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

Casandra

Casandra Test Code MC54950Version 1 (DRAFT)

Performing Lab

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

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

Clinical Use

Use

This test is used for evaluating patients suspected of having stiff-person syndrome (classical or focal forms such as stiff-limb or stiff-trunk) and progressive encephalomyelitis with rigidity and myoclonus. Stiff-person spectrum disorders include classical stiff-person syndrome, focal stiff-person forms, and progressive encephalomyelitis with rigidity and myoclonus (PERM). Paraneoplastic and idiopathic autoimmune causes can be differentiated by a neuronal IgG antibody profile. Common manifestations include stiffness, spasms, heightened startle responses, and falls. The GAD65 antibody serves as a common biomarker for stiff-person spectrum and is linked to autoimmune diseases like type 1 diabetes and thyroid disease, usually without accompanying cancer.

Special Instructions

This test should not be requested for patients who have recently received radioisotopes due to potential assay interference. The waiting period for specimen collection depends on the isotope, dose, and clearance rate. Specimens with residual radioactivity will be retained and tested once sufficiently decayed. Refer to the Autoimmune Neurology Test Ordering Guide for phenotype-specific options.

Limitations

Negative results do not exclude diagnosis of stiff-person spectrum disorder or PERM. Caution is advised for GAD65 antibody values below 20 nmol/L, as these may occur in a small percentage of the general population. GAD65 autoimmunity is associated with other autoimmune diseases like type 1 diabetes and hypothyroidism, which might cause neurological symptoms.

Test Details

New York Approved