A row over funding for Alzheimer's drugs on the NHS is to go to the Court of Appeal.
The drugs cost about £2.50 a day
The manufacturer of one drug - Aricept - has been fighting a decision to restrict access to patients in the later stages of the disease.
The National Institute for Health and Clinical Excellence concluded the drugs are not cost effective for patients in the early stages of Alzheimer's.
The decision was upheld by the High Court earlier this year.
Drugs company Eisai brought the case to the High Court with support from fellow drugs firms Pfizer and Shire and the Alzheimer's Society.
The legal debate is about whether NICE followed a fair and transparent process in reaching it's decision.
The court upheld NICE's decision that the drugs are only cost-effective in later-stage disease.
However, NICE was told to rewrite guidance on how the disease is assessed to take into account people with learning difficulties or those who speak English as a second language.
It was the first time a judicial review had been sought on NICE guidance.
NICE guidance in 2001 recommended the drugs - which can make it easier to carry out everyday tasks - should be used as standard.
But guidance published in November 2006, after months of appeals, stated that the drugs should only be prescribed to people with moderate-stage disease.
NICE said the drugs, which cost about £2.50 a day, did not make enough of a difference to recommend them for all patients and were not good value for money.
Dr Paul Hooper, executive vice president of Eisai Europe, said: "We are delighted that the court has granted us permission to appeal the decision of the High Court which supported NICE's lack of transparency over the way that cost effectiveness has been calculated.
"It is disgraceful that NICE can restrict medicines used to treat a most vulnerable group of patients based upon secret calculations."
A spokesperson for the Alzheimer's Society said: "We are pleased to hear the appeal against the NICE juducial review verdict has been given the go ahead.
"While the Alzheimer's Society is not pursuing its legal arguments further in court, we support any challenge that could mean people with Alzheimer's get fairer access to the only drug treatment for the disease."
NICE chief executive Andrew Dillon said: "We are disappointed.
"Going back to court will require us to divert energy and tax payer's money from the work we do."