Peripheral Nerve and Skeletal M uscle

1. Peripheral Nerve and Skeletal Muscle

2. General Reactions of the Motor unit • Segmental demyelination • Dysfunction of the Schwann cell or damage to the myelin sheath • Axonal degeneration and reinnervation of muscle • Wallerian degeneration • Denervation atrophy • Reactions of the Muscle fiber • Segmental necrosis • Vacuolation, alterations in structural proteins or organelles, and accumulation of intracytoplasmic deposits • Regeneration • Fiber hypertrophy

3. Diseases of Peripheral Nerve • Inflammatory neuropathies • Infectious polyneuropathies • Hereditary neuropathies • Acquired metabolic and toxic neuropathies • Traumatic neuropathies • Tumors of peripheral nerve – chapter 28

4. Inflammatory Neuropathies • Immune-mediated neuropathies • Guillain-Barre syndrome (acute inflammatory demyelinating polyradiculoneuropathy) • 2/3 preceded by a flu-like illness • Infections or prior vaccination • Ascending paralysis • Chronic inflammatory demyelinating polyradiculoneuropathy

5. Infectious Polyneuropathies • Leprosy ( Hansen Disease) • Diphtheria • Varicella-Zoster Virus

6. Hereditary Neuropathies • Hereditary motor and sensory neuropathies • HMSN I – charcot-Marie-Tooth disease, peroneal muscular atrophy, hypertrophic neuropathy • HMSN II • HMSN III – Dejerine-Sottas neuropathy • Hereditary sensory and autonomic neuropathies – Table 27-2 • Familial amyloid polyneuropathies – transthyretin gene • Peripheral neuropathy accompanying inherited metabolic disorders – Table 27-3

7. Acquired Metabolic and Toxic Neuropathies • Peripheral neuropathy in Adult-Onset DM • Distal symmetric sensory or sensorimotor neuropathy, autonomic neuropathy, focal or multifocal asymmetric neuropathy • Metabolic and nutritional peripheral neuropathies • Uremic • Thiamine – neuropathic beriberi • Vitamin B12, B6, E • Alcoholism • Neuropathies associated with malignancy • Brachial plexopathy, obturator palsy, cranial nerve palsies, polyradiculopathy, paraneoplastic • Toxic neuropathies • Industrial or environmental chemicals, biologic toxins, therapeutic drugs, organic compounds

8. Traumatic Neuropathies • Laerations • Avulsions • Traumatic neuroma • Compression neuropathy ( entrapment) • Carpal tunnel syndrome • “Saturday night palsy

9. Diseases of Skeletal Muscle • Degeneration atrophy – Spinal muscular atrophy, panfascicular atrophy, Werdnig-Hoffmann – floppy infant • Muscular dystrophies • Ion channel myopathies (Channelopathies) • Hyperkalemic, hypokalemic, normokalemic periodic paralysis • Malignant hyperpyrexia (hyperthermia) • Congenital myopathies – Table 27-6 • Myopathies associated with inborn errors of metabolism • Lipid and mitochondrial ( ragged red fibers and parking lot inclusions) • Inflammatory myopathies – dermatomyositis, polymyositis, inclusion body myositis • Toxic myopathies – Thyrotoxic, ethanol, drug-induced • Diseases of the neuromuscular junction – myasthenia gravis, Lambert-Eaton • Tumors of skeletal muscle – chapter 26

10. Muscular Dystrophies • X-linked MD • Duchenne – more severe • Becker • Dystrophin mutations • Variations in fiber size, increased number of internalized nuclei, degeneration, necrosis, and phagocytosis of muscle fibers, regeneration of muscle fibers, proliferation of endomysial connective tissue, muscle s eventually totally replaced by fat and CT • Other = Limb girdle MD • Myotonic dystrophy