engleski

Between Neuroradiology and Neurophysiology: New Insights in Neural Mechanisms

Starting from the assumption that nerves are not simply inert tubular structures limited to the conduction of sensory and motor information, but that they do also show inherent protective mechanisms that may impact on their very function, this doctoral dissertation is going to present arguments to support the notion that i) nerves move, and that their movements can be quantified using appropriate non- invasive techniques, and ii) the human body does present some innate mechanisms to protect nerves from excessive mechanical forces. In this thesis T2 weighted turbo spin echo fat saturation magnetic resonance sequences were used to visualize the conus medullaris displacement in response to unilateral and bilateral SLR following the notion that the magnitude of conus medullaris displacement in response to SLRs is proportional to the displacement of L5 and S1 nerve roots and dependent on the number of nerve roots involved in the movement (i.e. unilateral and bilateral SLRs), as dictated by the “principle of linear dependence” here presented for the first time. Furthermore, surface electromyography was employed to quantify muscular responses to neural mechanical testing in in-vivo and structurally intact human subjects in order to explore whether muscles can be reflexively activated in order to protect the nerves by i) avoiding further elongation of neural bed, ii) shortening the neural pathway in order to decrease tensile stress. The neuroradiology line results show that the conus medullaris displaces consistently in response to SLRs and that the magnitude of displacement is doubled with bilateral SLR, suggesting that a linear relationship may exist between magnitude of conus displacement and number of nerve roots involved into this movement. Moreover, the unpublished data presented in this thesis shows that this relationship is maintained at higher degrees of hip flexion. The neurophysiology line results show that changes in myoelectric activity in the test muscles are an expression of a specific protective response related to mechanical force acting on peripheral neural tissues, and that these can be modified with positions that decrease tensile forces from the brachial plexus and peripheral nerves. The unpublished data related to this line of research shows clearly that this activity is modulated and highly specific. With the cumulative results of these two lines of research, in which nerves are shown to move in response to body movements (neuroradiology) and muscular protective mechanisms in response to mechanical stress applied on peripheral nerves are proved to exist (neurophysiology), we hypothesize that the sliding of neural structures in anatomical tunnels and canals may be a protective effect which preserves the spinal cord, neural roots and peripheral nerves from strain and compression, and that inherent protective mechanisms are activated in case sliding effect fails. Importantly, it seems that these reactions do bear aspects of predictability.

nerve ; nerve root ; spinal cord ; sciatica ; radiculopathy ; low back pain ; straight leg raise ; muscle ; electromyography ; epicondylalgia ; elbow ; tennis elbow syndrome ; radial nerve ; nociceptive flexion reflex.

nije evidentirano