| dc.description.abstract | Since the discovery of olfactory dysfunction in Parkinson’s disease (PD) and Alzheimer’s
disease (AD) just over three decades ago, research into olfactory dysfunction in PD and AD
has grown vastly. It appeared that olfactory dysfunction is similar in PD and AD. However,
recent studies show that the severity of olfactory dysfunction differs between PD and AD.
Olfactory dysfunction in PD appears to be stable during disease progression and severity
except for odour discrimination. In AD however, olfactory dysfunction in identification,
discrimination and threshold is associated with severity and the degree of dementia. It has
been found that both PD an AD are preceded at approximately five years by olfactory
dysfunction before the presence of typical symptoms. Typical symptoms for PD are
bradykinesia, rest tremor and rigidity. For AD typical symptoms are cognitive impairment and
memory deficits. Also, olfactory dysfunction can identify future PD or AD developers from
an at risk group. However, the predictive value of olfactory dysfunction in a general
population is unknown.
Another difference can be found in treatment response. Olfactory dysfunction improves in
AD with acetylcholinesterase inhibitors (ChEI), where in PD, olfaction is unaffected by
typical dopaminergic treatment. There are a number of explanations for this difference,
among which is that the underlying mechanism in PD is more complex and comprises
multiple system, e.g. dopaminergic system and acetylcholinesterase (AChE) activity. It has
recently been suggested that the AChE is more important in olfactory dysfunction in PD than
the dopaminergic system.
Olfactory testing appears very useful in early detection and differential diagnosis and
could be very useful in clinical settings, but further research is needed to investigate the
underlying mechanisms and possibilities for inclusion in treatment. Also, further research
could focus on the link between movement and olfaction as seen in animals. Another possible
line of research is that of olfaction and emotion or lack thereof as seen in both PD and AD. | |
