Voltage-gated potassium channel (VGKC) antibody encephalitis describes a small group of autoimmune encephalitides with antibodies against components of the voltage-gated potassium channel. It is one of the most common forms of autoimmune limbic encephalitis in the absence of primary extra-CNS tumors.
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Clinical presentation
Clinical presentation is variable and often depends on the exact antibody implicated 5:
- anti-LGI1 encephalitis
- limbic encephalitis
- faciobranchial dystonic seizures
- hyponatremia
- anti-CASPR2 encephalitis
- limbic encephalitis
- neuromyotonia
- Morvan syndrome
- anti-VGKC encephalitis but negative to anti-LGI1 and anti-CASPR2
- highly variable clinical presentation
Pathology
The encephalitis is thought to be due to antibodies against voltage-gated potassium channel (VGKC) complexes, in particular the proteins leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) 5. However, there are additional patients who test positive to the VGKC immunoassay but then also do not have antibodies against either LGI1 or CASPR2 5.
Radiographic features
One study showed that a majority of patients had unilateral or bilateral amygdala with or without hippocampal enlargement and T2 hyperintensity at some time point during the course of the disease. Also, restricted diffusion and mild ill-defined enhancement demonstrated in approximately 50% and 25% of patients, respectively. Extratemporal involvement is rare. In the long term, mesial temporal sclerosis may be seen as high as 50% of patients 1.
Treatment and prognosis
Management does not differ from other causes of autoimmune encephalitis, namely with immunotherapy and symptomatic management.
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