From his previous renal cancer history, T4 vertebral metastasis were highly suspected, which was furtherly verified by needle biopsy pathological results. Symptoms, clinical examinations, and medical images were all consistent with that solitary metastasis from renal carcinoma, which caused neurological deficits below the lesion site. About the surgery indications for vertebral metastasis, palliative decompression surgery can be suggested in the treatment of acute spinal cord compression for relieving symptoms and improving quality of life [11,12]. For more invasive surgery, e.g., en bloc resection of tumor, should be only considered when solitary lesion site is present and optimistic prognosis is expected [13,14]. To determine the most reasonable treatment plan for the patients with metastasis, Tomita's Scoring System are widely used to assess the patient's prognosis [11] [15]. According to the scoring system, grade of malignancy of the primary tumors, visceral and bone metastases are overall considered. About this patient, he was scored 3/10, which indicated he probably had a long-life expectancy, and the aim of surgery was long term local control, to achieve this, TES is the most promising method.
What was confusing was that the muscle power of lower limbs started to get paralyzed 10 hours after operation. Though, no similar delayed paraplegia were reported before, the most likely reasons for paraplegia after TES are spinal cord injury, epidural hematoma formation, and spinal cord ischemia [16-18]. In operation, special attention was paid to protect spinal cord, all procedures close to it were very careful, and no injury of spinal cord was noticed, which was verified by the fact that neurological status immediately after operation was just as the preoperative situation, and intraoperative spinal function monitoring may help identify spinal cord injury in time [19]. Concerning the discharge from drainage tube was about 1000ml on the first day after operation, so it was obviously unobstructed. Furtherly, no spinal cord compression was found in emergent CT scan images. Therefore, epidural hematoma and other spinal cord compressive factors were excluded. Therefore, spinal cord ischemia may be the main reasons for postoperative paralysis. It is well known that blood supply for spinal cord in thoracic segment is mainly from anterior spinal artery with poor collateral circulation [20], and the blood supply is easy to be influenced by atherosclerosis, operative maneuvers, blood pressure and vasoconstriction. In this case, a pair of segmental arteries had to be embolized before operation to reduce blood loss, which may reduce blood supply to the target spinal cord but should not be significantly, and no neurological deterioration was found in this case after that procedure. For TES, preoperative embolization was reported to be safe and can reduce intraoperative blood loss significantly, however, paraplegia arising from the procedure was not reported [20-21]. Except for one pair of embolized segmental arteries, operators confirmed no damage to other blood supplies. Besides, blood pressure also plays an important role in blood supply of spinal cord [8], when we think of the issue of low blood pressure (70/40mmHg) did happen after the use of cefuroxime sodium during vertebral prosthesis implantation, which was a delicate moment for spinal cord, because manipulation, low blood pressure and preoperative embolization may together reduce the blood supply to spinal cord. Now therefore, it is highly suspected that on the basis of atherosclerosis, antibiotics or other medicines caused anaphylactic low blood pressure, at the same time, operations may interrupt the circulation of spinal cord, they both together led to thrombosis of anterior spinal artery. Even worse, norepinephrine and fluid supplementation were given to elevate blood pressure, when blood pressure got elevated, ischemia-reperfusion injury may furtherly damage spinal cord, and Riluzole was substantiated to reduce this injury [22]. Physical examinations found incomplete paraplegia, that was complete loss of power but without sensory abnormalities and without sphincter dysfunction, which were consistent with syndrome of anterior spinal artery infarction (pseudo-poliomyelitic form), because of ischemia of anterior horns [23]. Several top experts in surgical treatments of vertebrae metastasis were consulted about this case, for example, Boriani, Jianru Xiao, etc., who all agreed that it may be caused by intraoperative hypotension. Therefore, blood pressure must be kept at an appropriate range during TES of thoracic metastases.
Allergic rashes were found after operation, and cefuroxime sodium may be the most likely allergen, even though preoperative skin testing was negative. That is because degradation of cephalosporins are multiple and unstable antigenic fragments which are not fully understood. Without validated reagents and reference standard for cephalosporin skin testing, false-negatives or positives are inevitable [24,25].
Literature review
After TES, the maximum rate of neurological deterioration was reported to be 29%, and preoperative neurological deficits, postoperative cerebrospinal fluid leakage, and surgical site infections were risk factors for poor activities of daily living (ADLs) after surgery [26]. However, to the best of our knowledge, no cases of delayed paraplegia after TES were reported. Except for epidural hematoma formation, the interruption of blood supply to spinal cord should be fully alert. For this case, the feeling deficit after surgery was termed conductive tract dissociative sensory disorder, which are typical symptoms of embolization of anterior spinal artery [23]. Neurosurgeons always think that appropriately lowered blood pressure can reduce bleeding and improves the surgical field, which may be true [27]. However, it is a dilemma in this case, low blood pressure was deemed to be the main reason for symptoms of spinal cord ischemia, and a couple of minutes of low blood pressure may result in spinal shock. Therefore, elevating mean systemic blood pressure is an effective method of increasing blood flow to spinal cord [8]. From our experiences, mean systemic blood pressure should be kept above 100mmHg during perioperative period. Intraoperative monitoring of somatosensory evoked potentials (SSEP) during surgical procedures may help identify ischemia of spinal cord in time. Continuous monitoring amplitude and latency of SSEP, and an increase of 10% latency was reported to be a sign of reduction of spinal cord perfusion [19].
Before operation, preconditioning hyperbaric oxygen can induce tolerance of spinal cord against ischemia and attenuate early apoptosis of spinal cord cells by upregulation of antioxidant enzymes, which was verified in rabbits and rats [28-29]. To speak of the rehabilitation measures, hyperbaric oxygen treatment may play a role in function recovery of spinal cord after ischemia [30]. About this case, hyperbaric oxygen treatment was started 3 days after operation, 90 minutes each day, and obvious improvements of both lower limbs’ power could be seen (from ASIA B to D), while it still needs more data to evaluate its effectiveness on spinal cord ischemia. Although there is widespread controversy, methylprednisolone is often used in acute spinal cord injury [31]. For this case, 30mg methylprednisolone per Kg of body weight was given intravenously within 15 minutes once neurological deterioration was found, and the medicine was used as reported in literatures [31]. Besides, dehydrate agents, neurotrophic and neuroprotective agents can be considered to protect and facilitate rehabilitation of spinal cord function, but there are short of consistent clinical evidence [22,32-33]. Although often overlooked, compensation collateral circulation, including the system of epidural arcades in the immediate setting, and paraspinal collaterals in the long run, may play a role in functional recovery of spinal cord [34]. Thrombus recanalization, even rare, may be another reason for the recovery of spinal cord function [35]. Therefore, spasmolytic, anticoagulants and other drugs which improve circulation also can be used in appropriate time.