Concern is mounting among AMs and MPs about proposals to send patients from north Wales to Swansea or Cardiff for brain operations.
Edwina Hart has said she wants Welsh patients treated in Wales
It is understood Labour Wrexham MP Ian Lucas has written to Health Minister Edwina Hart expressing the worries of a group of north Wales MPs.
Other AMs and MPs have already raised issues about the effect on patients.
Ms Hart has said an expert group will look at how it would work, and that nobody would be disadvantaged.
Neurosurgery treats disorders of the nervous system, including diseases of the head, brain and spine.
In Wales, adult neurosurgery is performed in both Cardiff and Swansea.
But patients from north Wales currently travel the relatively short distance across the English border to The Walton Centre for Neurology and Neurosurgery in Liverpool for treatment.
In 2006, plans to create a single service in Cardiff were announced after a Health Commission Wales report.
A high-profile campaign against the proposal ensued until July when Ms Hart put the plans on hold, saying she wanted a fresh approach and would keep the unit in Swansea's Morriston Hospital open.
But Ms Hart said she wanted to make sure as many non-emergency operations as possible were done in Swansea and Cardiff, warning that Wales could lose part of its service unless best use was made of it.
'Very well served'
However, Labour Clwyd South AM Karen Sinclair has called the move unsustainable and unacceptable.
She said her constituents were currently "very very well served by Walton".
"The road network is excellent and it's imperative we make sure we get the best services in the right place for people in north Wales.
"It's a matter of representing the people of north Wales and reflecting the views of the people.
"This proposal has come to the table and people are very very worried about it," Ms Sinclair added.
Ann Lloyd, chief executive of NHS Wales, said officials were gathering information to review the service and to look at the "current flow of patients away from Wales".
"We need to see if it's possible to redirect them without any disadvantage to any patient.
"The whole aim of this is to provide as best a possible service to the people in Wales," Ms Lloyd added.
In addition, she said, a number of patients from south, mid and west Wales were also treated in England.
The panel, which includes representatives from across Wales, including from patient groups, will consider whether patients requiring planned care could be treated in the established centres in Wales.
Last month, Conservative Clwyd West AM Darren Millar, said the current arrangement for north Wales patients was satisfactory, and it was "totally unacceptable" to expect patients to make a 400-mile round trip.
Clwyd West Conservative MP David Jones has also questioned Ms Hart's grasp of geography when she told him that patients in north Wales would not be disadvantaged if the changes went ahead.
The panel looking at how the set-up would work is due to report in October.