THE STEREOTACTICAL PHENOMENA in

Traumatic Brain Injury Biomechanics -

deep cerebral lesions and brain concussion

Traumatic Brain Injury (TBI) is the consequence of the spatiotemporal pressure variations occuring inside the brain during head traumas. The spatial distribution of the pressure gradient (PG) is responsible for the cerebral lesions' localisation and the consequent neurological signs. Beside skull's deformation caused by the contact loading and determining skull vibrations and/or fractures, current biomechanical theories concern two inertial phenomena: the linear acceleration and the rotational head movements. The first theory explains the superficial brain lesions and is widely accepted. The second theory better explain the deep cerebral lesions and the concussion mechanism but is still controversed. The stereotactical approach here exposed mainly considers the approximately spherical shape of the interface skull-brain. The skull-brain relative movements, caused by the acceleration phenomena - linear or rotational - and by the skull vibrations, generate secondary pressure waves with approximately spherical wave fronts that concentrically propagate toward the deep cerebral structures. The wave front's spoke and its surface progressively decreases. According to the energy conservation law, the amplitude of the pressure waves progressively increases. Thus, the PG will be maximal in the geometrical centre of the implied skull vault segment. The stereotactical phenomena can explain common posttraumatic neurological signs and cerebral lesions and is compatible with previously reported experimental findings. Its complementarity with the other biomechanical theories could allow us to integrate the TBI biomechanics in a common concept in order to better understand the TBI pathophysiology and also related pathological entities like boxers' chronic encephalopathy or even Alzheimer's disease. Further experimental and especially human observational research on the TBI biomechanics is needed.