Use of T2 signal intensity of cerebellar neoplasms in pediatric patients to guide preoperative staging of the neuraxis.

OBJECT: The question of whether to obtain routine or selective preoperative imaging of the neuraxis in pediatric patients with cerebellar neoplasms remains a controversial topic. Staging of the neuraxis is generally considered beneficial in patients with neoplasms associated with an elevated risk of leptomeningeal dissemination (LD). When these studies are obtained preoperatively, there is a decrease in the number of false-positive images related to debris in the immediate postoperative period. Additionally, knowledge of the extent of spread has the potential to affect the risk/benefit analysis of aggressive resection. Although the majority of pediatric neurosurgeons surveyed choose to obtain selective preoperative imaging of the neuraxis in cases of cerebellar neoplasms "with findings suggestive of high-grade pathology," an evidence-based protocol in the literature is lacking. The goal of this study was to assess radiological characteristics of tumors with an elevated risk of LD and identify a method to help guide preoperative imaging of the neuraxis. METHODS: The authors first reviewed the literature to gain an appreciation of the risk of LD of pediatric cerebellar neoplasms based on underlying histopathology and/or grade. Available evidence indicates preoperative imaging of the neuraxis in patients with Grade I tumors to be of questionable utility. In contrast, evidence suggested that preoperative imaging of the neuraxis in patients with Grades II-IV neoplasms was clinically warranted. The authors then evaluated an extensive base of neuroradiological literature to identify possible MR imaging and/or CT findings with the potential to differentiate Grade I from higher-grade neoplasms in pediatric patients. They analyzed the preoperative radiological findings in 50 pediatric patients who had undergone craniotomy for resection of cerebellar neoplasms at Vanderbilt Children's Hospital since 2003 with reference to 7 chosen radiological criteria. Logistic regression models were fit using radiological features to determine the best predictors of Grades II-IV tumors. Receiver operating characteristic methods were used to identify diagnostic properties of the best predictors. RESULTS: The relative T2 signal intensity (RT2SI), an indirect measure of the water content of the solid component of the tumor, was best able to identify neoplasms with an elevated risk of LD. An RT2SI value of 0.71 was selected by the authors as the best operating point on the curve. Of the 31 neoplasms retrospectively designated as hypointense T2-weighted lesions (RT2SI ≤ 0.71), 30 (97%) were Grade II or higher. All medulloblastomas, ependymomas, and high-grade (Grades III and IV) neoplasms were hypointense T2-weighted lesions. Of the 19 T2-weighted hyperintense neoplasms (RT2SI > 0.71), 16 (84%) were Grade I and 3 were Grade II. CONCLUSIONS: Measurement of the RT2SI can help predict Grade II-IV tumors at an elevated risk of leptomeningeal spread and guide staging of the neuraxis. Pediatric patients with cerebellar neoplasms found to have an RT2SI of less than or equal to 0.71 are recommended for neuraxis imaging prior to surgery.

Asymptomatic same-site recurrent disc herniation after lumbar discectomy: results of a prospective longitudinal study with 2-year serial imaging.

STUDY DESIGN: This is a prospective cohort study with serial imaging. OBJECTIVE: We set out to determine the incidence of symptomatic and asymptomatic same-level recurrent disc herniation and assess their effect on 2-year outcome. SUMMARY OF BACKGROUND DATA: The reported incidence of symptomatic same-level recurrent disc herniation after lumbar discectomy varies widely in retrospective studies. To date, the incidence of radiographic same-level recurrent disc herniation has not been studied prospectively with sequential imaging. Furthermore, the clinical relevance of recurrent disc herniation on magnetic resonance imaging (MRI) after discectomy remains unknown, particularly in patients with poorly specific pain after surgery. METHODS: One hundred eight patients undergoing lumbar discectomy for a single-level herniated disc at five institutions were prospectively observed for 2 years. Computed tomography (CT) and MRI of the lumbar spine were obtained every 3 months to assess reherniation and disc height loss. Leg and back pain visual analog scale (VAS), Oswestry Disability Index (ODI), and quality of life (SF-36 physical component) were assessed 3, 6, 12, and 24 months after surgery. RESULTS: No patients demonstrated residual disc on postoperative MRI. By 2 years after discectomy, 25 (23.1%) patients had demonstrated radiographic evidence of recurrent disc herniation at the level of prior discectomy on serial imaging (mean ± SD, 11.8 ± 8.3 months after surgery). Radiographic disc herniation was asymptomatic in 14 (13%) patients and symptomatic in 11 (10.2%) patients. The occurrence of symptomatic recurrent disc herniation was associated with worse 2-year leg pain (VAS-LP, P=0.002) and disability (ODI, P=0.036) but not quality of life (SF-36) or disc height loss. The occurrence of asymptomatic reherniation was not associated with disc height loss or any outcome measure (VAS, ODI, and SF-36) by 2 years. CONCLUSION: Nearly one-fourth of patients undergoing lumbar discectomy demonstrated radiographic evidence of recurrent disc herniation at the level of prior surgery, the majority of which were asymptomatic. Asymptomatic disc herniation was not associated with clinical consequences by 2 years. Clinically silent recurrent disc herniation is common after lumbar discectomy. When obtaining MRI evaluation within the first 2 years of discectomy, providers should expect that radiographic evidence of reherniation may be encountered and that treatment should be considered only when correlating radicular symptoms exist.

Rod derotation techniques for thoracolumbar spinal deformity.

OBJECTIVE: The operative correction of scoliosis requires multiple intraoperative techniques and tools to achieve an adequate result. Frequently, multiple methods are used to accomplish this, such as rod cantilever techniques, in situ bending, Smith-Petersen and pedicle subtraction osteotomies, closed reduction methods, and rod derotation techniques. Rod derotation techniques will be reviewed and discussed in this article. METHODS: A review of the available literature on anterior and posterior rod derotation is performed with a case example of the authors' experience utilizing this technique. RESULTS: Rod derotation is one technique that can transform a pathological scoliotic curve to normal physiological kyphosis or lordosis by simply rotating a rod intraoperatively. CONCLUSION: In this article, the authors present rod derotation as a valuable technique in the surgical arsenal for the treatment of scoliosis, including a discussion of the technique and its limitations.