Dynamic connectivity patterns predict cognitive decline after neurosurgery

In a collaboration between the CCA VUmc Brain Tumor Center, Amsterdam Neuroscience, and the VUmc MEG center, we investigated the association between dynamics of “functional connectivity” and cognitive outcome in patients undergoing neurosurgery. The study, which was published in Scientific Reports, shows that preoperative measurement of these dynamics may be essential for predicting whether patients will or will not develop problems with their cognitive functioning after undergoing neurosurgery.

Resective neurosurgery, which is a commonly used treatment for brain tumors and other lesions causing epileptic seizures, sometimes leads to postoperative cognitive deterioration. Unfortunately, it has been difficult to predict which patients are at risk for developing these impactful cognitive problems. Therefore, we used an innovative approach to determine the characteristics of communication patterns throughout the brain before and after such surgery. We hypothesized that a pathologically increased level of communication, particularly of the regions in the brain that are already considered ‘hubs’, would be indicative of future cognitive problems. A rail network offers a nice analogy of this ‘hub overload’ hypothesis. If a train or rail becomes defect at some time, other trains may be rerouted. This causes an increase of trains passing through the surrounding train stations. The increase in traffic flow may cause delays in the regularly scheduled trains passing through these stations, which may then spread through an even bigger number of train stations. Now imagine that the first defect train was situated near a hub train station: this would probably cause an even bigger, and faster, cascade of delays throughout the entire rail network. Likewise, large amounts of traffic flow through a healthy brain network, particularly via the hub regions. In the case of a local problem, such as a brain tumor or other lesion, the rerouting of flow may be related to hub overload and be predictive of subsequent deterioration of the brain network.

Twenty-eight patients with lesions causing epilepsy (mostly primary brain tumors) underwent magnetoencephalography, which is a unique technique used to measure brain activity in real-time. Patients 
also underwent neuropsychological assessments preoperatively and 1-year after neurosurgery to test their cognitive functioning. Patients’ hub load was determined by investigating communication and dynamics of hub regions with the rest of the brain. Results show that deteriorating memory functioning was indeed correlated with higher hub load. Moreover, it was even possible to predict which patients would develop cognitive problems using only the preoperative hub load measurement. Although the study needs to be replicated, these findings suggesting that this measure of hub load may be used as a prognostic marker for tailored treatment planning in surgical candidates.

Shanna goes to Nottingham

By Shanna

On the 1st of February I started a two-month visit to the Sir Peter Mansfield Imaging Centre in Nottingham (UK) with the group of Matt Brookes. This center is amongst others equipped with 3 MRI scanners (1.5T, 3T, 7T) and an MEG system and is part of the School of Physics and Astronomy. Their research aims to bring together the scientist developing new medical imaging techniques with the clinicians and scientists who use them.

After a warm welcome and meeting a lot of new people, the hard work has started. The main goal of my visit is to learn how to work with neural mass models to be able to simulate the activity of neural networks. These models will be specified for and verified with MS and neuro-oncological data. The focus thereby is on hub-specific degeneration within the networks of both diseases. I will relate this degeneration to the cognitive performance of these patients and ultimately hope to be able to predict the cognitive status of MS and neuro-oncological patients over time.

During my visit, I will be supervised by Dr. Prejaas Tewarie and I will collaborate closely with Professor Coombes of the department of Mathematics.

HersenMagazine interview

The HersenMagazine (published by the Hersenstichting, a Dutch foundation focusing on the brain) interviewed Linda about networks and neuroscience for their January issue on ‘connection’. The spread is below, and you can find Linda’s research dream here (all in Dutch)!