Movement disorders, dystonia and chorea: SAQ

This girl presents the classic picture of Sydenham chorea, the neurologic manifestation of acute rheumatic fever, which follows group A streptococcal infection by weeks to months and is a major Jones criterion. The asymmetric flowing movements, the emotional lability and obsessional behaviour, the hypotonia, the motor impersistence with a milkmaid grip and darting tongue, and the preceding sore throat fit the diagnosis, and the echocardiographic mitral regurgitation confirms rheumatic carditis. [4]

Question 1 (10 marks)

Define the movement disorder this girl shows, outline your diagnostic workup, and describe your immediate and long-term management. [4]

This girl has chorea, defined as flowing, unpredictable, semi-purposeful movements that the child cannot suppress, with motor impersistence shown by the milkmaid grip and the darting tongue. The diagnosis is Sydenham chorea, which is a major criterion of acute rheumatic fever following group A streptococcal infection. [4]

My diagnostic workup confirms recent streptococcal infection and assesses the heart. I send anti-streptolysin O and anti-DNase B titres and a throat swab, request an echocardiogram and electrocardiogram because rheumatic carditis may be clinically silent, and arrange a basic infection and autoimmune screen. An EEG is sent only if there is doubt about whether the movements represent a seizure. The diagnosis is clinical, based on the Jones criteria, and the antibody results support rather than establish it. [4]

My immediate management is supportive, with a calm environment, rest, and attention to hydration, safety, and the emotional distress that accompanies the illness. For moderate or severe chorea I add a symptomatic drug such as valproate, carbamazepine, or a neuroleptic, titrated to control the movements. For severe or refractory chorea, the evidence supports a short course of corticosteroids. I do not use metoclopramide, because dopamine-blocking antiemetics can worsen movement disorders and precipitate an acute dystonic reaction. [5]

My long-term management is secondary penicillin prophylaxis to prevent recurrence of acute rheumatic fever and to protect the heart. I start intramuscular benzathine penicillin G every four weeks, at a dose of 600,000 units for a child weighing 27 kilograms or less and 1,200,000 units for a heavier child. This girl weighs 32 kilograms, so she receives 1,200,000 units every four weeks, continued into early adulthood per the local rheumatic fever guideline. I arrange paediatric cardiology follow-up for surveillance of the rheumatic heart disease, and I address the cultural and remote-access needs of her family with an Aboriginal health worker and a clear retrieval and follow-up pathway. [4]

Question 2 (10 marks)

The second child, the 8-year-old boy with dystonic cerebral palsy, has status dystonicus. Outline your immediate assessment and resuscitation, your escalating management, and the precipitants you would search for. [6]

Status dystonicus is a life-threatening movement disorder emergency, and my immediate priority is to triage him to intensive care or a high-dependency setting without delay. The threats are airway compromise, respiratory failure when the chest wall is involved, and rhabdomyolysis with acute kidney injury from muscle breakdown. [7]

I secure the airway and breathing, establish intravenous access, and check creatine kinase, renal function, and urine myoglobin, because his creatine kinase of 18,000 units per litre confirms significant rhabdomyolysis and demands aggressive intravenous hydration to protect the kidneys. I control his pain, because dystonia hurts and uncontrolled pain feeds the spasm, and I place him on cardiac and respiratory monitoring. [6]

I hunt for and treat the precipitant, because removing the trigger is part of the cure. The common precipitants in a child with dystonic cerebral palsy are infection, a medication change or withdrawal, pain, constipation, gastro-oesophageal reflux, urinary infection, dental disease, and an evolving hip subluxation. In a non-verbal child I have a low threshold for treating pain and for investigating a hip, because a worsening dystonia in cerebral palsy is a hip or a pain problem until proven otherwise. [7]

My escalating management follows the status dystonicus ladder. I deploy temporising doses of a benzodiazepine such as diazepam or midazolam to settle the spasm and buy time, and I start or up-titrate enteral anti-dystonia drugs such as trihexyphenidyl, baclofen, and tetrabenazine. If the spasms will not settle, I sedate, paralyse, and ventilate him in intensive care while the dystonia-directed therapy takes effect, and I give early consideration to intrathecal baclofen or deep brain stimulation for refractory disease. I arrange tertiary paediatric neurology and neurosurgery input, and at discharge I provide the family with a written dystonia action plan and a clear safety-net for escalation. [6][7]