Cognitive and olfactory function profiles of frontotemporal lobar degeneration

Abstract

Objective To describe the cognitive and olfactory function profiles of frontotemporal lobar degeneration (FTLD). Methods A total of 52 FTLD patients admitted to Tianjin Huanhu Hospital from July 2014 to April 2017 were enrolled. Cognitive function was assessed by the Mini⁃Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA), and neuropsychiatric behavior was assessed by Neuropsychiatric Inventory (NPI). Quantitative olfactory function was assessed by T&T olfactory meter and olfactory fMRI, and changes in glucose metabolism in brain tissues were assessed by 18F⁃fluoro⁃2⁃deoxy⁃D⁃glucose (18F⁃PDG) PET. Results The cognitive dysfunction of 52 patients was mainly manifested as executive dysfunction (71.15%, 37/52), disinhibition (59.62%, 31/52), indifference (44.23%, 23/52), lack of empathy (40.38%, 21/52), memory loss (32.69%, 17/52), hyperstomia (25%, 13/52) and language disorder (3.85%, 2/52). MMSE score was 18 (4, 20), MoCA score was 11 (3, 15), and visuospatial and executive function, attention, language function, abstraction, delayed recall, and orientation were all lower than normal reference values. NPI score was 24 (7, 39), and the main manifestations were apathetic, irritable, excited, and high/euphoric. According to the T&T olfactory meter recognition domain, one case (3.45%) had normal sense of smell, 12 cases (41.38%) had mild hyposmia, 9 cases (31.03%) had moderate hyposmia, 5 cases (17.24%) had severe hyposmia, and 2 cases (6.90%) had anosmia. Olfactory fMRI showed that patients developed adaptation to odor when olfactory stimulation with gas concentration was successively from low to high (0.10%, 0.33%, 1.00%). 18F⁃FDG PET showed symmetric (2 cases) or asymmetric (4 cases) predominance of the frontal and/or temporal lobes. Conclusions In FTLD patients, executive dysfunction and neuropsychiatric behavior abnormalities were more common, while memory impairment appeared later. Abnormal olfactory function may also occur, but olfactory adaptation still exists. Neuropsychological test combined with 18F⁃FDG PET is helpful for early diagnosis and differential diagnosis.

Keywords

• frontotemporal lobar degeneration
• cognition disorders
• olfaction disorders
• neuropsychological tests
• magnetic resonance imaging
• positron ⁃ emission tomography
• fluorodeoxyglucose f18