Ekbom’s delusion as a prelude to Cotard’s syndrome, has not heretofore been described.

Case study: A 45-year-old woman with a past diagnosis of bipolar disorder with psychotic features was admitted, having been up all night conversing with spirits, proclaiming that she had made a deal with Satan. Convinced that her grandmother was possessed by the devil, she smashed her grandmother’s head with a two-by-four. Results: Mental Status Examination: self conversing with her eyes darting around the room. Poor hygiene. Behavior: guarded and withdrawn. Oriented x2. Speech: hyperverbal. Insight and judgment: poor. Mood: hostile, aggressive, and angry. Thought process disorganized, incongruent, and tangentiality. She was convinced she was infested with little black bugs crawling around her insides which had been placed there by the devil. After two days of olanzapine she reported the bugs were no longer present, but rather that she herself was dead and that her organs were decomposing, which persisted through the remainder of the hospitalization.

Neuroimaging abnormalities in Ekbom’s syndrome involve the striatum, basal ganglia (putamen and caudate nucleus), insular and cingulate cortices, cortex (prefrontal, right parietal, and temporal lobes), right lingual and orbitofrontal gyri, and thalamus. In Cotard’s syndrome, abnormalities have been identified in the striatum, frontal and temporal lobes, and right-sided and bilateral hemispheres. An overlap between the delusions exists in the striatum, inferior parietal, and temporal lobes. A single lesion in the nondominant inferior parietal lobe may cause both syndromes, due to its substantial interconnection with the temporo-limbic areas. Since the parietal lobe is also involved in somatosensory processing, peradventure distorted sensory perception with associated sensation of formication may have been the nidus for the delusional infestation as well as a nidus for the perception of thanatos habitus. Such misperception may have then been amplified into a delusion because of a hyperconnection between the parietal lobe and the limbic system. This may represent a variant of the two-factor hypothesis of delusions whereby a distorted sensory perception is then misrepresented in a delusion. Dysfunction of the right hemisphere, which normally acts to censor the left, allows the delusion to manifest. A single lesion of the inferior parietal lobule may be sufficient for both sensory distortions and loss of inhibition of delusional interpretation of distorted sensation by the frontal lobe, yclept the sensorialist hypothesis.

In those with monothematic delusions, the search for transient fluctuation in delusional states may be revealing.

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