Efficacy of Riluzole in Hereditary Cerebellar Ataxia

The hereditary cerebellar ataxias include diverse neurodegenerative disorders. Hereditary ataxias can be divided into autosomal dominant ataxias (ADCAs), autosomal recessive ataxias (ARCAs), X-linked, and mitochondrial ataxias on the basis of mode of inheritance. The key feature in all these disorders is ataxia typically characterised by poor balance, hand incoordination, postural or kinetic tremor, dysarthria and dysphagia.

To date no treatment has been shown to slow progression of the disease and symptomatic therapies are limited to few options that are partially effective.

Purkinje cells project inhibitory signals to the deep cerebellar nuclei(DCN) which have a critical role in cerebellar function and motor performance. DCN neurons fire spontaneously in the absence of synaptic input from Purkinje neurons and modulation of the DCN response by Purkinje input is believed to be responsible for coordination of movement, while uncontrolled spontaneous firing of DCN neurons may underlay cerebellar ataxia. Recent studies have demonstrated that small-conductance calcium-activated potassium (SK) channels inhibitor are able to increase DCN firing rate. Since SK channels are critical regulators of DCN firing rate, SK openers such as the drug riluzole may reduce neuronal hyperexcitability and thereby be useful in the therapy of cerebellar ataxia.

On this base the investigators published a pilot study in patients with chronic cerebellar ataxia (Ristori et al., Neurology 2010) investigating safety and efficacy of riluzole or placebo administration for 8 weeks. The results demonstrated a significative improvement in International Cooperative Ataxia Rating Scale (ICARS) global score after four weeks and after 8 weeks in the riluzole arm.

The present protocol is aimed at verifying the safety and efficacy of riluzole administration for a longer period, in a larger sample size of patients, with more stringent diagnostic criteria (hereditary cerebellar ataxia), respect to the above pilot study. Sixty patients will be enrolled in a double-blind, placebo-controlled trial. By central randomisation, patients will take 50 mg of riluzole or placebo twice daily for 12 months. Treatment effects will be assessed by comparing the ICARS and Scale for the Assessment and Rating of Ataxia (SARA) before treatment and during therapy at months 3, 6, 9 ,12.