Les ataxies cérébelleuses autosomiques récessives

Autosomal recessive cerebellar ataxias (ARCA) are complex and heterogeneous inherited neurodegenerative diseases that usually affect the cerebellum and/or the spinocerebellar tract, the posterior column of the spinal cord and the peripheral nerves. Cerebellar ataxia is mostly prominent and frequently associated with several neurological or extra-neurological signs, responsible for major disability before the age of 30. Friedreich's ataxia (FRDA) is the most frequent ARCA. During the past fifteen years, several rarer entities such as ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2), ataxia with vitamin E deficiency (AVED), and autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) have been identified. ACAR may be divided into three groups: cerebellar ataxia with pure sensorial neuronopathy; cerebellar ataxia with sensorimotor axonal neuropathy; cerebellar ataxia without neuropathy (i.e. ataxia of purely cerebellar origin that may be associated with other neurological or extra-neurological signs). Thus, results of electromyography are of interest for the classification of ARCA as well as for the etiological investigation. In the same way, whether there is a clear cerebellar atrophy or not on the brain MRI is a key point. However both electromyography and MRI may be normal at disease onset and should be repeated later in such cases. Several ARCA share defects in the same molecular pathways such as DNA repair deficiency (AOA1, ataxia telangiectasia [AT]…), RNA termination disorder (AOA2), mitochondrial defect (FRDA, sensory ataxic neuropathy with dysarthria and ophthalmoplegia [SANDO]), lipoprotein assembly defects (AVED, abetalipoproteinemia (ABL)), chaperone proteins disorders (ARSACS, Marinesco-Sjögren syndrome [MSS]) or peroxysomal diseases (Refsum disease [RD]). The most frequent ARCAs, especially FRDA, must not be overlooked as well as the ARCA for which a treatment is available (AVED, ABL, cerebrotendinous xanthomatosis, Wilson's disease and RD for instance).