Neuropathic Pain Reduced by Specific Electrical Stimulation

The ventral posterolateral nucleus (VPL) used to enhance the analgesic effect of deep brain stimulation (DBS) is an effective target for pain modulation, according to research published in the Journal of Korean Neurosurgical Society.

Investigators from various research centers in Korea used 15 male mice models divided into 3 groups in order to observe the effect from VPL stimulation. The 3 groups were normal group, neuropathic pain group, and neuropathic pain plus DBS group. The mice in the third group were subjected to 15 days of electrical stimulation and the target was VPL, the researchers noted.

The researchers also tested behaviors in the mice as a pain measurement. The results were recorded at 1 hour before stimulation to initiate a baseline measurement, 1 hour after start of stimulation, and 1 hour after stimulation had concluded.

After the 15 days of stimulation, pain scores dropped from 9.8-10 with a pain response time of 10-17 seconds at baseline, to a score of 4.8-6.8 and 1.4-6.8 seconds during DBS. At the 1 hour post stimulation measurements, pain scores had increased again to 9.4-10 with duration of 7.7-21.8 seconds, which the researchers called essentially a reversion to the baseline values.

The researchers additionally compared the DBS group to the other groups at each point of the stimulation measurements to verify if stimulation directly decreased pain. They were able to confirm that this was the case in the animal models.

“VPL DBS effectively decreased pain score, and it gradually reversed when electrical stimulation was ceased,” the authors wrote. “In electrical stimulation, pain score got started dropping after the electrical stimulation started, and reached a maximum level within 30 minutes.”

The researchers noted that in prior studies have not used the same method on the animal models as this study did. Other studies have used pinprick tests as measurements for hyperalgesia, not allodynia, which is what these researchers used.

“[VPL DBS] reduces not only the pain response score but also duration of showing painful response in neuropathic pain,” the authors concluded. “Moreover, the method for measuring the duration of feeling pain would be beneficial to experimenters in animal studies.”