Ephaptic transmission as an explanatory mechanism of radicular pain.To the Editor: Lower back pain with radicular radicular /ra·dic·u·lar/ (rah-dik´u-lar) of or pertaining to a root or radicle. ra·dic·u·lar adj. 1. Relating to a radicle. 2. Relating to the root of a tooth. symptomatology symptomatology /symp·to·ma·tol·o·gy/ (simp?to-mah-tol´ah-je) 1. the branch of medicine dealing with symptoms. 2. the combined symptoms of a disease. symp·to·ma·tol·o·gy n. is a common clinical entity that affects hundreds of thousands of people every year. In the vast majority of these cases, disk herniation herniation /her·ni·a·tion/ (her?ne-a´shun) abnormal protrusion of an organ or other body structure through a defect or natural opening in a covering, membrane, muscle, or bone. is evident on the patients' radiologic evaluation. However, as occasionally encountered in our institution, a fraction of these patients harbor disk prolapse prolapse Protrusion of an internal organ out of its normal place, usually of the rectum or uterus outside the body when supporting muscles weaken. The membrane lining the rectum can push out through the anus, most often in old people with constipation who strain during which is minimal or moderate, but definitely disproportionate to their symptomatology. A common intraoperative finding in this group of patients is an enlarged and rich epidural venous network, sometimes with compression of the exiting nerve root caused by the enlarged epidural veins. The theory of ephaptic transmission seems to be a very appealing explanatory pathophysiologic mechanism of low back pain and radicular symptomatology in these patients. (1,2) The very same theory has been widely accepted in the pathogenesis of neuralgia of the cranial nerves; idiopathic trigeminal neuralgia cases are most often attributed to irritation of the trigeminal nerve by adjacent venous structures. In recent years, this theory has been proposed by some clinical investigators as a mechanism responsible for peripheral nerve pain. (3-5) A variety of primary causes of epidural venous enlargement have been implicated. Trauma, herniated disks, tumors, as well as congenital causes and vascular malformation may lead to engorgement engorgement /en·gorge·ment/ (en-gorj´ment) 1. local congestion; distention with fluids. 2. hyperemia. engorgement distention. of the epidural venous network and subsequently to compression of neural structures. Recently, Paksoy et al (3) found that 0.13% of patients who presented to their clinic with low back pain or sciatica demonstrated epidural or paravertebral venous enlargement secondary to inferior vena caval obstruction. They concluded that inferior vena caval thrombosis or compression should be suspected in cases of low back pain and radicular symptoms with signs of venous enlargement on MRI. It is the authors' belief that thorough preoperative evaluation of the epidural venous network could be beneficial in patients with lower back symptomatology. Venous compression of nerve roots may be a significantly underestimated cause of these patients' symptoms. In addition, dissection of the symptomatic neural structure from any enlarged epidural veins could be important for the patients' improvement. We believe that the existence of an enlarged epidural venous network along with the morphology of the involved exiting nerve root (edematous or ischemic Ischemic An inadequate supply of blood to a part of the body, caused by partial or total blockage of an artery. Mentioned in: Antiangiogenic Therapy, Subarachnoid Hemorrhage, Ventricular Fibrillation ischemic ) represent two parameters that could significantly influence the patients' clinical outcome. References 1. Seltzerz DM. Ephaptic transmission in chronically damaged peripheral nerves. Neurology 1979;29:1061-1064. 2. Tomasulo RA. Aberrant conduction in human peripheral nerve: Ephaptic transmission? Neurology 1982;32:712-719. 3. Paksoy Y, Gormus N. Epidural venous plexus enlargements presenting with radiculopathy and back pain in patients with inferior vena cava inferior vena cava n. Abbr. IVC A large vein formed by the union of the two common iliac veins that receives blood from the lower limbs and the pelvic and abdominal viscera and empties into the right atrium of the heart. obstruction or occlusion. Spine 2004;29:2419-2424. 4. LaBan MM, Ay-Ming W, Shetty A, et al. Varicosities of the paravertebral plexus of veins associated with nocturnal spinal pain as imaged by MR venography Venography Definition Venography is an x-ray test that provides an image of the leg veins after a contrast dye is injected into a vein in the patient's foot. . Am J Phys Med Rehabil. 1999;78:72-76. 5. Hammer A, Knight I, Agarwal A. Localized venous plexi in the spine simulating prolapse of an intervertebral intervertebral /in·ter·ver·te·bral/ (-ver´te-bral) situated between two contiguous vertebrae; see under disk. in·ter·ver·te·bral adj. Located between vertebrae. disc: a report of six cases. Spine 2003;28:E5-E12. Theofilos Machinis, MD Kostas N. Fountas, MD, PHD Department of Neurosurgery Medical Center of Central Georgia The Medical Center of Central Georgia (MCCG) is a 637-bed hospital located in Macon, Georgia. MCCG is the second largest hospital in Georgia. MCCG is a teaching hospital affiliated with Mercer University Medical School and Level I trauma center. Macon, GA |
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