Olfactory and imaging features in atypical Alzheimer's disease

Abstract

Cognition and speech disorders are the most common symptoms of dementia in neurodegenerative disease. Here, we present a detailed clinical evaluation of a case of logopenic variant of primary progressive aphasia (lv-PPA), an atypical form of Alzheimer disease (AD), including cognitive testing over time, brain imaging, electrophysiology, and tests of olfactory function. We present the case of a 58-year-old man suffering from progressive language difficulties who was finally diagnosed with lv-PPA. Clinical data included neuropsychological examinations, electrophysiology tests, neuroimaging, biomarkers, olfactory tests, and olfactory functional magnetic resonance imaging (fMRI). The patient suffered from language disorders, including stumbling speech and forgetting appropriate words and how to pronounce some words. This had started 2 years earlier, and he had begun to deteriorate in recent months. In addition to his speech disorder, scores on the Mini Mental State Examination and Montreal cognitive assessment indicated that his cognition was affected. Structural imaging revealed no obvious hippocampal atrophy (score of 1), and molecular imaging showed hypometabolism and amyloid deposits in the temporal parietal region. The patient also presented with olfactory impairment. Although his odour detection threshold was normal, his cognitive threshold for scent recognition was significantly increased. Olfactory fMRI showed that activation of the whole brain and primary olfactory cortex was rare. This case provides evidence suggesting that lv-PPA is an atypical form of AD, with symptoms including speech disorders and impaired cognition. This patient with lv-PPA presented with olfactory impairment.