Monday, February 11, 2008

Late onset Friedreich ataxia: phenotypic analysis, MRI findings and review of the literature

Bhidayasiri R, Perlman SL, Pulst SM, Geschwind DH. Arch Neurol 2005; 62: 1865-1869.

Definition: age greater than 25, associated with expansion of GAA repeats in the 1st intron of the X25 gene on chromosome 9.

13 patients are described. All had gait and limb ataxia. Many had dysarthria, oss of vibratory sense and abnormal eye movements. More often they had lower limb spasticity, retained reflexes and no sphincter disturbance or cardiomyopathy. Many had vermian cerebellar atrophy. The authors conclude that patients with the above presentation should be tested for GAA expansion in the FA gene.

This contrasts to the Quebec Cooperative Study criteria that defined FA as beginning before age 20 or the Harding criteria that defined FA as having onset before age 25. LOFA overall had more retained reflexes, slower progression, present neuropathy on nerve conduction testing, and less associated conditions (diabetes, scoliosis and cardiomyopathy).

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