Neurosciences Institute, Maine Medical Center Portland, ME, USA.
Front Hum Neurosci. 2013 Mar 18;7:85. doi: 10.3389/fnhum.2013.00085. eCollection 2013.
Hypertonia and hyperreflexia are classically described responses to upper motor neuron injury. However, acute hypotonia and areflexia with motor deficit are hallmark findings after many central nervous system insults such as acute stroke and spinal shock. Historic theories to explain these contradictory findings have implicated a number of potential mechanisms mostly relying on the loss of descending corticospinal input as the underlying etiology. Unfortunately, these simple descriptions consistently fail to adequately explain the pathophysiology and connectivity leading to acute hyporeflexia and delayed hyperreflexia that result from such insult. This article highlights the common observation of acute hyporeflexia after central nervous system insults and explores the underlying anatomy and physiology. Further, evidence for the underlying connectivity is presented and implicates the dominant role of supraspinal inhibitory influence originating in the supplementary motor area descending through the corticospinal tracts. Unlike traditional explanations, this theory more adequately explains the findings of postoperative supplementary motor area syndrome in which hyporeflexia motor deficit is observed acutely in the face of intact primary motor cortex connections to the spinal cord. Further, the proposed connectivity can be generalized to help explain other insults including stroke, atonic seizures, and spinal shock.
张力亢进和反射亢进是上运动神经元损伤的典型表现。然而，急性低张力和反射缺失伴运动障碍是许多中枢神经系统损伤后的标志性发现，如急性中风和脊髓休克。历史上的理论试图解释这些矛盾的发现，提出了许多潜在的机制，这些机制主要依赖于下行皮质脊髓传入的丧失作为潜在的病因。不幸的是，这些简单的描述始终不能充分解释导致这种损伤后急性反射减退和延迟反射亢进的病理生理学和连接。本文强调了中枢神经系统损伤后急性反射减退的常见观察，并探讨了潜在的解剖学和生理学。此外，还提出了潜在连接的证据，并暗示了源自辅助运动区的至上性抑制影响的主导作用，该影响通过皮质脊髓束下行。与传统解释不同，该理论更充分地解释了术后辅助运动区综合征的发现，在该综合征中，尽管初级运动皮层与脊髓的连接完整，但仍会出现反射减退和运动功能障碍。此外，所提出的连接性可以推广到其他损伤的解释中，包括中风、张力性发作和脊髓休克。
