Myotonic Dystrophy
Last modified: 06 March 2022, 7:01:40 PM AEDT
- Dystrophia myotonica
Definition / diagnostic criteria1 / 8
- myotonia = increased muscle tone = muscle contractures
Classification2 / 8
- DM1
- usually begins in hands, feet, neck, face
- arrhythmias
- dilated cardiomyopathy
- DM2 = Steinert disease
- generally milder
- most common myotonic syndrome
Aetiology / Causes / Risk Factors3 / 8
- hereditary
- AD inheritance
Pathophysiology4 / 8
- abnormal Na/Cl channels
- result = muscle in abnormal hyperexcitable state
- muscle contracts but is unable to relax after contraction
Complications5 / 8
- A = Airway
- aspiration risk from weakness of pharyngeal muscles
- B = Respiratory
- weakness of respiratory muscles, leading to restrictive lung disease
- C = Cardiovascular
- arrhythmias
- dilated cardiomyopathy
- D = Neurological
- Hypersomnia + central sleep apnoea + OSA
- myotonic crisis
- triggers
- drugs (SCh, neostigmine)
- surgery = manipulation, electrocautery, nerve stimulator
- hypothermia / shivering
- management
- phenytoin / procainamide / quinine / IM lidocaine
- ⬆VA
- ineffective = NMBA, IV anaesthesia
- triggers
Anaesthetic considerations6 / 8
- Pre-op
- MDT discussion around plans for surgery
- Intra-op
- caution myotonic crisis
- drugs = SCh, ChEi
- A = aspiration risk
- C = anticipate HDI
- D = ⬆sensitivity to CNS depressants (propofol, opioids, BDZ, barbituates)
- E = maintain normothermia, prevent shivering
- caution myotonic crisis
- Post-op
- B = anticipate need for postop ventilation
Common questions / related topics7 / 8
- pregnancy
- high risk patient
- ⬆muscle weakness, heart failure, uterine atony, PPH
- NA preferred for labour / VD / CS