Approximately 360,000 individuals in the UK suffer from focal epilepsy, a condition in which seizures spread from one part of the brain. Around a third of these patients experience persistent seizures despite taking medication, and surgery remains the only treatment capable of curing their condition. Epileptic seizures are the sixth leading cause of hospital admissions. For surgeons to perform the necessary operation, they must accurately identify the brain lesions (damaged tissue) responsible for triggering seizures. By visualizing these lesions on MRI scans, surgeons can significantly increase the chances of the patient being seizure-free after surgery. Ultra-high-field 7T MRI scanners provide much higher resolution scans than the NHS’s standard 3T MRI scanners, enabling better detection of these lesions in patients with drug-resistant epilepsy. However, most NHS hospitals use even lower field strength, such as 1.5T scanners. Despite the advantages of 7T MRI, these scans are prone to signal dropouts, particularly in the temporal lobes, which is the area most commonly affected by epilepsy. Now, a new study published in Epilepsia has presented a technique to address this issue.

The research team from the University of Cambridge’s Wolfson Brain Imaging Centre (Cambridge, UK), in collaboration with colleagues from Université Paris-Saclay (Paris, France), applied a technique called ‘parallel transmit,’ which uses eight transmitters instead of the usual single transmitter to avoid the signal dropouts. The team tested this method with 31 drug-resistant epilepsy patients to assess whether the parallel transmit 7T scanner could outperform conventional 3T scanners in detecting brain lesions. Their findings revealed that the parallel transmit 7T scanner uncovered previously undetected structural lesions in nine patients. It also confirmed suspected lesions identified with the 3T scanner in four patients, and showed that suspected lesions in another four patients were not present. In more than half of the cases (57%), the parallel transmit 7T scans provided clearer images than the standard single-transmit 7T scans, while the remaining cases produced equally clear images.

Single-transmit scanners never surpassed the performance of parallel transmit scanners. Based on these results, the management of epilepsy was altered for more than half of the patients (18 patients, or 58%). Nine patients were offered surgery to remove the lesions, and one was recommended for laser interstitial thermal therapy, a procedure that uses heat to eliminate the lesion. For three patients, the scans revealed more complex lesions, which meant surgery was no longer an option. Five patients with larger or differently located lesions were offered stereotactic electroencephalography (sEEG), a procedure involving electrodes inserted into the brain to pinpoint the lesions. While sEEG is typically not used due to its cost and invasiveness, the detailed 7T scans made it feasible for the patients most likely to benefit from it. When patients were asked about their experience with the procedure, they reported only minor and occasional discomfort, such as dizziness when entering the scanner and increased claustrophobia due to the head coil. This suggests that parallel transmit 7T MRI is generally well tolerated by patients.

“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,” said Dr. Thomas Cope from the University’s Department of Clinical Neurosciences, and a Consultant Neurologist at CUH. “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.” 

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