Month: October 2013

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Intraoperative optical imaging for functional mapping

Intraoperative optical imaging for functional mapping

J Neurosurg 119:853–863, 2013

Intraoperative optical imaging (IOI) is an experimental technique used for visualizing functional brain areas after surgical exposure of the cerebral cortex. This technique identifies areas of local changes in blood volume and oxygenation caused by stimulation of specific brain functions. The authors describe a new IOI method, including innovative data analysis, that can facilitate intraoperative functional imaging on a routine basis. To evaluate the reliability and validity of this approach, they used the new IOI method to demonstrate visualization of the median nerve area of the somatosensory cortex.

Methods. In 41 patients with tumor lesions adjacent to the postcentral gyrus, lesions were surgically removed by using IOI during stimulation of the contralateral median nerve. Optical properties of the cortical tissue were measured with a sensitive camera system connected to a surgical microscope. Imaging was performed by using 9 cycles of alternating prolonged stimulation and rest periods of 30 seconds. Intraoperative optical imaging was based on blood volume changes detected by using a filter at an isosbestic wavelength (delta = 568 nm). A spectral analysis algorithm was used to improve computation of the activity maps. Movement artifacts were compensated for by an elastic registration algorithm. For validation, intraoperative conduction of the phase reversal over the central sulcus and postoperative evaluation of the craniotomy site were used.

Results. The new method and analysis enabled significant differentiation (p < 0.005) between functional and nonfunctional tissue. The identification and visualization of functionally intact somatosensory cortex was highly reliable; sensitivity was 94.4% and specificity was almost 100%. The surgeon was provided with a 2D high-resolution activity map within 12 minutes. No method-related side effects occurred in any of the 41 patients.

Conclusions. The authors’ new approach makes IOI a contact-free and label-free optical technique that can be used safely in a routine clinical setup. Intraoperative optical imaging can be used as an alternative to other methods for the identification of sensory cortex areas and offers the added benefit of a high-resolution map of functional activity. It has great potential for visualizing and monitoring additional specific functional brain areas such as the visual, motor, and speech cortex. A prospective national multicenter clinical trial is currently being planned.

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Anatomical variation of superior petrosal vein and its management during surgery for cerebellopontine angle meningiomas

Anatomical variation of superior petrosal vein and its management during surgery for cerebellopontine angle meningiomas

Acta Neurochir (2013) 155:1871–187

No systematic study is yet available that focuses on the surgical anatomy of the superior petrosal vein and its significance during surgery for cerebellopontine angle meningiomas. The aim of the present study was to examine the variation of the superior petrosal vein via the retrosigmoid suboccipital approach in relation to the tumor attachment of cerebellopontine angle meningiomas as well as postoperative complications related to venous occlusion.

Forty-three patients with cerebellopontine angle meningiomas were analyzed retrospectively. Based on the operative findings, the tumors were classified into four subtypes: the petroclival type, tentorial type, anterior petrous type, and posterior petrous type. According to a previous anatomical report, the superior petrosal veins were divided into three groups: Type I which emptied into the superior petrosal sinus above and lateral to the internal acoustic meatus, Type II which emptied between the lateral limit of the trigeminal nerve at Meckel’s cave and the medial limit of the facial nerve at the internal acoustic meatus, and Type III which emptied into the superior petrosal sinus above and medial to Meckel’s cave.

In both the petroclival and anterior petrous types, the most common vein was Type III which is the ideal vein for a retrosigmoid approach. In contrast, the Type II vein which is at high risk of being sacrificed during a suprameatal approach procedure was most frequent in posterior petrous type, in which the superior petrosal vein was not largely an obstacle. Intraoperative sacrificing of veins was associated with a significantly higher rate of venous-related phenomena, while venous complications occurred even in cases where the superior petrosal vein was absent or compressed by the tumor.

The variation in the superior petrosal vein appeared to differ among the tumor attachment subtypes, which could permit a satisfactory surgical exposure without dividing the superior petrosal vein. In cases where the superior petrosal vein was previously occluded, other bridging veins could correspond with implications for the crucial venous drainage system, and should thus be identified and protected whenever possible.

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Postoperative Displacement of Deep Brain Stimulation Electrodes Related to Lead-Anchoring Technique

Postoperative Displacement of Deep Brain Stimulation Electrodes Related to Lead-Anchoring Technique-1

Neurosurgery 73:681–688, 2013

Displacement of deep brain stimulation (DBS) electrodes may occur after surgery, especially due to large subdural air collections, but other factors might contribute.

OBJECTIVE: To investigate factors potentially contributing to postoperative electrode displacement, in particular, different lead-anchoring techniques.

METHODS: We retrospectively analyzed 55 patients (106 electrodes) with Parkinson disease, dystonia, tremor, and obsessive-compulsive disorder in whom early postoperative and long-term follow-up computed tomography (CT) was performed. Electrodes were anchored with a titanium microplate or with a commercially available plastic cap system. Two independent examiners determined the stereotactic coordinates of the deepest DBS contact on early postoperative and long-term follow-up CT. The influence of age, surgery duration, subdural air volume, use of microrecordings, fixation method, follow-up time, and side operated on first was assessed.

RESULTS: Subdural air collections measured on average 4.36±6.2 cm3. Three-dimensional (3-D) electrode displacement and displacement in the X, Y, and Z axes significantly correlated only with the anchoring method, with larger displacement for microplate-anchored electrodes. The average 3-D displacement for microplate-anchored electrodes was 2.3 ± 2.0 mm vs 1.5 ± 0.6 mm for electrodes anchored with the plastic cap (P = .030). Fifty percent of the microplate-anchored electrodes showed 2-mm or greater (potentially relevant) 3-D displacement vs only 25% of the plastic cap–anchored electrodes (P < .01).

CONCLUSION: The commercially available plastic cap system is more efficient in preventing postoperative DBS electrode displacement than titanium microplates. A reliability analysis of the electrode fixation is warranted when alternative anchoring methods are used.

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