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Can loss of sense of smell predict Alzheimer’s

The first lapses of memory go hand in hand with a loss of the sense of smell: The olfactory centre in the brain of Alzheimer’s patients is wasting away. The olfactory bulb starts to shrink at a very early stage of the disease, at a time when retentiveness is only slightly affected. It is possible to detect the shrinkage of the olfactory bulb with magnetic resonance imaging, as the latest findings by scientists of the Department of Psychiatry at the University Hospital of Heidelberg have revealed. The study of the new diagnostic marker was published in May 2009 in the “Journal of Alzheimer’s Disease”.

Alzheimer’s is the most common type of dementia in people over 65 years of age: In Germany, about 1.2 million people suffer from Alzheimer’s, and the number is growing. Before the first Alzheimer symptoms become obvious, superfluous proteins are deposited in what is known as amyloid plaques and neurofibrils. They damage the neurones, which eventually die and cause the brain substance to shrink. Alzheimer’s cannot be cured; the drugs that are currently available can only delay the course of the disease. The early diagnosis of the disease has many advantages for the patients: the early treatment of the disease with specific drugs can delay severe symptoms and alleviate associated disorders.

Alterations in patients with memory disorders

Prof. Dr. Johannes Schröder, Head of Gerontopsychiatric Research, Centre for Psychosocial Medicine, University Hospital Heidelberg © private

Scientists in the Division of Gerontopsychiatry at the Hospital of Psychiatry at the University of Heidelberg compared three groups of patients: those with slight cognitive impairments, which are seen as the potential prestages of dementia; those with clinically manifest Alzheimer's disease and healthy volunteers. They found that patients with memory disorders had a smaller olfactory bulb than healthy volunteers. This size difference was particularly obvious in patients in whom Alzheimer's disease had already manifested itself.

The volume of the central temporal lobe also decreases. This is a brain area, located close to the olfactory bulb, which contains important memory and speech faculty structures. Back in 2003, the team under the leadership of Dr. Johannes Schröder, head of the Division of Gerontopsychiatry, found using MRI (magnetic resonance imaging) that the temporal lobe becomes damaged very early in the course of Alzheimer's, i.e. before disease-related performance deficiencies become obvious. Since the olfactory bulb is also affected in the early stages of disease, its volume can be an additional parameter in diagnosing Alzheimer's.

Heidelberg memory outpatient clinic offers early screening and intervention

The treatment of, and research into, mental disorders at an advanced age – in particular cognitive impairments, dementia and depressive disorders – are the major focus for researchers in the Division of Gerontopsychiatry at the Hospital for General Psychiatry at the University of Heidelberg. The highest priority is the screening and early intervention: the division has been offering consultation hours for patients experiencing reduced mental capacity for 18 years and has, in the last few years, expanded the possibilities for outpatient and semi-residential screening and differential diagnostics. Around 300 patients and their families come to the outpatient clinic per year.

Philipp A. Thomann, Vasco Dos Santos, Ulrich Seidl, Pablo Toro, Marco Essig and Johannes Schröder: "MRI-Derived Atrophy of the Olfactory Bulb and Tract in Mild Cognitive Impairment and Alzheimer's Disease", Journal of Alzheimer's Disease 2009 May;17(1):213-21
Dr. Philipp Thomann
Hospital for General Psychiatry
Centre for Psychosocial Medicine
Tel.: +49 (0)6221 / 56 / 38 091
E-mail: philipp.thomann(at)med.uni-heidelberg.de
Website address: https://www.gesundheitsindustrie-bw.de/en/article/press-release/can-loss-of-sense-of-smell-predict-alzheimer-s