CPT® Code 81184

CACNA1A (calcium voltage-gated channel subunit alpha1 A) (eg, spinocerebellar ataxia) gene analysis; evaluation to detect abnormal (eg, expanded) alleles

The CPT® Code 81184 pertains to the molecular genetic testing of the CACNA1A gene, which encodes the calcium voltage-gated channel subunit alpha1 A. This gene is critically involved in the functioning of calcium channels that facilitate the transport of calcium ions across cell membranes, playing a vital role in neuronal communication and neurotransmitter release. The CACNA1A gene is located on the short arm of chromosome 19 at position 13.13 (19p13.13). The analysis performed under this code specifically aims to evaluate and detect abnormal alleles, particularly those associated with spinocerebellar ataxia type 6 (SCA6), a hereditary condition characterized by progressive degeneration of the cerebellum and spinal cord. In SCA6, a specific region of the CACNA1A gene exhibits a trinucleotide repeat pattern of CAG (cytosine-adenine-guanine), which typically repeats between 4 to 18 times in unaffected individuals. However, in affected individuals, this repeat can expand to between 20 to 33 times, correlating with the onset and severity of symptoms. Symptoms of SCA6 may include ataxia, dystonia, tremors, dysarthria, nystagmus, and diplopia, with the number of CAG repeats influencing the age of onset. The testing provided by code 81184 is essential for identifying these expanded alleles, thereby aiding in the diagnosis and understanding of the genetic basis of this condition.