Postoperative spinal epidural hematomas, although rare, are classic complication of spinal surgery. The incidence were reported by Scavarda et al.5
and Lawton et al.6
(0.1%), Uribe et al. (0.22%).1
Uribe et al. also reported the series of delayed postoperative spinal epidural hematoma (DPOSEH) defined as neurologic deterioration more than 3 days after operation, the incidence as 0.17%.
In our series, SEH occurred at a rate of 0.24% and 0.19% excluding SEH after invasive procedure. 2 cases (0.05%) showed a feature of DPOSEH. We also examined 5 patients (excluded in our study) with hematoma developed in the soft tissues after cervical anterior fusion. They showed swelling on the neck and respiratory distress as initial symptom of hematoma in a common feature. After surgically treated, they were recovered normally and showed no neurological impairment.
The decision to reoperate after spinal surgery because of neurologic deterioration with a support of complementary radiologic investigation is common in the present time. Epidural hematoma should be suspected in patients presenting with a new postoperative deficit,2
and rapid surgery is a determinant factor of a full neurologic recovery.5
However, postoperative cord dysfunction may also be caused by spinal cord injury during surgery and incorrect alignment of the spine associated with graft complication.7
So the accurate radiologic diagnosis before reoperation is prerequisite for successful treatment. MRI has replaced computed tomography or myelography as the screening test for the diagnosis of SEH. The sagittal MRI and parasagittal images usually demonstrate that the lesion is present in the dorsal epidural space and in some cases extends laterally. The MRI features were quite specific for hemorrhage, including isointense signal on T1-weighted images, high signal on T2-weighted images in acute cases and increased signal intensity on both T1 - and T2 -weighted images in subacute cases.8-11
In a case of hyperacute stage of the hematoma, contrast-enhanced MR images may be useful. After IV contrast(Gadolinium) material administration, sizeable dotted enhancement was noted in the hematoma, thus suggesting the extravasation of contrast-enhanced blood. Furthermore, a sizeable enhancement in the hyperacute stage of the hematoma itself might indicate continuing bleeding.12
MRI was more helpful than CT in defining the extent, volume and precise location of epidural hematoma in our series.
Multilevel surgical procedures and the presence of a preoperative coagulopathy are established significant risk factors for epidural hematoma after spinal surgery.2
Groen et al.8
reported larger exposures of the epidural space may increase the risk of insidious bleeding from the prominent internal vertebral venous plexus and subsequently form a hematoma as well. Spontaneous epidural hematomas have been reported in those with liver disease and coagulopathy.13
In our series, only 2 patients had abnormal coagulation function tests at the time of the initial operation. Patient 3 had been treated with coumadization for deep vein thrombosis and patient 8 had liver cirrhosis with HCV infection. In the normal coagulation function test group, patient 5 had a medical history of end stage renal disease and treated with hemodialysis, patient 9 was diagnosed as metastatic vertebral tumor from multiple myeloma assumed as having inadequate coagulation function, but not revealed at preoperative coagulation function test. From a results of our study, we assume that the primary disease having a tendency of bleeding, such as tumor with high vascularity (3 cases in our study), may contribute to increase the risk of spinal epidural hematoma. Although blood loss during operation, 1278 mL in average, was larger than usual spinal operation, there was insufficient evidence of assuming it as a risk factor of spinal epidural hematoma. Although the neurosurgeon was confident at the end of the initial surgery, inadequate hemostasis during this procedure cannot be definitely ruled out as a causal factor. Extra precautions for meticulous hemostasis during the surgical procedure should be considered in patients who require multilevel decompressions and/or have a preoperative coagulopathy.
The postoperative outcome after decompression was thought to be related to the preoperative neurological deficit (complete or incomplete motor or sensory deficit) and time interval to the decompression. Delamarter et al.14
demonstrated in a dog study that when compression of the spinal cord lasted 6 hours there was no neurologic recovery and that there was progressive necrosis of the spinal cord. Vandermeulen et al.15
found that most patients with an SEH that were decompressed surgically within 8 hours made good or partial recovery of neurologic function. In our study, the average operative interval of complete recovery group (29.3 hours) was shorter than incomplete recovery group (66.3 hours) but it was too small number of population to prove the risk factor. Immediate surgical evacuation of the hematoma resulted in neurological improvement in eight of our nine patients, demonstrating that the preoperative ASIA neurological grade may be helpful as a predictor of neurologic outcome of all postoperative symptomatic epidural hematoma patients. 1 case (patient 9) with preoperative complete neurologic deficit had no improvement at the last follow up. Our findings are consistent with other clinical reports describing the relationship of rapidity of surgical decompression, neurologic grade and outcome.4,16-20
By the results of our study, it is important to diagnose an epidural hematoma as soon as possible and to evacuate hematoma immediately. The retrospective design and the rarity of the complication limit this study. The rare occurrence of this complication precludes any other reasonable study design unless there is a multicenter effort. The incidence of coagulopathies may not be accurate because some coagulopathies may be undiagnosed or unreported. Future studies to elucidate more risk factors and factors predisposed to improve surgical outcome would benefit from a multicenter effort to address the rare occurrence of postsurgical epidural hematomas.