Brain activity in the right-frontal pole and lateral occipital cortex predicts successful post-operatory outcome after surgery for anterior glenoumeral instability

Abstract

Shoulder apprehension is more complex than a pure mechanical problem of the shoulder, creating a scar at the brain level that prevents the performance of specific movements. Surgery corrects for shoulder instability at the physical level, but a re-dislocation within the first year is rather common. Predicting which patient will be likely to have re-dislocation is therefore crucial. We hypothesized that the assessment of neural activity at baseline and follow-up is the key factor to predict the post-operatory outcome. 13 patients with shoulder apprehension (30.03 ± 7.64 years) underwent clinical and fMRI examination before and one year after surgery for shoulder dislocation contrasting apprehension cue videos and control videos. Data analyses included task-related general linear model (GLM) and correlations imaging results with clinical scores. Clinical examination showed decreased pain and increased shoulder functions for post-op vs. pre-op. Coherently, GLM results show decreased activation of the left pre-motor cortex for post-surgery vs. pre-surgery. Right-frontal pole and right-occipital cortex activity predicts good recovery of shoulder function measured by STT. Our findings demonstrate that beside physical changes, changes at the brain level also occur one year after surgery. In particular, decreased activity in pre-motor and orbito-frontal cortex is key factor for a successful post-operatory outcome.

Figure 1

Paired t-test results. Significant differences were found in all the clinical scores at follow-up compared to baseline (p < 0.001). In particular considering ROWE, SST, SSV and WOSI scores an increased shoulder performance was found, while for pain VAS scores a decrease in pain levels were assessed. Mean and standard error were shown.

Figure 2

Task related GLM results.Task related GLM shows higher activation in Baseline vs. Follow-up for apprehension videos vs. control videos notably in the left motor and premotor cortex, somatosensory cortex, lateral occipital cortex, and para-hippocampal gyrus. Results show brain areas surviving TFCE correction. P values < 0.05 were considered as significant. No significant differences were found for the other comparisons.

Figure 3

Post-hoc correlation analyses between the GLM activations at T1 and the clinical Simple Shoulder Test scores at T2. Higher activation in in the right-frontal pole and right occipital cortex correlates with SST scores at follow-up. Results show brain areas surviving TFCE correction. P values < 0.05 were considered as significant. No significant correlations were found for the other test scores.