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Muscular System Suresh Agarwal, M.D. Page 3 Muscular System Neuromuscular Physiology Neuromuscular Disorders Compartment Syndrome Rhabdomyolysis

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Presentation on theme: "Muscular System Suresh Agarwal, M.D. Page 3 Muscular System Neuromuscular Physiology Neuromuscular Disorders Compartment Syndrome Rhabdomyolysis"— Presentation transcript:


2 Muscular System Suresh Agarwal, M.D.

3 Page 3 Muscular System Neuromuscular Physiology Neuromuscular Disorders Compartment Syndrome Rhabdomyolysis

4 Page 4 Neuromuscular Physiology: The Motor Unit Lower Motor Neurons = Alpha Motor Neurons Alpha Motor Neuron Cell Bodies –Cranial Musculature: In the Brainstem –Somatic Cells: In the Anterior Horn of the Spinal Cord Nerve Roots Plexus Peripheral Nerves Terminal Ramifications Motor Neuron Synapse

5 Page 5 The Motor Unit Neuromuscular Junction Presynaptic Acetylcholine Release Postsynaptic Acetylcholine Binding –Increases Muscle End-Plate Potential –Threshold Level > Depolarizes Calcium Ions Released from Sarcoplasmic Reticulum Excitation-Contraction Coupling > Muscle Contraction Acetylcholine Degraded by Cholinesterase Lab10/IMAGES/MOTOR%20END%20PLATES%20SMAL L%201.jpg AAAAAAAASk/3BRF9vWKgYY/s400/Neuro- Muscular+Junction.jpg

6 Page 6 Neuromuscular Disorders CI342MUSSYS002.gif Neuromuscular diseases leading to critical illness –Guillain-Barre Syndrome –West Nile Virus Acute Flaccid Paralysis Syndrome –Myasthenia Gravis Neuromuscular diseases caused by critical illness –Critical Illness Polyneuropathy & Myopathy

7 Page 7 Neuromuscular Disorders Acute Inflammatory Demyelinating Polyradiculoneuropathy (a.k.a. Guillain-Barre Syndrome) Motor >>Sensory Peripheral Neuropathy Monophasic Nadir at 4 weeks Immune mediated Exact etiology unknown Demyelinating Neuropathy Primary Axonopathy content/uploads/2009/11/guillain-barre- syndrome.jpg

8 Page 8 Guillain-Barre Syndrome ? Preceding disease or condition Gangliosides Campylobacter jejuni ba/Campylobacter.jpg/450px-Campylobacter.jpg

9 Page 9 Guillain-Barre Syndrome Clinical Findings –Subacute –Progressive weakness –Starts in legs –Sensory complaints –No objective sensory deficits –Diminished or absent deep tendon reflexes Myelin nated_neuron.jpg 9e201156f86664c970c-320pi

10 Page 10 Guillain-Barre Syndrome CSF findings, around 2nd week –Elevated protein –No pleocytosis srecov.gif

11 Page 11 Guillain-Barre Syndrome Electrodiagnostic Studies Motor and Sensory Nerve Conduction Studies Needle Electromyography Findings: –Segmental nerve demyelination –Multifocal conduction blocks –Slow Conduction Velocity –Consistent with a Peripheral Neuropathy 7/08/01/health/adam/9238.jpg

12 Page 12 Guillain-Barre Syndrome Management Vent support Autonomic Dysfunction Immunotherapy –Plasma exchange –High dose IVIg Rehabilitation pic.jpg

13 Page 13 West Nile Virus West Nile Virus Acute Flaccid Paralysis Syndrome –Flavivirus –Birds and mosquitoes (Culex) –Late summer or Fall wsroom/images/ jpg mages/nrmicro1326-f2.jpg

14 Page 14 West Nile Virus 3 Different Clinical Manifestations 1.Asymptomatic infection 2.Mild febrile syndrome West Nile Fever approx. 20% 3 – 6 days duration 3.Neuroinvasive disease West Nile meningitis or encephalitis approx. 1 in 150 Wee0M: pl/hi/health/03/travel_health/diseases/img/ westnile.jpg

15 Page 15 West Nile Virus Acute Flaccid Paralysis Syndrome –“poliomyelitis-like” –Ventral Horns and Ventral Roots –Acute –Asymmetrical –Flaccid –No Sensory Deficits –No diffuse reflex deficits –No bowel or bladder dysfunction logy2.jpg

16 Page 16 West Nile Virus – Acute Flaccid Paralysis Syndrome Electrodiagnostic testing –Normal sensory potentials –No findings of segmental demyelination (unlike Guillain-Barre) –Low amplitude muscle action potentials I n affected areas –Significant denervation changes in affected areas MRI CSF –Mild pleocytosis (lymphocytic) –Mild to Moderate increase in protein –No change in glucose 2000/Polio/Reflexcopy.jpg

17 Page 17 West Nile Virus – Acute Flaccid Paralysis Syndrome Diagnosis –Reverse-transcriptase PCR (insensitive) –Antibody-capture ELISA (IgM) Treatment –Supportive –?IVIg –?Antiretroviral medications Prognosis for recovery of strength is poor images/mosquito.jpg

18 Page 18 Myasthenia Gravis Autoimmune attack on acetylcholine receptor Fluctuating weakness Progressive with sustained exertion Incidence: –Early adulthood: –Women > Men –Later adulthood: –Women = Men

19 Page 19 Myasthenia Gravis Clinical Presentation Muscle fatigue –Worst with prolonged exertion Ocular muscles –Ptosis –Diplopia Bulbar muscles –Dysphagia –Dysarthria Respiratory Failure

20 Page 20 Myasthenia Gravis Diagnosis Clinical presentation Edrophonium testing Electrophysiologic studies –Repetitive nerve stimulation Antibody Testing –Acetylcholine receptor –Muscle specific receptor tyrosine kinase (MuSK) 10-3_ach.jpg

21 Page 21 Myasthenia Gravis Myasthenic Crisis –20% of patients with MG –Respiratory failure –Precipitating factors Bronchopulmonary processes Aspiration Sepsis Surgical procedures Immune modulation tapering Corticosteroids Pregnancy Certain Drugs Neuromuscular blocking agents –Sensitive to Nondepolarizing agents –Resistant to Depolarizing agents Thymomas –More fulminate disease –30% of patients with myasthenic crisis

22 Page 22 Myasthenia Gravis Treatment –Immunomodulating Methods Plasma exchange (short-term) –Myasthenic crisis –Surgical preparation –Increased strength after 2 to 3 exchanges IVIg (short-term) –Alternative to plasma exchange –Possible longer period until onset of effect Corticosteroids –Occasionally used –Prolonged crises –Transient increase in weakness

23 Page 23 Myasthenia Gravis Treatment –Cholinesterase inhibitors Cholinergic Crisis –Possible increase in weakness –Muscle fasciculations –Muscarinic symptoms Avoid repeated/escalating doses Discontinue after intubation Acetylcholine Receptor nic_Acetylcholine_receptor.png

24 Page 24 Myasthenia Gravis Thymus –Abnormal in 75% –Thymoma in 25% Benign Malignant Thymectomy –Necessary for thymoma –Controversial for patients without know thymic abnormalities –Disease course often abates gate/images/si2141.jpg

25 Page 25 Critical Illness Polyneuropathy & Myopathy Generalized weakness Axonal Predisposing Factors –Critical Illness –Sepsis –Multiple system organ failure Prolonged mechanical ventilation

26 Page 26 Critical Illness Polyneuropathy & Myopathy Common Antecedents –Sepsis –Multiple System Organ Failure Pathophysiology –ICU days –Number of invasive procedures –Hyperglycemia –Hypoalbuminemia –Severity of MSOF –Neuromuscular Blocking Agents –Corticosteroids

27 Page 27 Critical Illness Polyneuropathy & Myopathy Clinical Features –Muscle weakness and wasting –Parasthesias –Distal Sensory Loss Deep Tendon Reflexes –Diminished or absent _waste_MPA.jpg

28 Page 28 Critical Illness Polyneuropathy & Myopathy Nerve Conduction –Normal nerve conduction speed –Decreased muscle action potential amplitude –Decreased sensory nerve action potential amplitude Needle Electrode –Denervation Histopathology –Primary axonal degeneration mages/nrneurol f1.jpg

29 Page 29 Critical Illness Polyneuropathy & Myopathy Prognosis –Underlying critical illness –Increased ventilator dependence –Functional recovery in several months Padding and Positioning to prevent compression neuropathies s/2/MedicalLibraryAssets/Medical/CubitalTu nnel_small.jpg Ulnar Nerve Compression

30 Page 30 Compartment Syndrome Open or Closed Fractures Fixed Compartment Tissue edema and bleeding Blood flow impeded –Capillaries –Arterioles Factors effecting tissue necrosis –Amount of Pressure –Duration of increased pressure –Sensitivity of the tissue to ischemia Right Buttock Compartment Syndrome gif

31 Page 31 Compartment Syndrome Tissue Ischemia –Nervous tissue Functional abnormalities after 30 minutes Irreversible damage after 12 to 24 hours –Muscle Functional abnormalities after 2 to 4 hours Irreversible damage after 4 to 12 hours Increased capillary permeability -> Edema Necrotic Muscle tentmgr/files/a384bb3c7b77e154ad25c613 6d7be344/miscdocs/lab_manual_extremity _chapter_4__2_.pdf

32 Page 32 Compartment Syndrome Risk factors –Severity of fracture –Extent of soft tissue injury –Compressive devices Anti-shock trousers Tourniquets –Systemic hypotension ants.jpg

33 Page 33 Compartment Syndrome Most common location = Anterior Compartment of the Lower Leg Usually from closed tibia fracture Other sites –Thigh –Arm –Buttock –Foot

34 Page 34 Compartment Syndrome Diagnosis Clinical –Tense compartment to palpation –Severe pain with passive range of motion –Severe compartment tenderness –Impaired sensory exam –Decreased distal perfusion –Pulseless = Too Late Extensive tissue necrosis present –Serial Exams are Critical corner/cme/rheumatology- rounds/images/rounds11/slide22.jpg

35 Page 35 Compartment Syndrome Measurement of Compartment Pressures –Unresponsive patients –Pressure > 30 to 45 = Indication for Fasciotomies –Diastolic BP – Compartment Pressure < 30 = indication for Fasciotomies corner/cme/rheumatology- rounds/images/rounds11/slide22.jpg

36 Page 36 Treatment –Surgical Fasciotomies –Fasciotomy within 12 hours = 68% normal functional result –Hydration –Monitor electrolytes –Monitor for infection of fasciotomy sites Compartment Syndrome Fasciotomy_leg.jpg

37 Page 37 Lower Leg Fasciotomies 2 incisions 4 compartments Anterolateral Incision ery/ jpg

38 Page 38 Lower Leg Fasciotomies Medial Incision Incision 1 fingerbreadth posterior to medial edge of the tibia Liberal Length Avoid saphenous vein Divide fibers of soleus from tibia Neurovascular bundle y/ jpg Posteriomedial Incision

39 Page 39 Upper Leg Fasciotomies 3 Compartments –Anterior –Posterior –Medial Compartment syndrome rare 3 compartments blend with the hip Lateral incision usually sufficient Occasionally requires medial incision files/a384bb3c7b77e154ad25c6136d7be344/miscd ocs/lab_manual_extremity_chapter_4__2_.pdf

40 Page 40 Foot Compartment Syndrome 4 Compartments Interosseus or Intrinsic Compartment –4 intrinsic muscles between 1 st and 4 th metatarsals Medial Compartment –Abductor hallicus and flexor hallicus brevis Central or Calcaneal Compartment –Flexor digitorum brevis, quadratus plantae, and the adductor hallicus Lateral Compartment –Flexor digiti minimi brevis, abductor digiti minimi r/files/a384bb3c7b77e154ad25c6136d7be344/mis cdocs/lab_manual_extremity_chapter_4__2_.pdf

41 Page 41 Foot Compartment Syndrome Up to 10% of calcaneal fractures 41% of crush injuries to the foot No classic sign of CS Most reliable sign: tense bulging tissue - es/a384bb3c7b77e154ad25c6136d7be344/miscdocs/ lab_manual_extremity_chapter_4__2_.pdf

42 Page 42 Forearm and Hand Fasciotomies Compartment syndromes are less common than in the leg Supracondylar humerus fx > antebrachial compartment syndrome Anterior compartment realeased with volar incision Dorsal incision if necessary jpg jpg

43 Page 43 Hand Fasciotomies Compartment syndrome of the hands is rare –? From Trauma –More often iatrogenic (A-line or IV infiltrate) 10 Osseofascial Compartments –Carpal tunnel release –1 or 2 dorsal incisions No sensory nerve symptoms Pressure > 20mmHg = CS Dorsal Interosseus Compartment Fasciotomies es/ jpg Thenar and Hypothenar Compartment Fasciotomies es/ gif

44 Page 44 Rhabdomyolysis Damage to skeletal muscle –Crush Injures cells Decreases perfusion –Metabolic –Cell lysis due to edema Calcium in sarcoplasmic reticulum –Muscle contractions Depletes ATP Damage to mitochondrion –Reactive oxygen species Neutrophils migrate –Increased inflammatory response Muscle compresses local structures > Compartment Syndrome > Decreased Perfusion Muscle cells release potassium, phosphate, myoglobin, creatine kinase and uric acid

45 Page 45 Rhabdomyolysis Myoglobin –Nephrotoxic Muscle swelling –Intravascular volume deficit –Renal hypoperfusion Uric acid –Precipitates in renal tubules Myoglobin –Accumulates in renal tubules

46 Page 46 Rhabdomyolysis Myoglobinuria –Plasma myoglobin > 1.5 mg/dL –Myoglobin casts cause nephron obstruction –Urine Acidification Tea-colored urine Urine dipstick + for blood Urine – for red blood cells on microscopy content/uploads/2009/12/image_34.jpg

47 Page 47 Rhabdomyolysis Management –Replete Volume –Mannitol Increases flushing of myoglobin from renal tubules Effective radical scavenger –Sodium bicarbonate Alkalization of Urine Decreases cast formation Decreases direct toxic effect of myoglobin on the renal tubules content/uploads/2007/06/jimstanisg1.jpg

48 Page 48 Myositis Ossificans Severe blunt trauma Intra-muscular hematoma Delayed ossification of the soft tissue Suspected to be due to premature return to strenuous activity Most common sites: - arms - quadriceps Treatment - Conservative - Rarely, surgical debridement _4acef1936b33836.jpg

49 Page 49 Image Sources XVlqSv6hA8/s400/icu.gif 9vWKgYY/s400/Neuro-Muscular+Junction.jpg gif jpg /PIIS fx1.lrg.jpg 320pi

50 Page 50 Image Sources MOTOR%20END%20PLATES%20SMALL%201.jpg jpg jpg jpg jpg png jpg

51 Page 51 Image Sources gif Luis and Ng Journal of Medical Case Reports :6 doi: / /Medical/CubitalTunnel_small.jpg jpg D5D3A36.jpg mg/westnile.jpg

52 Page 52 Image Sources _4a6dba 08992cc.jpg /L_IMG_fig11.jpg Textbook of Critical Care. Fink MP, Abraham E, Vincent JL, Kochanek P (ed) 5th ed : Philadelphia : Elsevier Saunders, 2005

53 Page 53 Image Sources Trauma, 4th edMattox KL, Feliciano DV, Moore EE, eds. New York, NY: McGraw-Hill, 2000 v/bookshelf/picrender.fcgi?book=gene&part=hna&blobname=hna-Fig1.jpg ptor.png 0px-Campylobacter.jpg

54 Page 54 Image Sources =/Surgery/en/_img/surgery/FurtherReading/PFxM2/ jpg Disease.jpg g

55 Page 55 References _with_shilajit/images/muscle.jpg rounds/images/rounds11/slide22.jpg

56 Page 56 References syndrome.jpg

57 Page 57 References f1.jpg content/uploads/2008/08/muscle_man_running.jpg com/content/figures/ l.jpg b77e154ad25c6136d7be344/miscdocs/lab_manual_extremity_chapt er_4__2_.pdf nt1.jpg

58 Page 58 References 36.jpg ex.png rics/copingwithintensivecareunit/images/ventilator.gif

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