Change in Excitability of Cortical Projection After Modified Catheter Balloon Dilatation Therapy in Brainstem Stroke Patients with Dysphagia: A Prospective Controlled Study

Abstract

Although the modified balloon dilatation therapy has been demonstrated to improve pharyngeal swallowing function post stroke, the underlying neural mechanisms of improvement are unknown. Our aims are (1) to investigate the effect of modified balloon dilatation on the excitability of corticobulbar projections to the submental muscle in dysphagic patients with brainstem stroke and (2) the relation between changes in excitability and pharyngeal kinematic modifications. Thirty patients with upper esophageal sphincter (UES) dysfunction due to unilateral brainstem stroke were recruited into two groups. The patients in dilatation group received modified balloon dilatation and conventional therapies, and those in control were only treated by conventional therapies (twice per day). The amplitudes of bilateral submental motor evoked potentials (MEPs) induced by transcranial magnetic stimulations over bilateral motor cortex, diameters of UES opening (UOD) and maximal displacement of hyoid (HD) were all assessed at baseline and the endpoint of treatments. Repeated ANOVA analysis revealed significant main effect of group, time and MEP laterality on MEP amplitudes (p = 0.02). There were no differences in the pretreatment measures between groups (all p > 0.05). After treatment, the amplitudes of affected submental MEP evoked by ipsilateral cortical pulse as well as UOD and HD were significantly different in dilatation group compared to control (amplitude: p = 0.02, UOD: p < 0.001, HD: p = 0.03). The differences of pre- and post-treatment amplitudes of the affected MEP evoked by ipsilateral stimulation showed a positive correlation with the improvement of HD (dilatation: R ² = 0.51, p = 0.03; control: R ² = 0.39, p = 0.01), rather than UOD in both groups (all p > 0.05). In conclusion, modified balloon dilatation therapy can increase the excitability of affected projection in patients with unilateral brainstem stroke.

Keywords: Balloon dilatation therapy; Brainstem stroke; Corticobulbar; Deglutition; Deglutition disorders; Motor evoked potential.

Fig. 1

Schematic diagram of submental MEP. The cortical stimulation ipsilateral to the brainstem lesion would be classed as the ipsilateral. The muscle ipsilateral to the brainstem lesion was regarded as “affected muscle” due to the nerve supply impairment. Affected the affected submental muscle, unaffected the unaffected submental muscle, ipsi the cortex ipsilateral to the brainstem lesion, contra the cortex contralateral to the brainstem lesion. The dashed arrow represents the affected projection

Fig. 2

Comparisons of the amplitudes of submental MEP within group and between groups. Dashed bracket represents the comparison between two groups for each laterality. Dashed parenthesis represents the comparison of the affected and unaffected submental pretreatment MEP within group. Brackets represent the comparisons of pre- and post-treatment MEPs. *p < 0.05, error bar represents standard error. IA the affected submental MEP induced by ipsilateral stimulation, CA the affected submental MEP induced by contralateral stimulation, IU the unaffected submental MEP induced by ipsilateral stimulation, CU the unaffected submental MEP induced by contralateral stimulation

Fig. 3

Comparisons of hyoid displacement and the diameters of UES opening between two groups. *p < 0.05, NS represents no significance, error bar represents standard error. HD hyoid displacement, UOD maximal diameters of UES opening

Fig. 4

Correlation of improvement of kinematic parameters and amplitude changes of submental MEP evoked by ipsilateral stimulation before and after treatment in both groups. Significant linear fit lines were showed between the affected MEP and HD in two groups