Longitudinal Changes in Functional Connectivity of the Caudate Is Associated With Recovery From Bell's Palsy

Abstract

Several studies have demonstrated through resting-state functional magnetic resonance imaging (fMRI) that functional connectivity changes are important in the recovery from Bell's palsy (BP); however, these studies have only focused on the cortico-cortical connectivity. It is unclear how corticostriatal connectivity relates to the recovery process of patients with BP. In the present study, we evaluated the relationship between longitudinal changes of caudate-based functional connectivity and longitudinal changes of facial performance in patients with intractable BP. Twenty-one patients with intractable BP underwent resting-state fMRI as well as facial behavioral assessments prior to treatment (PT) and at the middle stage of treatment (MT); and 21 age- and sex-matched healthy controls (HC) were recruited and received the same protocol. The caudate was divided into dorsal and ventral sub-regions and separate functional connectivity was calculated. Compared with HC, patients with intractable BP at the PT stage showed decreased functional connectivity of both the dorsal and ventral caudate mainly distributed in the somatosensory network, including the bilateral precentral gyrus (MI), left postcentral gyrus, media frontal gyrus, and superior temporal gyrus (STG). Alternatively, patients in the MT stage showed decreased functional connectivity primarily distributed in the executive network and somatosensory network, including the bilateral cingulate cortex (CC), left anterior cingulate cortex (LACC), inferior prefrontal gyrus (IFG), MI, STG, and paracentral lobe. The longitudinal changes in functional connectivity of both the dorsal and ventral caudate were mainly observed in the executive network, including the right ACC, left CC, and IFG. Functional connectivity changes in the right ACC and left IFG were significantly correlated with changes in facial behavioral performance. These findings indicated that corticostriatal connectivity changes are associated with recovery from BP.

Keywords: Bell’s palsy; caudate; functional connectivity; functional magnetic resonance imaging; longitudinal changes.

Figure 1

Representation of the four caudate regions of interest. The above panel shows the left dorsal caudate and left ventral caudate onto sagittal brain views. The bottom panel shows the right dorsal caudate and right ventral caudate onto sagittal brain views.

Figure 2

Bar graph shows the facial performance scale in HC and patients with BP. Normal facial functional performance of HC was presented more significantly than that of patients in the MT and PT stages, and patients in MT stage presented significantly better performance compared to patients in PT stage (p < 0.05). HC, Healthy Controls; PT, patients with BP prior to treatment; MT, patients with BP at middle stage of treatment.

Figure 3

Group differences in functional connectivity between patients with BP in the PT stage compared with HC (p < 0.01, corrected with false discovery rate). (A) Functional connectivity of the left dorsal caudate; (B) functional connectivity of the left ventral caudate; (C) functional connectivity of the right dorsal caudate; (D) functional connectivity of the right ventral caudate. LMI, left precentral gyrus; LSI, left postcentral gyrus; LSTG, left superior temporal gyrus; LTH, left thalamus; LMFG, left medial frontal gyrus; RMI, right prefrontal gyrus.

Figure 4

Group differences in functional connectivity between patients with BP in the MT stage compared with HC (p < 0.01, corrected with false discovery rate). (A) Functional connectivity of the left dorsal caudate; (B) functional connectivity of the left ventral caudate; (C) functional connectivity of the right dorsal caudate; (D) functional connectivity of the right ventral caudate. LSTG, left superior temporal gyrus; LMI, left precentral gyrus; LIFG, left inferior frontal gyrus; LCC, left cingulate cortex; RCC, right cingulate cortex; LACC, left anterior cingulate cortex; RACC, right anterior cingulate cortex; LPACLB, left paracentral lobe.

Figure 5

Group differences in functional connectivity between patients with BP in the MT stage compared with patients with BP in the PT stage (p < 0.01, corrected with false discovery rate). (A) Functional connectivity of the left dorsal caudate; (B) functional connectivity of the left ventral caudate; (C) functional connectivity of the right dorsal caudate. LIFG, left inferior frontal gyrus; LCC, left cingulate cortex; RACC, right anterior cingulate cortex.

Figure 6

The graph shows the overlapped brain regions in the longitudinal changes of caudate-based functional connectivity and demonstrates relationships between functional connectivity changes and facial function improvements in patients with BP. R, coefficient of correlation; FC, functional connectivity; LIFG, left inferior frontal gyrus; LCC, left cingulate cortex; RACC, right anterior cingulate cortex.