Magnetic Resonance Imaging of Regional Hemodynamic and Cerebrovascular Recovery after Lateral Fluid-Percussion Brain Injury in Rats

Abstract

Hemodynamic and cerebrovascular factors are crucially involved in secondary damage after traumatic brain injury (TBI). With magnetic resonance imaging, this study aimed to quantify regional cerebral blood flow (CBF) by arterial spin labeling and cerebral blood volume by using an intravascular contrast agent, during 14 days after lateral fluid-percussion injury (LFPI) in rats. Immunohistochemical analysis of vessel density was used to evaluate the contribution of vascular damage. Results show widespread ipsilateral and contralateral hypoperfusion, including both the cortex and the hippocampus bilaterally, as well as the ipsilateral thalamus. Hemodynamic unrest may partly be explained by an increase in blood vessel density over a period of 2 weeks in the ipsilateral hippocampus and perilesional cortex. Furthermore, three phases of perilesional alterations in CBF, progressing from hypoperfusion to normal and back to hypoperfusion within 2 weeks were shown for the first time in a rat TBI model. These three phases were similar to hemodynamic fluctuations reported in TBI patients. This makes it feasible to use LFPI in rats to study mechanisms behind hemodynamic changes and to explore novel therapeutic approaches for secondary brain damage after TBI.

Chronic Hyperperfusion and Angiogenesis Follow Subacute Hypoperfusion in the Thalamus of Rats with Focal Cerebral Ischemia

“…In our study, the dosage of anesthesia was consistently moderated to be minimal by measuring the breathing rate throughout imaging, and all results comparisons were made with sham-operated rats undergoing the same procedures. The measurement of blood-derived physiological variables such as pH, pO 2 , and pCO 2 would provide additional support to a proposal of physiological normality during MRI, yet this has been successfully achieved during longer (90 minutes) imaging sessions in our previous studies under similar conditions (Hayward et al, 2010). Further, catheter insertion and removal would interfere with the behavioral performance tests.…”

Monitoring Functional Impairment and Recovery after Traumatic Brain Injury in Rats by fMRI

“…[2][3][4][5] The molecular and cellular reorganization patterns that follow TBI are accompanied by hemodynamic alterations. [6][7][8][9][10] Depending upon severity, TBI can lead to long-lasting disabilities, such as motor and cognitive impairment, psychiatric comorbidities, and post-traumatic epilepsy. 3,11,12 The therapeutic window for recovery-enhancing treatments and antiepileptogenesis includes the time period of secondary damage and consequent repair.…”

Cerebrovascular Connexin Expression: Effects of Traumatic Brain Injury

“…However, other investigators observed an inconsistent correlation between CBF and vascular remodeling after TBI. Hayward and colleagues reported significant changes in CBF and vascular density in rats within 14 days (Hayward et al, 2011) and 8 months (Hayward et al, 2010) after lateral fluid-percussion TBI. Significant hypoperfusion, then normalization of CBF, then subsequent hypoperfusion, were observed along with an increase in cerebral vascular density during the 14-day monitoring period after TBI (Hayward et al, 2011).…”

“…Hayward and colleagues reported significant changes in CBF and vascular density in rats within 14 days (Hayward et al, 2011) and 8 months (Hayward et al, 2010) after lateral fluid-percussion TBI. Significant hypoperfusion, then normalization of CBF, then subsequent hypoperfusion, were observed along with an increase in cerebral vascular density during the 14-day monitoring period after TBI (Hayward et al, 2011). In contrast, at 8 months postinjury, although CBF and vascular density correlated in a few brain regions (e.g., thalamus), in general, they were not significantly related (Hayward et al, 2010).…”