Alterations in brain functional connectivity associated with pain relief following intradiscal injection of condoliase: A prospective observational study

Background

Lumbar disk herniation, a common cause of low back and lower limb pain (hereafter referred to as low back pain [LBP]), is associated with the degeneration of the nucleus pulposus, leading to nerve root compression. Chemonucleolysis using condoliase is a minimally invasive treatment for lumbar disk herniation. Although most pain treatments focus on peripheral and spinal reorganization, little is known about changes in brain activity before and after treatment. This study investigated the neural basis of treatment efficacy by comparing brain activity before and after intradiscal condoliase injection from the perspective of functional brain networks.

Methods

Twenty-one patients with LBP who received intradiscal condoliase injections were included. Clinical evaluations and resting-state brain activity measurements were conducted 3 months after treatment. Brain activity before and after treatment was compared in patients whose pain intensity was reduced by over 50 %.

Results

Of the 21 patients, 18 showed reduced pain. In these 18 patients, functional connectivity between the anterior insula–seeded salience network (SN) and regions including the brainstem and cerebellar vermis significantly decreased post-treatment. Conversely, functional connectivity between the rostral prefrontal cortex–seeded SN and regions, including the precentral and postcentral gyri, significantly increased. Connectivity between the supramarginal gyrus–seeded SN and the temporal occipital fusiform cortex and the inferior temporal gyrus (temporooccipital region) also significantly increased.

Conclusions

Intradiscal condoliase altered the functional connectivity between the SN and other brain regions. These findings suggest that functional reorganization of SN-related networks may be involved in the therapeutic effects of pain relief.

Significance statement

Our findings demonstrate that pain relief following condoliase injection is accompanied by functional reorganization within salience network–related brain connectivity, thereby providing new insights into the central mechanisms underlying therapeutic effects in low back pain.