A New Classification and Feature of L1/2 Disk Herniation
Authors: Okuyama K. G. , Sasaki H. 
Published: June 2012

Introduction It is of no doubt that very rare incidence and anatomical complexity of L1/2 disk herniation are main reasons for diagnostic difficulty of disk hernia at the L1/2 level. The purpose of the current study is to propose a new classification of L1/2 disk herniation and to reveal its specific neurosymptomatology. Materials and Methods Between 1988 and 2010, we surgically treated 20 patients, 13 men and 7 women, with L1/2 disk herniation. All medical records including the surgical finding, X-rays, CT myelograms, and magnetic resonance imaging (MRI) were thoroughly reviewed, and their clinical and radiological appearance was described according to a classification of L1/2 disk 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 3 patients, at the L1/2 disk level in 12 patients, and at the L2 vertebral body level in 5 patients. In six patients, disk herniation was present cephalad to the end of the spinal cord. Total 7 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. FNST and SLRT were positive in six and four of the seven patients, respectively. Total 4 of the 20 patients were defined as Epiconus group. No LBP had developed prior to the symptoms in the lower extremity. All patients have demonstrated sensory change and/or pain radiating below the knee joint. Motor weakness in Iliop. M. and Quad. M. 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 PTR and ATR. Total 4 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 Iliop. M., Quad. M. and Ant. Tib. M. was recorded in three of the four patients. The residual 4 of the 20 patients were included in mixed group. Conclusion Neurosymptomatology of L1/2 disk herniation based on the classification: (1) radicular group, (2) epiconus group, (3) conus medullaris group, (4) cauda equina group, and (5) mixed group, is very pragmatic to understand its complicated features. Patients in Radicular group characteristically demonstrate sensory disturbance and pain in the groin site or the anterolateral aspect of the thigh. Motor weakness in the lower extremities is a dominant sign both in epiconus and cauda equina group. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Aronson HA, Dunsmore RH. Herniated upper lumbar discs. Journal of Bone Joint Surgery American Volume 1963;45A: 311–317 Albert TJ, Balderston RA, Heller JG, et al. Upper lumbar disk herniations. Journal of Spinal Disorders 1993;6:351–359 Suzuki H, Yamamoto M, Chiba M, et al. Operative treatment of L1/2 lumbar disk herniation. Seikei Geka 1996;47:1419–1423(in Japanese) Tsuboi S. A morphological study on the thoracic and lumbar vertebral foramina. Hirosaki Med J1976;28:116–139 (In Japanese with English abstract) Matsumoto M, Fugimura S, Suzuki N, et al. Clinical features and surgical treatment of L1-L2 disk herniation. Seikei Geka 1994;50:331–333 (In Japanese) Tokuhashi Y, Matsuzaki H, Uematue Y, Oda H. Symptoms of thoracolumbar junction disk herniation. Spine 2001;26:E512-E518 Yokogushi K, Yokozawa H, Asano M, Uchiyama E, Owada O, Ono N. Four operative cases of the L1/2 disk herniation. J East Jpn Orthop Traumatol 1990;2:454–457 (In Japanese) Hamanishi C, Horikoshi M, Tanaka S. Distribution of the conus medullaris on the MRI. Cent Jpn J Orthp Traumat 1994;37:695–696, (In Japanese with English abstract) Fineschi G. Disk hernia L2 and L1 root syndrome. First anatomo-clinical and diagnostic contribution. Chir Organi Mov 1971;60:15–26 ( in Italian with English abstract) Taneichi H. Neurosymptomatology of spinal disorders and injuries in the thoracolumbar junction. Nissekikaishi 12: 510–515, 2001 ( in Japanese) Sato K, Kikuchi S. An anatomical study of spinal cord segmentation the thoracolumbar spine. Spine and Spinal Cord 1996;9:947–951 ( in Japanese with English abstract)