• Zhiyang Song, Björn A Meyerson, and Bengt Linderoth.
• Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
• Neuromodulation. 2015 Dec 1; 18 (8): 714-20.

ObjectivesConflicting data regarding the efficacy of high-frequency spinal cord stimulation (HF SCS) has prompted the issue of the possible importance of the shape of the stimulating pulses. The aim of this pilot study was to compare HF SCS applied with monophasic and biphasic pulses of two different durations with conventional SCS in a rat model of neuropathic pain.Materials And MethodsRats were operated with lesions of sciatic nerve branches according to the spared nerve injury procedure (SNI). Animals, which developed pathological tactile hypersensitivity after surgery, were implanted with four-polar miniature SCS leads. SCS was applied during 60 min with either conventional current parameters (monophasic pulse width [PW]: 200 μsec; 50 Hz and amplitude 80% of the motor threshold [MT]), or with high-frequency SCS (1 kHz) with monophasic or biphasic pulses, the latter with pulse widths of either 24 (12 + 12) or 48 (24 + 24) μsec. The outcomes were examined regarding change of tactile hypersensitivity during the one-hour SCS period and with two tests of thermal sensitivity.ResultsConventional monophasic SCS, as well as HF SCS applied with monophasic PW = 24 μsec or with biphasic PW = 48 (24 + 24) μsec, had similar suppressive effects on tactile hypersensitivity. Solely, HF SCS applied with biphasic pulses with a total PW of 24 (12 + 12) μsec demonstrated no effect. Thermal hypersensitivity was unaffected by HF SCS with all pulse varieties.ConclusionsThere is no significant difference in efficacy between HF SCS applied with low amplitude ("subparesthetic") monophasic and biphasic pulses. However, short PWs providing only 12 μsec of cathodal stimulation was ineffective, presumably because of insufficient electric charge transfer from the lead contacts to the nervous tissue.© 2015 International Neuromodulation Society.

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