The diagnostic value of magnetic resonance imaging measurements for assessing cervical spinal canal stenosis in relationship with the measurement of normal reference values of spinal canal diameter and space available for cord (SAC) at mid sagittal level

Abstract

Background: Assessment of cervical spinal stenosis, which is not very uncommon presentation among adult age group, is necessary for planning of the management protocol, especially regarding surgical intervention, if necessary. Specific measurements used for assessing spinal canal stenosis, the spinal canal diameter and space available for cord (SAC) at mid sagittal level are considered  to be very important ones. To determine the normal range of the absolute values of these two parameters in the local population and their importance in predicting cervical canal stenosis, we selected 100 asymptomatic adult subjects of each of both sexes and 50 symptomatic subjects of each of both sexes. Materials & Methods: In the present study, for asymptomatic subjects selected from the patients referred to MRI Center, IPGME&R for MRI of brain due to some unrelated ailment or from the patients of adult age group needing spinal MRI screening without any manifestation related to diseases involving the cervical part of spine & cord. For symptomatic subjects selected from the patients referred to the MRI center of IPGME&R for cervical spinal MRI study to evaluate for cervical spinal canal stenosis with various symptoms such as neck or shoulder pain and stiffness, paresthesia of hands & feet, slowly progressive spastic paraparesis, other upper motor neuron signs of lower limb, dermatomal sensory loss, weakness of small muscles of hands etc. Results: Sensitivity of cervical canal diameter as a marker of canal stenosis in predicting symptoms was 62% (95%CI 47.17-75.35) with specificity 91%, positive predictive value (PPV) 77.5% and negative predictive value (NPV) 82.73%. Sensitivity of SAC as a maker of cervical canal stenosis in predicting symptoms was 66 % (51.23-78.79) with specificity 93%, PPV 82.5 %, and NPV 84.55%. Finally at C7 level, r is>0.8 so strong +ve correlation between canal diameter (CAD) & space available for cord (SAC) at C7 cervical level. Sensitivity of cervical canal diameter & SAC both as the marker of canal stenosis in predicting symptoms was 82% (68.56- 91.42) with specificity 87%, PPV 75.93 % and NPV 90.60 %. Conclusion: It is well recognized that mid sagittal spinal canal diameter and space available for the cord (SAC) in cervical vertebrae (C3 to C7) varies considerably in normal adult population of both the sexes and decrease in them will result in cervical stenosis symptoms. We know that when sensitivity more than 70%, it indicates predictability. In present study we find that sensitivity is 82%. So we may conclude that in case of patient having symptoms of cervical stenosis, canal diameter and space available for cord both measurements are important.