Ataxia in Children
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Direct answer
Ataxia in children is incoordination of gait and limb movement caused by cerebellar, vestibular or proprioceptive dysfunction. Acute cerebellar ataxia after a viral illness is usually self-limiting, whereas a posterior fossa tumour produces ataxia with raised intracranial pressure. Friedreich ataxia is a progressive autosomal recessive cause that adds areflexia and cardiomyopathy.
What you must remember
- Acute cerebellar ataxia: a sudden unsteady gait in toddlers, often after varicella or Epstein-Barr virus infection, usually resolving within weeks.
- Posterior fossa tumour: medulloblastoma, pilocytic astrocytoma and ependymoma, with morning vomiting and headache.
- Friedreich ataxia: a GAA trinucleotide repeat expansion in the FXN gene on chromosome 9, with autosomal recessive inheritance.
- Friedreich features: absent ankle reflexes, extensor plantar responses, pes cavus, scoliosis and hypertrophic cardiomyopathy.
- Ataxia-telangiectasia: oculocutaneous telangiectasia, immunodeficiency and raised serum alpha-fetoprotein.
- Sensory ataxia: loss of joint position sense that worsens with eyes closed on Romberg testing.
- Red flags: headache, vomiting, head tilt, nystagmus or new cranial nerve signs need urgent MRI.
Comparing the three most-tested causes
Ataxia questions usually turn on the time course and the associated features, so the table compares the three commonest exam answers side by side. Time course is the first discriminator to take from the history, because it often separates a self-limiting illness from a progressive or structural cause.
| Feature | Acute cerebellar ataxia | Posterior fossa tumour | Friedreich ataxia |
|---|---|---|---|
| Onset | Sudden, over hours to days | Subacute, over weeks | Gradual, over years |
| Typical age | Toddlers, one to three years | School age | Childhood to adolescence |
| Reflexes | Preserved | Preserved | Absent at the ankles |
| Associated features | Recent viral illness | Vomiting, headache and head tilt | Pes cavus, scoliosis and cardiomyopathy |
| Course | Usually recovers | Depends on the tumour | Progressive |
A sudden onset after infection favours acute cerebellar ataxia, while progressive ataxia with areflexia points to Friedreich ataxia. Ataxia accompanied by raised intracranial pressure features mandates urgent MRI to exclude a posterior fossa tumour, and the examiner expects candidates to act on that finding first.
Where the exam tries to catch you
Ataxia questions often reward candidates who check red flags before reassuring the family.
- Trap: ordering extensive investigations for a well child with post-viral ataxia Correct: most cases recover, so observation and reassurance are appropriate once red flags are excluded.
- Trap: attributing ataxia with morning vomiting to a viral illness Correct: these features point to a posterior fossa tumour and need urgent MRI.
- Trap: expecting normal reflexes in Friedreich ataxia Correct: ankle reflexes are lost early and plantar responses are extensor, which separates it from cerebellar disease.
- Trap: ignoring telangiectasia in a child with ataxia and recurrent infections Correct: ataxia-telangiectasia is suggested by telangiectasia, immunodeficiency and raised alpha-fetoprotein.
Frequently asked questions
What causes acute cerebellar ataxia in young children?
Acute cerebellar ataxia in young children is most often post-infectious, following varicella, Epstein-Barr virus or other viral infections. It usually resolves over weeks, and most children recover fully without specific treatment.
Which features suggest a posterior fossa tumour in a child with ataxia?
Posterior fossa tumours such as medulloblastoma cause ataxia with morning vomiting, headache, head tilt and signs of raised intracranial pressure. Any child with these features needs urgent MRI of the brain rather than reassurance alone.
What is the genetic basis of Friedreich ataxia?
Friedreich ataxia is an autosomal recessive disorder caused by a GAA trinucleotide repeat expansion in the FXN gene on chromosome 9. The expansion reduces frataxin, which leads to progressive ataxia and cardiomyopathy.
How does ataxia-telangiectasia differ from Friedreich ataxia?
Ataxia-telangiectasia is an autosomal recessive disorder with oculocutaneous telangiectasia, immunodeficiency and raised serum alpha-fetoprotein. Friedreich ataxia lacks these features and is instead characterised by areflexia, pes cavus and hypertrophic cardiomyopathy.
Why does the Romberg sign matter in a child with ataxia?
The Romberg sign separates sensory ataxia, where loss of joint position sense worsens with eyes closed, from cerebellar ataxia. A positive Romberg sign points towards peripheral neuropathy or dorsal column disease rather than the cerebellum.