In 2009 Mr. Rainwater was diagnosed with progressive supranuclear palsy, a degenerative neurological disease.

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Rainwater is suffering from progressive supranuclear palsy, a brain disease referred to as PSP, Fortune reported in November, adding that he requires 24-hour care.

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In a study published last year in the journal Cortex, Dr. Rankin and her colleagues studied the ability to detect sarcasm in 102 patients who had been diagnosed with four progressive diseases that lead to memory loss: frontotemporal dementia, Alzheimer's disease, progressive supranuclear palsy and vascular-cognitive impairment.

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Dr Turner, 66, from Bath, had a progressive and incurable degenerative disease called supranuclear palsy.

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