Massaging over the greater occipital nerve reduces the intensity of migraine attacks: evidence for inhibitory trigemino-cervical convergence mechanisms

Activation of the trigemino-cervical system constitutes one of the first steps in the genesis of migraine. The objective of this study was to confirm the presence of trigemino-cervical convergence mechanisms and to establish whether such mechanisms may also be of inhibitory origin. We describe a case of a 39-years-old woman suffering from episodic migraine who showed a significant improvement in her frontal headache during migraine attacks if the greater occipital nerve territory was massaged after the appearance of static mechanical allodynia (cortical sensitization). We review trigemino-cervical convergence and diffuse nociceptive inhibitory control (DNIC) mechanisms and suggest that the convergence mechanisms are not only excitatory but also inhibitory.

Ativação do sistema trigemino-cervical constitui um dos primeiros passos na gênese da crise de migrânea. O objetivo do estudo foi descrever um caso clínico que sugere a existência de mecanismos de convergência trigemino-cervical (CTC) e que esses possam ser do tipo inibitórios. Nós descrevemos o caso de mulher de 39 anos com migrânea episódica que mostrou significante melhora em sua cefaléia frontal durante suas crises quando realizava massagem sobre o território do nervo occipital maior ipsilateral a dor. A melhora clínica só ocorria quando a paciente apresentava alodinia mecânica estática (sensibilização cortical). Neste estudo nós revisamos os conceitos de CTC e de mecanismos de controle inibitório nociceptivo difuso (MCIN), sugerindo que este último é um elemento comprobatório da presença de CTC do tipo inibitório durante as crises de migrânea.

Manual acupuncture and its peripheral mechanisms: involvement of nociceptors in muscle / 全日本鍼灸学会雑誌

Peripheral mechanisms that induce analgesic effects in manual acupuncture were studied in urethane-anesthetized rats. Unitary extracellular recordings were made from spinal wide dynamic range (WDR) neurons and repetitive electrical stimuli were delivered to the excitatory receptive fields to determine a noxious index. First, the analgesic effects of manual acupuncture and a noxious pinch to the skin (Diffuse Noxious Inhibitory Controls: DNIC) were compared. Second, manual acupuncture was applied to different structures at the acupuncture point, such as the skin, skin plus muscle, and muscle. In a third experiment, the analgesic effects of intramuscular injection of 4.5% NaCl and manual acupuncuture were compared. Manual acupuncture and a noxious pinch exhibited a very similar time course and magnitude of inhibitory effects on C-evoked discharges. As for differential stimulation of the acupuncture point, application of the needle to the skin only was less effective than to the skin plus muscle or the muscle only. Both intramuscular injection of 4.5% NaCl and manual acupuncture reduced C-evoked discharges while injection of isotonic saline produced almost no inhibitory effects. These data suggest that application of manual acupuncture might arouse noxious sensations that result in activating pain inhibitory processes. Moreover, it is thought that excitation of polymodal receptors in the muscle is a critical factor in inducing analgesic effects in manual acupuncture.