A Court of Appeal hearing over whether doctors have the right to withdraw life-prolonging treatment is under way.
Leslie Burke won the original case
Leslie Burke, who has a degenerative brain condition, won a landmark ruling last year to stop doctors withdrawing food and drink when he cannot speak.
The 45-year-old feared General Medical Council rules on artificial nutrition may allow his wishes to be over-ruled.
In the original case, the judge said the rules should be redrafted, but the GMC said it wants clearer guidance.
Mr Burke, from Lancaster, has cerebellar ataxia - an umbrella term for nervous system disorders that cause lack of co-ordination, and can lead to difficulty walking and confine sufferers to a wheelchair.
It can cause slurred speech and problems with swallowing, and lead to loss of sight and hearing - but mental faculties are not affected.
Speaking before the hearing started on Monday, he said he was concerned the GMC guidance would mean doctors would stop feeding him once he was unable to communicate.
He said it could take him days to die if that happened, during which time he would be completely aware of what was happening.
"That is not a dignified way to go."
Mr Burke took his case to court because he believed the GMC rules were incompatible with the European Convention on Human Rights, which enshrines the right to life.
The original ruling said doctors could not withdraw artificial nutrition when a patient is unable to communicate and had earlier instructed them not to even if the doctors believe it is in their best interests
The GMC has appealed the verdict as artificial nutrition is classed as a treatment and it raises questions about medical intervention
The GMC also wants clearer guidance on what doctors should do if a patient has not left instructions
The GMC guidance covered situations where death is not imminent, but doctors believe a patient's condition is so severe, and their prognosis so poor, that artificial nutrition or hydration - giving water - causes more suffering than benefit.
It said that if patients are no longer able to communicate their views, doctors must judge what the patient would want, taking earlier instructions into account.
But it effectively gave doctors the final say on what should happen.
Mr Justice Munby ruled last July that Mr Burke had the right to have artificial nutrition continued even when it comes to the point where he cannot communicate as that is his wish.
Since the original ruling, the GMC has told doctors to adhere to the judge's verdict.
But it is appealing the decision as officials believe it is unclear how the judgement applies to other forms of treatment - artificial nutrition is classified as treatment under the council's guidance - that may be keeping a patient alive, such as antibiotics, or respiratory intervention.
They also want to clarify on what basis a doctor can withdraw treatment if a patient has not given any instruction.
Ruth Evans, chairman of the GMC's standards and ethics committee, said: "Some patients will want everything possible to be done, while others will want to avoid too much medical intervention, when they are nearing the end of life."
And Professor Irene Higginson, who specialises in palliative care and gave evidence on behalf of the GMC in the original hearing, said there were cases where giving food and water artificially could do more harm than good.
But Roger Goss, co-director of Patient Concern, which is also represented at the hearing, said it was wrong to class artificial nutrition as treatment.
"Feeding someone through a tube because they cannot swallow is not treatment, and should not be treated as such. Doctors should not have the right to take this away against a patient's wishes."