myotonic dystrophy - anaesthetic considerations

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Myotonic dystrophy Case Presentation March 2013

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Myotonic dystrophy

Myotonic dystrophyCase PresentationMarch 2013


OutlineCaseBackgroundSigns and symptomsTreatmentConsiderations for anaestheticSummary

Case46 year old maleKnown myotonic dystrophyRight open ankle fusion & osteotomy


Background (1)LOTS OF NAMESMyotonic DystrophySteinerts DiseaseDystrophica MyotonicaMyotonica AtrophicaBatten-CurschmannsHoffmans

Background (2)Chronic, slowly progressing, highly variable, multisystem diseaseM=F1 per 7000/8000 peopleAutosomal dominant DMPK gene, nucleotide repeat disorder, anticipation2 types:Type 1Type 2 - Proximal Myotonic Myopathy (PROMM)

First described by Steinert in 1909 in Germany 9 cases. Described later that year in UK about 5 cases including 3 family members (siblings) with the characteristic faces.Certain areas of DNA have repeated sequences of two or three nucleotides.; number of repeats is proportional to severity of diseaseOn average 50% chance passed onto child - Normally the symptoms of the disease become more severe and the age at onset becomes earlier in successive generations of a family i.e. ANTICIPATION

Type 2:Distinct features proximal muscles, muscle pain, no facial weakness, no congenital form.Different genetic abnormality (chromosome 3 not 19); 4 amino acid repeat rather than 3 amino acid repeatSimilarities autosomal dominant, muscle weakness, myotonia, cataracts, cardiac conduction defects, gonadal atrophy5

Signs and symptoms (1)Neuro:Wasting/weakness of musclesMyotoniaCognitive impairmentBehavioural problemsExcessive sleepiness

CVS:Heart conduction defects; arrhythmiasCardiomyopathyResp:Regular chest infectionsAspirationHypoventilation, OSA

Weakness is very variable and may range from mild to severe. It particularly involves the face and eyelids (ptosis), jaw, neck (SCM), distal limbs (forearms and hands, lower legs and feet). Diaphragm and intercostals. It can affect speech and result in a lack of facial expression

Myotonia is difficulty in relaxing a muscle after it has been contracted, for example it may be difficult to let go after gripping something. Myotonia tends to affect grip more than other muscles, but can affect the tongue

Chest and Breathing problems- Chest infections may result from weakness of breathing muscles or from food entering the lungs as a result of poor swallowing. Inadequate breathing during the night may lead to disturbed sleep, difficulty waking, morning headaches, loss of appetite and daytime sleepiness. Cause of death in 40%


Signs and symptoms (2)Endocrine:Insulin resistance, hypothyroidismMale infertilityPremature frontal baldingOpthalmology:CataractsPtosisGISwallowing problemsGallstonesConstipation/diarrhoeaSkeletalScoliosisTalipes

(DM same incidence as general population)Swallowing problems due to oesophageal dysfunction


Useful clinical clue for diagnosis:Failure of spontaneous letting go of the hands following strong handshakes due to myotonia

Myotonia = delayed relaxation of muscles after contraction


Definitive diagnosis by:DNA analysisEMGSlit lamp exam of lensSerum CKSerum FSH, testosteroneECGMuscle biopsy

DNA analysis - Can see on chromosome and how many repeats have got


TreatmentNo cure or treatmentManage complications orthotics, pacemakers, physio, mobility aids

Myotonic Dystrophy & Anaesthesia

Anaesthetic related problemsDiagnosisGetting correct historyCardio-respiratory complicationsAspiration risk? Difficult airwayAnalgesic/anaesthetic drugsNeuromuscular blocking drugsMyotonia triggersPregnancy

Pre-assessmentPrecise diagnosis Full discussion with patient & family re: potential risks/benefitsAssessment of function & co-morbidities InvestigationsAnaesthetic planPlanning post-op care

Precise diagnosis not always possible as occasionally anaesthesia is required for diagnosis14

Cardiac investigationsRoutine ECGAbnormality may not be apparent on ECGIf symptomatic24 hr ECG tapeInvasive electrophysiological studiesECHOIf asymptomatic annual ECG, 24hr tape every 2 years, TTE every 5 years

24 hr tape - if lots of ventricular arrhythmias then consider IED)


Respiratory investigationsCXRSubclinical aspiration commonPulmonary function testsSpirometryABG

Restrictive picture on pulm func tests due to the scoliosis16

Airway problems? RSIAspiration riskAvoid suxamethonium? Intubation difficulty

Peri-operative managementSensitivity to sedative, analgesic, anaesthetic drugsNeuromuscular blockade NDMR in reduced doses (10 - 20%); avoid suxamethoniumClose temperature controlUse of regional anaesthesia if possible

Sensitivity to sedatives or painkillers hence less likely to be able to cough and clear their secretions as prolonged apnoea and respiratory depression; also inhalational drugs like isoflurane can prolong QTAtracurium is a popular choice due to its spontaneous Hoffman degradation but the key to muscular blockade is careful titration and close monitoring with a peripheral nerve stimulator (PNS)Suxamethonium causes prolonged myotonia so avoidIn those with cardiovascular complications and autonomic dysfunction, severe hypotension may result from neuroaxial blockade


Peri-operative complicationsOSA, aspirationDysrrythmias, cardiac failureAutonomic dysfunctionMyotoniaRhabdomyolysis

MyotoniaCan be precipitated by:suxamethonium anticholinesterases opioids alterations in temperature/shivering acidosis

Suxamethonium gives prolonged myotonia, and not able to reverse so AVOIDNDMR reversal with neostigmine can precipitate myotoniaConsequences of hypothermia can include triggering of muscle spasms, increased sensitivity to muscle relaxants and aggravation of rhabdomyolysis


Post-operativelyTiming of extubationAvoid hypothermiaMonitor electrolytesMay need higher level of care post op (HDU, ITU)High index of suspicion for respiratory complicationsOpioids with caution for post op analgesia

Not to extubate until patient able to maintain adequate tidal volumes and airway reflexes returned (as resp failure and aspiration too high risk) mandatory physioAvoid shivering as triggers myotoniaParticularly K+ in light of high rhabdomyolysis risk (could urine dip for myoglobin or serum CK)Opioids can depress respiration as well as slow gastric transit and thus increase aspiration risk


Pregnancy in MDIncrease in myotonic symptomsAtonic uterusPPH commonMother can pass on congenital form to baby

CaseSpinal sited with 2.2ml 0.5% heavy marcain and 0.3mg diamorphineNo sedation requiredOxygen via simple hudson facemaskUneventful anaesthetic

SummaryLarge spectrum of signs & symptomsOften misdiagnosed or underdiagnosed conditionKnowledge & awareness of condition means the avoidable & expected complications can be minimised

Referenceshttp://www.myotonicdystrophysupportgroup.orgFRCA Neuromuscular disorders and anaesthesia (2009) Video Platform Neuromuscular Disease