Objective: We aim through this study to describe the electrophysiological features of the different Autosomal recessive cerebellar ataxias (ARCA) in our population in order to guide the diagnostic procedures.

Background: ARCAs constitute a heterogeneous group of rare neurodegenerative diseases. The clinical presentations of different ARCA are generally similar and intricate, making the diagnosis challenging and delaying its management. The electrophysiological features, particularly the electromyogram (EMG) and the visual evoked potentials (VEP), can help guide our diagnostic approach.

Method: A retrospective descriptive study was conducted at the neurology department of the National Institute of Neurology of Tunis over 41 years (1982-2023), involving 122 patients [figure 1] with a genetically confirmed diagnosis who underwent EMG exploration. The majority of these patients were also assessed by VEP.

Results: The EMG was normal in most of AVED patients (75%). However, it revealed sensory axonal neuropathy in 73% of FA cases and 19% of AVED cases. On the other hand, the EMG showed sensory-motor axonal neuropathy in AOA2 cases (90%), AOA1 cases (82%), ARSACS cases (62%), GBA2 cases (66%), ABL cases (67%), both CDG cases, and some FA cases (24%). Remarkably, an axono-demyelinating neuropathy was exclusively found in the ARSACS group (38%). The VEP study was normal in all the AOA2 cases, 38% of AVED cases, 27% of FA cases, 25% of ARSACS cases, and 1 ABL case. It also revealed axonal optic neuropathy (ON) in 58% of AVED cases, 11.5% of FA cases, and 1 GBA2 case. Demyelinating ON was found in 75% of ARSACS cases and in 46% of FA cases. However, axono-demyelinating ON was observed in 15% of FA cases and in 1 GBA2 case. The auditory evoked potentials (AEPs) were altered in 27% of FA patients, all ABL patients, and 1 out of the 2 AVED patients explored.

Conclusion: ARCA can thus be classified into those without neuropathy, those with pure sensory neuropathy, sensory-motor axonal neuropathy, and axono-demyelinating neuropathy. Additionally, they can be classified into those with or without optic neuropathy. This classification can guide genetic diagnosis.

Different ARCA forms in our Tunisian population

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MDS Abstracts - https://www.mdsabstracts.org/abstract/electrophysiological-study-of-122-tunisian-patients-with-autosomal-recessive-cerebellar-ataxia/