Sporadic Degenerative Ataxia With Adult Onset: Natural History Study

Progressive ataxia frequently starts in adults without a familial background. These patients may suffer from an acquired ataxia or a genetically determined ataxia despite negative family history. In the majority of them, however, a genetic or acquired cause of ataxia cannot be identified suggesting a sporadic degenerative ataxia. They can be subdivided into two groups. In one group, the underlying brain disease is multiple system atrophy (MSA), specifically MSA of cerebellar type (MSA-C). The characteristic clinical feature of MSA is the presence of severe autonomic failure defined by orthostatic hypotension or urinary incontinence. The second group is distinguished from MSA-C by the lasting absence of severe autonomic failure. These patients have been designated as sporadic adult onset ataxia of unknown aetiology (SAOA). In the first years after ataxia onset, a distinction between MSA-C and SAOA is often not possible.

There are only few studies comparing the phenotype of MSA-C and SAOA, and longitudinal studies focussing on the evolution of the phenotype of these disorders are completely lacking. In particular, the progression rate of SAOA compared to MSA-C has not been defined. In addition, it is unknown which factors predict the development of MSA-C vs. SAOA, and at which time after onset of ataxia, a reliable distinction between both disorders is possible.

To answer these questions, we plan to create a European registry of patients with sporadic degenerative ataxia of adult onset and to perform a natural history study. The planned study will also allow to collect blood samples and other biomaterials from patients with sporadic ataxia, which will be useful for future genetic and biomarker studies.

Inclusion criteria

• Progressive ataxia
• Disease onset after the age of 40 years
• Informative and negative family history (no similar disorders in first- and second-degree relatives; parents older than 50 years, or, if not alive, age at death of more than 50 years, no consanguinity of parents)

Exclusion criteria

• No established acquired cause of ataxia

Clinical exclusion criteria:

• No onset of ataxia in association with stroke, encephalitis, sepsis, hyperthermia or heat stroke;
• no chronic diarrhea;
• no unexplained visual loss;
• no alcohol abuse;
• no chronic intake of anticonvulsant drugs;
• no other toxic causes; no malignancies;
• no rapid progression (development of severe ataxia in less than 12 weeks);
• no insulin-dependent diabetes mellitus

Imaging exclusion criteria:

• No evidence of multiple sclerosis, ischemia, hemorrhage or tumor of the posterior fossa;
• absence of signal abnormalities on T2/FLAIR-images except abnormalities compatible with MSA

Laboratory exclusion criteria:

• Negative molecular genetic testing for FRDA (only required if there is no cerebellar atrophy on MRI, SCA1, SCA2, SCA3, SCA6, FMR1 premutation (only required if prominent tremor, cognitive impairment and signal abnormality on T2/FLAIR images in the middle cerebellar peduncle);
• antineuronal antibodies negative (only required, if disease duration less than 3 years);
• normal levels of vitamin B12;
• VDRL negative;
• normal thyreoid function