Anesthetic delivered through the nostril to a nerve bundle sitting just behind the nasal cavity. No needle, no sedation, and you are upright the whole time.
What the sphenopalatine ganglion does
The sphenopalatine ganglion is a small collection of nerve cell bodies behind the nose, roughly level with the middle of the cheekbone. It is the relay point for much of the autonomic supply to the face — the tearing, the nasal congestion, the flushing and the drooping eyelid that accompany a cluster attack are that system firing. It also carries sensory fibres relevant to migraine and to facial pain.
Because it sits immediately behind the nasal mucosa, it can be reached topically. That anatomical accident is what makes this one of the least invasive nerve blocks in medicine.
How it is done
You lie back or recline. A thin soft catheter is passed along the floor of the nostril and local anesthetic is delivered against the mucosa over the ganglion. It is held in place for a few minutes, then the other side is done. Most people describe pressure and a bitter taste at the back of the throat rather than pain.
The whole thing takes about fifteen minutes. There is no injection into the face, no imaging, and no recovery period beyond sitting up slowly.
How well it works, honestly
The evidence for SPG blocks is real but more modest than for oxygen in cluster headache. Trials have generally shown a meaningful reduction in pain scores over the days following treatment rather than a reliable instant abort, and the effect size varies considerably between studies and between people. It is a reasonable option when a headache is not responding to first-line treatment, when you cannot tolerate the usual drugs, or when you want to avoid an injection — not a guaranteed switch.
Common after-effects are minor: a numb throat for an hour or so, a bitter taste, occasional brief nosebleed. It is avoided if you have an active nasal infection or a recent nasal fracture.