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Relation between trinucleotide GAA repeat length and sensoryneuropathy in Friedreich's ataxia |
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| Authors: | L Santoro G De Michele A Perretti C Crisci S Cocozza F Cavalcanti M Ragno A Monticelli A Filla G Caruso |
| Affiliation: | Department of Clinical Neurophysiology, Federico II University, Naples, Italy. |
| Abstract: | OBJECTIVE—To verify ifGAA expansion size in Friedreich's ataxia could account for theseverity of sensory neuropathy. METHODS—Retrospectivestudy of 56 patients with Friedreich'sataxia selected according to homozygosity for GAA expansion andavailability of electrophysiological findings. Orthodromic sensoryconduction velocity in the median nerve was available in all patientsand that of the tibial nerve in 46 of them. Data of sural nerve biopsy and of a morphometric analysis were available in 12 of the selected patients. The sensory action potential amplitude at the wrist (wSAP)and at the medial malleolus (m mal SAP) and the percentage ofmyelinated fibres with diameter larger than 7, 9, and 11 µm in thesural nerve were correlated with disease duration and GAA expansionsize on the shorter (GAA1) and larger (GAA2) expanded allele in eachpair. Pearson's correlation test and stepwise multiple regression wereused for statistical analysis. RESULTS—A significantinverse correlation between GAA1 size and wSAP, m mal SAP, andpercentage of myelinated fibres was found. Stepwise multiple regressionshowed that GAA1 size significantly affects electrophysiological andmorphometric data, whereas duration of disease has no effect. Conclusion—Thedata suggest that the severity of the sensory neuropathy is probablygenetically determined and that it is not progressive |
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