神経ブロック時の眼窩下神経の形態学的変化

抄録

A high dose local anesthetic, 5% lidocaine, and a semi-permanent neurolytic agent, 99% alcohol, were infused at the infraorbital foramen. The purpose of the paper is the progression in morphological change was observed light microscopically and electron, from nerve injury to regeneration. Immediately after drug injection, there were no significant changes seen in either the alcohol or lidocaine treated groups. One day after drug injection, both the alcohol treated group and the lidocaine treated group showed almost complete destruction of the myelinated nerve fibers within the fascicle. In the alcohol treated group, this damaged state persisted for 1 month post-injection. In the lidocaine treated group, however, there was a 50% reduction in the number of damaged myelinated fibres by the 3 day post-injection. In the alcohol treated group, it was observed that between 2 months and 3 months post-injection. 75% of the myelinated nerve fibers were less than 5μm in diameter, while 20% were thick myelinated nerve fibers greater than 5μm. 6 months after the injection, it was observed that 70% of myelinated nerve fibers were of thick diameter, whilst 30% were thin. These values were very similar to those seen in the control group. In the lidocaine treated group, it was observed that from 1 week to 6 months post-injection, the percentage of myelinated nerve fibers less than 5μm gradually decreased, while the percentage of fibers greater than 5μm increased. Approximately 5% of the fibres remained damaged. Our results demonstrate that the percentage of thick myelinated nerve fibers increased between 3 months and 6 months post-injection. This period correlates well with the period of time taken for clinical re-block administration. This correlation suggests that it takes a set amount of time for regenerative nerve fibers within the fascicle to grow to a length exceeding 5μm and become functional. This further suggests that sensory function is regained even before the ratio of thick and thin myelinated nerve fibers returns to normal levels.