A group of 25 leading doctors claim a funding dispute is preventing some Parkinson's patients from receiving adequate treatment in Scotland.
Since 2013, people living with severe neurological conditions in the east of Scotland have had to travel to England for potentially life-changing surgery.
The medics have raised concerns about a delay in establishing a national centre for deep brain stimulation (DBS).
Health Secretary Shona Robison has pledged to resolve the issue.
She said the Scottish government was working with health boards to ensure funding is in place for the new DBS centre.
'Fair and equal access'
After a long campaign by clinicians and charities, NHS Scotland made a national DBS centre the top priority for specialist service provision last October.
However, in an open letter to the minister, the clinicians said they were "disappointed" that plans for the centre in Glasgow had been delayed while "NHS boards argue with Scottish government over funding".
They added: "We believe that Scotland has waited far too long for a single national centre of excellence that will enable all our patients to have fair and equal access to a high quality, safe, planned DBS service within Scotland."
What is deep brain stimulation?
- DBS involves inserting electrodes in the brain to reduce physical shaking.
- It is often the last option for people who have very serious symptoms which cannot be controlled through medication alone.
- The surgery is offered to people with Parkinson's, "essential tremor" and dystonia, which is a rarer neurological disorder affecting movement.
People who live in the west of Scotland can undergo the brain surgery in Glasgow but those in the north and east must travel to England for assessment, surgery and post-operative care.
The current situation is "highly unsatisfactory and inequitable", the doctors said.
The letter continued: "We have major concerns about accessibility, patient wellbeing, clinical care and sustainability.
"Travelling long distances to centres in England for pre-operative assessment, the surgical procedure itself and multiple follow-up appointments are particularly daunting for this group of patients with complex healthcare needs."
Speaking to BBC Radio Scotland's Good Morning Scotland programme, Ms Robison said: "It's not right that patients travel to England and we will resolve this as set out in a letter to these doctors, reassuring them of that."
In a statement, a spokesman for the Scottish government said it recognised the situation for DBS patients in the north and east was "not ideal", given the long distances they have to travel.
He added: "The National Specialist Services Committee has approved the proposal to establish a national DBS service in Scotland and we are working very closely with NHS boards to ensure the funding is in place, as soon as possible, for a sustainable service going forward."