Ataxia in children: SAQ

The first child has post-infectious acute cerebellar ataxia. He has an acute onset of a wide-based, staggering gait over one day, one to three weeks after a varicella illness, with a normal conscious state, a purely cerebellar pattern of truncal and gait ataxia with dysmetria and slurred speech, and a normal neurological examination apart from the ataxia. His red-flag screen is entirely negative, with no headache, no vomiting, no papilloedema, no head tilt, no cranial nerve palsy, no altered conscious state, and no focal deficit. This combination is the classic, safe pattern of post-infectious acute cerebellar ataxia, the single most common cause of acute ataxia in a preschool child, and the prognosis is excellent. The second child has Friedreich ataxia, with the cardinal combination of a progressive limb and gait ataxia, absent lower limb reflexes, extensor plantar responses, loss of position and vibration sense, pes cavus, scoliosis, and a hypertrophic cardiomyopathy.

Question 1 (10 marks)

Outline your diagnosis, investigation plan, and management for the four-year-old boy, and explain how you would recognise and act on the red flags that would change that plan. ^[1]

My diagnosis is post-infectious acute cerebellar ataxia. The four features that make the diagnosis are the acute onset of a wide-based gait over hours to a day, the preceding varicella illness one to three weeks earlier, the preschool age, and the purely cerebellar pattern with a normal conscious state and a normal examination apart from the ataxia. The condition is the single most common cause of acute ataxia in young children, and the diagnosis is clinical. ^[1]

My investigation plan is to perform no routine tests and no imaging. The diagnosis is clinical, and a child who meets the classic pattern with a normal conscious state and a negative red-flag screen does not need a blood test, a lumbar puncture, or a scan. I would perform a toxicology screen only if I suspected ingestion, which I do not in this child with a clear post-infectious history and no access to medications reported. I would perform a lumbar puncture and imaging only if the red-flag screen or the course changed the picture. ^[1]

My management is reassurance, observation, and safety-netting advice. I would counsel the family that the condition is self-limiting and that the large majority of children recover fully over weeks to months without specific treatment, as the classic study by Connolly established. I would advise the family to return immediately if the child developed a headache, vomiting, drowsiness, a decline in the conscious state, or a worsening rather than an improving gait, and I would review the child in clinic until the ataxia resolved. ^[2]

The red flags that would change my plan are the features of a posterior fossa tumour, a cerebellitis, a central nervous system infection, or an ingestion. A headache that is worse in the morning or wakes the child from sleep, effortless early-morning vomiting, papilloedema, a head tilt, a new squint or cranial nerve palsy, a depressed or fluctuating conscious state, a progressive rather than improving course, fever with meningism, or opsoclonus and extreme irritability would each convert the plan from observation to urgent magnetic resonance imaging. The systematic review by Wilne confirmed that headache, nausea and vomiting, and gait abnormality are among the commonest features of a childhood central nervous system tumour, and the cardinal error is discharging a tumour as a post-infectious ataxia. ^[3]