Abstracts

Rationale: Rasmussen encephalitis (RE) is typically a childhood disease with intractable epilepsy and progressive hemiparesis, often treated with neurosurgery. Etiology is unknown, however, auto-antibodies against the ionotropic, glutamate receptor Glu-R3 and other epitopes, have been implicated. RE associated with anti-voltage-gated-potassium-channel antibodies (anti-VGKC-Abs) has not been described in Medline-indexed literature (search terms: Rasmussen, encephalitis, potassium). Like other diseases mediated by anti-VGKC-Abs, we hypothesized that this type of RE may be responsive to immunotherapy alone. We monitored response to various types of immunotherapy in a patient with RE and anti-VGKC-Abs. Methods: A 26 year-old developed hemiclonic seizures and intermittent epilepsia partialis continua (EPC) with right hemibody, clonic jerking. Seizures intermittently impaired cognition and vision. She developed a progressive dystonic hemiparesis. EEG revealed left-sided, periodic sharp waves near the vertex, left temporal spikes and PLEDs, and left-sided slowing. MRI revealed left-sided atrophy. SPECT showed decreased blood volume in the left frontal, temporal, and parietal lobes. Normal and negative serum studies included the CBC, metabolic panel, coagulation panel, ESR and C-reactive protein, ACE level, RPR, antibodies to DNA, SCL-70, Ro and La, serum IgA, IgG, IgM, anti-cardiolipin and anti-phospholipid antibodies, TSH, anti-thyroglobulin and anti-TPO antibodies, immunofixation electrophoresis, and paraneoplastic antibodies (Mayo Medical Laboratories). Negative CSF tests included cell counts, glucose, protein, and cytology. Abnormal results included a rheumatoid factor level of 23 IU/ml (normal < 20) and a high titer of anti-VGKC-Abs (Kv1.1-1.4) at 170 pmol/L (negative < 100, sampled prior to IVIg). In an unblinded fashion, we monitored clinical response to corticosteroids, IVIg, and plasmapheresis.Results: Trials of five anti-seizure medications were largely ineffective. High-dose corticosteroids and three courses of IVIg had no clear benefit, although disease progression was slow at baseline. Ultimately, two 5-day treatments of plasmapheresis reduced the amount and severity of hemiclonic jerking, seizure-propagation, and were associated with reductions hemidystonia and hemiparesis. The patient is now also participating in a treatment protocol using rituximab.Conclusions: The etiology of adult-onset, anti-VGKC-Ab-asssociated RE may be different than typical RE. Early response to plasmapheresis is encouraging. Anti-VGKC-Abs may be associated with limbic encephalitis, peripheral nerve hyperexcitability, and encephalopathy. Among six patients with epilepsy having elevated VGKC-Ab levels (reported by Majoie et al. 2006), none had refractory focal seizures. Anti-VGKC-Ab-mediated diseases are often reversible with immunotherapy while RE is usually not. Although further study is required, patients with adult-onset RE should be screened for anti-VGKC-Abs, as this could be a variant that is responsive to non-surgical therapy.