Neural Control of Cerebral Blood Flow: Scientific Basis of Scalp Acupuncture in Treating Brain Diseases

Scalp acupuncture emerged in the 1970s as a modern acupuncture therapy widely used in the treatment of brain diseases, especially acute ischemic stroke. Despite decades of successful clinical experience, the proposed mechanisms to explain its efficacy still lack significant scientific validation, limiting its integration into conventional medicine. This study presents a new perspective on the mechanisms of scalp acupuncture based on its effects on cerebral blood flow (CBF). Abundant evidence demonstrates that CBF significantly increases when specific scalp acupuncture points, areas, or nerves innervating the scalp are stimulated, correlating with immediate or long-term improvements in symptoms of brain diseases.

The neural pathways that improve CBF through stimulation of the trigeminal, facial, and cervical nerves have been gradually elucidated. The presence of scalp acupuncture points or core areas frequently used for brain diseases can be rationally explained by the characteristics of nerve distribution, including nerve overlap or convergence in certain parts of the scalp. These characteristics also suggest that the role of these scalp acupuncture points or areas is relatively specific, not due to a direct correspondence between the current hypothetical scalp acupuncture points and areas and the functional zones of the cerebral cortex. Scalp acupuncture demonstrates notable instantaneous effects, with up to 60.71% of patients with intracerebral hemorrhage showing immediate improvement, while no similar effect was observed in the medication and surgical hematoma aspiration groups.

Many brain diseases are associated with reduced CBF, including Huntington disease, Alzheimer disease, Parkinson disease, and post-stroke sequelae. Stimulation of the trigeminal nerve, which innervates most cerebral arteries, has at least three effects on cerebral vasculature, all leading to increased CBF: antidromic pathway, trigeminal parasympathetic pathway, and central pathway. The facial nerve, through its parasympathetic fibers, rapidly dilates cerebral arteries via the sphenopalatine ganglion. The cervical nerves affect CBF through connections with the trigeminal and facial nerves, or through the superior cervical ganglion.

The relative specificity of scalp acupuncture in regulating CBF manifests in several ways: scalp stimulation shows significant improvement in CBF compared to stimulation of other body parts; there is regional specificity, with different scalp areas affecting different cerebral vascular territories; unilateral stimulation may have bilateral effects; and the degree of improvement relates to stimulation parameters. Clinical implications include clarification of indications (all patients with brain diseases and reduced CBF would be candidates), point selection based on solid scientific foundations (locations innervated by overlapping nerves), and the use of CBF changes as a rapid objective marker to evaluate therapeutic effects.