Symptomatic thoracic disc herniation is an uncommon problem. Although the reported incidence of symptomatic thoracic disc herniations is relatively low, asymptomatic thoracic disc protrusions are estimated to be as high as 37% [8
]. Protruded thoracic disc causing cord compression is estimated to 0.25-0.75 per cent of all symptomatic intervertebral discs [9
]. Asymptomatic thoracic disc herniations are accidentally diagnosed with MRI.
Our case illustrates a demonstration to remember potential causes of transient or permanent neurological deficits following epidural anesthesia. Complications of regional spinal anesthesia are; intravascular injection of anesthetic media throughout spinal veins causing toxicity, inaccurately introduced anesthetic agent into the subarachnoid space which may cause central nervous system (CNS) dysfunction, high level anesthesia causing respiratory or CNS dysfunction, and dorsal pain or post-anesthesia headache. Potential causes of paraplegia coincident with spinal anesthesia includes: epidural and subdural hematoma associated with systemic heparinization or platelet dysfunctions, spinal cord ischemia associated with thrombosis of anterior spinal artery, spinal cord traumas related to direct needle injuries or chemical toxicity of the anesthetic agents [10
]. In our case, lack of evidence for hematoma and normal signal intensity of the spinal cord in MRI ruled out these complications. In a recent report by Chan et al an elderly male in whom hypotension and sudden onset paraplegia had occurred following epidural anesthesia has been presented. The patient has been reported to have atherosclerosis and thrombogenic risk factors that had an impact on spinal cord circulation. On repeated MRI scans diffuse ischemic findings have been demonstrated which were highly specific for spinal cord ischemia [12
Blood supply of the spinal cord may be affected by combination of various factors [2
]. There is a minimum perfusion pressure to maintain spinal perfusion and to prevent spinal cord infarction. Hypotension during epidural anesthesia is an expected complication but dropped systolic pressure more than 60-80 mmHg increases the risk of spinal cord ischemia. As in our case with hyperkyphosis during the procedure may increase the risk of spinal cord ischemia if there is an underlying precipitating factor like thoracic disc protrusion compressing the spinal cord. Besides, introducing excessive amount of anesthetics into the epidural space may cause an increase in cerebrospinal fluid pressure and vascular stasis as well [15
]. Using adrenalin boost the effect of anesthetic’s activity but doses more than 1:160 000 dilution may cause thrombosis or vasospasm in the spinal cord vasculature [2
]. Additionally, individual characteristics of the spinal cord vasculature and segmental deficiency of the anterior spinal artery may further precipitate the risk of ischemia in some patients [1
Reactivation of earlier disc diseases with spinal procedures is reported to be rare [17
]. In our patient, a large disc protrusion far from the catheter level without any additional pathology has been demonstrated on MRI. Based on medical records and patients self report, we found that patient’s thoracic disc herniation was asymptomatic prior to the operation. However, it is not clear that positioning for epidural procedure or surgical intervention had a role to aggravate disc protrusion or not.
In summary, we underscore the necessity to be aware of preceding disc protrusions or other factors, which had detrimental role in spinal cord perfusion, as a cause of persistent or transient paraplegia before epidural anesthesia.