A Stirling man with motor neurone disease (MND) spent 12 hours lying on the floor after a fall while his carer brother was in self-isolation with suspected coronavirus.
Dean Barrett could not visit his brother Richard for two weeks after developing symptoms of the virus.
He said he was denied crisis care for his brother by social services.
The local social care partnership said it offered respite care to Richard, 50, but he turned it down.
He told them he wanted to remain in his own home.
Richard Barrett, a former self-employed painter and decorator, was diagnosed with MND last year.
His brother said he has a rapidly-progressing form of the disease and his condition has "deteriorated very quickly",
But an assessment in January deemed his condition not severe enough to qualify for home care, Dean added.
Now Dean cares for his brother by tidying and cleaning the house, helping with his shopping and looking out for his "general wellbeing".
But for the last two weeks he has been self-isolating with Covid-19 symptoms and was unable to visit his brother.
He said he asked social services if they could check in on him in the morning and evening.
"She came back and said there is no crisis care whatsoever in place, and they're struggling to get any care for him at the moment," he said.
"My frustration at the whole thing is Richard is probably up there with the main groups at risk with the coronavirus and there is no crisis care in place for this."
Mr Barrett said that his brother, who now has difficulty walking, subsequently had a fall and spent the night on the floor.
He said: "We had to phone my mother-in-law, who's 66, and she had to drive round there, try and get in the house and lift him up.
"She's at that age where that's a struggle for her as well."
'Doing all it could'
Susan Webster from support charity MND Scotland said: "This current crisis is highlighting a situation that's already very, very difficult and this virus is making the situation so much worse.
"People like Richard, who really desperately need care are struggling to get it and that just shouldn't be happening."
Clackmannanshire and Stirling Health and Social Care Partnership said it was committed to "doing all it could" to help the most vulnerable in society throughout the Covid-19 outbreak.
A spokesman for the partnership said: "Mr Richard Barrett was offered respite care, which he declined due to his desire to remain independent, and we remain in contact with him to ensure he has the required essentials.
"Stirling Carers are also contacting all registered carers in Stirling to provide support in creating an emergency care plan in case carers are unable to carry out their caring role."