The goal of this clinical investigation of a medical device is to test the safety of graphene based electrodes when used during surgery for resection of brain tumors. The main questions that it aims to answer are:

• To understand the safety of the Graphene Cortical Interface when used during brain tumor surgery (primary objective);
• To assess the quality of the brain signals recorded with the Graphene Cortical Interface, their ability to stimulate the brain, how stable their function is over the duration of an operation, and their suitability for use in the operating theatre (secondary objectives).

Participants will undergo tumor surgery as usual with the study electrodes being tested alongside a standard monitoring system. If they are awake for part of their surgery they may be asked to complete specific tasks such as naming objects from a list modified for the study, to evaluate the capability to decode brain signals (exploratory objective). They will be monitored subsequently for any complications including undergoing an additional MRI scan 6 weeks after their surgery.

During surgical operations within the brain such as the removal of a tumor, electrodes are commonly used to map specific brain functions or monitor brain activity. These are most commonly flexible plastic devices with embedded metallic contacts that allow electrical activity in the brain to be detected and measured. They may also be used to stimulate precise areas of the brain to either trigger or block a response such as the contraction of a muscle. This allows the surgeon to define which regions of the brain are involved in controlling critical functions such as movement or speech so that these areas can be protected during the operation.

There remain limitations with the design and physical characteristics of commercially available electrodes for use during brain operations. These include the limited ability of conventional materials to fold over the complex shape of the brain and the need to use comparatively large metallic contacts to detect the tiny electrical signals. This study will be the first to introduce a new generation of electrodes which have been designed to overcome these limitations. They are extremely thin and flexible allowing them to follow the surface of the brain and to be used in locations within and around the brain for which the standard electrodes are unsuitable. The contact surfaces that detect electrical activity and enable and stimulate the brain have been replaced with graphene which is a novel carbon-based material. The use of graphene allows electrodes to be made that are more sensitive to the tiny electrical signals of the brain. This means that they can be much smaller and closer together providing increased detail in the recording and potentially enabling signals to be detected that would previously have required such long recordings that they could not be used to guide decision making during surgery.

Inclusion Criteria:

• Solitary supratentorial tumor radiologically consistent with glioma (intrinsic primary brain tumor) on standard diagnostic MRI;
• Planned for surgery under awake conditions or under general anesthesia with intra-operative electrocorticography (ECoG);
• English as first language for those subjects with tumors associated with language areas;
• Karnofsky performance score > 70 and World Health Organization (WHO) performance status score ≤ 1;
• Willing and able to understand and provide informed consent for participating in the study.

Exclusion Criteria:

• Contraindications to magnetic resonance imaging (e.g., incompatible implanted devices);
• Previous cranial surgery or radiotherapy;
• Subjects expected to undergo craniotomy of less than 5 cm in maximum diameter (bone to bone)
• Known extracranial malignant neoplasm;
• Pregnant or lactating women;
• Renal impairment sufficient to limit Gadolinium administration (EGFR <60 ml/min)
• For those subjects with tumors associated with language areas, any contraindication which could preclude them from performing the whole awake intra operative tasks at the discretion of the Investigator (e.g., language function not suitable for monitoring tasks)