From the Guidelines
Spinocerebellar ataxia type 20 (SCA20) causes dentate calcification due to genetic mutations affecting calcium regulation in the brain, as evidenced by recent studies on cerebellar ataxia 1. The exact mechanism of dentate calcification in SCA20 is not fully understood, but it is believed to be related to disruptions in normal calcium homeostasis in neurons, particularly in the cerebellum's dentate nucleus. Some key points to consider in the diagnosis and management of SCA20 include:
- The use of imaging techniques such as MRI to detect abnormal iron deposition or calcification in the dentate nucleus 1
- The importance of a thorough clinical neurologic examination and history to diagnose SCA20, as conventional neuroimaging may be unremarkable in early disease 1
- The need to exclude nondegenerative central etiologies of ataxia, such as mass lesions or infarcts, through imaging and other diagnostic tests 1
- The current lack of specific treatment to prevent or reverse dentate calcifications, with management focusing on supportive care and symptom control for affected individuals. It is essential to prioritize the most recent and highest-quality study, which in this case is the 2024 study on acr appropriateness criteria for dizziness and ataxia 1, to guide diagnosis and management decisions.
From the Research
Spinocerebellar Ataxia 20 (SCA20) and Dentate Calcification
- SCA20 is a rare, slowly progressive dominantly inherited disorder characterized by dentate calcification from an early stage of the illness 2.
- The disease is distinct from other forms of spinocerebellar ataxia, with symptoms including dysarthria, spasmodic dysphonia, and palatal tremor, but not gait ataxia 3.
- Dentate calcification in SCA20 occurs in the absence of abnormalities of calcium metabolism, and is a key feature that distinguishes it from other forms of SCA 3.
- The genetic abnormality responsible for SCA20 has been tentatively identified as a 260-kb duplication in the pericentric region of chromosome 11, although confirmation awaits description of further families 2.
- The pathogenesis of SCA20 is not fully understood, but it is thought to involve damage to the cerebellar module, including the cerebellar cortex, dentate nuclei, and inferior olivary nuclei 4.
Comparison with Other Forms of Spinocerebellar Ataxia
- SCA20 is one of several forms of spinocerebellar ataxia, a genetically heterogeneous group of autosomal dominantly inherited progressive disorders 5.
- Other forms of SCA, such as SCA1, SCA2, and SCA3, are caused by pathological cytosine-adenine-guanine (CAG) trinucleotide repeat expansions, and are characterized by polyglutamine-containing intranuclear and cytoplasmic inclusion bodies 4.
- In contrast, SCA20 is not caused by a CAG repeat expansion, and its pathogenesis is thought to involve different mechanisms 2.
- Despite these differences, all forms of SCA share a common clinical hallmark of loss of balance and coordination, accompanied by slurred speech, and are characterized by prominent damage to cerebellar Purkinje neurons 5.