Abstract
Subdural hematoma (SDH) is the most common finding after abusive head trauma (AHT). Hemispheric hypodensity (HH) is a radiological indicator of severe brain damage that encompasses multiple vascular territories, and may develop in the hemisphere(s) underlying the SDH. In some instances where the SDH is predominantly unilateral, the widespread damage is unilateral underlying the SDH. To date, no animal model has successfully replicated this pattern of injury. We combined escalating severities of the injuries and insults commonly associated with HH including SDH, impact, mass effect, seizures, apnea, and hypoventilation to create an experimental model of HH in piglets aged 1 week (comparable to human infants) to 1 month (comparable to human toddlers). Unilateral HH evolved over 24 h when kainic acid was applied ipsilateral to the SDH to induce seizures. Pathological examination revealed a hypoxic-ischemic injury-type pattern with vasogenic edema through much of the cortical ribbon with relative sparing of deep gray matter. The percentage of the hemisphere that was damaged was greater on the ipsilateral versus contralateral side and was positively correlated with SDH area and estimated seizure duration. Further studies are needed to parse out the pathophysiology of this injury and to determine if multiple injuries and insults act synergistically to induce a metabolic mismatch or if the mechanism of trauma induces severe seizures that drive this distinctive pattern of injury.
Highlights
Traumatic brain injury (TBI) is the leading cause of acquired death and disability in children, and in children under age 2, the majority of severe TBI is due to abusive head trauma (AHT).[1]
Active caspase-3 was expressed by many non-pyramidal neurons or glial cells in both sham piglets and piglets receiving model injuries (Fig. 5G, sham piglet). This series of investigations has produced a model that enables the creation of hemispheric damage largely restricted to the hemisphere underlying the Subdural hematoma (SDH) in a pattern similar to children with radiographical unilateral hemispheric hypodensity.[6,7]
The tissue damage extends beyond the cortical impact site and the area covered by the unilateral SDH, and encompasses the entire cerebral cortex with relative sparing of deep nuclei, apart from in the most severe cases
Summary
Traumatic brain injury (TBI) is the leading cause of acquired death and disability in children, and in children under age 2, the majority of severe TBI is due to abusive head trauma (AHT).[1] Acute subdural hemorrhage (or hematoma; SDH) is the most common intracranial abnormality resulting from AHT and is observed radiologically in 81–91% of cases.[2,3,4] Hemispheric hypodensity (HH) is an injury pattern observed radiologically that is unique to infants and toddlers where there is uniform loss of gray-white differentiation in the entire hemisphere associated with the SDH encompassing all three vascular territories despite patent, large vessels.[3,4,5] The HH pattern may be visible by imaging within hours of arrival to the hospital or may evolve over days.[6] Significant biomechanical forces result in SDH, subarachnoid hemorrhage, often with evidence of an impact event (skull fracture, scalp contusions, or subgaleal hematomas), and apnea.[7] Eventual atrophy of the entire cortical ribbon in the hemisphere underlying the SDH may result in a lifetime of severe motor impairment (hemiparesis or quadraparesis), cognitive impairment, post-traumatic epilepsy, and blindness, or may result in death.[6,8,9]
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