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A 16-year-old girl presented because her mother had noticed her speech had changed over the preceding 3 months. She had also been clumsy since the age of 10 years. Her family history was unremarkable. On examination, there was dysarthria with a full range of eye movements but the saccades were broken up. Tone and power were normal but there were occasional choreiform movements. She was areflexic with flexor plantar responses. She had symmetrical limb ataxia and a broad based gait. Sensory testing was normal. There were no telangiectasias.
What is your differential diagnosis and which investigations would you recommend at the first consultation?
The clinical picture is predominantly of cerebellar ataxia with mild chorea and possible sensory involvement (areflexia in the presence of normal tone and power). The main differential can be broken down into genetic and acquired causes. A symmetrical ataxia progressing over several years is not typical of acquired causes but nonetheless the initial emphasis should be on diagnosing a reversible condition; the commoner acquired causes which may present with an isolated ataxia are listed in table 1.
Initial blood tests were normal: full blood count, urea and electrolytes, bone profile, liver function, angiotensin converting enzyme, lupus anticoagulant, α-fetoprotein, vitamins A and E, antitissue transglutaminase and anti-Purkinje cell antibodies, and white cell lysosomal enzymes. Antinuclear antibodies were present at 1:100 but anti-dsDNA and extractable nuclear antigens were normal. MR brain, chest x-ray and ECG were all normal. Further investigations included a normal CSF (glucose, protein and cytology, no oligoclonal bands) but nerve conduction studies revealed absent sensory action potentials with normal motor action potentials and motor conduction velocities.
What differentiates an acquired from an inherited ataxia?
The young age of onset and the suggestion that the problem has been progressing slowly …
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