A hand-held device that fires a magnetic pulse to the back of the head may offer new hope to migraine sufferers, research suggests.

In tests, the machine, a single-pulse transcranial magnetic stimulation (sTMS), delivered pain relief for up to 48 hours with no noticeable side effects.

It was used on patients with "aura" – neurological effects that precede the headache, such as lights or lines in front of the eyes, visual "blank spots", and tingling or numbness. It affects about 20 per cent to 30 per cent of patients.

A group of 201 patients were randomly assigned either to receive treatment or a "sham" machine that produced no magnetic pulse.

They applyied two pulses 30 seconds apart as soon as possible after the onset of aura symptoms.

Of the 164 patients who treated at least one attack, 39 per cent from the sTMS group were pain free after two hours compared with 22 per cent of the "sham" group. Patients rated the device an average eight out of 10 for "user friendliness".

TMS works by changing the pattern of firing of neurons in the brain. Since its discovery in 1985, it has been used for anatomic brain mapping and diagnostic and therapeutic purposes.

Findings from the new study, led by Dr Richard Lipton, from the Albert Einstein College of Medicine in New York, are reported in the journal the Lancet Neurology.

The researchers wrote it could be "a promising acute treatment".

Migraine is often treated with drugs called triptans, but these are not effective or approved during the aura phase of an attack.