A dimensional approach to thought disturbances in epilepsy: Utility in psychosis and behavioural syndromes

To the Editor

In some patients with epilepsy, boundaries between preoccupations, overvalued ideas and delusions can be blurred. We present a case which illustrates the related diagnostic challenges and discuss potential solutions.

A 23-year-old man began to experience seizures and likely peri-ictal visual hallucinations in the same year after a motor vehicle accident without lesions on 3-Tesla magnetic resonance imaging (MRI). Electroencephalography supported independent bitemporal epileptic foci. Postictal psychotic episodes with delusions of grandeur and manic features began 2 years later. Five years thereafter, he developed a persistent belief that all his ongoing life experiences since the accident might not be real, but rather imagined in the context of his life ‘flashing before his eyes’ over seconds as he is still actually going through the accident anticipating collision and impending death. This belief was persistently preoccupying and distressing, but not always held with absolute conviction. He entertained it as a possibility that could not be scientifically excluded. The degree of conviction, preoccupation, distress and overall functioning considerably improved on olanzapine.

This case exemplifies the not uncommon encounter in the neuropsychiatry of epilepsy involving poorly defined boundaries between preoccupations, overvalued ideas and delusions. Related differentials include (1) idiosyncratic non-psychotic beliefs; (2) preoccupation with past, affectively salient, peri-ictal psychotic experiences; (3) chronic psychosis with an element of retained insight such that bizarre beliefs are present but not held with absolute certainty; (4) thought perseveration due to frontal network behavioural syndrome; and (5) emphasis on philosophical themes as described by Waxman and Geschwind (1975). Our case possibly involved a combination of the latter three, with a predominant psychotic component that responded to olanzapine.

What further confounds this differential is that phenomenology might evolve over time, for example, during progression from recurrent episodes of postictal psychosis to chronic interictal psychosis, or after improved seizure control and/or antipsychotic treatment. Superimposed on this might be the dysexecutive and behavioural consequences of frontal network dysfunction, due to a structural lesion or chronic recurrent seizures. Literature in this area includes mostly categorical descriptions of phenomenology (Adachi and Akanuma, 2016) rather than extensive descriptions of variation across the above syndromes in terms of the degree of conviction, preoccupation and distress associated with beliefs. The authors propose the use of dimensional instruments, for example, the Psychotic Symptom Rating Scales (PSYRATS; Haddock et al., 1999), to characterize these parameters and lend further insight into (1) phenomenological distinction between these disorders, (2) their potential interplay in terms of cross-sectional overlap and longitudinal evolution, and (3) the influence of treatment and variations in seizure control on different aspects of phenomenology.