In 1958, Rasmussen described three children in whom the clinical problem consisted of intractable focal epilepsy (the epilepsia partialis continua described above) in association with a progressive hemiparesis. The cerebral cortex disclosed a mild meningeal infiltration of inflammatory cells and an encephalitic process marked by neuronal destruction, gliosis, neuronophagia, some degree of tissue necrosis, and perivascular cuffing. Many additional cases were soon uncovered and Rasmussen was able to summarize the natural history of 48 personally observed patients (see the often cited monograph by Andermann and the more recent review by Bien and colleagues 2005). Adult cases are known and they tend to have a milder and more protracted course as noted by Villani and coworkers. Some have focal cortical myoclonus.
An expanded view of the syndrome has added several interesting features. The affected children are typically ages 3 to 15 years, more girls than boys. Half of them have epilepsia partialis continua. The progression of the disease leads to hemiplegia or other deficits and focal brain atrophy, and even total hemiatrophy, in most cases. The neuropathology of five cases revealed extensive destruction of the cortex and white matter with intense gliosis and lingering inflammatory reactions.
The CSF shows a pleocytosis and sometimes oligoclonal bands but these are not uniform findings. Focal cortical and subcortical lesions are usually visualized by MRI and are bilateral in some cases. The finding of antibodies to glutamate receptors (GluR3) in a proportion of patients with Rasmussen encephalitis has raised interest in an immune causation (see review by Antel and Rasmussen). The autoimmune hypothesis has been supported by the findings of Twyman and colleagues that these antibodies cause seizures in rabbits and lead to the release of the neurotoxin kainate in cell cultures. However, Wendl’s group and others have found these antibodies and many others various types of focal epilepsy and have questioned their specificity.
The unrelenting course of the disease had in the past defied medical therapy. In some patients the process eventually burns out, but in those with continuous focal epilepsy the seizures continued despite all antiepileptic drugs. The use of high doses of corticosteroids, when started within the first year of the disease, proved beneficial in 5 of the 8 patients treated by Chinchilla and colleagues. Repeated plasma exchanges and immune globulin have also been tried, but the results are difficult to interpret. When the disease is extensive and unilateral, neurosurgeons have resorted to partial hemispherectomy.
PSYCHOGENIC NONEPILEPTIC SEIZURES (PNES, PSEUDOSEIZURES)
These common episodes, which simulate convulsive or nonconvulsive seizures, are not the result of a paroxysmal neuronal discharge. They are termed psychogenic nonepileptic seizures (PNES) and comprise a heterogeneous group of disorders that are easily mistaken for epileptic spells. Moreover, they comprise a large proportion of treatment resistant epilepsy and often are treated with multiple antiepileptic drugs, to which they are unresponsive. It has been estimated that 70 percent of people diagnosed with PNES have been previously diagnosed and treated for epilepsy. In large series, nonepileptic seizures comprise 4 percent of cases of transient loss of consciousness, 20 percent of referrals to specialist epilepsy services, and 50 percent of apparent status epilepticus. It should be emphasized that patients with true epileptic seizures can exhibit psychogenic ones as well, making the distinction between the two particularly difficult. It is this population that proves most vexing (and common) in specialty epilepsy services.