BOTOX should be prescribed on the NHS to provide pain relief for chronic migraine sufferers in Scotland, a charity has said.

Patients in England and Wales have been offered the muscle-paralysing injections on the health service since 2012 following recommendations by the National Institute for Health and Clinical Excellence (NICE) that it could an effective treatment for some migraine sufferers.

However, equivalent body in Scotland - the Scottish Medicines Consortium - has twice rejected applications to offer Botox on the NHS in Scotland as a migraine therapy, in 2011 and again in 2013. It blamed "a number of weaknesses in the clinical and economic data" submitted by the manufacturer which meant it "did not offer value for money".

It was estimated that around 4,700 patients in Scotland would be eligible for treatment in the first year of Botox being made available, costing the Scottish medicines budget an extra £108,000 annually - rising to £308,000 by year five. The SMC concluded that this would have "significant service implications" for the NHS.

However, charity Migraine Trust has urged the SMC to reconsider as it prepares to weigh up a third bid by drug company Allergan Ltd to make Botox - officially known as botulinum toxin type A - available to Scottish migraine patients.

Today is the deadline for patient interest groups to lobby the SMC in support of the new therapy. The watchdog will publish its decision on February 13 next year

Arlene Wilkie, the Scottish-born chief executive of the Migraine Trust, said she fears a bleak outlook for large numbers of chronic migraine sufferers north of the border if the SMC upholds its funding ban advice on Botox treatment.

Ms Wilkie said: “People living with this extremely debilitating and highly disabling chronic condition in Scotland deserve access to the best available treatment, in line with the rest of Britain."

A spokeswoman for the SMC said: “We are pleased to have received a resubmission for onabotulinumtoxin A (Botox) for the prophylaxis of headaches in adults with chronic migraine.

"The submission is currently being assessed and will be considered by our committee early in 2017.”

Tens of thousands of people in Scotland experience the chronic migraines, defined as having at least 15 headaches per month lasting four or more hours - at least eight of which are migraine attacks.

Migraines are thought to be caused by changes in the chemicals of the brain, in particular serotonin. As well as an intense throbbing pain, symptoms can include visual distortions such as zigzag or flashing patterns, nausea, vomiting or increased sensitivity to bright light, noise or smell.

In England and Wales, Botox can be prescribed to chronic migraine sufferers who have not responded to at least three prior preventative drug treatments.

Eligible patients receive intramuscular injection to between 31 and 39 sites around the head and back of the neck. A new course of treatment can be administered every 12 weeks.

While Botox has been popularised as the treatment-of-choice for celebrities seeking to stave off the ageing process by "freezing" wrinkles, two large clinical trials demonstrated that Botox injections cut the number of headache days per month among migraine sufferers by an average of eight after six months.

It is unclear why the treatment seems to work, but it has been suggested that Botox may reduce blood pressure within the brain by relaxing muscles around the head or that it could reduce the nerves’ ability to send pain signals during a migraine.

Research conducted by The Migraine Trust found that fewer than one in five (19 per cent) of chronic migraine sufferers in Scotland are satisfied with their current treatment.

Three in four sufferers (75 per cent) have already tried at least five medications.