Electroacupuncture of the Ophthalmic Branch of the Trigeminal Nerve: Effects on Prefrontal Cortex Blood Flow.

The current authors observed enhanced cerebral blood flow (CBF) in the prefrontal cortex (PFC) in response to 100-Hz electroacupuncture (EA) stimulation of the ophthalmic branch of the trigeminal nerve. However, it is not yet clear if responsiveness to 100-Hz EA depends on stimulus intensity. This study examined the effects of stimulus strength on PFC CBF during 100-Hz EA of the ophthalmic branch of the trigeminal nerve. Twelve subjects underwent 3 acupuncture sessions: I, control, no stimulation; II, 0.1 m EA; and III, 0.2 m EA). Needles were inserted 1 cm lateral of the head median line; the anterior insertion point was on the front hairline and the posterior insertion point was ∼7 cm behind the hairline. Stimulation frequency was set to 100-Hz. PFC CBF was measured in terms of oxygenated, deoxygenated, and total hemoglobin (OxyHb, DeoxyHb, TotalHb, respectively), using 16-channel (Ch) near-infrared spectroscopy. Stimulation of 0.2 m was associated with significant elevation of OxyHb levels in the 0.1 m condition in Chs 6, 10, and 12. Ch 2-6, 10, 12 signals were notably higher than in the control condition. Stimulation of 0.2 m and 0.1 m were associated with significant declines in DeoxyHb levels, compared to the control condition in Ch 4. Finally, 0.2 m stimulation in Chs 12 and 13 was associated with significant elevation of TotalHb levels in the control condition. Using 0.2-m stimulation, 100-Hz EA of the ophthalmic nerve enhances PFC CBF more strongly than 0.1-m stimulation.