The level-diagnosis of a lower lumbar disc herniation: the value of sensibility and motor testing.

Sensibility and motor power were prospectively tested in 52 consecutive hospitalized patients with a lower lumbar disc herniation, verified by operation. The test results were noted in a decision matrix, and the positive and negative predictive values were calculated. The positive predictive value of disturbed sensation in the L5 dermatome, paresis of dorsiflexion of the foot and extension of the 4 lateral toes as signs of a herniation from the fourth lumbar disc was calculated to be 76 per cent, 69 per cent and 76 per cent, respectively, and the negative predictive value in each case to be approximately 50 per cent. The positive predictive value of altered sensibility in the S1 dermatome as a sign of a herniation from the fifth lumbar disc was found to be 50 per cent and the negative predictive value to be 62 per cent. It is concluded, that these tests very often give diagnostically specific information in patients with a herniation from the fourth lumbar disc and should therefore be performed if a lumbar root compression is suspected. They are, however, of limited value in the case of a protrusion from the fifth lumbar disc.