Ataxia Flashcards
1
Q
Common causes of ataxia and how to investigate them
A
Causes: medication/ drugs, varicella infection, posterior fossa lesions or tumours, genetic and degenerative disorders (see below)
Ataxic cerebral palsy
Friedrich ataxia
- autosomal recessive- trinucleotide repeat disorder of Frataxin gene
- worsening ataxia. distal wasting of legs, absent lower limb reflexes, extensor plantar responses (pyramidal involvement), pes carvus and dysarthria
- impairment of joint position and vibration sensation, extensor plantars and optic atrophy
- investigations
- Nerve conduction studies show motor velocities >40 ms-1 in arms and absent sensory action potentials
- Genetic analysis.
- ECG - there may be ventricular hypertrophy and T-wave inversion.
- Exclude vitamin E deficiency.
- Blood tests: FBC, U&E and glucose
- Echocardiography - may show ventricular hypertrophy, septal hypertrophy and hypertrophic cardiomyopathy.
- MRI scan of the brain and spinal cord - shows characteristic atrophic changes, particularly of the cervical spinal cord.
- Brainstem auditory evoked responses and visual evoked potentials - may be abnormal.
- Genetic counselling and tests - prenatal diagnosis is available. Carrier testing for relatives of affected patients and their partners is also possible.
Ataxia telangiectasia
- disorder of DNA repair
- autosomal recessive
- gene ATM identified
- mild delay in motor development in infancy, oculomotor problems with inco-ordination and delay in pursuit of objects (oculmotor dyspraxia), difficulty with balance and co-ordination becoming evident at school age
Investigations
- Serum alpha-fetoprotein level (raised in 90%).
- Genetic testing for ATM genes and absence of ATM protein in nuclear extracts.
- In vitro radiosensitivity testing (colony survival assay).
- increased susceptibility to infection (IgA surface antibody defect)
- ALL development (10%)
- increased WCC to irradiation
