Stiff-Person Spectrum Disorders Evaluation, including Progressive Encephalomyelitis with Rigidity and Myoclonus, Spinal Fluid

Casandra

Casandra Test Code MC45508Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID SPPCCPT Codes 0431, 84182, 86255, 86256, 86341

Stiff-Person Spectrum Disorders Evaluation, including Progressive Encephalomyelitis with Rigidity and Myoclonus, Spinal Fluid

Clinical Use

Use

This test is useful for evaluating patients suspected of having stiff-person syndrome or progressive encephalomyelitis with rigidity and myoclonus, using spinal fluid specimens. Stiff-person spectrum disorders are characterized by central nervous system hyperexcitability leading to stiffness, spasms, heightened startle responses, and falls. Specific antibodies detected in these disorders include GAD65 and sometimes amphiphysin-IgG, which can indicate paraneoplastic conditions such as breast adenocarcinoma. Other associated antibodies include glycine receptor and dipeptidyl-peptidase-like protein-6 antibodies. The results, along with clinical and electrophysiologic characteristics, support diagnosis and management of these conditions.

Special Instructions

This test should not be requested for patients who have recently received radioisotopes due to potential assay interference. The specific waiting period before specimen collection depends on the isotope, its dose, and the clearance rate. Specimens are screened for radioactivity before analysis. If radioactivity is detected, the specimen will be held for one week to allow decay or cancelled if radioactivity persists.

Limitations

Negative test results do not exclude the diagnosis of stiff-person spectrum disorder or PERM. GAD65 antibody positive values below 20 nmol/L should be interpreted with caution, as low levels can occur in the general population and are associated with other autoimmune diseases. The presence of certain antibodies correlates with specific clinical presentations and can inform therapeutic responsiveness, but the absence of these antibodies does not rule out disease presence.

Test Details

New York Approved