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brain activity of healthy controls as well as patients these oscillations change during DRGS-mediated pain
with episodic migraine (EM) and chronic migraine (CM). relief.
The source-based oscillatory dynamics of the pain-re-
lated cortical regions, which comprises 10 node regions MATERIALS AND METHODS Thirteen chronic pain
(the bilateral primary [SI] and secondary somatosen- patients with implanted dorsal root ganglion stimula-
sory cortices, insula, medial frontal cortex, and anterior tors were included in the MEG analysis. MEG Record-
cingulate cortex [ACC]), were calculated to determine ings were performed at rest while the stimulator was
the intrinsic connectivity and node strength at 1 to turned ON or OFF. Numerical rating scale (NRS) scores
40 Hz. The total node strength within the pain-related were also recorded before and after DRGS was turned
cortical regions was smaller in the beta band in patients OFF and ON. Power spectral and source localization
with migraine (70 EM and 80 CM) than in controls (n = analyses were then performed on preprocessed MEG
65). In the beta band, the node strength and functional recordings.
connectivity values of patients with CM and patients
with EM differed from those of controls in specific corti- RESULTS With DRGS-OFF, patients in severe pain had
cal areas, notably the left SI (EM < control) and bilateral significantly increased cortical theta (4-7 Hz) power and
ACC (CM < control); moreover, the node strength was decreased cortical alpha (7-13 Hz) power compared to
lower in patients with CM than in those with EM. In patients reporting less pain. This shift in power toward
all patients with migraine, negative correlations were lower frequencies was contrasted by a shift toward the
observed between headache frequency and node higher frequency power spectrum (low beta 13-20 Hz
strength in the bilateral ACC. In conclusion, migraine is activity) during DRGS-mediated pain relief. A significant
characterized by reduced beta oscillatory connectivity correlation was found between the increase in low beta
within the pain-related cortical regions. Reduced beta activity and the degree of reported pain relief.
connectivity in the ACC is linked to migraine chronifica-
tion. Longitudinal studies should verify whether this CONCLUSION Our results demonstrate increased
oscillation change is a brain signature and a potential low-frequency power spectral activity in chronic pain
neuromodulation target for migraine. patients in the absence of stimulation which shifts
toward higher frequency power spectrum activity in
Pain (2021), Vol. 162, No. 10 (34534180) (6 citations) response to therapeutic DRGS. These cortical changes
in response to DRGS provide support for the use of
neuroimaging in the search for potential biomarkers of
Supraspinal Effects of Dorsal Root Ganglion pain.
Stimulation in Chronic Pain Patients (2021)
Keywords: Case series, DRG stimulation, MEG, chronic
Parker, Tariq; Huang, Yongzhi; Raghu, Ashley L B; pain, complex regional pain syndrome, failed back surgery
FitzGerald, James; Aziz, Tipu Z; Green, Alexander L syndrome, neuropathic pain, neurostimulation, peripheral
nerve stimulation, postherpetic neuralgia
Nuffield Department of Surgical Sciences, University of
Oxford, Oxford, UK; Academy of Medical Engineering and Neuromodulation: journal of the International
Translational Medicine, Tianjin University, Tianjin, China Neuromodulation Society (2021), Vol. 24, No. 4 (33974317)
(2 citations)
OBJECTIVES Dorsal root ganglion stimulation (DRGS)
has become a popular neuromodulatory treatment for
neuropathic pain. We used magnetoencephalography
(MEG) to investigate potential biomarkers of pain and
pain relief, based on the differences in power spectral
density (PSD) during varying degrees of pain and how

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