A modification of the classic technique for expansion duroplasty of the posterior fossa.

OBJECTIVE: Expansion of the posterior fossa is the goal in treatment of many neurosurgical diseases sharing a small posterior fossa and/or tightness at the level of foramen magnum. To further enhance the dural opening at the level of foramen magnum, a modification in the duroplasty technique is suggested. METHODS: A simple modification of the classic Y-shaped technique for expansion duroplasty of the posterior fossa is described. This includes an "inverse V-shaped" extension at the bottom of linear durotomy. RESULTS: The key advantage of this technique is creating more transverse expansion of the dural opening in the lower part of duroplasty. This technique has been used in six patients with no technical difficulties or complications. CONCLUSION: This new method of dural opening provides a safe and likely efficient addition to the traditional technique of posterior fossa durotomy.

Comparison of the reliability of brain lesion localization when using traditional and stereotactic image-guided techniques: a prospective study.

OBJECT: Accurate localization of brain lesions is of utmost importance. Traditional methods of localization that involve the use of neuroimaging and surface anatomy have been replaced in certain cases by using frameless stereotactic neuronavigational systems. Even though these systems have been found to be accurate, no studies have been conducted to investigate whether the systems provide improved localization accuracy compared with traditional methods. METHODS: Twenty-two patients undergoing image-guided surgery with the aid of the Stealth Neuro-Station were prospectively enrolled in this study. All patients underwent standard magnetic resonance or computerized tomography imaging, as well as special Stealth-sequenced imaging acquired using scalp fiducial markers. Traditional and Stealth estimates of the surface projection of lesions were determined, digitally photographed, and later compared. The mean (+/- standard deviation) error associated with traditional localization of lesions was 1.1 +/- 0.7 cm in the mediolateral plane and 1.3 +/- 1.1 cm in the anteroposterior plane. This error was not significantly affected by the size or location of the lesion. CONCLUSIONS: Findings of this study indicate that the conventional localization technique used to demarcate brain cortical and subcortical lesions has an error of approximately 1 to 1.5 cm in both the mediolateral and anteroposterior directions. This error can be reduced by judicious use of image-guided techniques.

The reliability of ultrasound measurements of carotid stenosis compared to MRA and DSA.

OBJECTIVE: Carotid ultrasound (US) is a screening test for patients with transient ischemic attacks (TIAs) or stroke who then undergo Digital Subtraction Angiogram (DSA) or Magnetic Resonance Angiography (MRA). Gold standard DSA is invasive with inherent risks and costs. MRA is an evolving technology. This study compares reliability of MRA and US modes with DSA in determining degree of internal carotid artery stenosis. METHODS: A five year retrospective analysis of 140 carotid arteries from patients who had carotid US and DSA, and possibly Magnetic Resonance Angiography was undertaken. Recorded US parameters were peak systolic velocity (PSV), end diastolic velocity (EDV), and ICA/CCA peak systolic velocity ratio. The MRA and DSA parameters used NASCET technique for measuring stenosis. Statistical analysis included ROC curves and Kappa computation. RESULTS: US grading of carotid stenosis can be made more reliable by choosing appropriate parameters. The best combination of sensitivity and specificity for stenosis > 70% in our hospital was seen at PSV > 173 cm/s (sensitivity 0.87, specificity 0.8, Positive Predictive Value (PPV) 0.70, Negative Predictive Value (NPV) 0.93, kappa 0.64 and weighted kappa 0.71). MRA kappa was 0.78, (sensitivity 0.75, specificity 1.0, PPV 1.0, NPV 0.85). CONCLUSIONS: US parameters should be validated in each centre. At best, US can only approximate the accuracy of DSA, probably due to inherent limitations of this modality. Magnetic Resonance Angiography has a perfect specificity and PPV but this technique needs to be standardized. Simultaneous use of MRA and US for screening increases sensitivity to over 0.9 without compromising specificity in > 70% stenosis.