Failure of ETV in patients with the highest ETV success scores.

OBJECTIVE Endoscopic third ventriculostomy (ETV) is a surgical alternative to placing a CSF shunt in certain patients with hydrocephalus. The ETV Success Score (ETVSS) is a reliable, simple method to estimate the success of the procedure by 6 months of postoperative follow-up. The highest score is 90, estimating a 90% chance of the ETV effectively treating hydrocephalus without requiring a shunt. Treatment with ETV fails in certain patients, despite their being the theoretically best candidates for the procedure. In this study the authors attempted to identify factors that further predicted success in patients with the highest ETVSSs. METHODS A retrospective review was performed of all patients treated with ETV at 3 institutions. Demographic, radiological, and clinical data were recorded. All patients by definition were older than 1 year, had obstructive hydrocephalus, and did not have a prior shunt. Failure of ETV was defined as the need for a shunt by 1 year. The ETV was considered a success if the patient did not require another surgery (either shunt placement or a repeat endoscopic procedure) by 1 year. A statistical analysis was performed to identify factors associated with success or failure. RESULTS Fifty-nine patients met the entry criteria for the study. Eleven patients (18.6%) required further surgery by 1 year. All of these patients received a shunt. The presenting symptom of lethargy statistically correlated with success (p = 0.0126, odds ratio [OR] = 0.072). The preoperative radiological finding of transependymal flow (p = 0.0375, OR 0.158) correlated with success. A postoperative larger maximum width of the third ventricle correlated with failure (p = 0.0265). CONCLUSIONS The preoperative findings of lethargy and transependymal flow statistically correlated with success. This suggests that the best candidates for ETV are those with a relatively acute elevation of intracranial pressure. Cases without these findings may represent the failures in this highly selected group.

Risk of radiation-induced malignancies from CT scanning in children who underwent shunt treatment before 6 years of age: a retrospective cohort study with a minimum 10-year follow-up.

OBJECT: A number of mathematical models predict the risk of future cancer from the ionizing radiation exposure of CT scanning. The predictions are alarming. Some models predict 29,000 future cancers and 14,500 deaths in the US will be directly caused by 1 year's worth of CT scanning. However, there are very few clinical data to justify or refute these claims. Young children are theoretically highly susceptible to the damaging effects of radiation. In this study, the authors examined children who underwent CSF shunt placement before 6 years of age. The authors chose to study shunt-treated patients with the assumption that these patients would undergo future imaging, facilitating surveillance. They chose a study period of 1991-2001 to allow more than 10 years of follow-up data. METHODS: The authors studied 104 consecutive children who underwent CSF shunt placement prior to 6 years of age and who had at least 10 years of follow-up data. Sixty-two of these patients underwent shunt placement prior to 1 year of age. The age at the initial scanning session, the number of future CT scanning sessions, diagnosis, and results of any future studies were recorded. The age-specific radiation dose was calculated for children younger than 1 year. Children younger than 1 year at the time of shunt placement were evaluated separately, based on the assumption that they represented the highest risk cohort. The authors examined all data for any evidence of future leukemia or head/neck tumor (benign or malignant). RESULTS: These children underwent a total of 1584 CT scanning sessions over a follow-up period of 1622 person-years. A total of 517 scanning sessions were performed prior to 6 years of age, including 260 in the 1st year of life. Children who underwent shunt placement before 1 year of age underwent an average of 16.3 ± 13.5 CT sessions (range 1-41). Children undergoing placement between 1 and 6 years of age received an average of 14.1 ± 12.5 CT studies (range 5-52). There were no subsequent tumors (benign or malignant) or leukemia detected. CONCLUSIONS: Previously published models predict a significant number of future cancers directly caused by CT scanning. However, there are very few published clinical data. In the authors' study, zero future radiation-induced malignancies were detected after routine CT scanning in a high-risk group. While the authors do not consider their single-institution study adequate to define the actual risk, their data suggest that the overall risk is low. The authors hope this study encourages future collaborative efforts to define the actual risk to patients.

Percutaneous pedicle screw placement with computer-navigated mapping in place of Kirschner wires: clinical article.

OBJECT: Percutaneous pedicle screw insertion techniques are commonly used to treat a variety of spinal disorders. Typically, Kirschner (K)-wires are used to guide the insertion of taps and screws during placement since the normal anatomical landmarks are not visualized. The use of K-wires adds risks, such as vascular and nerve injuries as well as increased radiation exposure given the use of fluoroscopy. The authors describe a series of patients who had percutaneous pedicle screws placed using a new computer-assisted navigation technique without the need for K-wires. METHODS: Minimally invasive percutaneous pedicle screw placement in the thoracic and lumbar spine was performed in a consecutive series of 15 patients for a variety of spinal pathologies. Intraoperative 3D CT images were obtained and used with a computer-assisted navigation system to insert an awl-tap into each pedicle. The tap location in the pedicle was marked with the navigation software, and the awl-tap was then removed. The navigation system was used to identify each landmark to insert the pedicle screw. Connecting rods were then inserted percutaneously under fluoroscopic guidance. Postoperative CT scans were obtained in each patient to evaluate screw placement. RESULTS: On postprocedure scanning, only 1 screw had a minor lateral and superior breach that was asymptomatic. To date, there have been no hardware failures. CONCLUSIONS: Percutaneous pedicle screws can be placed effectively and safely without the use of K-wires.