The patient will undergo their intracranial neurosurgical procedure as planned, using conventional brain retractors and neurosurgical equipment.

Standard neuromonitoring (EEG, MEP, SSEP) will be placed after the induction of neuroanaesthesia if indicated. Additional to whatever conventional EMBRI neuromonitoring is used, intraoperatively an ECoG array will be positioned under the retractor by the operating surgeon. Further electrode arrays may be placed on the cortical surface remote from the retractor as needed to establish a reference.

Typically we anticipate one ECoG array under the retractor blade with a reference array on an area of unretracted brain.

The primary outcome is to report the feasibility of integrating the ECoG brain retractor into standard traditional neurosurgical operative workflow based upon analysing prospective data including qualitative questionnaires administered to surgeons and scrub nurses, anonymised clinical data, and anonymised electrophysiological data.

The primary outcome is to produce a descriptive report of the electrophysiological data recorded and the challenges encountered in the delivery of the novel electrophysiological recording for patients undergoing planned neurosurgical procedures at the National Hospital for Neurology and Neurosurgery, London.

The secondary objective is to analyse the captured electrophysiological data to investigate any correlation between the electrophysiological signature and duration of retraction. Post-operative clinical data, such as MRI brain scans, can be reviewed to investigate any ischemic events.

We will perform an initial analysis of the electrophysiological data to see if neurophysiological stigmata of brain retraction injury can be identified, with the operation simultaneous recorded with the operative microscope.