SYNE1 encodes nesprin-1, a scaffold protein which is involved in the binding between cytoskeleton, nuclear envelope and other subcellular compartments. In 2007, recessive truncating SYNE1 mutations have been linked to a genetic form of pure cerebellar ataxia with adult onset and mild phenotype. Subsequent reports described a number of patients with SYNE1-ataxia and widespread neurological involvement including features of motor neuron disease. Recently, heterozygote missense SYNE1 mutations have been associated with muscular disorders, such as Emery-Dreifuss muscular dystrophy, arthrogryposis multiplex congenita and dilated cardiomyopathy. Herein we describe novel genotypic and phenotypic findings in an independent cohort of 5 patients with SYNE1-ataxia referring to the Department of Neurology of the Innsbruck Medical University and performed a review of the related literature. We report 3 novel mutations and describe for the first time myocardial involvement in a patient with a complicated spastic-ataxic phenotype and C-terminal mutation. In the literature, mutations associated with additional motor neuron signs spanned over the entire gene, but patients with a particularly severe phenotype and premature death bore C-terminal mutations. Our findings support a genotype-phenotype correlation in SYNE1-ataxia and suggest the need for a systematic cardiologic evaluation in the setting of complicated spastic-ataxia phenotypes. •SYNE1 encodes nesprin-1, a scaffold protein that is involved in the binding between cytoskeleton and nuclear envelope.•Truncating recessive SYNE1 mutations cause both pure cerebellar ataxia and complicated ataxia with motoneuron involvement.•Five further patients with SYNE1-ataxia and 3 novel pathologic variants are reported.•We report for the first time a myocardial involvement with premature death in a patient with complicated SYNE1-ataxia.•In our cohort and in the literature, severe phenotypes with premature death were associated with C-terminal SYNE1mutations.