Management of pregnancy with Thomsen’s disease
Srilatha Gorthi, Chitra Rajagopalan, John Jolly, Sarah Radbourne, Natalie Drury
Pinderfields Hospital, Mid Yorkshire Hospitals NHS Trust, Wakefield, UK
Pregnant women with neuromuscular disorders often pose a challenge to both obstetrician and anaesthetist. We report a rare case of pregnancy in a woman with Thomsen’s disease which is an autosomal dominant form of myotonia congenita (MC).It is characterized by delayed muscle relaxation after contraction due to dysfunctional chloride channel.
A 22 year old healthy primigravida presented in first trimester describing muscle stiffness and difficulty in initiating a movement or letting go of objects after a few minutes of resting. Her symptoms were similar to those of her father who had been diagnosed with Thomsen’s disease. Few of the other relatives on paternal side also suffered from muscle stiffness and rigidity that was not incapacitating (Figure 1). This pattern progressively worsened in pregnancy. We sought the input from obstetric anaesthetist, neurologist, geneticist and physiotherapist for appropriate planning and management of pregnancy and delivery.
On examination she had handgrip myotonia but, the lower limbs were not affected. She learnt ways of managing her symptoms by repeating same movements several times that relieved her stiffness. It is described as “warm-up effect” after exercise in MC. A diagnosis of Thomsen’s disease based on her history, symptoms and signs was made. Unlike myotonia dystonia, there is no single diagnostic test for Thomsen’s with more than 70 mutations identified thus far in muscle chloride channel gene[i].
The main consideration was regarding labour and delivery where cold temperature and shivering, painful intramuscular injections, use of diathermy and even physiological stresses of labour could precipitate myotonic spasms. Avoidance of an exacerbation of myotonia was paramount as this may not only affect the woman’s ability to progress with labour but also result in myotonic crisis, at its worst causing acute respiratory distress. This crisis can be precipitated by drugs such as depolarizing muscle relaxants (e.g. suxamethonium), adrenaline, beta-adrenergic agonists, and colchicine[ii].
Comprehensive written plans were put in place for labour and delivery with multidisciplinary input. She was given the option of trying for a vaginal delivery with early epidural and administration of phenytoin in case of myotonic crisis. Intramuscular injections were to be avoided and carboprost, if needed would be given subcutaneously. If tocolysis was needed, sublingual glyceryl trinitrate would be given instead of terbutaline. The antenatal course was uneventful and she went into spontaneous labour at 39+3 weeks gestation. She was kept warm and well hydrated. Intravenous oxytocin was used instead of intramuscular ergometrine. She delivered a healthy baby weighing 3.4kg vaginally uneventfully.
Myotonia or prolonged contraction of muscles is a nonspecific sign found in several other disorders including myotonic dystrophies, paramyotonia congenita and hyperkalaemic periodic paralysis. Significantly in MC, there is no muscle weakness. Many patients with Thomsen’s have only mild disease and do not require treatmenti. There is a usually strong family history with 50% chance of transmission to the infant.. This disease is also known as “fainting goat syndrome” whereby goats affected by MC do not actually faint but, they stiffen and often fall over (Figure 2). Early involvement of obstetric anaesthetist and neurologist is desired with written plans in place for labour management. Epidural anaesthesia and also spinal anaesthetic have been successful and general anaesthesia should be avoided if possibleii. Planned caesarean section[iii] as well as vaginal delivery[iv] has been described. Fluctuating muscle weakness occurring only during pregnancies has also been reported[v]. Diagnosis can be missed especially when symptoms are minimal and life- threatening muscular spasms can occur in undiagnosed myotoniasii,more so if emergency obstetric anaesthesia is needed.
A significant amount of robust logistical planning with multidisciplinary involvement is recommended to ensure a comprehensive birth plan is in place. These cases are uncommon thereby requiring high vigilance, effective communication and education to enable the clinicians to offer planned vaginal delivery with no detriment to feto-maternal outcome.
[i] Bradley WG, Daroff RB, Fenichel GM, Jankovic J. Neurology in clinical practice, Volume II: The Neurological Disorders. Fifth edition, 2008
[ii] Farbu E, Søfteland E, Bindoff LA. Anaesthetic complications associated with myotonia congenita: case study and comparison with other myotonic disorders. Acta Anaesthesiol Scand. 2003 May;47(5):630-4.