Psychogenic Nonepileptic Seizures Are Associated With Mild TBI

SAN DIEGO—Neurologists evaluating patients with a history of traumatic brain injury (TBI) and seizures should consider a diagnosis of psychogenic seizures, according to research presented at the 66th Annual Meeting of the American Epilepsy Society. The diagnosis may be suspected in patients with seizures related to mild TBI and in patients with a history of post-traumatic stress disorder (PTSD), said Martin Salinsky, MD, Director of the Veterans Affairs Medical Center in Portland.

"Just because a patient has a history of TBI and subsequently developed seizures does not necessarily mean that he or she has epilepsy," said Dr. Salinsky. About 25% of all patients evaluated in epilepsy monitoring units are discharged with a diagnosis of psychogenic seizures, which are alterations in behavior that resemble epileptic seizures, but do not result from paroxysmal neuronal discharges or any other physiologic abnormality. The exact prevalence of psychogenic nonepileptic seizures is unknown, however. In previous population-based studies of post-traumatic epilepsy, which were based on chart reviews or administrative databases, cases of epilepsy were rarely confirmed by EEG monitoring.

Psychogenic nonepileptic seizures are often mistaken for epilepsy and treated unsuccessfully with antiepileptic drugs. Patients with psychogenic seizures often are disabled, experience the side effects of treatment with antiepileptic drugs, and feel the psychosocial and economic effects associated with poorly controlled seizures.

Mild TBI Is Weakly Associated With Epilepsy
The first two studies to provide evidence for an association between head injuries and psychogenic seizures were published in Epilepsia in 1998, said Dr. Salinsky. Both studies were retrospective reviews of patients who had been diagnosed with psychogenic seizures on video EEG monitoring. Between one-quarter and one-third of the patients in both studies reported an antecedent head injury as the likely cause of the seizure.

Of the patients who suspected previous head injury as the cause of their seizures, about 80% had had a mild head injury, approximately 10% had had a moderate head injury, and about 10% had had a severe head injury. "This is not the distribution you would expect to see with post-traumatic epilepsy," which is more commonly associated with moderate to severe head injury than with mild head injury, said Dr. Salinsky.

Mild TBI is strongly associated with psychogenic seizures, but weakly associated with epilepsy. In a recent study, more than 80% of US veterans who entered an epilepsy monitoring unit with a history of mild TBI as a cause of their seizures were diagnosed with psychogenic seizures, said Dr. Salinksy. In contrast, approximately 90% of veterans with a history of severe TBI were diagnosed with epilepsy.

Post-Traumatic Stress Disorder May Contribute to Psychogenic Seizures
Psychogenic seizures are just as common in veterans as they are in civilians. But a new study showed that more than twice as many veterans (56%) as civilians (26%) had suspected a preceding head injury as the cause of the seizures. For veterans and civilians alike, most of the injuries were mild TBI, according to Dr. Salinksy.

In a recent analysis, veterans diagnosed with psychogenic seizures tended to have greater psychopathology (ie, more Axis I diagnoses) than veterans diagnosed with epileptic seizures. In particular, veterans diagnosed with psychogenic seizures were significantly more likely to have PTSD than veterans diagnosed with epileptic seizures. "Other than PTSD, differences between these two groups were relatively small and were not statistically significant," said Dr. Salinksy.

A multivariate analysis showed PTSD to be the only predictive factor for psychogenic seizures. "The odds ratio was fairly high, and the p value highly significant," said Dr. Salinsky. This finding mainly resulted from patients with a history of mild TBI, he added.

"In our veteran population, we are beginning to see a model develop whereby the development of psychogenic seizures in patients who have mild TBI may be mediated through the mechanism of PTSD," said Dr. Salinsky. Several studies suggest that health problems in veterans who have had mild TBI generally are mediated through PTSD. Perhaps not all psychogenic seizures in patients with TBI are mediated through PTSD, "but this does appear to be one valid mechanism in veterans, and perhaps in civilians as well," concluded Dr. Salinsky.