This thesis presents the design, fabrication and development of a multimodal, flexible probe in
order to monitor the electrical and chemical signatures of secondary brain injury (SBI). Recent
literature in this field indicates that SBI proliferates after severe initial damage to cortical
brain tissue in the cases of stroke, sub-arachnoid haemorrhage (SAH) and traumatic brain
injury (TBI) via the mechanism of a spreading depolarisation (SD). This proliferation can lead
to expanded injuries and worsened outcomes for patients who sustain these injuries.
A range of devices and techniques can be employed to monitor the developments of SBI. Pres-
sure monitoring (ICP), regional cerebral blood flow (CBF), brain tissue oxygenation (PbtO2),
electrocorticography (ECoG) and microdialysis (MD) monitoring, when used in conjunction
with medical imaging and systemic monitoring, can provide a clearer picture into the devel-
opment of secondary injury and brain health in at-risk regions. Unfortunately, due to the
penetrative nature of such devices and techniques, these forms of monitoring are not imple-
mented as readily by neurosurgeons and ultimately, the dynamic changes that occur during the
process of secondary brain injury can go undetected.
Of these monitoring techniques, ECoG and MD can provide key information for 1) detecting SDs
- the principle mechanism by which secondary brain injury proliferates and 2) monitoring the
health of brain tissue by detecting dynamic changes in small metabolites and neurotransmitters
such as glutamate, glucose and lactate.
In current clinical environments when both monitoring techniques are used, two separate, clin-
ically approved medical devices are utilised. In addition to the penetrative nature of the
microdialysis probe and the lack of integration between chemical and electrical sensing by
uncorrelated placement, vital diagnostic power is lost.
Here, a singular device with dual modalities has been developed in order to synchronise the
real-time monitoring of dynamic chemical and electrical changes whilst also delivering surface
microdialysis in a less penetrative form than the current clinical standard. The use of United
States Pharmocopeia (USP) Class VI approved polymer Parylene C as the base substrate
with enclosed electrodes, membranes and fluidic channels provides the basis for a new non-
penetrative device that can both chemically and electrically monitor the brain, providing real-
time information for neurocritical care clinicians.