MRI studies
Recent structural brain MRI studies support the concept that impaired somatosensory neural networks mediate the delusional symptoms of DI, but not in delusional disorders without somatic content. This was demonstrated in an MRI study by Dr. Lepping and others conducted in 18 patients with DI, 19 others with nonsomatic delusional disorders centered on themes of persecution or jealousy, and 20 healthy volunteers. The DI group had lower gray matter volume in prefrontal, thalamic, striatal, and insular regions of the brain compared to the other two groups.
Of note, mapping of the insula and dorsal striatum indicates they are part of the peripersonal space network, which integrates tactile and visual perceptions involving the area near the body surface. The insula also mediates feelings of pain and disgust.
Some of the same investigators have also recently reported brain MRI evidence specifically of cerebellar dysfunction in patients with DI, who displayed decreased gray matter volume in left lobule VIIa of the cerebellum and increased gray matter volume in bilateral lobule VIIa/crus II compared to patients with non-somatic delusions. This points to a role for impaired cerebellar neural networks related to somatosensory perception in patients with DI but not in those with non-somatic delusions.
Delusional infestation: What’s in a name?
for the disorder. That’s in part because the delusional focus in patients with this condition has shifted over time. In the 19th century, for example, affected patients often attributed their infestation to typhus.
In contemporary practice, roughly one-quarter of affected patients think they are infested by small inanimate objects, most commonly fibers or threads emerging from the skin, rather than by parasites, insects, or worms. In a study of 148 consecutive European patients with suspected DI, Dr. Lepping and coinvestigators reported only 35% believed they were infested by parasites.
“The name ‘delusional infestation’ emphasizes the constantly changing pathogens and covers all present and future variations of the theme that are bound to occur,” Dr. Lepping observed.
All speakers reported having no conflicts of interest.