Excessive sensitivity apparently plays a role in cluster headaches, and blocking the hypersensitive muscle trigger points with local anesthetic may be beneficial in treating the condition, according to results published in the journal Head & Face Medicine.

Cluster headaches cause sudden, severe pain, often centered in one eye. Though the headaches tend to be short, they run in cycles, which may cause several headaches in one day or every few days. Most people with cluster headaches experience pain-free periods of several weeks or more between each headache cycle. About 10 percent of sufferers, however, experience chronic cycles, which can last a year or more.

Dr. Elena P. Calandre and colleagues from the University of Granada, Spain, conducted a study of 12 patients with cluster headache to see if trigger points could be identified, and if so, whether anesthetic injections at the trigger points were helpful.

Four of the subjects experienced episodic cluster headache and eight experienced chronic cluster headache. All were totally refractory to their current prescribed drug therapy.

At least one trigger point was found in every patient. In five of six patients, the researchers were able to stop a cluster headache attack in progress with an anesthetic injection. In six of seven patients, the injections were successful in preventing attacks.

When anesthetic injections were combined with preventative drug therapy, significant improvement was observed in seven of eight chronic headache patients.

In terms of adverse effects, one patient reported pain at the injection site. Rebound headache following injection was observed in four patients.

"As it is estimated that between 10 and 20 percent of cluster patients are refractory to treatment or develop resistance to it, the potential role of...trigger point blockade should not be underestimated," Calandre and colleagues write.

"Trigger point injection is an easy to perform and well-tolerated therapy, its main drawback being that it is rarely wholly effective" when given alone, they note. "The combination of active trigger point (blockade) with prophylactic drug treatment in the treatment of refractory cluster headache remains a therapeutic option worthy to be investigated."