Causes and pathogenesis
Compression neuropathies occur due to mechanical impact on nerve trunks. The main causes are trauma, soft tissue compression, bone fractures, and hematomas. The key mechanism is chronic nerve compression within narrow anatomical tunnels. Such a condition can be provoked by an awkward posture, monotonous movements, as well as external pressure, for example, when using crutches or during sleep in an uncomfortable position (so-called "Saturday night palsy"). In some cases, entrapment develops due to edema of the canal contents or post-traumatic hematoma.
Clinical presentation
Clinical manifestations develop gradually. Sensory disturbances always appear first, since thick sensory fibers are larger than motor fibers. Patients experience paresthesias, hyperesthesia, hypoesthesia, and pain both within and beyond the innervation zone. A pathognomonic sign is Tinel's sign — pain and paresthesia upon percussion at the site of nerve compression.
Later, motor and autonomic-trophic disorders join: muscle weakness and hypotrophy. Examples of specific lesions:
- Carpal tunnel syndrome: the most frequent form of median nerve neuropathy, accounting for up to 2/3 of all entrapment pathologies.
- Radial nerve neuropathy: manifests as paralysis of the wrist and finger extensors ("wrist drop").
- Tarsal tunnel syndrome: characterized by nocturnal pain in the plantar surface of the feet and toes during walking, resembling intermittent claudication.
Diagnostics
To confirm the diagnosis and assess the severity of nerve trunk damage, a set of instrumental methods is used:
- ENMG (electroneuromyography) — a study of the conduction velocity of excitation along motor and sensory fibers.
- EMG (electromyography).
- Nerve ultrasound.
- MRI (if available).
Principles of treatment
Patient management tactics depend on the stage of the disease and the severity of symptoms.
Conservative treatment is used at the initial stages:
- Elimination of etiological and provoking factors (changing posture, avoiding repetitive movements).
- Orthopedic correction using splints and braces.
- Local therapy: administration of glucocorticoids directly into the canal (e.g., hydrocortisone).
- Symptomatic pharmacotherapy: non-narcotic analgesics, NSAIDs, and anticonvulsants (gabapentin, pregabalin, carbamazepine).
Surgical treatment is indicated when conservative measures are ineffective, in cases of severe functional deficits, or upon rapid progression of symptoms. The surgery consists of dissecting the compressing tissues (neurolysis) to create optimal conditions for the nerve trunk.
Sensory symptoms suffer first, Tinel's sign upon percussion inspires fear: where the nerve is compressed in the canal, pain and hypoesthesia reign.
Class and exam questions
What symptoms appear earliest in entrapment syndromes?
Sensory disturbances appear first — paresthesias, hyperesthesia, hypoesthesia, and pain, because thick sensory fibers are larger than motor fibers.
What is Tinel's sign?
This is a pathognomonic sign of compression neuropathy, manifested by increased sensitivity, pain, or paresthesias upon percussion at the site of nerve compression.
What are the indications for surgical treatment of entrapment syndromes?
Relative indications are the ineffectiveness of glucocorticoids or contraindications to them. Absolute indications are severe motor and sensory deficits, as well as rapid progression of symptoms.
What else to study on this topic
- Anatomical features of the tarsal and carpal tunnels
- Differential diagnosis of radial and common fibular nerve neuropathies
- Features of ENMG in compression syndromes
- Technique for local injection therapy with glucocorticoids
- Rehabilitation period and physiotherapy after neurolysis
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