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Nerves and muscles
- 1. Nerves and muscles Peripheral nerves
- 2. Normal nerve Principal structural components Nerve fibre – axons, schwann cells, myelin sheath Groups of nerve fibres:- surrounded by connective tissue sheath is a fascicle. Myelinated nonmyelinated are intermingled in a fascicle.
- 6. in this view of a transected equine sciatic nerve, epineurium (E) is present on the left side o of Fibrous perineurium (red arrows) surrounds individual nerve fascicles. Notice perineuralepithelium (green arrows) deep to the fibrous perineurium (see Fig. 8). The endoneurium surrounding individual myelinated fibers within the fascicle is barely evident at this magnification.
- 11. Pathology Schwan cells- segmental demyelination Axons - axonal degeneration either can lead to axonal regeneration or reinervation of the muscle. The process affects some schwann cells sparing others. The disintegrating meylin is engulfed by initially schwann and then by macrophages. The cells in endoneurium replace schwann cells. The new internodes are shorter.
- 13. Segmental demyelination Dysfunction of schwann cells :- -as in guillain-barre syndrome. Damage to myelin sheath:- -e.g. hereditary motor and sensory neuropathy. There is no primary abnormality of axon.
- 14. With sequential episodes of de and remyelination(onion bulbs) Axonal degeneration and muscle fibre atrophy primary destruction of the axon with secondary loss of its myelin sheath . Damage to axon can be local (trauma or ischemia) or more generalised affecting cell body or its axon (neuronopathy or axonopathy).
- 16. When axonal injury:- e.g. traumatic transaction of a nerve, the distal portion of fiber undergoes wallerian degeneration _the axon begins to breakdown and the effected schwann cells begin to catabolyze myelin and engulf axon fragments forming small oval compartments (myelin ovoids). Macrophages phagocytose axonal and myelin debris. The stump of proximal portion of the nerve shows degenerative changes in distal two or three internodes and then undergoes regenerative activity.
- 17. When axonal degeneration occurs the muscle fibers within the affected motor unit lose their neuronal input and undergo denervation atrophy. In cross section atrophic fibers are smaller and have a triangular shape. Some muscles cells show disorganized filaments in the center of fiber (target fiber).
- 18. Nerve regeneration and reinnervation of muscle Proximal stumps of degenerated axons sprout and elongate and the growth cones use schwann cells to guide them. Presence of multiple closely aggregated thinly myelinated small calibre axons is evidence of regeneration It is a slow process_1mm per day. Reinnervation of atrophic muscle fibers within an injured motor unit occurs when the axons belonging to an unaffected neighboring motor unit extend sprouts to reinnervate the deinnervated myosites and incorporate them into the healthy motor unit.
- 19. Reactions of the muscle fiber Segmental necrosis, destruction of a portion of the length of a myosite and infiltration by macrophages result in loss of muscle fiber the n deposition of collagen and fat vacuolation, alterations in structural protiens or organelles and accumalation of intracytoplasmic deposits
- 20. Regeneration occurs from satelite cells. The regenerating muscle fiber has a large internalized nucleus and prominent nucleoli and the cytoplasm laden with RNA is basophilic. Fiber hypertrophy
- 21. Diseases of peripheral nerves Inflamatory Traumatic Metabolic Toxic Genetic Neoplastic
- 22. Inflamatory neuropathies They can be either 1) Immune mediated or; 2) Infectious Immune mediated • Guillain-barre syndrome(acute inflammatory demyelinating polyradiculopathy) • Life threatening disease • Weakness in distal limbs(ascending paralysis ) • Histologically --- -inflammation of peripheral nerves Demyelination of spinal nerve roots
- 23. Pathogenesis 2/3of cases are preceded by acute influenza like illness from which patients recover and then symptoms appear. Infections associated with G B; Compylobacter jejuni. Cytomegalo virus. Ebstienebar virus. Mycoplasma pneumoniae. No consistant demonstration of infectious agent so immunological reaction is favoured as the underlying cause. Experimental proof of its being imunological reaction are there.
- 24. Morphology Perivenular and endoneurial infilteration by lymphocytes,macrophages and a few plasma cells. Inflammatory cells may be sparse around perivenous spaces or large throughout the nerve . demyelination, primary lesion but damage to axon is also characteristic in severe cases.
- 25. Clinical Course Ascending paralysis. Deep tendon reflexes disappear. Sensory involvement detected but is less troublesome. Nerve conduction velocity slowed. Increased protein in CSF. Patients spend weeks in hospital but recover normal functions with improved respiratory care and support.
- 26. Infectious Polyneuropathies Leporacy Periphral nerves involvement in both lepromatous and tuberculoid. In lepromatous schwann cells are invaded by mycobacterium laprae which proliferates and infects other cells. There is segmental demyelination and remyelination and loss of axons. There is endoneurial fibrosis and multilayered thickening of the perineurial sheaths.
- 27. Symmetric polyneuropathy that involves pain fibres: – loss of sensation contributes to traumatic ulcers in extremities. Tuberculoid leprosy shows active cell mediated immune response with nodular granulomatous inflammation in dermis which injures cutaneous nerves in the vicinity :– axons, schwann cells and myelin are lost Fibrosis of perineurium and endoneurium. Much more localized nerve involvement.
- 28. Diphtheria Peripheral nerve involvement – dephtheria exotoxin. Paresthesias, weakness, early loss of proprioception and vibratory sensations. Earliest changes seen in sensory ganglia because toxin enters as there is incomplete blood nerve barrier. There is segmental demyelination of axons of anterior and prosteior roots and mixed nerves.
- 29. Varicella-zoster virus • Most common virul infection of periphral nervous system. • Latent infection of neurons in sensory ganglia after chicken pox. • Reactivation – painful vasicular skin eruptions – thoracic and trigeminal. • Ganglia show neuronal destruction and loss, mononuclear infiltrate, nicrosis and hemorrhage is found. • Peripheral nerves show axonal degeneration. • Focal destruction if large motor neurons of anterior horn or cranial nerve motor nuclei at corresponding levels.
- 30. Hereditary Neuropathies Heterogeneous, progressive and disabling syndromes affecting peripheral nerves. They can be divided into several groups: 1. Hereditary motor and sensory neuropathies ( HMSN) 2. Hereditary sensory and autonomic neuropathies (HSAN) 3. Familial amyloid polyneuropathy 4. Peripheral neuropathy accompanying inherited metabolic disorders
- 31. HMSN type 1 Most common heriditory hypertrophic form. Presents in childhood or early adulthood. Characteristic progressive muscular atrophy of the calf – peroneal muscular atrophy. Patients maybe asymptomatic but present with distal muscle weakness, atrophy of calf or secondary orthopedic of the foot. Autosomal dominant. Limited in severity and normal lifespan. Common charcot- marie- tooth disease,
- 32. Molecular genetics Genetically heterogenous in HMSN 1A Duplication of large region of chromosome 17 – segmental trisomy. This segment includes gene for peripheral myelin protein 22. HMSN 1B – chromosome 1 genetic locus involves myelin protein zero – identical clinical phenotype. Another group chromosome 16 – gene mutation involved in protein degradation. Gene on chromosome X – gap junction protein connexin 32.
- 33. Morphology CMT1 is a demyelinating neuropathy . Demyelination and remyelination with multiple onion bulbs more in distal nerves. Axon is present in center of onion bulbs thin myelin sheath. Layers of schwann cell hyperplasia surrounding individual axons cause enlargement of perpheral nerves which are palpable – hypertrophic neuropathy. Autopsy shows degeneration of posterior columns of spinal cord.
- 34. HMSN 2 • Neuronal form autosomal dominant CMT2A • Nerve enlargement not seen • Signs and symptoms similar to HMSN1 • Linked to chromosome1. • Nerve biopsy shows loss of myelinated axons • These findings suggest primary cellular dysfunction is the axon or the neuron.
- 35. HSMN 3 (Dejerine - Sottas disease) Slowly progressive autosomal reccessive disorder. Begins in early childhood manifested by delaying developmental milestones. Both trunk and limb muscles are involved. Enlarged peripheral nerves can be detected. Deep tendon reflexes depressed, nerve conduction velocity slowed. Heterogenous – same genes involved as in HSMN1 Size of peripheral nerve fasicicles is increased with abundant onion bulb formation and segmental demyelination.
- 36. Aquired metabollic and toxic neuropathiesAdult – onset diabetes mellitus •Depends upon duration of disease •25 years of diabetes – 50% of patients clinically have peripheral neuropathy and 100% have conduction abnormalities electrophysiologicaly. •Clinicopathological patterns of nerve abnormalities are—distal symmetric sensory or sensorimotor neuropathy, autonomic neuropathy and focal or multifocal asymmetric neuropathy.
- 37. Morphology • Symmetric sensorimotor neuropathy---axonal neuropathy, some segmental demyelination. • Loss of small myelinated and nonmyelinated fibres but large fibres are also affected. • Endoneurial arterioles show thickening, hyalinization and intence PAS positivity in their walls. • Extensive reduplication of the basement membrane.
- 38. Clinical course Most common peripheral neuropathy is the symmetric neuropathy that involves distal sensory and motor nerves. Decreased sensation, loss of pain, ulcers. Dysfunction of autonomic nervous system.
- 39. Metabolic and nutritional peripheral neuropathies Renal failure-uremic neuropathy- distal symmetric neuropathy may be asymptomatic or muscle cramps, distal dysesthesias, diminished deep tendon reflexes axonal degeneration- primary event Regeneration and recovery common after dialysis Thiamine deficiency- axonal- neuropathic beri beri Vit B 12, B 6 and E- axonal neuropathies Chronic liver, respiratory and thyroid disease- peripheral neuropathy Associated with malignancies Industrial toxins
- 40. Traumatic Neuropathies Laceration Avulsion Traumatic neuroma Compression neuropathy- carpel tunnel syndrome, Saturday night palsy
- 41. Tumors of peripheral nerves Schwannoma-arise from neural crest derived schwann cells and are associated with neuro fibro mstosis type 2 Mutations in NF2 gene chromosome 22 Common location cerebello pontine angle- attached to the vestibular branch of the 8th nerve Patients present with tinnitus, hearing loss (acoustic neuroma, vestibular schwannoma) Extra dural associated with large nerve trunks
- 42. Morphology Well circum scribed, encapsulated masses attached to the nerve but can be separated Firm gray masses may have cystic and xanthomatous change Microscopically Antoni A pattern- elongated cells with cytoplasmic processes are arranged in fascicles in areas of moderate to high celularity with little stromal matrix; the nuclear free zones of processes that lye between the regions of nuclear palisading are termed verocay bodies
- 43. Antoni B pattern of growth-less densely cellular, loose mesh work of cells with micro cysts with myxoid change. Cell shape in both areas is elongated with regular oval nuclei S-100 positive
- 44. Neurofibroma 2 type: 1. Cutaneous, solitary; arise sporadically or with NF1- becomes large and penduclated. Malignant trasnformation small-cosmetic concerns. 2. Plexiform-NF1, difficulty in surgical removal when large trunks are involved since they have significant potential for malignant transformation
- 45. Morphology Cutaneous neurofibroma; present in dermis and subcutaneous fat, well delineated unencapsulated masses composed of spindle cells Non-invasive but sometimes enwrap, adnexal structures. Stroma is highly collagenized
- 46. Plexiform neurofibroma Anywhere along the nerve, large nerve trunk is most common sight Multiple, nerve is irregularly expanded as each of its fascicles is infiltrated by the neoplasm Nerve cannot be separated Poorly defined margins Microscopy- loose myxoid background with low cellularity. Cells are schwann cells, fibroblasts, inflammatory cells. Shredded collagen.
- 47. Normal muscle
- 51. Normal Skeletal Muscle • Two major types of fibres: Type 1 and Type 2 based on histochemistry and physiology. Type 1: • Type 1 fibres are high in myoglobin and oxidative enzymes, have many mitochondria, perform tonic contractions, dark staining for adenosine triphosphatase at pH4.2 but light stain at pH9.4.
- 52. Type 2 fibres are rich in glycolytic, enzymes ,rapid phasic contractions, they are dark staining on ATPase performed at ph 9.4 and light stain at ph 4.2. Motor neuron determines fibre type. All fibres of a single unit are of the same type. Fibres of a single motor unit are distributed across the muscles, giving rise to a checkerboard pattern. Endomysium, perimysium and epimysium.
- 53. Diseases of skeletal muscles • Denervation atrophy. • Either affects the anterior horn cells or its axons. Spinal muscular atrophy[infantile motor neuron disease]. • Progressive neurological illnesses. • Affects anterior horn cells , cranial motor neurons resulting in their loss. • Spinal muscular atrophy(SMA).----a distinctive group of autsomal recessive motor neuron diseases that begin in childhood or adolescence.
- 54. SMA is considered with chilhood myopathies. Its pathological findings in skelatal muscle are characteristic. Genetics survival motor neuron gene on chromosome 5. Homozygous deletion—in 90% of SMA Deletion of neuronal apoptosis inhibitory gene---- associated with severe clinical phenotype.
- 55. Spinal muscular atrophy with groups of atrophic muscle fibers resulting from denervation atrophy of muscle in early childhood.
- 56. Morphology Large no of atrophic fibres –a few micrometres in diameter .unlike groups of angulated atrophic fibres seen in denervation atrophy of muscles in adult. Panfascicular atrophy. Large fibres 2-4 times normal.
- 57. Clinical course SMA type 1—most common(werdnig- hoffman) –onset at birth or within 4 months—leads to death –3 yrs. Of life . SMA type2-SMA type 3.—present later —survive till later ages.
- 58. Muscular dystrophies Inherited disorders –hetrogenous-beginning in childhood. Progressive muscle weakness and wasting. Histologicaly—advanced cases –replacement by fibrofatty tissue.
- 59. X linked muscular dystrophy (duchenne and becker) DMD-most common and severe 1 in 3500 male. Clinically manifest by 5yrs.--- weakness – wheelchair --10—12yrs of age. Progressive death by 20s. BMD –less common –less severe –same genetic locus.
- 62. Physical therapists:- are concerned with enabling children to reach their maximum physical potential.
- 63. Aim is to: 1.Minimize the development of contractures and deformity by developing a program of stretches and exercises where appropriate 2.Anticipate and minimize other secondary complications of a physical nature 3.Monitor respiratory function and advice on techniques to assist with breathing exercises and methods of clearing secretions 4.Schedule weekly to monthly sessions at a massage therapist to decrease the present pain.
- 64. Dystrophin, an intracellular protein, forms an interface between the cytoskeletal proteins and a group of transmembrane proteins, the dystroglycans and the sarcoglycans. These transmembrane proteins have interactions with the extracellular matrix, including the laminin proteins. Dystrophin also interacts with dystrobrevin and the syntrophins, which form a link with neuronal-type nitric oxide synthetase(nNOS) and caveolin. Mutations in dystrophin are associated with the X-linked muscular dystrophies, mutations in caveolin and the sarcoglycan proteins with the autosomal limb girdle muscular dystrophies, and mutations in the a2-laminin (merosin) with a form of congenital muscular dystrophy
- 65. Pathogenesis and genetics DMD- BMD-CAUSED BY; Abnormality in gene located on X chromosome— encodes 427kd pr.-Dystrophin. Deletions—commonest. Frameshift and point mutations-for the rest. 2/3 familial. rest new mutations. Females –carriers—asymptomatic – increased serum cretine kinase risk of dilated cardiomyopathy.
- 66. Dystrophin –cytoplasmic pr.near plsmemembrane over Z- band-forms strong link to Actin. Forms an interface b.w intracellular contractile apparatus and extracellular c.t matrix DMD –muscle biopsy –staining and western blot --minimum dystrophin. BMD –diminished dystrophin –abnormal m.w
- 67. A, Duchenne muscular dystrophy (DMD) showing variation in muscle fibersize,increased endomysial connective tissue, and regeneratingfiber(bluhue) B –Western blot showing absence of dystrophin in DMD and altered dystrophin size in Becker muscular dystrophy (BMD) compared with control
- 68. Morphology Abnormalities common to DMD BMD Variation in fiber size due to small and large fibers –fiber splitting. Internalized nuclei. Degeneration, necrosis &phagocytosis. Regeneration of muscle fibers. Proliferation of endomysial c.t.
- 69. DMD—cases show enlarged rounded hyaline fibres –lost cross stiations—hypercontracted. .Both type 1,2 fibres involved. Later stages –muscles replased by fat c.t. Cardiac interstisial fibrosis in subendocardial layer. Clinical evidence of CNS dysfunction in DMD no pathologgical abnormality.
- 70. Clinical course Boys with DMD are normal at birth– early motor milestones met on time. Walking delayed, clumsiness inability to keep up with peers. Weakness in pelvic girdle muscles and then extend to shoulder muscles. Pseudohypertrophy– calf muscle. Cardiomyopathy-. Cognitive impairment.
- 71. Serum creatine kinase -----elevated in beginning – later decrease. Death ------–respiratory insufficiency,pulmonary infection,cardiac decomposition. Gene therapy------- hampered by the size of gene. Experimental animal ------–2 delivery systems. One---stem cell inj. In muscle. Second---engineerd gene which produces normal dystrophin carried by adeno virus is injected.
- 72. Boys with BMD develop symptoms at later age . Onset in late childhood slower and variable rate of progression. Many pt. have anormal life span.
- 73. Other Muscular Dystrophies Less common. Have distinct clinical and pathological features. Limb girdle muscular dystrophies; Type 1---autosomal dominant—six sub types Type 2---autosomal recessive—11 sub types Mutation of sacroglycan complex of protiens in 4 LGMD 2C,2D,2E,2F.
- 74. Myotonic Dystrophy MYOTONIA---the sustained involuntary contraction of a group of muscles. pt. complains of stiffness and have dificulty in releasing their grip e.g. handshake. Myotonia can be elicited by thenar percussion
- 75. Pathogenisis Autosomal dominant. CTG trinucleotide repeat expansion on chromosome 19. mRNA of dystrophia myotonia pr.kinase is affected. In normal subjects fewer than 30 repeats. Expansion of these repeats----disease several thousand repeats in severely affected. Phenomenon of anticipation.
- 76. Morphology Variation in fibre size. Striking increase in no.of intrnal nuclei— conspicuous chain on l.section. Ring fibre---subsarcolemal band of cytoplasm —contains myofibrils arranged circumferentialy. Irregular mass of cytoplasm extending from ring fibre is (sarcoplasmic mass). Only myotonic dystrophy shows changes in intrafusal fibres of muscle spindle, splitting ,necrosis ,regeneration.
- 77. Clinical course Presents in childhood with abnormalities in gait secondary to weakness of foot dorseflexors. Progresses to weakness of hand intrinsic musclesand wrist extensors. Atrophy of muscles of face ptosis—typical facial appearance. Cataracts detected early. Frontal balding ,gonadal atrophy,cardiomyopathy,smooth muscle involvement,decreased plasma IgG.
- 78. Ion Channel Myopathies Group of familial diseases. Myotonia . Relapsing episodes of hypotonic paralysis(after vigorous exercise,cold or high carb. Meal.)or both. Hyperkalemic,hypokalemic and normokalemic periodic paralysis.
- 79. Pathogenesis Mutations in genes encoding ion channels. Hyperkalemic periodic paralysis—gene mutation encoding sodium channel pr. (SCN4A) which regulates entry of sodium in muscle during contraction. Hypokalemic—gene encoding voltage gated L-type calcium channel.
- 80. Malignant hyperpyrexia; A rare clinical syndrome –tachycardia,tachypnia ,muscle spasm ,hyperpyrexia .----triggered by anesthetics---. Syndrome occurs in predisposed individuals with heriditory muscle diseases ----congenital myopathies,dystrophinopathies,metabolic myopathies. Upon exposure to anesthetics –uncontrolled eflux of Ca+ from sarcoplasm—tetany ,increased muscle metabolism ,heat production.
- 81. Congenital Myopathies Group of disorders defined largely on basis of pathological findings within muscles. Share common clinical features---early onset,non or slowly progressive,proximal or generalised muscle weakness ,and hypotonia. Floppy infants –hypotonia or joint contractures(arthrogryposis) ---both these things can be caused by neuromuscular dysfunction. List of these myopathies but Nemaline myopathy—one of the most distinctive types shows numerous rod shaped intracytoplasmic inclutions-(materia of z band)
- 82. A, Nemaline myopathy with numerous rod-shaped, intracytoplasmic inclusions (darkpurple structures). B, Electron micrograph ofsubsarcolemmalnemalinebodies,showingmaterial of Z-band density.
- 83. Myopathies of inborn errors of metabolism Lipid myopathies: Block in fatty acid oxidation and accumulation of lipid droplets within muscle. There is abnormality of carnitine transport or deficiency of mitochondrial dehydrogenase system. Pt. develop muscle pain ,tightness,myoglobinuria after execise or fasting. Cardiomyopathy and fatty liver may occur.
- 84. Mitochondrial myopathy (oxidative phosphorylation diseases). 1/5of pr.involved in oxidative phophorylation are encoded in mt.DNA mtDNA also encodes 22 transfer RNA and 2ribosomal RNA. rest of mt.enzymes are encoded in nucleus. Mitochondrial myopathies.-- Mt.DNA –maternal inheritance as oocyte contributes mitochondria to embryo.
- 85. 13 A, Mitochondrial myopathy showing an irregular fiber with subsarcolemmal collections of mitochondria that stain red with the modified Gomori trichrome stain (ragged red fiber). B, Electron micrograph of mitochondria from biopsy specimen in A showing "parking lot" inclusions.
- 86. Mitochondrial disease –present young adulthood – proximal muscle weakness –extraocular muscles (external ophthalmoplegia) Nurological symptoms Lactic acidosis Cardiomyopathy All above are called mt.enchephalomyopathies.
- 87. Morphology • Aggregates of abnormal mitochondria in muscle biopsy. • In early stages under sarcolema ,then extends throughout the fibre. • Distortion of myofibrils so fibre contour irregular on crossection----ragged red fibres. • E M –increased no. of mt. irregular shape • Paracrystaline parking lot inclusions or alteration in structure of cristae • Cytochrome oxidase –negative fibres.
- 88. Clinical Course & Genetics 3 types of mutations: 1.pt.mutations in mt. DNA. 2.mutations in nuclear DNA. 3.deletions or duplication of mt. DNA.
- 89. Inflammatory Myopathies • 3 groups of these: 1. Infections 2. Non infectious inflammatory 3. Systemic inflammatory. Non infectious inflammatory Heterogeneous gp. of disorder • Immune mediated characterized by injury &inflammation
- 90. • 3 disorders : 1.dermatomyositis 2.polymyositis 3. inclusion body myositis. Dermatomyositis Inflammation of skin and muscles. Skin rash accompany or precede onset of muscle disease. Lilac or heliotrope discoloration of upper eye lids with. Periorbital edema.
- 91. Dermatomyositis. Note the rash affecting the eyelids. B, Dermatomyositis. The histologic appearance of muscle shows perifascicular atrophy of muscle fibers and inflammation. C, Inclusion body myositis showing a vacuole within a myocyte.
- 92. -- Scaling erythmatous eruptions or dusky red patches over knuckles ,elbows knees(grotton lesions). Muscle weakness slow in onset bilaterally symmetrical accompanied by myalgias. Affects proximal muscles first.—getting up of chair ,climbing stairs –difficult. Fine movements affected late. Dysphagia in1/3 of pt. Interstitial lung disease ,vasculitis myocarditis may be present in some. Higher risk of cancers.
- 93. Polymyositis •It differs from dermato. By lack of cutaneous involvement and it is mainly in adults. •There may be heart lung and b.v involvement. Inclusion body myositis • Begins with involvement of distal muscles –especially extensors of knee(quadriceps) •And flexors of wrist ,fingers. •Weakness asymmetrical •Slow development over age 50 •Most sporadic –familial also present
- 94. Etiology & Pathogenesis In dermato. Capillaries target . Deposits of antibodies comliment in b.v.B cells ,CD4+Tcells present within muscle. Polymyositis cell mediated injury to musclers.CD8+Tcells ,macrophages near muscle.expession of HLA class1,11 molecules increased on sarcolemma of normal muscle. Antinuclear antibodies present in some cases. Inclusion body –less clear same as poly.but not respond to immunosuppressive therapy. Ammyloid pr. Tau pr. Related to age ,like Alzheimer.
- 95. Morphology Dermato: Inflammatory infilterate arround by and in perimysial c.t . Gps.of atrophic fibres prominent at periphery of fascicles(sufficient for diagnosis) Marked reduction in intramuscular capill. Necrotic muscle and regenerating also seen.
- 96. Polymyositis---inflammatory cells are in endomyceum .CD8+lymphos. Surround and in vade healthy muscle .necrotic and regenerating fibres seen throughout fascicles. No bv injury. Inclution body—presence of rimmed vacuoles within myosites highlighted by basophilic granules at their periphery. amyloid deposits stain with congo red . Inflamatory infilterate same as in poly.
- 97. Dignosis---EMG—informative. Clinical symptoms elevated creatine kinase Biopsy—for definitive dignosis. Immunosupressive therapy benificial in adults and juvenile dermato.and in poly but not in inclusion body.
- 98. Toxic Myopathies Thyrotoxic.: Proximal muscle weakness Exophthalmic ophthalmoplegia Hypothyroidism—cramping or aching of muscles. Fibre atrophy ,internal nuclei,glycogen aggregates. .Thyrotoxic myopathy –myofibre necrosis ,regeneration,intrstitial lymphocytosis.
- 99. Ethanol myopathy: Acute toxic syndrome—rhabdomyolysis – myoglobinuria---renal failure. Pain muscles ---on histo. Necrosis phagocytosis, regeneration ,evidence of denervation. Drug induced myopathy; steroid myopathy ---proximal muscle weakness in cushings syndrome or therapeutic use ;affects tyype 2 fibers. chloroquin---proximal myopathy.presence of vacuoles in myocytes 50% of fibers. type 1.
- 100. Diseases of neuromuscular junction • Myasthenia gravis: autoimmune mediated loss of acetylecholine receptors. 1-in 100,000. before 4o yrs. Common in women.older age equal occurance. thymic hyperplasia in 65% of patients. thymoma in15% of patients.
- 101. • Morphology: light micro.---unrevealing. In sever cases disuse changes in type 2 fibers.