The Role of the Cerebellum in Swallowing

Abstract

Swallowing is a complex activity requiring a sophisticated system of neurological control from neurones within the brainstem, cerebral cortices and cerebellum. The cerebellum is a critical part of the brain responsible for the modulation of movements. It receives input from motor cortical and sensory areas and fine tunes these inputs to produce coordinated motor outputs. With respect to swallowing, numerous functional imaging studies have demonstrated increased activity in the cerebellum during the task of swallowing and damage to the cerebellum following differing pathological processes is associated with dysphagia. Single pulses of transcranial magnetic stimulation (TMS) have been applied to the cerebellum and have been shown to evoke motor responses in the pharynx. Moreover, repetitive TMS (rTMS) over the cerebellum can modulate cerebral motor (pharyngeal) cortical activity. Neurostimulation has allowed a better understanding of the connections that exist between the cerebellum and cerebral swallowing motor areas in health and provides a potential treatment for neurogenic dysphagia in illness. In this review we will examine what is currently known about the role of the cerebellum in the control of swallowing, explore new findings from neurostimulatory and imaging studies and provide an overview of the future clinical applications of cerebellar stimulation for treating dysphagia.

Keywords: Cerebellum; Dysphagia; Neurostimulation; Swallowing.

Fig. 1

Dentate and potential fastigial cerebello-cortical motor pathways

Fig. 2

Cerebellar rTMS being delivered guided by MRI frameless stereotaxy (Image from GI Sciences University of Manchester dysphagia research group)

Fig. 3

The effects of active and sham contra-lesional cerebellar rTMS on cumulative aspiration scores (lower scores indicate more normal swallowing function). [34]

Fig. 4

Areas of increased blood flow following swallowing task. [51]

Fig. 5

Modular swallowing areas within the brain. Arrows show cortical parietal insula circuit and cerebellar modulation. Image simplified and adapted from [19]