, Volume 254, Issue 10, pp 1384-1389
Date: 15 Oct 2007

Sporadic adult onset ataxia of unknown etiology

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Abstract

Background

The sporadic adult onset ataxias of unknown etiology (SAOA) denote the non-hereditary degenerative adult onset ataxias that are distinct from multiple system atrophy (MSA).

Objective

To define and characterize the clinical phenotype of sporadic adult onset ataxia of unknown etiology (SAOA).

Design

A survey of clinical features, nerve conduction and evoked potentials, autonomic tests, and magnetic resonance imaging (MRI)-based brain morphometry was conducted in patients with SAOA.

Patients

Study subjects were a consecutive sample of 27 patients (11 male, 16 female) who met the diagnostic criteria for SAOA (age 55 ± 13 years; age at disease onset 47 ± 14 years; disease duration 8 ± 7 years).

Results

All patients presented with a cerebellar syndrome. The most frequent extracerebellar symptoms were decreased vibration sense in 70% and decreased or absent ankle reflexes in 33% of the patients. Nerve conduction studies revealed a polyneuropathy in 26% of the patients. Somatosensory evoked potentials were abnormal in 44%, and central motor conduction time in 17% of patients. Autonomic testing revealed an affected autonomic nervous system in 58% of patients. Voxel-based brain morphometry showed a predominant reduction of gray matter in the cerebellum which was significantly correlated with disease stages. A loss of white matter was found in both middle cerebellar peduncles and the outer edge of the pons.

Conclusions

The data show that SAOA is a predominantly, but not exclusively cerebellar disorder. Clinical, electrophysiological, and imaging findings showed some similarities with multiple system atrophy which raises the question of an overlap of these two disorders.