Detailed clinical characteristics of L1–2 disc herniation—a new classification and its features

Background It is no doubt that very rare incidence and anatomical complexity of L1/2 disc herniation are the main reasons for diagnostic difficulty of disc hernia at the L1/2 level. The purpose of the current study is to propose a new classification of L1/2 disc heniation and to reveal its specific neurosymptomatology. Methods Between 1988 and 2010, we surgically treated 20 patients, 13 men and 7 women with L1/2 disc herniation. All medical records including the surgical findings, X-rays, CT myelograms and MRI were thoroughly reviewed, and their clinical and radiological appearances were described according to a classification of L1/2 disc hernia, which had five subgroups: (1) radicular group, (2) epiconus group, (3) conus medullaris group, (4) cauda equina group and (5) mixed group. Results On MRI and/or CTM, the spinal cord was terminated at the L1 vertebral body level in three patients, at the L1/2 disc level in 12 patients, and at the L2 vertebral body level in five patients. In six patients, disc herniation was present cephalad to the end of the spinal cord. Seven of the 20 patients are defined as radicular group. Sensory disturbance and/or pain in the groin site or the anterolateral aspect of the thigh was present in all patients. Femoral nerve stretching test and straight leg raising test were positive in six and four of the seven patients, respectively. Four of the 20 patients were defined as epiconus group. No L.B.P. had developed prior to the symptoms in the lower extremities. All patients have demonstrated sensory change and/or pain radiating below the knee joint. Motor weakness in the iliopsoas muscle and the quadriceps muscle was recorded in two of the four patients. Three of the four patients had been suffering from so-called drop foot. Only one patient was included in conus medullaris group. The patient showed a severe urinary and bowel disorder with absence of patellar tendon reflex and Achilles tendon reflex. Four of the 20 patients were defined as cauda equina group. All patients have demonstrated sensory change and/or pain radiating below the knee joint. Motor weakness in the iliopsoas muscle, the quadriceps muscle and the anterior tibial muscle was recorded in three of the four patients. The residual four of the 20 patients were included in mixed group. Conclusions Neurosymptomatology of L1/2 disc herniation are based on the following classification: radicular group, epiconus group, conus medullaris group, cauda equina group and mixed group, is very pragmatic to understand because of its complicated features. Especially, patients in the radicular group demonstrate a sensory disturbance and pain in the groin site and/or the anterolateral aspect of the thigh. Motor weakness in the lower extremities is a dominant sign both in epiconus and cauda equina group.