Multimodal Functional Near-Infrared Spectroscopy in Monitoring Cerebral Haemodynamic: A Review Article

Functional near-infrared spectroscopy (fNIRS) is an optical imaging tool to study brain activities. Moreover, many researchers combined fNIRS with other modalities to gain a better understanding of the brain. This paper provides an overview of the combination of fNIRS with other imaging modalities in the detection and measurement of the cerebral hemodynamic. Cerebral haemodynamic such as the cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral blood oxygenation (CBO) are the important parameters in many neuroimaging studies. Cerebral hemodynamic had been studied by various medical imaging modalities. Initially, Xenon enhanced Computed Tomography (Xenon CT), Computed Tomography (CT) perfusion; Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET) are used to measure the cerebral hemodynamic. Recently, fNIRS is used to optically observe the changes in cerebral haemodynamic during brain activities and the combination of fNIRS with other modalities also become an interest to study the relations within brain activities and the cerebral hemodynamic. Therefore, this paper provides an overview of existing multimodal fNIRS in detection of cerebral haemodynamic changes and provides an important insight on how multimodal fNIRS aid in advancing modern investigations of human brain function. Keywords: multimodal imaging, fNIRS-fMRI, fNIRS-PET, fNIRS-EEG

Diagnosis, monitoring and prognosis of secondary brain damage in icu patients with traumatic brain injuries

Traumatic brain injury (TBI) is the brain injury that occurs whenever a physical force that impacts the head leads to neuropathology. The types of primary TBI are penentrating TBI or non-penetrating TBI and it can lead to intracerebral contusions, hemorrhages or extra-axial hematomas. Patients with TBI can also have skull fractures or concussions. The injury severity can be classified in many ways but the most established and common used is the Glascow Coma Scale (GCS). However, with the GCS, each of the severity criteria has limitations and might mot be an accurate predictor of TBI severity and outcome when used alone. For this reason it is often used in conjunction with other parameters (Abbreviated Injury Scale - AIS). Secondary Brain Damage is the injury that occurs to the TBI patient not at the time of the accident, but during the following minutes, hours or days. There are many mechanisms that lead to development of cerebral edema, blood-brain barrier disruption, vasospasm, increase in volume of bleeding, contusions and intracranial hypertension. These mechanisms can act either in cellular level or systemic level. The cellular mechanisms that lead to secondary brain damage include necrosis or apoptosis, mitochondrial dysfunction, excitotoxicicty, formation of free radicals, changes in cerebral glucose metabolism and inflammation. The mechanisms at systemic level include hypoxia-cerebral oxygenation, hypo or hypertension, hypo or hyper-capnia, anemia, hyponatremia and hyper or hypoglycemia. The first tool to diagnose severe TBI and secondary brain injury is neurological assessment. Neuroimaging is one of the most important ways for diagnosis. Computed Tomography (CT scan), Magnetic Resonance Imaging (MRI), cerebral angiography, transcranial Doppler, CT perfusion, Xenon CT, MRI diffusion, MRI perfusion, MRI spectrometry and Positron Emission Tomography (PET) are possible ways of imaging that not only help in the diagnosis but give important information that help in choosing the correct management. Moreover, neuromonitoring, helps in the correct management of the patient.

Early low cerebral blood flow and high cerebral lactate: prediction of delayed cerebral ischemia in subarachnoid hemorrhage

OBJECTIVEDelayed cerebral ischemia (DCI) following subarachnoid hemorrhage (SAH) is one of the major contributors to poor outcome. It is crucial to be able to detect early signs of DCI to prevent its occurrence. The objective of this study was to determine if low cerebral blood flow (CBF) measurements and pathological microdialysis parameters measured at the bedside can be observed early in patients with SAH who later developed DCI.METHODSThe authors included 30 patients with severe SAH. The CBF measurements were performed at Day 0–3 after disease onset, using bedside xenon-CT. Interstitial glucose, lactate, pyruvate, glycerol, and glutamate were measured using microdialysis.RESULTSNine of 30 patients developed DCI. Patients with DCI showed significantly lower global and regional CBF, and lactate was significantly increased in these patients. A high lactate/pyruvate ratio was also detected in patients with DCI.CONCLUSIONSEarly low CBF measurements and a high lactate and lactate/pyruvate ratio may be early warning signs of the risk of developing DCI. The clinical value of these findings needs to be confirmed in larger studies.