A case of episodic derealisation in focal cortical dysplasia: First looks at the whole elephant?

Derealisation remains a bewildering and obscure phenomenological entity with shifting identities on the dissociation spectrum of disorders. A consensus seems to have emerged that the symptom can be produced by a variety of agents which finally act through a common pathway whose identity remains elusive and whose components have thus far only emerged piecemeal. Temporal lobe dysfunction, a covert epileptogenic process and aberrations within a network comprising the amygdala, the anterior cingulate and the prefrontal cortices have all been implicated, however independently none account holistically for the peculiar phenomenology of derealisation. We present a case of focal cortical dysplasia of the right supramarginal gyrus, who reported with three distinct symptoms – panic episodes, a heightening of baseline anxiety and recurrent derealisation, all of which responded well to antiepileptic drugs. This represents the first case with evidence of dysfunction in all areas of the heteromodal association cortex (HASC), a neural network responsible for integration of sensory input and required to understand the significance of events and objects in the external environment. Derangements in the HASC have produced non-modality specific neuropsychiatric deficits, and the component anatomy can account well for the aberrations in emotion, perception and memory characteristic of derealisation. Collectively, the model provides a credible basis with which to explain the curious symptoms encountered in derealisation and provides a promising line of enquiry.