Purpose: To evaluate morphological and physiological changes during acute lethal subdural bleeding in 2 models of anaesthetized dogs.
Material and methods: In model I, blood from the aorta was led into a collapsed subdural rubber balloon while in model II, the blood was directed into the subdural compartment over the left cerebral frontoparietal lobe. Eight vital physiological parameters were continuously registered. MR imaging visualized the compression and displacement of cerebral tissue, and assessed the dynamic changes in cerebral tissue water.
Results: In model I, tissue herniation and compression of cerebral ventricles led to death at a haematoma volume corresponding to 8% of the intracranial volume. In model II, the extravasated blood progressed infratentorially and into the spinal sac with a volume that was 3 times larger than that of the lethal haematoma. Tissue water increased almost linearly during bleeding in both models.
Conclusion: The high level of mortality after acute subdural haematoma is caused by a reduction in intracranial volume tolerance with a critical decrease in cerebral perfusion pressure, resulting in a fatal cerebral ischaemia.