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Peripheral Nerve and Skeletal M uscle

Peripheral Nerve and Skeletal M uscle. 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

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Peripheral Nerve and Skeletal M uscle

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  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

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