremity: pronator teres syndrome, Guyon's canal syndrome, scalenus syndrome
- Ischemic nerve injuries during pressure increases in osteofascial compartments
- Principles of topical differential diagnosis between radicular paresis and mononeuropathy
- Lower extremity entrapment neuropathies: peroneal nerve compression and tarsal tunnel syndrome
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