A Surgery That Helps People Smile

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Study provides new insight into how radiation relieves chronic facial pain.
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Approximately 1,500 new cases of trigeminal neuralgia, a nerve disorder that causes severe facial pain, are diagnosed annually in Canada. The disorder occurs more frequently in women than men.
Trigeminal neuralgia (TN) is widely believed to be one of the most painful conditions that can affect a person. It is a nerve disorder in which mild facial stimulation—such as that caused by smiling or applying makeup—can trigger a jolt of severe pain on one side of the face.
 
Gamma knife radiosurgery can provide long-lasting pain relief to people suffering from TN. It involves the delivery of gamma radiation to the dysfunctional facial nerve causing the disorder. How gamma radiation affects the nerve and reduces chronic facial pain is not well understood.
 
To improve our understanding of this powerful treatment, Dr. Mojgan Hodaie, a Scientist at the Krembil Research Institute, led a study examining the irradiated nerve using diffusion tensor imaging (DTI). DTI is a commonly used medical imaging technique that provides information about the structure of cells in the body. 
 
As part of the study, Dr. Hodaie and her research team studied the DTI images and medical records of 55 TN patients who underwent gamma knife radiosurgery. DTI images of the irradiated nerve up to 24 months after surgery were examined. 
 
“In patients who experienced the highest levels of pain relief, we found evidence that radiation alters the physical structure of the cells comprising the nerve. Intriguingly, these alterations were delayed and only began appearing 12 and 24 months after treatment. In contrast, radiation did not affect the nerve structure in patients who experienced lower levels of pain relief,” explains Dr. Hodaie.
 
Based on their findings, the researchers postulate that radiation could be reducing pain by disrupting the nerve’s structure and its ability to transmit pain signals from the face to the brain.
 
“DTI appears to be an important marker for treatment response to radiation that should be incorporated into routine post-treatment care for classic trigeminal neuralgia,” says Dr. Hodaie. 
 
This work was supported by the Canadian Institutes of Health Research and the Toronto General & Western Hospital Foundation.
 
Shih-Ping Hung P, Tohyama S, Zhang JY, Hodaie M. Temporal disconnection between pain relief and trigeminal nerve microstructural changes after Gamma Knife radiosurgery for trigeminal neuralgia. J Neurosurg. 2019 Jul 12. doi: 10.3171/2019.4.JNS19380.

Dr. Mojgan Hodaie, Senior Scientist, Krembil Research Institute.