Powerful MRI brain scan technique enables Addenbrooke’s Hospital to offer life-changing surgery to epilepsy patients

Tiny differences in patients’ brains that cause treatment-resistant epilepsy can now be identified by ultra-powerful magnetic resonance imaging (MRI) scanners, scientists have shown.

The first study to use the approach has enabled doctors at Addenbrooke's Hospital in Cambridge to offer patients surgery to cure their condition.

For surgeons to perform this operation, they need to be able to see the diseased tissue - lesions - in the brain to work out what to remove to cure the patient’s epilepsy.

Being able to see these lesions on MRI scans can double the chances of the patient being free of seizures following surgery.

Ultra-high field 7T MRI scanners - which use a 7 Tesla magnetic field to provide detailed resolution brain scans - are double the strength of the NHS’s best 3T MRI scans and have been shown in other countries to be better at detecting these lesions in patients with drug-resistant epilepsy. Most NHS hospitals only have even weaker, 1.5T scanners.

However, 7T MRI scans are susceptible to dark patches known as signal dropouts, which often occur in the temporal lobes, where most cases of epilepsy arise.

But in new research published in Epilepsia, researchers at the University of Cambridge’s Wolfson Brain Imaging Centre and colleagues at the Université Paris-Saclay, trialled a technique known as ‘parallel transmit’, using eight transmitters around the brain rather than just one, to avoid the drop-outs.

Chris Rodgers, professor of biomedical imaging at the University of Cambridge, said: “It used to be the case that MRI scanners used a single radio transmitter, but in a similar way to how single wifi routers leave areas where you will struggle to get a signal, so these scanners would tend to leave blackspots on brain scans where it was hard to make out the relevant tissue.

“Now, by using multiple radio transmitters positioned around the patients’ head – like having a wifi mesh around your home – we can get much clearer images with fewer blackspots. This is important for the epilepsy scans because we need to see very precisely which part of the brain is misbehaving."

About 360,000 people in the UK have focal epilepsy, a condition that causes seizures to spread from part of the brain. A third of them have persistent seizures despite medication, and the only treatment that can cure this for them is surgery. Epileptic seizures are the sixth most common reason for hospital admission.

The new approach was tested with 31 drug-resistant epilepsy patients recruited at Addenbrooke’s.

The researchers found that the parallel transmit 7T scanner identified previously unseen structural lesions in nine patients, while confirming in four patients suspected lesions detected using 3T scanners. In a further four patients, it showed that suspected lesions could be disregarded.

Parallel transmit 7T images were clearer than conventional (‘single transmit’) 7T images in 57 per cent of the cases, with the other images equally clear. Single transmit scanners never outperformed parallel transmit scanners.

As a result of the findings, 18 patients (58 per cent) had the management of their epilepsy changed. Nine were offered surgery to remove the lesion, and one was offered laser interstitial thermal therapy, which uses heat to remove the lesion.

For three patients, the scans showed more complex lesions that meant surgery was no longer an option.

Due to the size or location of their lesions, five patients were offered stereotactic electroencephalography (sEEG), a technique for pinpointing the lesions using electrodes inserted into the brain.

The procedure is not used for everyone as it is very costly and invasive, but the 7T scans meant it could be offered to those patients it was most likely to help.

Dr Thomas Cope, from the university’s Department of Clinical Neurosciences, and a consultant neurologist at Cambridge University Hospitals, said: “Having epilepsy that doesn’t respond to anti-seizure medications can have a huge impact on patients’ lives, often affecting their independence and their ability to maintain a job. We know we can cure many of these patients, but that requires us to be able to pinpoint exactly where in the brain is the root of their seizures.

“7T scanners have shown promise over the past few years since their introduction, and now, thanks to this new technique, more epilepsy patients will be eligible for life-changing surgery.”

Patients reported only minor and occasional negative experiences, such as dizziness on scanner entry and additional claustrophobia from the head coil.

Prof Rodgers added: “The Paris group’s plug-and-play sequences avoid the need to calibrate the scanner at every visit, making it practical to use these scans for scanning patients.”