Incidence and lesions causative of delusional misidentification syndrome after stroke

To better elucidate the symptomatology and pathophysiological mechanisms underlying delusional misidentification syndrome (DMS), we investigated the incidence rate and symptomatic features of DMS following stroke and relationships among DMS, other neuropsychological symptoms, and lesion locations.

The present study included 874 consecutive patients (371 women; mean age ± standard deviation = 72.2 ± 11.7 years) who were admitted to the rehabilitation wards at two hospitals within 2 months of their first stroke. We examined the clinical features and lesion sites of patients with DMS and compared them with those of a control group of patients with hemi-spatial neglect without DMS using voxel-based lesion-symptom mapping (VLSM).

Among the 874 patients who experienced a stroke, we observed 10 cases of Fregoli syndrome. No other DMS subtypes were observed; however, eight patients exhibited somatoparaphrenia (five of them also had Fregoli syndrome) and one also exhibited reduplicative paramnesia. Right hemispheric lesions were found in all 10 cases. VLSM revealed statistically significant overlapping lesion sites specifically related to Fregoli syndrome when compared with the control group. The sites included the insula, inferior frontal lobe, anterior temporal lobe, and subcortical limbic system in the right hemisphere (i.e., areas connected by the uncinate fasciculus).

The DMS incidence was 1.1% among patients after stroke. All patients had Fregoli syndrome and half had somatoparaphrenia, suggesting that the two syndromes share an underlying pathology. Lesions found with Fregoli syndrome were concentrated around the right uncinate fasciculus; this has not been reported in previous research.