Neurosurgeon finds wriggling worm in patient's brain

How a brain scan for a lesion turned into a big surprise...
01 September 2023

Interview with 

Kieren Allinson


Worm cartoon


An operation developed an unexpected twist for an Australian woman recently when the neurosurgeon, working to investigate a large, unexplained lesion visible on her brain scan, pulled out a 8cm long wriggling worm! Not normally an infection seen in humans, the snake parasite had invaded her brain by mistake. Thankfully these sorts of events are rare, but Cambridge neuropathologist Kieren Allinson had a similar run-in with a worm in a patient’s brain himself a few years back. Chris Smith spoke to him about both of these extraordinary cases…

Kieren - This lady in Australia, I think she's 64, and she's had symptoms including abdominal pain and diarrhoea, night fevers, headaches, forgetfulness and psychosis, depression, sort of psychological symptoms. And she's presented to hospital in Canberra and she's had a brain scan and that's shown a lesion in her right frontal lobes. That's the front part of the brain and that's the part of the brain that we associate with controlling behaviour, inhibition, normal social behaviours and personality.

Chris - So that would fit with the fact that she had mood changes and some forgetfulness and so on.

Kieren - Yeah, absolutely. Yeah.

Chris - So what did they do next then? How did it come to light that there was a worm in her brain?

Kieren - So if normally someone has a lesion like this on a brain scan, it's most likely going to be a brain tumour. Sometimes infections, sometimes other things. She would've then gone to have neurosurgery and they would've operated to remove the lesion and to find out what it is.

Chris - Would that normally come to someone like you if a neurosurgeon does an intervention like that, would they normally send material to a pathologist to get them to tell them what it is?

Kieren - That's right. Yeah. So they'll take tissue during the operation and they'll send that to a pathology lab and then a pathologist like me and look at that on a microscope and try and work out what it is.

Chris - But I gather the neurosurgeon in this instance got something of a surprise and a shock when she got inside this woman's head.

Kieren - Yeah. So incredibly, she pulled out a eight centimetre long, or three inch long, worm, which was still motile, still wiggling about. And that obviously gave her a complete shock. It wasn't what she was expecting. And I think she then began to ring colleagues from microbiology and infectious disease, et cetera, to ask them what to do about this.

Chris - Some commentators have said that is a once in a career type thing, but you have some history with finding worms in people's heads yourself, haven't you?

Kieren - Yeah, that's right. So about 10 years ago, me and my colleague Andrew Dean, uwe were working at Addenbrooke's and we received a biopsy from a neurosurgeon. And it was an interesting case because the guy, he came from Hong Kong, he was a chef there. He also lived in the UK and he had a lesion in his brain, which had been followed up for a few years. And it actually moved. So on the initial scans it was on one side of the brain and a few years later it was on the other side of the brain. And when they finally biopsied it and sent it to us, it was a worm, a different type of worm called a sparganosis. So this was the one time where I've experienced this, a worm in the brain.

Chris - Did the neurosurgeons then realise what they were dealing with?

Kieren - No. So that's the main difference with these two stories. On this occasion, the worm was much smaller. It certainly wasn't eight centimetres long. It was around one centimetre long and very fine and thread-like, and they just put it in the pathology pot and sent it to us until we looked down the microscope, we didn't realise it was a worm.

Chris - How did you then work out what sort of worm it was once you had, this is your worm rather than the one in Australia?

Kieren - Andrew Dean took photos of it on the microscope and he sent those photos to an expert and he emailed back straight away saying, that's sparganosis. But then actually we also took some of that tissue and extracted DNA with a Sanger and they were able to confirm genetically that it had the DNA profile of a Sparganosis worm.

Chris - This is the Sanger Center at Hinxton that helped to sequence the human genome. You got them to read the genome of the worm and therefore work out what it was.

Kieren - Yeah, that's right. Yeah. And it was the first time that species had had its genome sequenced.

Chris - So in both cases we've ended up with weird worms in weird places in the brain, how do we think they got there?

Kieren - So they're both there by accident. Humans are not meant to be the hosts of these worms. The Australian one, the definitive host, the host in which it reproduces, is the carpet python. Small mammals and marsupials eat things contaminated with the faeces of the python. And then they get it and then a python eats them and that's the normal lifecycle. Whereas, in this case I have read that the lady in Australia has gone out foraging for her own stuff from the wild and it's felt that that was contaminated with a larva from the python. And that's how it's got into the human. But it's not meant to and there's no route for it to get from there. Back to its normal host of the python. The worm is not meant to be there and it's kind of reached a bit of a dead end by being there, I think. And it ends up in her brain of all the things you could have in your brain on an MRI scan, when you have a lesion in your brain on a scan, it's actually not a bad thing because it's treatable. And I heard she's doing well with antiparasitic therapy. So actually as gross as it sounds, having a worm in your brain, it's not that bad compared to the other things it could be.

Chris - I suppose there's a risk that she might have more worms. And will they therefore treat her to make sure that she hasn't got more lurking somewhere else that could also find their way into her brain ultimately?

Kieren - Yeah, that's right. So I heard she had lesions in her lungs and maybe in her spleen, but certainly in her lungs. And so she's receiving anti parasitic drugs like antibiotics, but for parasites, anti helminth therapy. So hopefully she'll make a full recovery with that.

Chris - And the worm that you studied, your chef from China, what was his story? How did he get it then?

Kieren - Supposedly from eating undercooked fish, an undercooked frog, undercooked amphibian, which is something that he did in Hong Kong. And that's how it got into him.

Chris - Was the story the same though in the sense that you end up with a parasite getting into the wrong host, us, and because it doesn't know how to behave in us. It does all the wrong things and ends up in all the wrong places.

Kieren - Yeah, that's right. Yeah. So it is an accidental host in a human and it's got nowhere to go from there. It can't get back into its normal lifecycle and it's a dead end really.

Chris - And did he recover with the removal of the worm and then treatment?

Kieren - Yes. You know, he made a full recovery.

Chris - So the odds are quite good for this lady?

Kieren - I think so, yeah. I hope she continues to recover well, yeah.

Chris - Discharged with the advice not to go foraging where pythons have pooed.

Kieren - That's right. Yeah. And that's his advice for anyone. I think.


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