Thousands of migraine sufferers could benefit from free Botox injections to combat the debilitating headaches if an official review gets the go ahead.
The potent anti-wrinkle jab was licensed to treat chronic migraines in July 2010 by the Medicines and Healthcare Products Regulatory Agency, with desperate patients paying between £400 and £600 to have it administered privately.
However, it is yet to be approved medically by leading health body, the National Institute for Healthcare and Clinical Excellence (NICE).
A review is taking place in June this year where NICE will decide whether the injection should be offered across the NHS in the UK and Wales.
Despite NICE stating that there is "insufficient evidence" that Botox benefits migraine pain, they are reaching out to the Allergan, the manufacturer, to provide more scientific evidence.
This will then be reviewed before a decision is made on whether the drug should be given the green light for widespread use on the NHS.
If approved, patients will only be eligible if their migraines have not improved after trying at least three preventive medications. Chronic headaches are defined as having at least 15 days a month over three months, of which 8 of these days are with a migraine.
Botox (or onabotulinum toxin A) was first prescribed in 1817 and works by paralysing the muscles. In migraines, Botox is believed to block overactive nerve impulses that trigger excessive muscle contractions, although these claims are currently under investigation.
Previous clinical trials published in the journal Headache, found that 70% of patients experienced 50% less headaches after having a fixed dose injection every 12 weeks for a year.
Although the treatment was well received, common side effects included neck pain, muscular weakness and drooping of the eyelid.
Professor Carole Longson, director of the health technology evaluation centre at NICE said in a statement: "Our independent committee is asking Allergan to provide further information and analysis as part of this public consultation, so that it has sufficient evidence to develop sound advice for the NHS regarding the use of Botox for the prevention of headaches in adults with chronic migraine.
"Without this additional evidence, potentially we will be unable to advise the NHS that this drug is good value for money for these adults because there are currently too many uncertainties. Until we publish our final guidance, NHS bodies should continue to make decisions locally on the funding of specific treatments."
Joanna Hamilton-Colclough, director of Migraine Action, says the comments made by NICE are “disappointing”.
Talking to The Huffington Post, Hamilton-Colclough said: "Since the licence was granted few patients who may benefit have been able to access the treatment via the NHS due to the lack of a NICE assessment of its clinical and cost effectiveness. Few will currently fund the treatment and those that do often do so only on a named patient basis after appeal.
"There is likely to be very little NHS availability of Botox unless a favourable decision from NICE is reached, and therefore the results of this interim report are disappointing.
"We regularly hear from patients on our helpline for whom traditional treatments have not worked and chronic migraine is having a severe impact on their personal and professional life.
"Their distress is compounded if their healthcare team believes that Botox could be the answer yet they are unable to access the treatment. Whilst a few are able to fund the treatment privately, for most this means continued suffering."
Dr Andrew Dowson, chairman of the Migraine Action’s medical advisory board agrees. He told The Huffington Post: "Whilst, like all migraine treatments, Botox isn't suitable or will work for everyone, I have seen the sometimes dramatic impact it can have on reducing the frequency and severity of migraines for some people.
"Whilst Botox is not a cheap solution I believe it would save the NHS and the wider economy money in the long run by reducing the need for repeat consultations and by improving the productivity of those with the condition.
"This NICE report is only an interim finding and it is hoped that after continued clarification, consultation and input from the manufacturers and other organisations that the final outcome will be more positive."
A migraine is a complex condition with a wide variety of symptoms other than a painful headache, like disturbed vision, sensitivity to light, sounds and smells and vomiting. Symptoms vary from person to person and attacks can last between four to 72 hours.
In 1998, the International Headache Society produced a classification system for migraines outlining the different types of headaches, with the most common being migraine with aura.
These have neurological symptoms like visual disturbances, which include blind posts, flashing lights and sometimes, temporary blindness.
Due to its complex nature, there isn't a single trigger or treatment for migraines. Common triggers include stress, lack of food, hormonal changes and lack of sleep and treatment includes anti-inflammatory medication, antihistamine or beta-blockers, as well as plenty of water, rest and sitting in a dark room (to alleviate visual disturbances).
According to the World Health Organisation (WHO), severe migraine attacks are classified as being just as disabling as dementia, quadriplegia (spinal cord injury) and psychosis. A study by the Migraine Trust found a third of Brits face discrimination at work because of their migraine attacks with 25 million days being lost from work worldwide due to migraines.
Migraines remain undiagnosed and under-treated in at least 50% of sufferers.