Lateral L3/4 herniated nucleus pulposus: clinical and imaging considerations.

This report examines 18 surgically proven L3/4 herniated nucleus pulposus (HNP), all having myelogram, CT and adequate neurological evaluation. It will focus on four cases where the herniation involved the neural canal (intervertebral canal). Comparison to the 14 spinal canal central herniations will be made. The clinical findings for lateral L3/4 HNP allowed a preimaging diagnosis to be made in three of the four cases. In the central group the correct preimaging diagnosis was made one of the 14 cases (P less than 0.01). There are numerous reasons why the central L3/4 HNP preimaging diagnosis is inaccurate as well as difficult to establish and these reasons are discussed in detail. The myelographic and CT findings of the lateral L3/4 HNP are clearly elaborated. All herniations were extruded. They poorly responded to conservative management. The duration of illness, onset of pain to surgical disk removal, for the lateral herniations was 34.8 days and, 154.4 days for the central group (P less than 0.05). The myelogram is a disappointing test in the diagnosis of lateral L3/4 HNP, but highly accurate in spinal canal L3/4 HNP. CT is a preferred imaging test being virtually positive in all cases.