Patients are offered a controversial operation that involves irreversible brain damage to alleviate symptoms.

Today’s announcement will make the funding of the service more secure.

Patients come from all over Scotland and elsewhere to have the expensive operation, which is funded by each patient’s own health authority.

Under the new arrangement, with Dundee formally identified as the national service provider, the neurosurgery unit at Ninewells will be allocated an annual budget.

The Scottish Executive said today that it made sense to commission on a Scotland-wide basis “low volume, high cost services of a very specialised nature”.

The operations are performed at Ninewells by consultant neurosurgeon Mr Sam Eljamel. He was in theatre today and unavailable for comment.

NMD is not a cure but can improve the quality of life for some patients with severe depression that has not responded to drug treatments and psychological therapies.

The operation is also offered to patients with the severe form of an anxiety disorder that leads to obsessive behaviour.

However, success is not guaranteed and the operation can pose serious risks to the patient, doctors can’t predict which patients will benefit and which will show little or no improvement.

In a recently published report on NMD in Dundee, Mr Eljamel and his co-author psychiatrist Professor Keith Matthews admitted there was an “imperfect evidence base” for NMD. The few studies carried out don’t explain exactly how or why the treatment works.

The service was established by the late Professor George Fenton and neurosurgeon Mr T. R. K. Varma. In the first 10 years of the service 28 patients from the UK and Ireland underwent NMD in Dundee.

Depression can be a lifelong illness and during NMD specific areas of the brain are destroyed in an attempt to alleviate the symptoms, but only after exhaustive attempts to find other treatment options.