Neurology patients in Dumfries and Galloway are facing potential delays in assessment and treatment.
It follows the resignation of the region's only consultant neurologist.
NHS Dumfries and Galloway said the chances of recruiting a replacement were low and it is urgently looking at alternative ways to maintain provision.
The service has 200 people currently waiting for out-patient appointments, with 30 already over the 12-week waiting-time guarantee.
The health board's chief operating officer, Jeff Ace, said it was critical to find a long-term solution which could provide specialist services while keeping "as much of the service as possible very local".
He added: "Clearly patients involved in the service will not wish to wait long periods of time.
"We will do everything we can to make sure that we minimise those waits and offer appropriate pathways to patients.
"It is a particularly tricky one for us to resolve quickly."