6.3. MRI findings versus symptoms and signs of sciatica (I)

The findings of this study indicate that MRI is unable to distinguish sciatic patients in terms of the severity of their symptoms, in contrast to results of some earlier studies (Thelander et al. 1994, Jönssön & Strömqvist 1996). This suggests that pain mechanisms other than the extent of disc herniation in MRI generate the subjective symptoms, and accords with the results of Modic et al. (1995), who showed that patients with or without disc herniation had similar disability. The lack of association between imaging and clinical findings was also observed in the study of Balague and co-workers (1999). Our result is further supported by the high prevalence of false-positive MRI findings among asymptomatic subjects (Boden et al. 1990, Jensen et al. 1994).

In a study population including symptomatics and asymptomatics, herniations were as common in both groups (Boos et al. 1995). The best predictor of symptoms was the extent of neural compromise. In the present study, neural compromise was not associated with the symptoms, but most of the patients had major neural compromise. Straight leg raising restriction was a good measure of nerve root entrapment, but it could not differentiate the subclasses of disc herniations. The association of SLR restriction and disability has also been observed by others (Thelander et al. 1992, Jönsson & Strömqvist 1995).

These findings are similar to those of a study in which patients with painful disc disruption but without deformation of the outer anular wall had similar leg pain to patients with more severe disruption deforming the outer wall (Ohnmeiss et al. 1997). Thus, an organic cause, like anular tear, of disability among sciatic patients may be present, even when MRI findings are minor; and vice versa, prominent MRI findings may not associate with any symptoms.