Magnetic resonance imaging of traumatic brain injury: a pictorial review

Traumatic brain injuries: a neuropsychological review

The best predictor of functional outcome in victims of traumatic brain injury (TBI) is a neuropsychological evaluation. An exponential growth of research into TBI has focused on diagnosis and treatment. Extant literature lacks a comprehensive neuropsychological review that is simultaneously scholarly and practical. In response, our group included, and went beyond a general overview of TBI's, which commonly include definition, types, severity, and pathophysiology. We incorporate reasons behind the use of particular neuroimaging techniques, as well as the most recent findings on common neuropsychological assessments conducted in TBI cases, and their relationship to outcome. In addition, we include tables outlining estimated recovery trajectories of different age groups, their risk factors and we encompass phenomenological studies, further covering the range of existing-promising tools for cognitive rehabilitation/remediation purposes. Finally, we highlight gaps in current research and directions that would be beneficial to pursue.

Gd accumulation in tissues of healthy mice upon repeated administrations of Gadodiamide and Gadoteridol

The aim of this work was to investigate, by five different administration protocols, the impact of the dosage, the time passed after the last injection and the frequency of injections, on accumulation and distribution of Gd-containing species in the body tissues of healthy mice upon repeated injections of Gadolinium Based Contrast Agents (GBCAs). Gadodiamide and Gadoteridol have been compared. The amount of Gd retained in several tissues/organs (cerebrum, cerebellum, spleen, liver, kidneys, eyes, skin, bone and muscle) has been assessed by ICP-MS upon administration of the GBCAs i) at three weeks or three months after the last administration, ii) when one, three or twelve doses of GBCA were administered and iii) when administrations were made every two weeks. Gd was found in all tissues after the administration of Gadodiamide. Conversely, in the case of Gadoteridol, Gd was detected only in spleen, kidneys, liver and bone. The amounts of Gd found in spleen, liver and kidneys markedly decrease upon increasing the time that has passed after the last administration, whereas, in the case of Gadodiamide, the decrease of Gd found in bone, cerebrum and cerebellum appears to occur at a much slower rate. Overall, areas of long term deposition appear to be bone and spleen for both GBCAs. In conclusion, our findings demonstrate that intravenous multiple administrations of GBCAs is associated with extensive multiorgan retention which is reduced but not eliminated by the use of the macrocyclic Gadoteridol as well as by adopting reduced and/or less frequent dosing.

Pulsed arterial spin labeling effectively and dynamically observes changes in cerebral blood flow after mild traumatic brain injury

Cerebral blood flow is strongly associated with brain function, and is the main symptom and diagnostic basis for a variety of encephalopathies. However, changes in cerebral blood flow after mild traumatic brain injury remain poorly understood. This study sought to observe changes in cerebral blood flow in different regions after mild traumatic brain injury using pulsed arterial spin labeling. Our results demonstrate maximal cerebral blood flow in gray matter and minimal in the white matter of patients with mild traumatic brain injury. At the acute and subacute stages, cerebral blood flow was reduced in the occipital lobe, parietal lobe, central region, subcutaneous region, and frontal lobe. Cerebral blood flow was restored at the chronic stage. At the acute, subacute, and chronic stages, changes in cerebral blood flow were not apparent in the insula. Cerebral blood flow in the temporal lobe and limbic lobe diminished at the acute and subacute stages, but was restored at the chronic stage. These findings suggest that pulsed arterial spin labeling can precisely measure cerebral blood flow in various brain regions, and may play a reference role in evaluating a patient's condition and judging prognosis after traumatic brain injury.

NIR light propagation in a digital head model for traumatic brain injury (TBI)

Near infrared spectroscopy (NIRS) is capable of detecting and monitoring acute changes in cerebral blood volume and oxygenation associated with traumatic brain injury (TBI). Wavelength selection, source-detector separation, optode density, and detector sensitivity are key design parameters that determine the imaging depth, chromophore separability, and, ultimately, clinical usefulness of a NIRS instrument. We present simulation results of NIR light propagation in a digital head model as it relates to the ability to detect intracranial hematomas and monitor the peri-hematomal tissue viability. These results inform NIRS instrument design specific to TBI diagnosis and monitoring.

Diffusion tensor imaging detects chronic microstructural changes in white and gray matter after traumatic brain injury in rat

Traumatic brain injury (TBI) is a major cause of disability and death in people of all ages worldwide. An initial brain injury caused by external mechanical forces triggers a cascade of tissue changes that lead to a wide spectrum of symptoms and disabilities, such as cognitive deficits, mood or anxiety disorders, motor impairments, chronic pain, and epilepsy. We investigated the detectability of secondary injury at a chronic time-point using ex vivo diffusion tensor imaging (DTI) in a rat model of TBI, lateral fluid percussion (LFP) injury. Our analysis of ex vivo DTI data revealed persistent microstructural tissue changes in white matter tracts, such as the splenium of the corpus callosum, angular bundle, and internal capsule. Histologic examination revealed mainly loss of myelinated axons and/or iron accumulation. Gray matter areas in the thalamus exhibited an increase in fractional anisotropy associated with neurodegeneration, myelinated fiber loss, and/or calcifications at the chronic phase. In addition, we examined whether these changes could also be detected with in vivo settings at the same chronic time-point. Our results provide insight into DTI detection of microstructural changes in the chronic phase of TBI, and elucidate how these changes correlate with cellular level alterations.