Evoked potential abnormalities in the various inherited ataxias

Abstract

Visual (VEP), brainstem auditory (BAEP), and somatosensory (SEP) evoked potential tests were performed in 45 patients representing ten types of inherited disorders in which ataxia was the most prominent symptom. Comparable VEP abnormalities were present among all types of patients. Normal BAEP tests were recorded in most patients except those with olivopontocerebellar atrophy. SEP results were often more severely abnormal in patients with Friedreich's ataxia. The observations emphasize the similarity in expression of different metabolic-degenerative disorders. When these tests are used clinically, certain features of evoked potentials (especially left-right symmetry) are typical of the inherited ataxias as a group. Few distinguishing features differentiate the individual disorders.

AAEM minimonograph 19: Somatosensory evoked potentials

“…79 Subclinical SEP abnormalities are not diagnostic of MS. Such SEP abnormalities may also be found in other disorders such as vitamin B 12 and vitamin E deficiency states, 42,69 hereditary spinocerebellar degenerations, 87,90 and hereditary spastic paraplegia. 110 The electrophysiologic findings, therefore, must always be interpreted in relation to the clinical context.…”

“…110 In these disorders and Friedreich's ataxia, there may also be abnormality of the visual and auditory evoked potentials. 90 In olivopontocerebellar atrophy, SEPs may be normal, 87 attenuated, or absent. 56 SEPs may be abnormal in patients infected with the human immunodeficiency virus (HIV).…”

“…78 Nuwer and colleagues found in Friedreich's ataxia that SEPs elicited from upperlimb nerves generally have delayed N20 peaks, but that the Erb's point potential is either normal or only minimally delayed when present. 87 In some cases the Erb's point potential may be markedly attenuated. 60 In patients with hereditary spastic paraplegia or hereditary cerebellar ataxia, there may be loss of spinal or cortical components or marked cortical delay, even when there is no clinical sensory loss.…”

Auditory Brainstem Response Patterns in Familial and Sporadic Olivopontocerebellar Atrophy

“…The auditory pathways of the brainstem may be involved in this disorder and the use of the audi tory brainstem responses (ABR) may provide an ade quate approach in documenting the impairment of these structures. In 1978 Gilroy and Lynn [8] suggested the usefulness of ABR in diagnosis of OPCA during life, but successive data in the literature were contradictory [3,5,6,[8][9][10][11]. The different criteria for classification and the small number of patients examined by some authors may account for these discrepancies but the variability of ABR patterns may be a direct expression of the heter ogeneity of the disorder.…”

Evoked Potential Studies in Friedreich's Ataxia and Progressive Early Onset Cerebellar Ataxia

“…Evoked potentials (EP) have also been recorded in ataxia telengiectasia, 32 olivopontocerebellar ataxias (OPCA) and various, mostly adult onset, cerebellar ataxias. 13,14,16,27,28,30 Apart from FA, progressive early onset cerebellar ataxias (PEOCA) have never been specifically studied from an EP point of view. We report here SEP recordings carried out in nine patients with PEOCA and compare the results obtained in these patients to those observed in 15 patients affected by FA.…”