VGKC (LGI1 AND CASPR2) ANTIBODY CSF

VGKC (LGI1 and CASPR2) Antibody, CSF

What it is

The VGKC (Voltage-Gated Potassium Channel) Antibody test in cerebrospinal fluid (CSF) detects autoantibodies against proteins associated with potassium channels, specifically LGI1 (Leucine-rich Glioma-Inactivated 1) and CASPR2 (Contactin-Associated Protein-like 2). These antibodies are linked to autoimmune neurological disorders that affect the brain, spinal cord, and peripheral nerves.

Uses

This test is used to support the diagnosis of autoimmune encephalitis, neuromyotonia, Morvan’s syndrome, and other VGKC-complex related neurological syndromes. It helps confirm immune-mediated causes of seizures, memory loss, movement disorders, and neuropathic symptoms. Identifying these antibodies in CSF provides strong evidence of central nervous system involvement.

Symptoms That May Lead to the Test

Doctors may order this test if you present with seizures of unknown cause, subacute memory loss, confusion, psychiatric symptoms, muscle twitching, neuropathic pain, or autonomic dysfunction (such as excessive sweating or irregular heart rate). In suspected autoimmune encephalitis, the CSF antibody test is often performed alongside serum antibody testing and brain imaging.

Abnormal Results

Positive LGI1 Antibodies: Associated with limbic encephalitis, seizures, hyponatremia (low sodium), and cognitive impairment. Often responsive to immunotherapy.

Positive CASPR2 Antibodies: Linked to Morvan’s syndrome, neuromyotonia (muscle stiffness, cramps), and sometimes limbic encephalitis. May involve both central and peripheral nervous systems.

Negative Results: Suggest no detectable VGKC-related autoantibodies. However, autoimmune disease may still be present and other antibody panels may be needed.

Risks

This test requires a lumbar puncture (spinal tap) to collect CSF, which carries some risks including headache, back discomfort, dizziness, or, rarely, infection or bleeding. The benefits of accurate diagnosis and targeted treatment outweigh these risks in suspected autoimmune neurological conditions.