General aim of the study is the improvement of the clinical knowledge of ultra-rare inherited metabolic and degenerative neurological diseases (prevalence less than 5:100,000) in adulthood through the systematic longitudinal collection of clinical, laboratory and instrumental data.

The study provides a collection of retrospective data from adult patients with ultra-rare inherited neurological diseases followed at "Carlo Besta" Neurological Institute from 1st January 2004 until March 2021. Further, prospective data will be collected starting from March 2021 (date of protocol approval) and spanning the next ten years. Normal clinical practice will be followed for collection of the prospective data. Follow-up assessment will be performed at least once a year to evaluate the disease course. Based on their clinical manifestations, patients will be assessed by using quantitative functional tests (clinimetric tests such as Timed Up and Go Test) and traditional ordinal scales (such as the scale for the assessment and rating of ataxia (SARA). Moreover, a varying of laboratory and instrumental tests (e.g., neuroimaging, neurophysiological investigations, etc.) will be used according to clinical practice in selected patients.

Inclusion Criteria:

• Age >= 18 years
• Subjects with ultra-rare inherited degenerative and metabolic neurological diseases
• Subjects with undiagnosed neurological diseases (when supposed to be inherited)

Exclusion Criteria:

• none

Adults with ultra-rare inherited degenerative and metabolic neurological diseases

Adults with undiagnosed neurological diseases (when supposed to be inherited)