- Exaggeration of deep jerks and extensor plantar response in syringomyelia, spinal tumour, amyotrophic lateral sclerosis and pachymeningitis. I

Reflexes - Exaggeration of deep jerks and extensor plantar response in syringomyelia, spinal tumour, amyotrophic lateral sclerosis and pachymeningitis. III. Investigations - 1. Haematological and biochemical - to demonstrate nature of primary disorder to which muscular wasting is secondary in case of systemic, inflammatory or metabolic disease 2 Serum creatine kinase (CK) - Very high levels in Duchenne and Becker dystrophies, acute polymyositis, and acute myoglobinuric myopathies. In other myopathies it may be normal or only moderately raised. 3. EMG - distinguishes myopathic weakness from that due to chronic denervation or to defective neuromuscular transmission as in myasthenic syndrome. 4. Nerve conduction velocity - Normal in myopathies and spinal muscular atrophies, reduced in demyelinating polyneuropathy. 5. Muscle biopsy and histochemical analysis - Infiltration with fat and connective tissue to varying extent in muscular dystrophies, often with abortive regenerative activity. In polymyositis necrotic changes with inflammatory cell infiltration in perifascicular distribution. Normal in most metabolic myopathies Electron microscopy useful in some metabolic and rare congenital myopathies. 25. PERIPHERAL NEUROPATHY Pathophysiology - Three basic pathological processes affect peripheral nerve fibres - 1. Wallerian degeneration - follows transection of an axon by crushing or injury, with the myelin sheath and axon degenerating distal to the site of division. 2. Axonal degeneration - Most common change, metabolism of the neurone usually affected, resulting in degeneration of the distal portion of the axon. 3. Segmental demyelination - results from disease of the Schwann cell or from a direct attack on the myelin, and the myelin sheath is primarily destroyed leaving the axon intact Clinical classification - 1. Mononeuropathy or focal neuropathy - Single nerve involved CAUSES - (a) COMPRESSION - e.g. compression of radial nerve against humerus (Saturday night palsy). (b) ENTRAPMENT -e.g. (i) Carpal tunnel syndrome - Compression of median nerve as it passes through the carpal tunnel in the flexor retinaculum at the wrist. Causes - (i) Wrist fracture. (ii) Arthritis of the wrist particularly RA. (iii) Soft tissue thickening in myxoedema and acromegaly. (iv) Oedema, notably associated with pregnancy Obesity. (v) No obvious cause. More common in women. Symptoms - Pain, numbness and paraesthesiae in the hand. Pain may radiate to through forearm and occasionally involve the whole arm. Typically pain is most troublesome at night or first thing in morning. Signs - Weakness of abductor policis brevis, with or without wasting, and also weakness of opponens. _ Sensory impairment -of median distribution. Positive Tinel sign - Gentle tapping over carpal tunnel causes paraesthesiae in part of the cutaneous distribution of the nerve. Treatment - (i) Mild case - Wrist splint, diuretics and injection of hydrocortisone into carpal tunnel may give temporary relief. (ii) In severe case - Surgical decompression of carpal tunnel. (c) OTHER CAUSES - Trauma, fractures operations, penetrating injuries, lacerations and injections. 2. Multiple mononeuropathy (mononeuritis multiplex or multifocal neuropathy) - More than one and at times many, individual nerves affected in a patchy distribution CAUSES - (a) Vascular - Diabetes, rheumatoid arthritis, polyarteritis nodosa, SLE, Wegner’s