Abstract

Objective: Semantic dementia (SD), a variant of Frontotemporal Dementia (FTD), is characterized by a progressive disturbance in language expression and loss of semantic memory. Autobiographical and episodic memory is reasonably preserved. Mean onset has been reported at 64.2 years with 45% of cases occurring in those over age 65. Prevalence estimates of 3% for variants of FTD among adults aged 85+ suggest that late onset SD, which may be misdiagnosed as atypical Alzheimer's disease, is more common than previously believed. The current case seeks to expand upon the limited literature regarding clinical characteristics of late onset SD. Method: An 88 year-old, Caucasian woman presented for evaluation of aphasic symptoms that reportedly followed a traumatic experience in March 2011. MMSE 8 months prior to the evaluation was 28/30. An MRI revealed age-related ischemic changes and atrophy. Medical history was notable for macular degeneration, atrial fibrillation, hyposmolality/hyponatremia, and anxiety. Results: Findings indicated a precipitous decline in functioning since previous MMSE. Testing had to be modified to accommodate severe impairments in confrontational naming, comprehension, fluency, and repetition. Syntax and grammar remained relatively intact. Speech was characterized by impairments in intonation, prosody, rhythm, and volume. Additional testing revealed dysdiachokinesia, dysgraphia, disorientation, and signs of executive dysfunction including utilization behavior, perseveration, and disinhibition. Conclusion(s): Current findings suggest that late onset SD may be characterized by a more precipitous decline in language and other cognitive skills compared to younger adults, highlighting the importance of differential diagnosis. Additional research is needed to distinguish late onset SD from other dementia illnesses.