Occupational peripheral nerve damage

Toxic damage

 * Toxic neuropathy
 * Typical character – symmetric, sensorimotor, distal polyneuropathy
 * Sensory fibers are affected first because their bodies are in the dorsal root ganglion (i.e. outside the blood-brain barrier).
 * It is distal because the part of the neuron that is furthest from the center of regeneration (i.e. from the cell body) suffers the most
 * The longer the axon, the more susceptible it is to damage

Symptoms

 * Sensory - Paresthesia or tingling especially at night. Reduction or disappearance of reflexes - distal ones disappear first (e.g. Achilles tendon reflex)
 * Motor disorders appear later – typically there is Peroneal paresis (patient can't extend (lift) toes)

Examination

 * Electromyography (Sural nerve, Tibial nerve)

Toxicity

 * Lead, Mercury
 * Organic solvents – carbon disulfide, hexane, trichloroethylene, acrylamide, polychlorinated biphenyl

Symptoms are nonspecific:

 * Mainly – alcoholic polyneuropathy (we will examine GGT (gamma-glutamyl transferase), CDT (carbohydrate-deficient transferrin))
 * Diabetic, Paraneoplastic (mainly lung, ovarian, or hematogenous)
 * Both in DM and in tumours, polyneuropathy can be the first symptom (must be considered when polyneuropathy occurs)

Therapy

 * Termination of toxic exposure, vitamins B1, B6, B12, E, vasoactive substances, nootropics, pain medications – anti-epileptics

Overuse damage
Other rare damages:
 * Tunnel syndromes
 * 80% of patients have carpal tunnel syndrome. Cubital tunnel syndrome is the second-most common


 * Peroneal nerve – compression when passing behind the head of the fibula (e.g. while squatting or kneeling)
 * Tibial nerve – pressure in the tarsal tunnel (when passing behind the inner ankle)
 * With frequent tiptoeing (plantar flexion) – Ballerinas (damage to the nerve by stretching), Jockeys (tightening in the stirrups), house painters (on stepladders)

Carpal tunnel syndrome

 * There will be some expansion of the carpal tunnel – it has two main etiologies
 * Endogenous - hormonal changes (the syndrome will manifest itself bilaterally), inflammation (tendovaginitis), and metabolic changes
 * Exogenous – post-traumatic, from manual work
 * The most common groups of activities leading to the syndrome:
 * Heavy physical work: flexor contractions (hammer, heavy loads)
 * Stereotypic repetition of finger flexion and extension (previously in milking cows, musicians, or typing)
 * Fine work with constant pinching of the fingers (watchmakers, fine mechanics)
 * Direct pressure on the wrist (dentists, scissor work, etc.)


 * Subjective symptoms:
 * First phase – morning numbness in the fingers
 * Second phase - nocturnal paresthesia
 * Third phase – daytime paresthesia (mainly when working with hands above the head (for example, holding on to a handrail in public transport))
 * Fourth stage – clumsiness of small movements


 * Objective signs – sensitivity disorders – we assess them on the 2nd finger (we compare sensation on the belly of the 2nd and 5th finger - the palmar part of the fifth finger is innervated by the ulnar nerve)
 * As stated, motor defects arise later – mainly abductor pollicis brevis muscle atrophy
 * The resulting atrophy of this muscle makes such a dimple laterally on the thenar eminence
 * We demonstrate the sign of a candle - hand palm-side up with the thumb sticking up, we push it into the palm and watch its resistance
 * Sensation on the thenar eminence is normal (the subcutaneous branch originates from the median nerve before entering the carpal tunnel)
 * Pseudoneuroma of the median nerve is formed - a spindle-like thickening of the nerve - as axoplasm (cytoplasm of axon) accumulates there due to the oppression
 * Provocation tests – Tinel's sign – perpendicular tapping of the retinaculum with fingers (direct percussion) causes paresthesias (burning or prickling sensation)
 * Wrist hyeprflexion will do the same
 * Objective examination - ENG (electroneurography) - the conduction speed of the axon on the forearm (before) and palm (after) will be normal, there is a slowdown in the tunnel

Dif. dg

 * Pronator teres syndrome (median compression more proximally on the forearm)
 * C6 root syndrome
 * Cervicobrachial syndrome

Therapy

 * Termination of exposure, splint positioning, vasoactive substances, NSAIDs, local corticoids
 * Invasive (last) option - surgery - usually the worker can no longer return to work, as the movement of the wrist is altered

Other Syndromes

 * Paresis of the ulnar nerve in the Ulnar nerve sulcus with claw hand deformity

Related articles

 * Ionising radiation

Source

 * BENEŠ, Jiří. Study materials  [online]. [feeling. 24/02/2010]. < http://jirben.wz.cz >.