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Early cerebrovascular response to head injury in immature and mature rats
P D Grundl1, K V Biagas, P M Kochanek
1Department of Anesthesiology/Critical Care Medicine, University of Pittsburgh School of Medicine, Pennsylvania.
Insights
Pediatric head injury shows earlier brain swelling and less severe blood flow reduction compared to adult injury. This animal model confirms age-related differences in traumatic brain injury response.
Area of Science:
- Neuroscience
- Pediatric Traumatology
- Comparative Physiology
Background:
- Clinical observations indicate children exhibit more pronounced cerebral edema and hyperemia following head injury than adults.
- Age-related differences in traumatic brain injury (TBI) response require investigation in controlled animal models.
Purpose of the Study:
- To investigate age-related differences in cerebral edema, infarct size, intracranial pressure, and cerebral blood flow following controlled TBI in an animal model.
- To compare the physiological responses to TBI in immature versus mature rats.
Main Methods:
- Anesthetized and ventilated mature and immature Wistar rats underwent controlled weight-drop TBI to the parietal cortex.
- Measurements included percent right hemispheric brain water (%RBW), infarct area, intracranial pressure (ICP), and local cerebral blood flow (ICBF) using 14C-iodoantipyrine autoradiography at various time points post-trauma.
Main Results:
- Immature rats showed earlier and sustained increases in %RBW compared to mature rats.
- Cerebral hypoperfusion (reduced ICBF) was less pronounced in immature rats than in mature rats post-TBI.
- Intracranial pressure increased in both groups at 24 hours, and infarct size did not differ significantly between age groups.
Conclusions:
- Immature rats exhibit an earlier onset of cerebral edema and a less severe reduction in cerebral blood flow post-TBI compared to mature rats.
- These findings support the hypothesis of age-related differences in TBI pathophysiology, with immature brains responding with earlier edema and relative preservation of blood flow.
Abstract:
Clinical studies suggest that children respond to head injury with more pronounced cerebral edema and hyperemia than do adults. We hypothesized that these age-related differences could be demonstrated in an animal model. Anesthetized and ventilated mature (2-3 months) and immature (3.5-4.5 weeks) male Wistar rats were traumatized by weight drop onto the exposed right parietal cortex. Trauma severity was adjusted to keep the ratio of force to brain weight constant. This resulted in an energy delivered to the brain of about 9 x 10(3) ergs.mm-2.g-1 brain in both age groups. Percent right hemispheric brain water (%RBW) was measured at 2, 24, 48, and 168 h posttrauma. Infarct area, intracranial pressure (ICP), and 14C-iodoantipyrine autoradiographic local cerebral blood flow (ICBF) were measured at 2 h or 24 h posttrauma. In mature rats, %RBW was unchanged at 2 h, but increased at 24 and 48 h (both p < 0.05). In immature rats, %RBW increased at 2 h and remained elevated at 24 and 48 h (all p < 0.05). Traumatic infarct area as a percent of hemispheric area at 24 h did not differ between age groups. In mature rats, at 2 h posttrauma ICBF was reduced (p < 0.05) in 16 of 17 regions but in only 4 of 17 regions in immature rats. ICBF as a percent of age-matched control values showed a greater reduction in mature vs immature rats in 9 of 16 regions (p < 0.05). ICP increased at 24 h posttrauma in both age groups. In immature rats posttrauma, brain water increased earlier and cerebral hypoperfusion was less marked than in mature rats.