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Henrik Giese, Karl-Titus Hoffmann, Andreas Winkelmann, Florian Stockhammer, George I. Jallo and Ulrich-W. Thomale

Object

The indications for stereotactic biopsies or implantation of probes for local chemotherapy in diffuse brainstem tumors have recently come under debate. The quality of performing these procedures significantly depends on the precision of the probes' placement in the brainstem. The authors evaluated the precision of brainstem probe positioning using a navigated frameless stereotactic system in an experimental setting.

Methods

Using the VarioGuide stereotactic system, 33 probes were placed into a specially designed model filled with agarose. In a second experimental series, 8 anatomical specimens were implanted with a total of 32 catheters into the pontine brainstem using either a suboccipital or a precoronal entry point. Before intervention in both experimental settings, a thin-sliced CT scan for planning was obtained and fused to volumetric T1-weighted MR imaging data. After the probe positioning procedures, another CT scan and an MR image were obtained to compare the course of the catheters versus the planned trajectory. The deviation between the planned and the actual locations was measured to evaluate the precision of the navigated intervention.

Results

Using the VarioGuide system, mean total target deviations of 2.8 ± 1.2 mm on CT scanning and 3.1 ± 1.2 mm on MR imaging were detected with a mean catheter length of 151 ± 6.1 mm in the agarose model. The catheter placement in the anatomical specimens revealed mean total deviations of 1.95 ± 0.6 mm on CT scanning and 1.8 ± 0.7 mm on MR imaging for the suboccipital approach and a mean catheter length of 59.5 ± 4.1 mm. For the precoronal approach, deviations of 2.2 ± 1.2 mm on CT scanning and 2.1 ± 1.1 mm on MR imaging were measured (mean catheter length 85.9 ± 4.7 mm).

Conclusions

The system-based deviation of frameless stereotaxy using the VarioGuide system reveals good probe placement in deep-seated locations such as the brainstem. Therefore, the authors believe that the system can be accurately used to conduct biopsies and place probes in patients with brainstem lesions.

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Mario Čabraja, Florian Stockhammer, Sven Mularski, Olaf Suess, Theodoros Kombos and Peter Vajkoczy

Object

Neurophysiological intraoperative monitoring (IOM) is regarded as a useful tool to provide information about physiological changes during surgery in eloquent areas of the nervous system, to increase safety and reduce morbidity. Nevertheless, numerous older studies report that very few patients benefit from IOM, and that there are high rates of false-positive and false-negative changes of neurophysiological parameters during surgery. There is an ongoing discussion about the effectiveness of neurophysiological IOM. This questionnaire study was performed to evaluate the attitude of neurosurgeons toward neurophysiological IOM and the availability of this tool.

Methods

One hundred fifty neurosurgeons from 60 institutions in 16 countries were asked to answer anonymously a questionnaire with 11 questions. The questionnaire covered aspects of personal experience, the neurosurgical institution, and availability of neurophysiological IOM as well as asking the surgeon's opinion of the procedure.

Results

One hundred nine questionnaires were returned (73%). Seven questionnaires were excluded because of failure to complete the form correctly or completely, leaving 102 respondents from 44 institutions in 16 countries in the study; 79.5% of the included institutions provided neurophysiological IOM. Young neurosurgeons did not put more trust in IOM than experienced neurosurgeons. With growing IOM experience, surgeons seem to allow less influence of the findings on the course of their operation. At large institutions in which > 1500 operations per year are done, IOM is performed by the neurosurgeons themselves in most cases. In institutions with fewer operations, the IOM team consists mostly of nonneurosurgeons. Regardless of the availability of neurophysiological IOM, all surgeons stated that IOM is gaining increasing importance.

Conclusions

Neurophysiological IOM represents an established tool in neurosurgery. Although the importance of IOM is emphasized by the majority of neurosurgeons, the relevance of this tool to the course of the operation changes with increasing neurophysiological IOM experience.

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Florian Stockhammer, Ulrich-Wilhelm Thomale, Michail Plotkin, Christian Hartmann and Andreas von Deimling

Object

Oligodendroglial tumors harboring combined 1p and 19q loss (1p/19q LOH) are characterized by a favorable prognosis and response to chemotherapy and radiotherapy, but detection of 1p/19q LOH relies on postoperative procedures. The authors investigated the potential of fluorine-18–labeled fluorodeoxyglucose (FDG) uptake in positron emission tomography (PET) to predict 1p/19q LOH preoperatively in tumors whose appearance on initial magnetic resonance images was consistent with that of low-grade glioma.

Methods

The study population comprised 25 patients who had undergone preoperative FDG-PET followed by tumor resection. Neuronavigation ensured a precise match of FDG uptake wi th the site of biopsy. All tumor specimens were graded according to the World Health Organization (WHO) classification system. Microsatellite analysis was used to identify 1p/19q LOH.

In this series, 16 of 25 gliomas corresponded to WHO Grade II. In eight of these 16, 1p/19q LOH was detected. Raised glucose utilization within the tumor was seen in the six of eight WHO Grade II gliomas with 1p/19q LOH and in none of the WHO Grade II gliomas without this genetic alteration (p = 0.003).

Conclusions

These findings demonstrate the potential of FDG-PET to predict 1p/19q LOH in WHO Grade II gliomas.

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Patrick Cramer, Ulrich-Wilhelm Thomale, Ali Fuat Okuducu, Arne J. Lemke, Florian Stockhammer and Christian Woiciechowsky

✓ The authors report the case of a 23-year-old man who presented with a C1–3 spinal mass. Following intraspinal decompression the tumor was histologically classified as an atypical meningioma (World Health Organization grade II). Two further surgical interventions resulted in almost total removal of the meningioma. In addition, radiotherapy was performed. During the 1.5-year follow-up period the diagnostic examinations identified a local tumor recurrence, an intraspinal C-6 metastasis, and a segmental instability with anterior C2–3 slippage and C3–4 kyphosis. The tumor was resected and occipitocervical stabilization was performed. Histological examination showed no change in malignancy. Despite additional hydroxyurea-based chemotherapy, the patient presented 4 months later with a hemiparesis and a massive recurrence of the tumor mass involving the posterior fossa and the upper thoracic spine. Because there were no further therapeutical options, the patient died. The authors discuss more aggressive therapeutic options in addition to surgery in patients with metastatic atypical meningiomas. The results in the reported case indicate that meningiomas associated with cerebrospinal fluid metastasis may represent a higher grade of malignancy.