Nobuhiro Tanaka, Yoshinori Fujimoto, Tadayoshi Sumida, Hideki Manabe, Kazuyoshi Nakanishi, Yasushi Fujiwara, Naosuke Kamei, Toshio Nakamae, Bunichiro Izumi and Mitsuo Ochi
In this retrospective analysis the authors describe the long-term clinical results of microsurgical transdural discectomy with laminoplasty (MTDL) in patients with cervical disc herniation (CDH).
Thirty patients (21 males, 9 females; mean age at surgery 55 years) with CDH had surgical treatments consisting of MTDL between 1990 and 1998. All patients demonstrated signs or symptoms of cervical myelopathy and/or radiculomyelopathy. Clinical outcomes were evaluated by the Japanese Orthopaedic Association (JOA) scoring system and by recovery rate (RR). The degenerative grades of the intervertebral discs were also evaluated based on preoperative, postoperative, and final follow-up MR images. The average follow-up period was 14.1 years (range 10–22 years).
Twenty (67%) of the 30 patients completed the follow-up in this study. The preoperative JOA scores in these patients averaged 11.8, and the postoperative scores at the final follow-up averaged 15.5 (average RR 69.6%). None of these patients required reoperation after MTDL. Although disc degeneration progressed during the follow-up period, there were no cases of clinical deterioration, recurrence of disc herniation, or postoperative kyphotic deformity.
Sufficient clinical results were obtained after the MTDL for a long-term follow-up period exceeding 10 years. The MTDL may be an option for an alternative procedure if the patients are correctly selected and the procedure is safely performed.
Kazuyoshi Nakanishi, Nobuhiro Tanaka, Naosuke Kamei, Toshio Nakamae, Bun-ichiro Izumi, Ryo Ohta, Yuki Fujioka and Mitsuo Ochi
The pathophysiology of occult tethered cord syndrome (OTCS) with no anatomical evidence of a caudally shifted conus and a normal terminal filum is hard to understand. Therefore, the diagnosis of OTCS is often difficult. The authors hypothesized that the posterior displacement of the terminal filum may become prominent in patients with OCTS who are in a prone position if filum inelasticity exists, and they investigated prone-position MRI findings.
Fourteen patients with OTCS and 12 control individuals were examined using T2-weighted axial MRI with the patients in a prone position on a flat table. On each axial view, the distance between the posterior and anterior ends of the subarachnoid space (A), the distance between the posterior end of the subarachnoid space and the terminal filum (B), the distance between the posterior end of the subarachnoid space and the dorsal-most nerve among the cauda equina (C), and the distance between the posterior end of the subarachnoid space and the ventral-most nerve (D) were measured. The location ratios of the terminal filum, the dorsal-most nerve, and the ventral-most nerve were calculated by the ratio of A to B (defined as TF = B/A), A to C (defined as DN = C/A), and A to D (defined as VN = D/A), respectively. Patients underwent sectioning of the terminal filum with the aid of a surgical microscope. The low-back pain Japanese Orthopaedic Association score was obtained before surgery and at the final follow-up visit.
On prone-position axial MRI, the terminal filum was separated from the cauda equina and was shifted caudally to posterior in the subarachnoid space in all patients with OTCS. The locations of the caudal cauda equina shifted to ventral in the subarachnoid space. The TF values in the OTCS group were significantly lower than those in the control group at the L3–4 (p = 0.023), L-4 (p = 0.030), L4–5 (p = 0.002), and L-5 (p < 0.001) levels. In contrast, the DN values in the OTCS group were significantly higher than those of the control group at the L-2 (p = 0.003), L2–3 (p = 0.002), L-3 (p < 0.001), L3–4 (p < 0.001), L-4 (p = 0.007), L4–5 (p = 0.003), and S-1 (p = 0.014) levels, and the VN values in the OTCS group were also significantly higher than those of the control group at the L2–3 (p = 0.022), L-3 (p = 0.027), L3–4 (p = 0.002), L-4 (p = 0.011), L4–5 (p = 0.019), and L5–S1 (p = 0.040) levels. Sections were collected during surgery for histological evaluation, and a decreased elasticity within the terminal filum was suggested. Improvements in the Japanese Orthopaedic Association score were observed at the final follow-up in all patients.
The authors' new method of using the prone position for MRI shows that the terminal filum is located significantly posterior and the cauda equina is located anterior in patients with OTCS, suggesting a difference in elasticity between the terminal filum and cauda equina.