Delusions, illusions and hallucinations in epilepsy: 1. Elementary phenomena

Area of Science:

• Neuroscience and Psychiatry
• Epileptology
• Clinical Neurophysiology

Background:

• Hallucinations in epilepsy present complex phenomenological and mechanistic challenges.
• Divergent definitions of hallucinations, delusions, and illusions exist between neurology and psychiatry.
• Psychiatry relies on psychopathology for syndrome delineation, while neurology focuses on localized epileptic activity.

Purpose of the Study:

• To comprehensively review the phenomenology and mechanisms of hallucinatory experiences in epilepsy from neurological and neuropsychiatric perspectives.
• To compare clinical and electrophysiological features of epileptic hallucinations with primary psychoses.
• To examine definitions and elementary hallucinatory phenomena, contrasting psychiatric and neurological approaches.

Main Methods:

• Review of clinical and electrophysiological features of hallucinatory phenomena in epilepsy.
• Analysis of data from intracranial stereoelectroencephalography (SEEG) and brain stimulation during epileptic seizures.
• Comparison of findings with primary psychotic disorders.

Main Results:

• Limited anatomical specificity for many hallucinatory states in epilepsy; stimulation of different areas can yield similar phenomena, and vice versa.
• Elementary hallucinations from primary visual and auditory cortices show higher anatomical specificity.
• Involvement of the limbic cortex is essential for complex hallucinatory states, indicating involvement of widely distributed neuronal networks even in focal epilepsy.

Conclusions:

• Neurological approach, using SEEG, suggests a more unified view of hallucinations, illusions, and delusions due to overlapping physiological bases.
• Psychiatric distinctions, while clinically useful, do not align with discrete electrophysiological signatures for these phenomena.
• Epileptic seizures, particularly in mesial temporal lobe, insula, and limbic cortices, involve widespread networks, explaining the diverse hallucinatory experiences.