Uncommon presentation of voltage-gated potassium channel complex-antibody mediated central nervous system disease with eye movement disorder and ataxia

The clinical spectrum of antibody mediated CNS diseases has been rapidly expanding over the last few years. M. is a 17-year-old girl with new onset of clinical symptoms and accompanying voltage-gated potassium channel (VGKC) complex antibodies.

The patient developed acute eye movement disorders (fine motor chaotic not directed eye tremble with an increase in intensity on fixation), ataxia (video) with marked vertigo, and nausea leading to complete incapacitation and being bedridden.

CSF analyses demonstrated normal cell count with evidence of a disrupted blood-brain barrier with oligoclonal bands and intrathecal IgG synthesis. Brain MRI showed a small unspecific periventricular white matter lesion.

Assay of antineuronal antibodies exhibited elevated VGKC complex antibodies (135 pmol/L, n < 85 pmol/L). Antibodies against LHI1 and CASPR2 (the known antigen targets of VGKC complex) were negative. Presuming an autoimmunological pathogenesis steroids and intravenous immunoglobulins were given with unsatisfactory benefit.

We expanded therapy with plasma exchange (6 sessions and concomitant prednisolone). After 2 sessions, rapid and near complete recovery was seen. The patient was able to read and write, and the gait pattern was normal. Under immunosuppressive therapy using mycophenolate mofetil, the girl, 5 months after plasma exchange, remains in stable clinical condition and works as an Au pair abroad. VGKC antibodies are no longer detectable.

A malignant lesion could not be detected in our patient. The successful treatment employing plasmapheresis points to the antibodies as the relevant pathophysiological agent for the described eye movement disorder and ataxia.

To our knowledge, this is the first case of a VGKC complex antibody-mediated syndrome presenting as a primary movement disorder of the eyes.