An epidural hematoma is defined as symptomatic bleeding within the spinal neuraxis.
The pathogenesis is still unknown although many theories exist, including epidural venous bleeding, epidural arterial bleeding, and bleeding from vascular malformations,
Coagulopathies, traumatic needle insertion during placement of an epidural catheter or performance of a spinal anesthetic and spontaneous bleeding are all thought to play a role in the development of epidural hematomas. In a metaanalysis of 613 case reports from 1826-1996, the primary etiology of epidural hematoma was idiopathic, followed by complications from anticoagulant therapy and vascular malformations. The fifth most common cause was spinal and epidural procedures in the presence of anticoagulation while the tenth most common etiology was spinal and epidural procedures without anticoagulation. [Kreppel, D, Antoniadis, G, Seeling, W. Spinal Hematoma: A literature survey with Meta-analysis of 613 patients. Neurosurg Rev. 26: 1-49, 2003.]
Onset is usually within 0 to 2 days.
Symptoms include both motor and sensory deficits, changes in bowel and bladder function, and less likely is back pain.
The Facts about Epidural Hematomas
Much of what is known about epidural hematomas comes from case reports. In a literature review from 1906-1994 by Vandermeulen et al, sixty-one patients were diagnosed with a spinal hematoma that occurred after an epidural (46) or spinal (15). Forty-two of these (68%) occurred in patients with documented hemostatic abnormalities. Fifteen of these occurred after reportedly difficult catheter placement. Fifteen of 61 reported blood after catheter insertion. Thirty-two patients had an indwelling epidural catheter when they were diagnosed and 15 of 32 hematomas occurred immediately after removal of the catheter. In this literature review, 13% of diagnosed hematomas were without risk factors. The presenting symptoms included progression of sensory or motor block in 68% of cases or bowel/bladder dysfunction in 8% of cases. Only 38% of patients had partial neurologic recovery.[Vandermeulen EP, Van Aken H, Vermylen J, et al: Anticoagulants and Spinal-Epidural anesthesia. Anesth Analg 79: 1165-1177, 1994.]
Risk Factors for Major Bleeding during Anticoagulation
Increased age, history of GI bleeding, aspirin use during anticoagulation, length of therapy, female gender, and intensity of anticoagulant effect (ie INR 2-3 less likely to cause major bleeding than INR >4)are all known risk factors for bleeding during anticoagulation and also increase the risk of an epidural hematoma. [Levine, MN, Raskob G, Landefelt S, Kearon C. Hemorrhagic complications of anti-coagulant treatment. Chest 2001; 110: 108S-121S.]
Computed tomography or CT myelogram used to be imaging modality of choice prior to MRI. One reason CT has fallen out of favor is that the findings of epidural hematoma can mimic an extruded disc or free fragment disc herniation. The “gold standard” for diagnosis now is magnetic resonance imaging (MRI). In the acute stage(<24hrs) the blood is iso-intense on T1 with a homogenous high signal on T2. Greater than 24 hours out, there is a high signal on T1 weighted images with the same signal as CSF on T2 weighted images. [Ng WH, Lim CC, Ng PY, Tan KK. Spinal epidural hematoma: MRI-aided diagnosis. J Clin Neuroscience. 9:92-94, 2002.]