Independent US presidential candidate Robert F. Kennedy Jr believed he may have been attacked by a worm that ate part of his brain and then died inside his head, US media reported on Wednesday.

Kennedy, 70, made the claim in a 2012 deposition as part of his divorce from his second wife, according to the New York Times, which said the scion of the storied political clan reported severe memory loss and mental fog.

A New York surgeon who reviewed his brain scans told Kennedy his health issues could have been "caused by a worm that got into my brain and ate a portion of it and then died," the White House hopeful reportedly told attorneys.

Kennedy -- a nephew of former president John F. Kennedy and known informally as RFK Jr -- says he recovered from the 2010 incident and that he did not require treatment for the infection, according to the Times.

Around the same time, Kennedy -- who has described a variety of ailments over the years, including an irregular heartbeat -- said he was suffering from mercury poisoning, which can lead to neurological issues.

AFP has not independently reviewed the deposition but a spokesperson for Kennedy's campaign said he had "traveled extensively in Africa, South America and Asia" as an environmental advocate and contracted a parasite during one of those trips.

The Times, citing speculation from doctors who had not examined Kennedy, reported that he might have developed a neurological condition caused by a pork tapeworm larva that would likely have survived on nutrients from the body rather than eating his brain.

Kennedy, a long-time vaccine skeptic, has presented himself on the campaign trail as more vibrant and youthful than the frontrunners -- 81-year-old President Joe Biden and Republican challenger Donald Trump, 77.

Health and wellbeing are at the heart of his campaign and he is often pictured on social media taking part in outdoor activities and watersports -- sometimes shirtless.

The environmental lawyer is boasting double-digit support ahead of November's election, and polling has gone back and forth on whether he is hurting Biden or Trump more.

"The (parasite) issue was resolved more than 10 years ago, and he is in robust physical and mental health," his spokesman said.

"Questioning Mr. Kennedy's health is a hilarious suggestion, given his competition."