Somatic Symptom Disorder in Semantic Dementia: The Role of Alexisomia.

Background: Semantic dementia (SD) is a neurodegenerative disorder characterized by loss of semantic knowledge. SD may be associated with somatic symptom disorder due to excessive preoccupation with unidentified somatic sensations.

Objective: To evaluate the frequency of somatic symptom disorder among patients with SD in comparison to comparably demented patients with Alzheimer׳s disease.

Methods: A retrospective cohort study was conducted using clinical data from a referral-based behavioral neurology program. Fifty-three patients with SD meeting criteria for imaging-supported semantic variant primary progressive aphasia (another term for SD) were compared with 125 patients with clinically probable Alzheimer disease. Logistic regression controlled for sex, age, disease duration, education, overall cognitive impairment, and depression.

Results: The prevalence of somatic symptom disorder was significantly higher among patients with SD (41.5%) compared to patients with Alzheimer disease (11.2%) (odds ratio = 6:1; p < 0.001). Somatic symptom disorder was associated with misidentification and preoccupation with normal bodily sensations such as hunger, bladder filling, borborygmi, rhinorrhea, and reflux; excessive concern over the incompletely understood meaning or source of pain or other symptoms; and Cotard syndrome or the delusion that unidentified somatic symptoms signify death or deterioration.

Conclusions: SD, a disorder of semantic knowledge, is associated with somatic symptom disorder from impaired identification of somatic sensations. Their inability to read and name somatic sensations, or "alexisomia," results in disproportionate and persistent concern about somatic sensations with consequent significant disability.