Abstracts

Rationale: Status Epilepticus (SE) is a relatively common and frequently devastating neurological emergency. In the vast majority of cases, a plausible explanation for SE is evident. In a small fraction of cases, the underlying aetiology is not apparent despite extensive evaluation. Among these cases of cryptogenic SE, perhaps the most difficult to understand are patients who present de novo with refractory SE. Typically, the working diagnosis is that of ‘viral encephalitis’ on the basis of CSF and imaging findings in conjunction with the absence of an alternative explanation. However, in the final analysis, a specific pathogen may not be isolated and the CSF and imaging abnormalities may reflect the seizure activity itself. We report our experience with previously-normal patients with new onset refractory SE of unclear cause.Methods: We describe 6 adults with de novo refractory SE. The designation of 'de novo' mandated that all patients were neurologically normal prior to the incident illness, and in particular did not have a history of seizures. After extensive investigations, an underlying cause for the SE was not found, resulting in the aetiologic designation of ‘cryptogenic’. Results: All patients needed prolonged ICU care with continuous EEG monitoring, and were treated with infusion therapies due to refractory SE. Both the short-term, in-hospital and long-term morbidities were high. The average age was 27.1 years (range 21-36 years). Five cases were female. Five cases experienced a non-specific mild febrile illness within two weeks of the SE. Of the 5 cases that survived, the average length of hospital stay was 41 days. The other case died on day 9, due to fulminant cardiac failure. Post mortem histopathological evaluation of this case was non-diagnostic. One patient had right frontal biopsy and two cases had therapeutic cortical resections. Neuropathological examination revealed non-specific changes with lymphocytic infiltration and microglial activation. All cases showed a modest CSF pleocytosis with normal protein level. MR imaging revealed either normal findings or typical peri-ictal cortical abnormalities, in a regional distribution. One case had high levels of anti-thyroglobulin antibody, raising the possibility of Hashimoto’s encephalopathy, but did not respond to successive treatment with intravenous steroids, intravenous immunoglobulin therapy, or plasmapheresis. In each case, all of the abnormalities evident during the initial and subsequent evaluation could be attributed to the ictal activity itself. Conclusions: We describe our clinical experience with this rare form of SE and postulate an autoimmune basis for the illness. These cases have unifying features, namely young age, normal pre-morbid neurologic health, female preponderance, prodromal mild non-specific febrile illness, and a poor clinical outcome. We postulate that these cases may represent a form of parainfectious encephalitis with acute symptomatic status epilepticus as a major manifestation. Early recognition and introduction of immunosuppressive therapies may be warranted in this form of status epilepticus to avert a poor clinical outcome.