© UnknownTheory: Russian historian Lev Lurie believes Lenin, could have been poisoned by his political rival and successor Joseph Stalin
Russian historian Lev Lurie, believes that while Lenin was already in poor health having suffered several strokes, Stalin may have finished him off after a bitter feud.
Lenin, who had initially supported Stalin's rise to power, later began aligning himself with Leon Trotsky.
In notes dictated before his death, Lenin criticises Stalin's rude manners and ambitious nature.
He even suggested that Stalin should be removed from his position of General Secretary of the Communist Party.
Poisoning would later become Stalin's preferred method for dealing with his enemies, Lurie points out.
He added: 'The funny thing is that the brain of Lenin still is preserved in Moscow, so we can investigate.'
Popular theory maintains that Lenin died from the sexually-transmitted disease syphilis.
© UnknownStalin was reportedly furious after Lenin aligned himself with Trotsky (pictured)
His embalmed body still lies on public display in a Red Square mausoleum almost 20 years after the collapse of the communist state he helped bring to life.
Mr Lurie and UCLA neurologist Dr. Harry Vinters reviewed Lenin's records for an annual conference at the University of Maryland School of Medicine on famous people's deaths.
Dr Vinters put forward a separate theory, maintaining that stress or a family medical history could have accounted for Lenin's death
Prior to his death, the 53-year-old Soviet leader's health had been growing worse over time.
In 1921, he forgot the words of a major speech and he had to learn to speak again and write with his left hand after one stroke.
A subsequent major stroke later left him paralyzed on one side and unable to speak.
An autopsy found blood vessels in his brain were extremely hardened, results that have been difficult to understand, said Dr. Philip Mackowiak, who organizes the yearly event.
'Number one, he's so young and number two, he has none of the important risk factors,' Mackowiak said.
Lenin didn't smoke - he never let smokers near him. He also didn't have diabetes, wasn't overweight and the autopsy didn't find any evidence of high blood pressure, Mackowiak said.
There was 'considerable suspicion' among Russians at the time of Lenin's death that syphilis was to blame, Mackowiak said.
However, family history appears to have worked more against Lenin, Vinters said.
Lenin was treated for syphilis using the primitive medications available at the time, and while the sexually transmitted disease can cause strokes, there is no evidence from his symptoms or the autopsy that was the case with Lenin, Vinters said.
© ReutersLenin's embalmed body still lies on public display in a Red Square mausoleum almost 20 years after the collapse of the communist state he helped bring to life
Stress also is a risk factor for strokes, and there's no question the communist revolutionary was under plenty of that, the neurologist said.
'People were always trying to assassinate him, for example.' Dr Vinters said.
Dr Vinters, who reviewed autopsy records and the leader's clinical history, said toxicology tests that might have revealed poisoning were not conducted during the autopsy.
Reports from the time also show Lenin was active and talking a few hours before his death.
'And then he experienced a series of really, really bad convulsions which is quite unusual for someone who has a stroke,' Vinters said.
The conference is held yearly at the school, where researchers in the past have re-examined the diagnoses of figures including King Tut, Christopher Columbus, Simon Bolivar and Abraham Lincoln.
I'd say most likely true. Its how most psychopaths in power 'deal' with another person who is a threat to them.