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

Casandra

Casandra Test Code MC41427Version 1 (DRAFT)

Performing Lab

Lab Mayo Clinic LabLab Test ID SPPCI

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

Clinical Use

Use

This test is useful for the interpretation and evaluation of stiff-person spectrum disorders, including classical forms such as stiff-limb or stiff-trunk and progressive encephalomyelitis with rigidity and myoclonus (PERM). These conditions are characterized by central nervous system hyperexcitability, leading to symptoms such as stiffness, spasms, heightened startle responses, and falls. The clinical manifestations vary, affecting the lower back, extremities, or general body, and can include encephalopathy and autonomic dysfunction in some cases. Serum and cerebrospinal fluid analyses are important for differentiating idiopathic autoimmune causes from paraneoplastic ones, primarily identified through specific neuronal IgG antibody profiles such as GAD65, Amphiphysin-IgG, GlyR-IgG, and DPPX antibodies.

Special Instructions

This test is not orderable as a standalone test but is part of a broader evaluation profile for stiff-person spectrum disorders. The interpretation provided will include detailed analysis of antibody presence in the spinal fluid, linked to clinical findings for a comprehensive assessment. It is performed at the Mayo Clinic Laboratories' main campus in Rochester.

Limitations

Negative results do not exclude the diagnosis of stiff-person spectrum disorders or PERM. Caution should be exercised with GAD65 antibody levels below 20 nmol/L, as low-level positive results are present in a small percentage of the general population. Interpretation of results should consider potential interference from other autoimmune diseases like type 1 diabetes or thyroid disorders, which may cause neurological symptoms. The test is not applicable for cases involving antibodies not covered or detailed in the profile.

Test Details

New York Approved