Diagnosis When all components of the lumbar disc syndrome are present, diagnosis is virtually assured. With persistent symptoms, many neurologists prefer to corroborate their clinical impression with MRI of the spine from L3 to S1 (Fig. 10-4). This, of course, is not necessary if the pain is manageable and surgery is not contemplated (see further on). MRI is favored over CT because of the advantages of the sagittal image and the clarity of the anatomic relationships between discs and nerve roots (Epstein). MRI also excludes herniations at other sites or an unsuspected tumor. As indicated earlier, in cases in which MRI is not possible or it has been unrevealing, we often turn to CT with myelography for a refined definition of the root sleeves and use the EMG to corroborate subtle findings. At the lumbosacral junction there is a wide gap between the posterior margins of the vertebrae and the dural sac, so that a lateral or central protrusion of the L5-S1 disc may fail to distort the dural margin and remain undetected on myelography.
The needle EMG study is abnormal, showing fibrillation potentials in denervated muscles after 1 or 2 weeks of symptoms in more than 90 percent of cases according to Leyshon and colleagues but less frequently in other studies. Loss or marked asymmetry of the H reflex is another useful indication of S1 radiculopathy, but this finding simply corroborates the loss of an Achilles reflex. The finding of denervation potentials in the paraspinal muscles (indicating root rather than peripheral nerve lesions) and in muscles that conform to a root distribution is also helpful, but at least 2 or 3 weeks must have elapsed from the onset of root pain for these findings to be present. We emphasize that, while useful information is gained from EMG, it is not routinely required and often provides mainly corroborating data.
Many disc abnormalities observed on MRI and loosely referred to as “herniation” are actually disc bulges and can be considered incidental findings, unrelated to the patient’s symptoms. Jensen and colleagues, in an MRI study of the lumbar spine in 98 asymptomatic adults, found that in more than half there was a symmetrical extension of a disc (or discs) beyond the margins of the interspace (bulging). In 27 percent, there was a focal or asymmetrical extension of the disc beyond the margin of the interspace (protrusion), and in only 1 percent was there more extreme extension of the disc (extrusion). These findings emphasize the importance of using precise terms in describing the imaging abnormalities and evaluating them strictly in the context of the patient’s symptoms.
Treatment of Ruptured Lumbar Disc
In the treatment of an acute or chronic rupture of a lumbar disc, it seems reasonable to advise avoidance of physical activities and positions that cause pain, and suggested bed rest if it appears to be helpful to the patient. But even this time-honored tenet has been strongly questioned by the results of several studies (Vroomen et al). It would appear that the main benefit is simply that time has passed and the expected resolution of pain has taken its course in many patients. The patient may suffer minor recurrence of pain but should be able to continue some of his usual activities. The results of several surveys give guidance that is conservative in the treatment of sciatica in so far as sciatica resolves without treatment in one-third of patients within 2 weeks and in 3 quarters of patients within 3 months (see Vroomen et al 2002).