Spinocerebellar ataxias (SCAs) are progressive and fatal neurodegenerative diseases. The most frequent forms are polyglutamine SCAs due to expansions in coding CAG repeats: ATXN1/SCA1, ATXN2/SCA2, ATXN3/SCA3, CACNA1A/SCA6, ATXN7/SCA7, TBP/SCA17 and ATN/DRPLA. These SCAs show faster disease progression than SCAs which are due to conventional mutations or intronic expansions [1]. Among polyQ SCAs, SCA1 has the shortest survival rate [2] with the strongest risk factors for death being the presence of dysphagia and higher relative scores on the Scale for the Assessment and Rating of Ataxia (SARA)[3]. The aim of this study was to explore how the neurodegenerative process may explain shorter survival in SCA1 patients. Neuropathological studies indicate that brainstem involvement is a major feature in SCA1 [4], including the structures responsible for the process of swallowing [5]. Motor neurons of the brainstem and cervical spinal cord degenerate in SCA1 knock-in (Atxn1154Q/+) mice, in particular in the hypoglossal nucleus (nucleus of cranial nerve XII)[6].

Impairment of the XII cranial nerve is involved in dysphagia and dysarthria. The different phases (lingual, pharyngeal and oesophageal) of swallowing are altered in almost all SCA patients with consequent dysphagia. Dysphagia represents a risk factor for aspiration pneumonia, weight loss and malnutrition and is usually alleviated by a nasogastric tube, parenteral nutrition or percutaneous endoscopic gastrostomy.