The sphenopalatine ganglion (SPG) is associated with the trigeminal nerve, the major nerve involved in headache (HA) disorders (see Figure 1).1 The mechanism behind migraines is not fully understood, but it’s thought that blocking the SPG may help relieve migraine pain.1,2
The SPG is the main source of cranial and facial parasympathetic innervation. The autonomic nerves of the SPG supply the lacrimal glands, which produce tears, as well as the sinuses, which can produce the nasal discharge or congestion associated with some migraines.2-4
SPG’s Role in Headaches
When a headache occurs, meninges inflammation activates pain receptors. These receptors send pain impulses through the trigeminal nerve, which then sends a signal to the brain that is perceived as pain. In cluster and migraine HA, pain signals pass through the SPG, connecting with autonomic nerves, which produce eye tearing or nasal discharge. This is called the trigeminal autonomic reflex.3,4
During a migraine, parasympathetic outflow from the SPG causes vasodilation of cranial blood vessels. This dilation allows for inflammatory mediators to activate meningeal nociceptors, which are responsible for the migraine pain. It’s theorized that a patient who experiences parasympathetic symptoms during migraines (eg, nausea, emesis, sweating, lacrimation, etc.) may benefit from SPG blocking because the SPG propagates these parasympathetic signals.3,4
A prospective, randomized and double-blinded placebo-controlled study published in JAMA in 1996 showed potential benefit for using intranasal lidocaine when compared with saline alone.5 The study included a total of 81 patients with a chief complaint of headache who fulfilled criteria for International Headache Society. The primary outcome measure found at least a 50 percent reduction of headache within 15 minutes of treatment. Fifty-five percent of patients had at least a 50 percent reduction of headache compared with 21 percent of patients in the control group, and nausea and photophobia were significantly reduced. Rescue medication for headache relief was needed in 28 percent of patients in the lidocaine group versus 71 percent of patients in the control group. Of those patients who showed initial improvement, only 42 percent relapsed versus 83 percent in the control group.