43.脊髓橫斷時會立即呈現下列何種症狀？
(A)脊髓休克（spinal shock）
(B)肌肉痙攣（muscle spasticity）
(C)過度反射（hyper-reflexia）
(D)腦死（brain death）

脊髓損傷患者，常見的症狀與徵象主要為脊髓休克：即受傷部位以下立即喪失所有的反射、運動、感覺及自主神經功能，造成肢體麻痺、呼吸困難、尿液滯留、腸蠕動變慢等臨床表徵，時間可能持續數天至數星期。

其次為神經性休克：主要是因交感神經衝動無法傳出，使周邊血管擴張、心輸出量減少，而呈現神經休克狀態，特別是第6胸椎以上受傷者，患者容易出現低血壓、心跳過慢、中心靜脈壓下降、甚至於體溫過低情形。

Spinal shock was a loss of sensation accompanied by motor paralysis with initial loss but gradual recovery of reflexes, following a spinal cord injury (SCI) – most often a complete transection.

Phase 1 is characterized by a complete loss—or weakening—of all reflexes below the SCI. This phase lasts for a day. The neurons involved in various reflex arcs normally receive a basal level of excitatory stimulation from the brain. After an SCI, these cells lose this input, and the neurons involved become hyperpolarized and therefore less responsive to stimuli.

Phase 2 occurs over the next two days, and is characterized by the return of some, but not all, reflexes below the SCI. The first reflexes to reappear are polysynaptic in nature, such as the bulbocavernosus reflex. Monosynaptic reflexes, such as the deep tendon reflexes, are not restored until Phase 3. Restoration of reflexes is not rostral to caudal as previously (and commonly) believed, but instead proceeds from polysynaptic to monosynaptic. The reason reflexes return is the hypersensitivity of reflex muscles following denervation – more receptors for neurotransmitters are expressed and are therefore easier to stimulate.

Phases 3 and 4 are characterized by hyperreflexia, or abnormally strong reflexes usually produced with minimal stimulation. Interneurons and lower motor neurons below the SCI begin sprouting, attempting to re-establish synapses. The first synapses to form are from shorter axons, usually from interneurons – this categorizes Phase 3. Phase 4 on the other hand, is soma-mediated, and will take longer for the soma to transport various growth factors, including proteins, to the end of the axon.