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Is it MG Crisis?

Is it MG Crisis?. Dr Chan Yan Fat Alfred Caritas Medical Center 20/01/2009. Background history. 82-year-old woman, ex-smoker Mother of 6 children Resident in Canada and being FU at there Post-radioactive-iodine hypothyroidism Asthma with nil attack for years Essential hypertension

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Is it MG Crisis?

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  1. Is it MG Crisis? Dr Chan Yan Fat Alfred Caritas Medical Center 20/01/2009

  2. Background history • 82-year-old woman, ex-smoker • Mother of 6 children • Resident in Canada and being FU at there • Post-radioactive-iodine hypothyroidism • Asthma with nil attack for years • Essential hypertension • Ocular myasthenia gravis (MG) since 2002

  3. Long term medication • L-thyroxine 75 microgram daily • Candesartan 8mg daily • Ventolin 2 puffs Qid PRN • Becotide 2 puffs BD • Pyridostigmine (Mestinon) 60mg BD

  4. History of present illness • Visit Hong Kong since one week ago • Upper respiratory infection since arrival • Fever and sputum for 3 days, and put on oral Levofloxacin 100mg BD + Romilar • Subjective double vision for one day, with bilateral upper limb weakness + numbness, but still able to walk • While at Precious blood Hospital, developed choking and SOB

  5. To CMC AED 9/3/08 at 1900 • BP 202/89, pulse 72, SaO2 88% room air • GCS 15/15, Fever 38.0 degree • Speak full sentence, SaO2 96% at 2L O2 • “muscle weakness” at 4/5 • Chest clear; PFR 170  170  150 • Impression: mild MG • Decision: consult ICU

  6. Direct ICU admission • Failed bedside swallowing test • Impaired abduction of eyes at both side • No facial weakness or fatigability • Power: bilateral upper limb 4-/5 bilateral LL 4/5 proximal; 5/5 distal • Bilateral down-going plantar • Normal deep tendon reflex

  7. Differential diagnosis • Generalized myasthenia gravis (MG) with ocular and bulbar involvement • Thyroid ophthalmopathy + myopathy • Brainstem pathology • Motor cranial nerve pathology • Pharyngeal-cervical-brachial variant of Gullain-Barre Syndrome

  8. Impression at ICU Generalized MG with bulbar involvement Precipitated by……

  9. Famous MG precipitating causes • Antibiotics:aminoglycosides; macrolides; fluoroquinolone; tetracyclines • Anesthetic: lidocaine; procaine; NMB • Cardiac: betablocker; CCB; procainamide • Steroids • Anticonvulsant: phenytoin; gabapentin • Others: Opiods; thyroxine; diuretics; anti-cholinergics; iodinated contrasts; URI

  10. Management by on-call MO • Keep NPO for possible intubation later • Increase Mestinon 60mg tds • Insert RT for medication • Check CBP/RFT/LFT/INR/ABG/ESR • Blood, sputum and urine for culture • Serum viral titre • Urgent plain CT brain

  11. Blood test • WCC 15.4 (Neutrophil 85.4%) • Hemoglobin 13.5 with MCV 89.9 • ESR 87 • CK 145; albumin 37, globulin 42 • RFT and LFT normal • TSH 1.79 (0.50-4.70) • pH 7.41, CO2 42.6, O2 176, HCO3 26

  12. Progress on 10/3/08 at ICU D2 • Subjective deterioration and require frequent suction of oral secretion/ sputum • Examination in AM around: • Hoarseness and weak cough • Drooling of saliva • Poor AE over both chest • Impression: MG crisis

  13. Bronchoscopy • Very poor cough effort • Continuous aspiration of saliva and upper airway secretion into lower tract • BAL done at right lower lobe for virus study and bacterial culture

  14. Management at ICU day 2 • Endotracheal intubation • Start IV Augmentin for chest infection • Start iv Intragram (IVIG) 21g (BW 53kg), plan daily dose for 5 days • Trace old record from Canada family doctor about the diagnosis and previous workup of myasthenia gravis

  15. Progress at ICU day 4 • All ocular movement is full, no ptosis • Hand-grip 3/5; right wrist flexion 2/5; rest of upper limb power 0/5 ! • Both thigh 3/5, both ankle 4/5 • Absent deep tendon reflex of lower limb, markedly decreased at upper limb • Paraesthesia over 4 limb, nil sensory level • BP 100/55, fever down

  16. Atypical presentation of MG! Deterioration with iv Ig Other pathology?

  17. Pros Symmetrical proximal muscle weakness Previous ocular MG Bulbar symptom Precipitating factors of crisis seen Cons Different symptom and sign from past Severity of physical sign not fluctuating Global areflexia Sensory symptoms Can it be due to MG crisis

  18. Management at ICU day 4 • Stop Intragram • Off Mestinon  plan to have more MG workup first e.g. electrophysiology • Urgent MRI cervical spine to upper thoracic spine to look for cord lesion • Trace again past medical record from Canada doctor by relative

  19. Urgent MRI report • Serpentine intradural extramedullary flow-related signals and flow voids are demonstrated from C5 to T9 level, but no definite intramedullary involvement. • No hemorrhage or abnormal signal in cord • No mass effect on cervical/ thoracic cord • Impression: spinal vascular malformation, likely spinal dural AV fistula

  20. Pros Tetraparesis Areflexia Hypotension Normal cognitive function all along MRI showed vascular lesion around cord Cons Proximal affected preferentially No sensory level Bulbar symptoms Ophthalmoplegia, though improved Normal cord signal Can it be spinal cord insult?!

  21. Progress at ICU day 5 • Orthopedics  intramedullary lesion better be managed by neurosurgery • Neurosurgery  no evidence of acute element for intervention, suggest to transfer patient when nil airway problem • ICU  noted good respiratory effort with spontaneous tidal volume >400ml. Failed extubation because of aspiration problem

  22. Progress at ICU day 6 (1) Medical summary from Canada • Patient presents as ptosis and diplopia in June 2002. Nil peripheral/ bulbar or respiratory involvement • Nil Tensilon test, nil anti-acetylcholine receptor antibody checked • Prompt effect with Mestinon • CT thorax showed no thymoma

  23. Progress at ICU day 6 (2) • Proximal muscle power 2/5, distal 4/5 • Double-blinded Tensilon test  no significant change in limb power • Bedside EMG: no typical decrement of amplitude with repetitive stimulation • Acetylcholine receptor binding antibody  10.57 (<0.45, ELIZA method)

  24. Every sign must have explanation

  25. Neurologist (ICU Day 7) • All along no cognitive impairment • No objective sensory deficit • Diplopia on presentation, though remitted • Bulbar symptom: choking/ hoarseness • Both shoulder and hip power 2/5 • Both ankle/wrist and hand power 4/5 • Global areflexia + withdrawal plantar • Impression: Miller Fisher syndrome

  26. Retrospectively, look at the graph of vital signs…….

  27. Temp 40 39 38 37 Off sedation On sedation Off sedation BP/P 240 220 200 180 160 140 120 100 80 60 SBP Temp Pulse ICU intubation 8P 9/3 8A 10/3 8P 10/3 8A 11/3 8P 11/3

  28. Management at ICU day 7 (1) • Contrast CT brain  nil significant lesion • Lumbar puncture  Protein 1.85, glucose 4.0 (serum 9.0)  unfit for cell count  PCR for HSV/ VZV not detected • Check ANF/ANCA/Anti-cardiolipin/ lupus anticoagulant/ cold agglutinin/ atypical pneumonia titer/ CMV and EBV serology

  29. Management at ICU day 7 (2) • Check Anti-Ganglioside Q1b antibody by private lab • Give 3 more days of Intragram 21g daily • Plan perform nerve conduction test on working day to detect any features of polyneuropathy, and to differentiate demyelinating/ axonal degeneration if any

  30. Progress at ICU day 9 • Shoulder/ elbow power 4-/5; hand 5/5 • Hip/ knee power 3/5; ankle 4/5 • Nerve conduction test bedside • Absent F wave response in 5 nerves • Prolonged distal latency • Amplitude and velocity within normal • No conduction block; sural nerve spared • Axonal degeneration; motor dominant

  31. Progress at ICU day 10 • Proximal power 4/5, distal power 5/5 • Right brachioradialis reflex intact, right knee jerk has minimal response • Complained of severe headache and low back pain. ?neck stiffness on exam • ?Mechanical injury of AVM during LP

  32. CT brain + C-spine + L-spine • Brain showed nil significant abnormality • No abnormal vasculature in cervical cord • Small enhancing vessels along surface of thecal sac at level down to L2 • No evidence of bleeding from vessel

  33. Our decision

  34. Further progress • Off RT and oral diet tolerated since day 11 • Discharge to general ward on day 15 • Anti-Ganglioside Q1b 105 (<20) • ANF 1: 80; Anti-ds DNA 13 (<35) • C-ANCA weak +ve; PR3-ANCA 6 (<20) • Cold agglutinin 8 (<32) • Lupus anticoagulant not detected • Anti-cardiolipin IgG 9.5 (weak +ve)

  35. At rehabilitation • Repeated NCT on day 19 showed improving polyneuropathy. Yet EMG showed equivocal MG features • Repeated Tensilon test on day 25  Still NEGATIVE result • Neurology opinion  not to resume Mestinon since MG not the dominant illness • Home on day 48

  36. Neurology FU • No ocular/ bulbar or peripheral symptom • Private MRI brain and brain stem  bilateral frontal lobe atrophy only • Imp: assay for AChR binding antibody in HA is ELIZA, may not be specific enough • Decision: check AChR binding antibody (RIA) + AChR modulating antibody + AChR blocking antibody

  37. Myasthenia Gravis overview • Autoimmune disease • Antibodies against post-synaptic acetylcholine receptor (AChR), or receptor associated protein (muscle-specific TK) • Fluctuating weakness of muscles in various combination of ocular; bulbar; limb; resp • Two clinical form: Ocular vs. Generalized

  38. Presenting symptoms • Ocular: >50%. Among ocular presentation, >50% progress to generalized in 2 years • Bulbar: 15%. Dysarthria/ dysphagia and fatigable chewing • Proximal limb: <5% as presenting symptom • Rare: isolated neck; isolated resp; isolated distal limb weakness

  39. Bedside diagnostic test of MG • Tensilon test: • Sensitivity is 0.92 for ocular; • Sensitivity is 0.88 for generalized • False +ve: MND; brainstem tumor • Ice-pad test: • Best use for ocular MG • Sensitivity: 0.94 for ocular; • Sensitivity: 0.82 for generalized Neuromuscular disorders 2006; 16: 459-67

  40. Ice test 2 min ice Ophthalmology 1999: 106:1282

  41. Electrophysiological studies Repetitive nerve stimulation (RNS) • Motor nerve is stimulated 6-10 times under low frequencies (2-3 Hz) • Positive result if decrement in compound muscle action potential >10% within 4-5 stimuli • Post-activation exhaustion • Post-tetanus potentiation • Sensitivity: 50% if ocular • Sensitivity: 75% if generalized

  42. MG Normal 30 seconds post-ex Post-activation exhaustion

  43. Acetylcholine receptor antibodies • Binding antibody • Most sensitive: 0.93 in severe generalized MG • False +ve in Eaton-Lambert; MND; myositis • Positive in SLE; PBC; thymoma; relative of MG • Blocking • Found in 50% of generalized disease • May be seen in 1% of MG with negative binding antibody • Modulating • Increases sensitivity only ~5% to binding antibody Neurology 1997; 48 (5): S23-27

  44. Other antibodies • Striational antibody (anti-striated muscle) • Present in 30% of MG only, but 80% in those thymoma-assocated MG • Useful marker of thymoma at age 20-50 • Muscle-specific receptor TK (MuSK) • Present in 50% of Ach-R Ab negative case • ?Different pathogenesis with seropositive • Oculobulbar rather than pure ocular • Nil thymoma or even ?thymic atrophy • Respond less to cholinesterase inhibitor Semin Neurol 2004; 24:31

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