Hadzic's Regional Anesthesia > Part XI. Neurologic Complications of Regional Anesthesia > Chapter 69. Neurologic Complications of Peripheral Nerve Blocks: Mechanisms & Management Basic Considerations Steven Deschner, MD, Alain Borgeat, MD, Admir Hadzic, MD

Clinical Classification of Acute Nerve Injuries

"Classification of acute nerve injuries is useful when considering the physical and functional state of damaged nerves. In his classification, Seddon¹¹ introduced the terms neurapraxia, axonotmesis, and neurotmesis (Table 69–2); Sunderland¹² subsequently proposed a five-grade classification system.Rather than a relatively clear injury caused by sharp needle cuts, intraneural injection has the potential to create structural damage to the fascicle(s) that is more extensive and less likely to heal (Figure 69–2). Indeed, the devastating sequelae of sensory and motor loss after injection of various agents into peripheral nerves has been well documented.¹³ Nearly all experimental studies on this subject have demonstrated that the site of injection is critical in determining the degree and nature of injury. More specifically, to induce neurologic injury, the injectate must be injected intrafascicularly; extrafascicular injections of the same substance typically do not cause nerve injury.¹⁴ Thus, the main factor leading to a substantial peripheral nerve damage associated with injection techniques is injection of local anesthetic into a fascicle. This causes mechanical destruction of the fascicular architecture and sets into motion a cascade of pathophysiologic changes, including inflammation, cellular infiltration, axonal degeneration, and others—all possibly leading to nerve scarring and permanent neurologic impairement.Little is known about how to avoid an intraneural..."