Epilepsy and behaviour disorders

Single case reports of behavioural and personality disorders in patients with severe brain lesions often appear dramatic. However, with respect to focal epilepsies, these reports nevertheless raise the question of whether there might be parallels in the behaviour when epilepsy affects the same brain regions. With the exception of rare cases of ictal aggression, postictal confusional states or psychosis (Marsh and Krauss, 2000), behaviour and personality disorders observed in patients with FLE appear less severe. Furthermore, as with TLE, one can hardly expect to find the prototypical 'frontal epileptic personality' or Wesensanderung. Personality is by definition more trait than state dependent and, particularly in epilepsy, it is quite difficult to determine whether a given behaviour has trait characteristics or not.

Table 12.1. Factors affecting cognitive and mood states in epilepsy

States of epilepsy preictal ictal postictal interictal

(seizure free after successful surgery) Seizures frequency generalization nonconvulsive status epilepticus Epileptic dysfunction local versus distant effects Lesion e.g. alien tissues vs. migration and developmental disorders (confounded with different ages at lesion/epilepsy onset) extent, location, lateralization Antiepileptic drugs positive vs. negative psychotropic effects individual incompatibility drug-induced encephalopathy intoxication

Conclusions about persistence and continuity require follow-up observations with longer time intervals. In epilepsy several factors can be discerned, which can lead to more or less reversible changes in patients' cognitive abilities and mood states (see Table 12.1). Furthermore, although we can now look back on a long history of successful epilepsy surgery, it is still not clear to what degree the fact of having seizures is a prerequisite of behaviour and mood disorders in epilepsy.

The patient with epilepsy must always be seen in his state relative to seizures, e.g. whether he is ictal, postictal or interictal. According to recent findings with regard to seizure prediction by nonlinear measures of complexity loss as recorded by intracranial EEG, significant seizure-precipitating drops in complexity, i.e. synchronization, can be recorded long before the seizure starts (Elger and Lehnertz, 1998). Accordingly, one must assume also preictal states, which would fit well with patients' reports of increased dysphoric mood and cognitive problems before the seizure starts. Finally, since many patients can now become seizure-free on a long-term basis by epilepsy surgery, one can suggest an additional state of well-controlled epilepsy after successful epilepsy surgery.

Epileptic activity can affect distant brain areas and cause cognitive and behaviour problems not related to the primary lesion or epileptogenic zone (Shulman, 1984). Notwithstanding seizures and epileptic activity, one must also differentiate the underlying pathologies, which can be more or less systemic, have different ages of onset in life, and thus have different effects on brain maturation and the development of cognition and personality. We must finally consider influences of often longstanding antiepileptic medication in these patients. Antiepileptic drugs may have positive or negative psychotropic side effects, and can show incompatibilities in the individual patient (Schmitz, 1999). Interactive effects of pathology, epilepsy and treatment must be considered. Apart from idiosyncratic actions, drugs can have different effects in lesion and nonlesion patients, and they may act differently dependent on seizure control.

Taking this into consideration, it will be shown in the next sections that there is nevertheless evidence of specific behavioural abnormalities in patients with FLE, which can be interpreted within a theoretical framework of frontal lobe dysfunction. This will be outlined with the example of interictal behaviour as assessed by neuropsychological examination and self-report measures concerning quality of life, everyday activities, personality and psychiatric symptoms. In addition, seizure semiology and impairment during frontal lobe seizures and frontal nonconvulsive status epilepticus will be considered, to convey an idea of what the behavioural consequences of impaired frontal lobe functions in FLE might be.

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