Edith Pyett, herself a former care assistant, suffered the worst dehydration a doctor had ever seen after a week in Eastbourne's Belmont Care Centre, an inquest has been told.
The home's deputy manager, Annette Ducille- Horton, admitted failing to enter Mrs Pyett's Alzheimer's disease - which left her incontinent and unable to feed herself - in her care plan because she could not spell it.
She said: "I had not come across it before. I thought it was Old Timers' disease."
Mrs Pyett's husband, James, 77, a retired hospital porter, told the jury at the inquest in Eastbourne how he had been shocked to see her condition after just seven days in care.
He took his wife out of the home in Pevensey Bay Road and she was later admitted to hospital where she died from renal failure on 7 March 2002.
Mr Pyett, of Castle View Gardens, Westham, near Pevensey, who had cared for his wife 24 hours a day since she developed her illness in 1995, said: "I hardly recognised her. She was unkempt and her hair was all over the place. It was permed the week before she went in.
"Her head and eyes were rolling all over the place. I thought she was very ill. Her eyes were sunken. She seemed dehydrated."
He added: "I told the staff I was appalled. I had to get her home. My main priority was to get her somewhere safe, somewhere comfortable."
Post-mortem tests showed Mrs Pyett's kidneys had failed due to severe dehydration.
Pathologist Dr Jane Mercer, who carried out the tests, said levels of dehydration she found in Mrs Pyett were the worst she had seen.
She said: "It was extremely severe. I have not seen worse results."
The hearing continues.