Davina McCall has said she is to undergo brain surgery after being diagnosed with a “very rare” tumour known as a colloid cyst.

The 57-year-old TV presenter said the benign brain tumour was found after she was offered a health check-up as part of her menopause advocacy work.

But what are colloid cysts, and how can they be treated?

Dr Karen Noble, director of research, policy and innovation at Brain Tumour Research, spoke to the PA news agency about this particular health condition, how it is diagnosed and the medical treatments available.

What is a colloid cyst and are they dangerous?

Colloid cysts are generally slow-growing, non-cancerous brain tumours located in the third ventricle, a fluid-filled cavity in the centre of the brain.

Though they are benign, colloid cysts need monitoring as their growth may cause a build-up of fluid in the brain known as hydrocephalus.

Dr Noble said: “The thing with non-cancerous brain tumours that we tend to say is ‘benign is not fine’ – because these cysts are a field with fluid that can cause swelling in the brain.

“Due to their location, some cysts can cause what we call hydrocephalus – a build-up of fluid in the brain which can lead to an increase in pressure.

“That’s what the concern is with these types of cysts.”

What are the symptoms of a colloid cyst?

“If they’re small, these cysts don’t cause any symptoms,” Dr Noble said.

“But once a cyst becomes large, then it will potentially lead to this increase of pressure in the brain that can cause symptoms like headaches, nausea, visual disturbances, and, as Davina McCall mentioned, memory problems and a bit of confusion.”

They can also cause difficulty walking and changes in personality, Dr Noble added.

Colloid cysts are often discovered by accident during imaging for other conditions, with MRI or CT scans.

“The issue is that those symptoms could apply to many types of brain tumours, but also lots of other potential conditions – and that is why brain tumours are generally so difficult to diagnose,” Dr Noble said.

Although patients who do experience these symptoms are unlikely to have a brain tumour, those who do often tend to go back “four or five times to their GP” before they are diagnosed.

This is also why nearly 40% of brain tumour patients are diagnosed through A&E.

Praising McCall for being open about her diagnosis and “raising awareness of brain tumours” after she shared news of her health condition online, Dr Noble said: “This will absolutely help with others recognising potential symptoms and talking to their doctors.”

Who is at risk of developing a colloid cyst?

Colloid cysts are rare and thought to make up less than 2% of primary brain tumours – that is, tumours that form directly on the brain, as opposed to a tumour that appears when a cancer located somewhere else in the body spreads to other sites.

Dr Noble said: “Between 12,000 and 16,000 people are diagnosed with a primary brain tumour in the UK each year.

“About 2% of those people – so less than 300 a year – will get diagnosed with a colloid cyst.”

However, according to Brain Tumour Research, brain tumours are “indiscriminate” and can affect anyone at any age.

Colloid cysts in particular are mainly identified in 30 to 60 year-olds, Dr Noble said – but the reason why they form in the brain remains unclear.

“The causes of colloid cysts are not known – it is believed to be a hangover from embryonic development, but it’s not certain,” Dr Noble said.

“By that sense, it sounds as though people are born with it, and then by a certain age it can start to cause some issues such as the symptoms we have discussed.”

How do doctors treat a colloid cyst?

Though treatments vary from person to person, there are usually two main options when it comes to treating a colloid cyst.

Dr Noble said: “If the cysts are small – that is less than 9mm in size – doctors will monitor them over time with regular MRI scans to be able to assess whether they are continuing to get bigger and whether there’s any risk of causing increased pressure in the brain.

“Then the other option is surgery.”

In a video on Instagram, McCall described her tumour as “big”, at 14mm wide, adding: “It needs to come out, because if it grows, it would be bad.”

McCall said she will have the cyst removed through a craniotomy, a major surgical procedure to temporarily remove part of the skull so surgeons can get access to the brain and remove the cyst from it.

Fortunately, the prognosis following a craniotomy to remove a colloid cyst is “very good,” Dr Noble said.

“If surgeons are able to completely remove the cyst, then it’s excellent news”, she added.