Multimodal evoked potentials in spinocerebellar ataxia types 1, 2, and 3

Spinocerebellar ataxias (SCA) are a clinically heterogeneous group of disorders that are characterized by ataxia and an autosomal dominant pattern of inheritance. The aim of our study was to describe the findings of evoked potentials (EPs) among genetically proven SCA types 1, 2, and 3 and to additionally evaluate if EPs can be used to differentiate between them.

Forty-three cases of genetically proven SCA (SCA1 = 19, SCA2 = 13, and SCA3 = 11) were evaluated with median somatosensory-EP (mSSEP), visual-EP (VEP), and brainstem auditory-evoked response (BAER) by standard procedures and compared with normative laboratory data. An EP was considered abnormal if latency was prolonged (>mean + 3 standard deviation (SD) of laboratory control data) or the waveform was absent or poorly defined. The waves studied were as follows: mSSEP - N20, VEP - P100 and BAER - interpeak latency 1-3 and 3-5.

EPs were abnormal in at least one modality in 90.9% of patients. The most common abnormality was of BAER (86.1%) followed by VEP (34.9%) and mSSEP (30.2%). The degree of abnormality in VEP, mSSEP, and BAER among patients with SCA1 was 42.1, 41.2, and 73.3%, respectively; among patients with SCA2 was 38.5, 27.3, and 100%, respectively; and among patients with SCA3 was 18.2, 37.5, and 88.9%, respectively. The differences between the subgroups of SCAs were not statistically significant.

BAER was the most frequent abnormality in SCA types 1, 2, and 3; abnormalities of mSSEP were comparable in the three SCAs; whereas, abnormality of VEP was less often noted in SCA3.