Tense, nervous headache? Where most might reach for an aspirin or paracetamol, US researchers suggest the deadly botulism toxin - the ingredient of Botox jabs - could be the answer.

Small amounts have been shown to be effective at preventing debilitating headaches, say researchers Wake Forest University Baptist Medical Center.

Injections of the botulinum toxin worked for 92% of patients whose headaches had not responded to traditional medications.

Over 130 patients who experienced migraine headaches, tension headaches or chronic headaches on more than at least 15 days per month.

It's appalling to use it clinically until the evidence is in

Professor Peter Goadsby, Institute of Neurology

Most had already tried at least three headache drugs without success.

Patients had from one to four Botox treatments at three-month intervals.

After each treatment, they were asked to rate the results on a scale of one to five, ranging from no improvement, through mild improvement to a moderate, good or excellent effect.

Improvements

Overall, 84% of patients reported improvements.

Of those who had four treatments, 92% reported improvement with an average score of 4.3.

Botox, known for its use in cosmetic surgery, partially paralyzes muscles for about three months.

For headache treatment, it is injected into muscles around the eyes and forehead and sometimes the jaw.

If a patient's headaches involve the entire head, additional injections are given in the upper back of the neck and shoulders.

Migraine headaches affect about 10% of people in the UK.

'Appalling'

Researchers announced their findings at a press conference prior to the annual meeting of the American Headache Society in Seattle.

Todd Troost, professor of neurology at Wake Forest, who led the study said Botox could be less expensive and have fewer side effects than many medications used for headache prevention.

"Botox� is becoming one of the main preventive therapies for headache."

Professor Troost, who has treated more than 350 patients with Botox, added: "When it is effective, the need for daily medications or acute medicines for severe attacks is significantly reduced or eliminated.

"There were significant improvements that appear to be progressive and may also be cumulative."

He said many patients with chronic headaches often conventional medicines often did not work, so many overused the drugs.

Professor Troost said these patients should be considered for preventive therapy.

Professor Peter Goadsby, of the Institute of Neurology at University College London had concerns about the use of botox.

He told a national newspaper: "There are insufficient trials published on this yet. It's appalling to use it clinically until the evidence is in."