Abstracts

Rationale: Pseudoseizures consist of a sudden episode of change in behavior or psychic state that is not associated with an identifiable process, and during which there is an absence of characteristic epileptiform changes on electroencephalogram (EEG). In cancer patients who present with symptoms suggestive of epilepsy, further evaluation may reveal cerebral metastasis, or less often, a paraneoplastic syndrome. . Despite psychiatric co-morbidity in cancer patients, pseudoseizures are rarely identified. Methods: We report a case of a 60 year-old female who presented with multiple daily episodes of generalized body jerks and stiffening with retained conciousness, three months after diagnosis of thymic carcinoma. An extended video-EEG study recorded multiple episodes without clear electrographic correlates. Furthermore, no interictal discharges could be identified. Neurological exam and brain MRI were normal. A serum paraneoplastic panel was negative. Accordingly, she was diagnosed with pseudoseizures. However, her neurological status changed over the following weeks. She became unresponsive and had multifocal myoclonus. Repeat brain MRI showed abnormal T2 signals in bilateral medial temporal lobes, thalami, insula, caudate, superior frontal and cingulate gyri, which were consistent with limbic encephalitis. Repeat EEG recordings showed frequent generalized interictal discharges and electrographic seizures. The patient was treated with multiple anti-epileptic medications with minimal benefit and died soon thereafter. Results: Subsequent CSF studies showed immunoreactivity with rat hippocampal neurons, suggesting paraneoplastic syndrome.Conclusions: Pseudoseizures can be misdiagnosed in patients with paraneoplastic syndrome due to lagging neuroimaging and electrographic evidence. Repeat EEG and neuroimaging studies are warranted to exclude pseuo-pseudoseizures in this patient population when clinical suspicion is high.