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Program Information. Muscular System. Suresh Agarwal, M.D. Muscular System. Neuromuscular Physiology Neuromuscular Disorders Compartment Syndrome Rhabdomyolysis. www.health-res.com/EX/08-05-01/als1.jpg. Neuromuscular Physiology: The Motor Unit. Lower Motor Neurons = Alpha Motor Neurons

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  1. Program Information

  2. Muscular System Suresh Agarwal, M.D.

  3. Muscular System Neuromuscular Physiology Neuromuscular Disorders Compartment Syndrome Rhabdomyolysis www.health-res.com/EX/08-05-01/als1.jpg

  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 palrehab.net/images/spin20.jpg

  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 education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab10/IMAGES/MOTOR%20END%20PLATES%20SMALL%201.jpg bp3.blogger.com/_v2GFIISzHOU/SAjilu3b8kI/AAAAAAAAASk/3BRF9vWKgYY/s400/Neuro-Muscular+Junction.jpg

  6. Neuromuscular Disorders • 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 www.factmonster.com/images/ESCI342MUSSYS002.gif

  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 www.infiniteunknown.net/wp-content/uploads/2009/11/guillain-barre-syndrome.jpg

  8. Guillain-Barre Syndrome ? Preceding disease or condition Gangliosides Campylobacter jejuni upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Campylobacter.jpg/450px-Campylobacter.jpg

  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 upload.wikimedia.org/wikipedia/commons/c/c1/Myelinated_neuron.jpg drdavis.typepad.com/.a/6a00d834525ed169e201156f86664c970c-320pi

  10. Guillain-Barre Syndrome • CSF findings, around 2nd week • Elevated protein • No pleocytosis neuromuscular.wustl.edu/pics/diagrams/emg/gbsrecov.gif

  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 graphics8.nytimes.com/images/2007/08/01/health/adam/9238.jpg

  12. Guillain-Barre Syndrome Management Vent support Autonomic Dysfunction Immunotherapy Plasma exchange High dose IVIg Rehabilitation repairstemcell.files.wordpress.com/2009/03/ms-pic.jpg

  13. West Nile Virus West Nile Virus Acute Flaccid Paralysis Syndrome Flavivirus Birds and mosquitoes (Culex) Late summer or Fall media.publicbroadcasting.net/kera/newsroom/images/3197830.jpg www.nature.com/nrmicro/journal/v4/n1/images/nrmicro1326-f2.jpg

  14. West Nile Virus 3 Different Clinical Manifestations • Asymptomatic infection • Mild febrile syndrome West Nile Fever • approx. 20% • 3 – 6 days duration • Neuroinvasive disease West Nile meningitis or encephalitis • approx. 1 in 150 t2.gstatic.com/images?q=tbn:vSeOC3WZ2Wee0M:http://news.bbc.co.uk/nol/shared/spl/hi/health/03/travel_health/diseases/img/westnile.jpg

  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 www.tmin.ac.jp/english/dept/07/neurology2.jpg

  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 In affected areas Significant denervation changes in affected areas MRI CSF Mild pleocytosis (lymphocytic) Mild to Moderate increase in protein No change in glucose www.brown.edu/Courses/Bio_160/Projects2000/Polio/Reflexcopy.jpg

  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 www.co.klamath.or.us/healthDept/images/mosquito.jpg

  18. Myasthenia Gravis Autoimmune attack on acetylcholine receptor Fluctuating weakness Progressive with sustained exertion Incidence: Early adulthood: Women > Men Later adulthood: Women = Men www.hakeem-sy.com/main/files/images/MyastheniaGravis.JPG

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

  20. Myasthenia Gravis Diagnosis Clinical presentation Edrophonium testing Electrophysiologic studies Repetitive nerve stimulation Antibody Testing Acetylcholine receptor Muscle specific receptor tyrosine kinase (MuSK) www.mda.org/publications/images/q10-3_ach.jpg

  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. 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. Myasthenia Gravis Treatment Cholinesterase inhibitors Cholinergic Crisis Possible increase in weakness Muscle fasciculations Muscarinic symptoms Avoid repeated/escalating doses Discontinue after intubation Acetylcholine Receptor upload.wikimedia.org/wikipedia/commons/6/6e/Nicotinic_Acetylcholine_receptor.png

  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 www.aurorahealthcare.org/healthgate/images/si2141.jpg

  25. Critical Illness Polyneuropathy & Myopathy Generalized weakness Axonal Predisposing Factors Critical Illness Sepsis Multiple system organ failure Prolonged mechanical ventilation www.pathologyoutlines.com/images/softtissue/06_13.jpg

  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. Critical Illness Polyneuropathy & Myopathy Clinical Features Muscle weakness and wasting Parasthesias Distal Sensory Loss Deep Tendon Reflexes Diminished or absent vasculitis.med.jhu.edu/typesof/images/Muscle_waste_MPA.jpg

  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 www.nature.com/nrneurol/journal/v5/n7/images/nrneurol.2009.75-f1.jpg

  29. Critical Illness Polyneuropathy & Myopathy Prognosis Underlying critical illness Increased ventilator dependence Functional recovery in several months Padding and Positioning to prevent compression neuropathies Ulnar Nerve Compression meddb.eznetpublish.ihealthspot.com/portals/2/MedicalLibraryAssets/Medical/CubitalTunnel_small.jpg

  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 casesjournal.com/content/figures/1757-1626-2-190-3.gif

  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 www.operationgivingback.facs.org/stuff/contentmgr/files/a384bb3c7b77e154ad25c6136d7be344/miscdocs/lab_manual_extremity_chapter_4__2_.pdf

  32. Compartment Syndrome Risk factors Severity of fracture Extent of soft tissue injury Compressive devices Anti-shock trousers Tourniquets Systemic hypotension www.nexternal.com/medtech/images/MastPants.jpg

  33. Compartment Syndrome • Most common location = Anterior Compartment of the Lower Leg Usually from closed tibia fracture • Other sites • Thigh • Arm • Buttock • Foot orthoinfo.aaos.org/figures/A00204F01.

  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 www.hopkins-arthritis.org/physician-corner/cme/rheumatology-rounds/images/rounds11/slide22.jpg

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

  36. Compartment Syndrome • Treatment • Surgical Fasciotomies • Fasciotomy within 12 hours = 68% normal functional result • Hydration • Monitor electrolytes • Monitor for infection of fasciotomy sites upload.wikimedia.org/wikipedia/commons/d/da/Fasciotomy_leg.jpg

  37. Lower Leg Fasciotomies • 2 incisions • 4 compartments • Anterolateral Incision Anterolateral Incision Anterolateral Incision img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1270542-199.jpg

  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 Posteriomedial Incision Posteriomedial Incision img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1270542-169.jpg

  39. 3 Compartments Anterior Posterior Medial Compartment syndrome rare 3 compartments blend with the hip Lateral incision usually sufficient Occasionally requires medial incision Upper Leg Fasciotomies www.operationgivingback.facs.org/stuff/contentmgr/files/a384bb3c7b77e154ad25c6136d7be344/miscdocs/lab_manual_extremity_chapter_4__2_.pdf

  40. Foot Compartment Syndrome 4 Compartments • Interosseus or Intrinsic Compartment • 4 intrinsic muscles between 1st and 4thmetatarsals • 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 www.operationgivingback.facs.org/stuff/contentmgr/files/a384bb3c7b77e154ad25c6136d7be344/miscdocs/lab_manual_extremity_chapter_4__2_.pdf

  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 www.operationgivingback.facs.org/stuff/contentmgr/files/a384bb3c7b77e154ad25c6136d7be344/miscdocs/lab_manual_extremity_chapter_4__2_.pdf

  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 img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1268992-1269081-126919.jpg img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1268992-1269081-1269193.jpg

  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 Thenar and Hypothenar Compartment Fasciotomies jmedicalcasereports.com/content/figures/1752-1947-1-6-2.gif Dorsal Interosseus Compartment Fasciotomies jmedicalcasereports.com/content/figures/1752-1947-1-6-1.jpg

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

  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 lifeinthefastlane.com/wp-content/uploads/2009/12/image_34.jpg

  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 bioephemera.com/wp-content/uploads/2007/06/jimstanisg1.jpg

  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 www.radiologyassistant.nl/images/thmb_4acef1936b33836.jpg

  49. Image Sources bp2.blogger.com/_OY2fM522a9Y/SBZ0DYml2xI/AAAAAAAABA4/KXVlqSv6hA8/s400/icu.gif bp3.blogger.com/_v2GFIISzHOU/SAjilu3b8kI/AAAAAAAAASk/3BRF9vWKgYY/s400/Neuro-Muscular+Junction.jpg bioephemera.com/wp-content/uploads/2007/06/jimstanisg1.jpg casesjournal.com/content/figures/1757-1626-2-190-3.gif ccforum.com/content/figures/cc2978-1.jpg dericbownds.net/uploaded_images/myoglobin.jpg download.thelancet.com/images/journalimages/0140-6736/PIIS0140673609600398.fx1.lrg.jpg drdavis.typepad.com/.a/6a00d834525ed169e201156f86664c970c-320pi

  50. Image Sources • education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab10/IMAGES/MOTOR%20END%20PLATES%20SMALL%201.jpg • graphics8.nytimes.com/images/2007/08/01/health/adam/9238.jpg • img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1268992-1269081-1269193.jpg • img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1268992-1269081-1269194.jpg • img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1270542-169.jpg • img.medscape.com/pi/emed/ckb/orthopedic_surgery/1230552-1270542-199.jpg • img.medscape.com/pi/emed/ckb/pediatrics_general/1331341-1331932-982711-1723745.png • jmedicalcasereports.com/content/figures/1752-1947-1-6-1.jpg

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