Noradrenergic Pathway to the Cerebellum: the Study Must Go On

In 1967, Andén, Fuxe, and Ungerstedt demonstrated the presence of monoamine-containing fibers in the rat cerebellum. Over the past 50 years, this finding has provided clinical relevance of the noradrenergic system to the cerebellum. Cerebellar dysfunction and noradrenergic system may relate to tremor in Parkinson disease and essential tremor, motor learning, and the vestibulo-ocular reflex in spinocerebellar ataxias. Cognition and emotion may also be linked to the cerebellar noradrenergic system, in relation to the symptoms of Alzheimer disease, dementia with Lewy bodies, and attention-deficit/hyperactivity disorder. Despite recent technological advances in neuroimaging for evaluating the noradrenergic system, we need more evidence to understand the precise pathophysiological relationship between the cerebellum and the noradrenergic system and its clinical implications.