Objective: The aim of our study is to compare the epidemiological, clinical, paraclinical and follow-up features of AOA1 and AOA2 in order to identify distinctive characteristics.

Background: Ataxia with oculomotor apraxia type 1 (AOA1) is phenotypically similar to ataxia with oculomotor apraxia type 2 (AOA2), presenting with a progressive ataxia associated with dysarthria, oculomotor apraxia, abnormal movements and sensory-motor neuropathy, making it difficult to distinguish between them.

Method: This was a retrospective, descriptive and analytical study conducted in the neurology department of the Mongi Ben Hmida National Institute of Neurology in Tunis between 1982 and 2023. We collected epidemiological, clinical, paraclinical and evolutionary data from our patients with genetically confirmed AOA1 and AOA2. For each patient, we calculated the SARA score and specified the disease progression index (PI): which corresponds to the SARA score divided by the duration of disease progression. Eventually, different results were compared.

Results: We included 28 patients with AOA2 and 14 patients with AOA1. The median age of disease onset was significantly lower in the AOA1 group (5 years vs. 15.5 years; p=0.001). There was a difference in geographical distribution between the two groups. Indeed, AOA1 patients were predominantly from the northern regions of Tunisia (92.9% vs. 42.9%, p=0.007). Compared with the AOA2 group, intellectual disability, amyotrophy, dystonia, patellar areflexia and pes cavus were significantly more frequent in the AOA1 group (p<0.001, p<0.001, p=0.007, p=0.029, p=0.01, respectively). The clinical presentation was more severe in AOA1 patients, with a significantly higher SARA score (31.78±8.29 vs. 22.25±5.58; p<0.001), higher grabatization rate and earlier grabatization age (p=0.029 and p<0.001, respectively). Cerebro-spinal imaging abnormalities were more frequent in AOA2 patients (p=0.026). We found an association between hypercholesterolemia and hypoalbuminemia with AOA1, with p=0.002 and p=0.001, respectively. However, elevated alpha-foeto-protein was significantly associated with AOA2 with p<0.001.

Conclusion: Our study has enabled us to gain a better understanding of the particularities of these two similar diseases in order to guide the genetic study.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/aoa1-versus-aoa2-a-comparative-study-of-a-tunisian-cohort/