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Stefanie Bette, Jens Gempt, Thomas Huber, Claire Delbridge, Bernhard Meyer, Claus Zimmer, Jan S. Kirschke and Tobias Boeckh-Behrens

OBJECTIVE

Recent studies have indicated that a signal intensity increase of the fluid within the resection cavity on FLAIR images may predict tumor recurrence after glioma surgery. The aim of this study was to assess the increase in FLAIR signal intensity in a large patient cohort and in subgroups to assess its prognostic value for early tumor recurrence in glioma patients.

METHODS

A total of 212 patients (213 cases) who had undergone surgery for an intracranial glioma (WHO Grade IV [n = 103], WHO Grade III [n = 57], and WHO Grade II [n = 53]) were included in this retrospective study. FLAIR signal within the resection cavity at the time of tumor recurrence/last contact and on the previous MRI study was assessed qualitatively and quantitatively. Appearance of FLAIR signal increase was studied over time using Kaplan-Meier estimates in subgroups.

RESULTS

Patients with WHO Grade II glioma and connection of the resection cavity to CSF who did not undergo radiotherapy did not regularly develop this sign and were excluded from further analysis. For the remaining 87 cases, FLAIR signal intensity increase was observed in 27 cases. Recurrent disease was found in 26 of these 27 cases, resulting in a specificity of 80.0%, a sensitivity of 31.7%, and positive and negative predictive values of 96.3% and 6.7%, respectively. In 4 cases this sign had been observed prior (range 2.8–8.5 months) to tumor recurrence defined by standard criteria. Quantitative analysis underlined the results of qualitative analysis, but it did not add a diagnostic value.

CONCLUSIONS

Signal intensity increase of the fluid within the resection cavity on FLAIR images is a rare but highly specific and early sign for tumor recurrence/tumor progression in completely and incompletely resected high-grade glioma without connection of the resection cavity to CSF and with radiotherapy.

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Chiara Negwer, Nico Sollmann, Sebastian Ille, Theresa Hauck, Stefanie Maurer, Jan S. Kirschke, Florian Ringel, Bernhard Meyer and Sandro M. Krieg

OBJECTIVE

Diffusion tensor imaging (DTI) fiber tracking (FT) has been widely used in glioma surgery in recent years. It can provide helpful information about subcortical structures, especially in patients with eloquent space-occupying lesions. This study compared the newly developed navigated transcranial magnetic stimulation (nTMS)-based DTI FT of language pathways with the most reproducible protocol for language pathway tractography, using cubic regions of interest (ROIs) for the arcuate fascicle.

METHODS

Thirty-seven patients with left-sided perisylvian lesions underwent language mapping by repetitive nTMS. DTI FT was performed using the cubic ROIs–based protocol and the authors' nTMS-based DTI FT approach. The same minimal fiber length and fractional anisotropy were chosen (50 mm and 0.2, respectively). Both protocols were performed with standard clinical tractography software.

RESULTS

Both methods visualized language-related fiber tracts (i.e., corticonuclear tract, arcuate fascicle, uncinate fascicle, superior longitudinal fascicle, inferior longitudinal fascicle, arcuate fibers, commissural fibers, corticothalamic fibers, and frontooccipital fascicle) in all 37 patients. Using the cubic ROIs-based protocol, 39.9% of these language-related fiber tracts were detected in the examined patients, as opposed to 76.0% when performing nTMS-based DTI FT. For specifically tracking the arcuate fascicle, however, the cubic ROIs-based approach showed better results (97.3% vs 75.7% with nTMS-based DTI FT).

CONCLUSIONS

The cubic ROIs-based protocol was designed for arcuate fascicle tractography, and this study shows that it is still useful for this intention. However, superior results were obtained using the nTMS-based DTI FT for visualization of other language-related fiber tracts.

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Nico Sollmann, Noémie Wildschuetz, Anna Kelm, Neal Conway, Tobias Moser, Lucia Bulubas, Jan S. Kirschke, Bernhard Meyer and Sandro M. Krieg

OBJECTIVE

Navigated transcranial magnetic stimulation (nTMS) and diffusion tensor imaging fiber tracking (DTI FT) based on nTMS data are increasingly used for preoperative planning and resection guidance in patients suffering from motor-eloquent brain tumors. The present study explores whether nTMS-based DTI FT can also be used for individual preoperative risk assessment regarding surgery-related motor impairment.

METHODS

Data derived from preoperative nTMS motor mapping and subsequent nTMS-based tractography in 86 patients were analyzed. All patients suffered from high-grade glioma (HGG), low-grade glioma (LGG), or intracranial metastasis (MET). In this context, nTMS-based DTI FT of the corticospinal tract (CST) was performed at a range of fractional anisotropy (FA) levels based on an individualized FA threshold ([FAT]; tracking with 50%, 75%, and 100% FAT), which was defined as the highest FA value allowing for visualization of fibers (100% FAT). Minimum lesion-to-CST distances were measured, and fiber numbers of the reconstructed CST were assessed. These data were then correlated with the preoperative, postoperative, and follow-up status of motor function and the resting motor threshold (rMT).

RESULTS

At certain FA levels, a statistically significant difference in lesion-to-CST distances was observed between patients with HGG who had no impairment and those who developed surgery-related transient or permanent motor deficits (75% FAT: p = 0.0149; 100% FAT: p = 0.0233). In this context, no patient with a lesion-to-CST distance ≥ 12 mm suffered from any new surgery-related permanent paresis (50% FAT and 75% FAT). Furthermore, comparatively strong negative correlations were observed between the rMT and lesion-to-CST distances of patients with surgery-related transient paresis (Spearman correlation coefficient [rs]; 50% FAT: rs = –0.8660; 75% FAT: rs = –0.8660) or surgery-related permanent paresis (50% FAT: rs = –0.7656; 75% FAT: rs = –0.6763).

CONCLUSIONS

This is one of the first studies to show a direct correlation between imaging, clinical status, and neurophysiological markers for the integrity of the motor system in patients with brain tumors. The findings suggest that nTMS-based DTI FT might be suitable for individual risk assessment in patients with HGG, in addition to being a surgery-planning tool. Importantly, necessary data for risk assessment were obtained without significant additional efforts, making this approach potentially valuable for direct clinical use.

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Nico Sollmann, Dominik Weidlich, Barbara Cervantes, Elisabeth Klupp, Carl Ganter, Hendrik Kooijman, Claus Zimmer, Ernst J. Rummeny, Bernhard Meyer, Thomas Baum, Jan S. Kirschke and Dimitrios C. Karampinos

OBJECTIVE

Lumbosacral radicular syndrome (LRS) is a very common condition, often requiring diagnostic imaging with the aim of elucidating a structural cause when symptoms are longer lasting. However, findings on conventional anatomical MRI do not necessarily correlate with clinical symptoms, and it is primarily performed for the qualitative evaluation of surrounding compressive structures, such as herniated discs, instead of to evaluate the nerves directly. The present study investigated the performance of quantitative imaging by using magnetic resonance neurography (MRN) in patients with LRS.

METHODS

Eighteen patients (55.6% males, mean age 64.4 ± 10.2 years), with strict unilateral LRS matching at least one dermatome and suspected disc herniation, underwent high-resolution 3-T MRN using T2 mapping. On T2 maps, the presumably affected and contralateral unaffected nerves were identified; subsequent regions of interest (ROIs) were placed at preganglionic, ganglionic, and postganglionic sites; and T2 values were extracted. Patients then underwent an epidural steroid injection (ESI) with local anesthetic agents at the site of suspected nerve affection. T2 values of the affected nerves were compared against the contralateral nerves. Furthermore, receiver operating characteristics were calculated based on the measured T2 values and the responsiveness to ESI.

RESULTS

The mean T2 value was 77.3 ± 1.9 msec for affected nerves and 74.8 ± 1.4 msec for contralateral nerves (p < 0.0001). In relation to ESI performed at the site of suspected nerve affection, MRN with T2 mapping had a sensitivity/specificity of 76.9%/60.0% and a positive/negative predictive value of 83.3%/50.0%. Signal alterations in affected nerves according to qualitative visual inspection were present in only 22.2% of patients.

CONCLUSIONS

As one of the first of its kind, this study revealed elevated T2 values in patients suffering from LRS. T2 values of lumbosacral nerves might be used as more objective parameters to directly detect nerve affection in such patients.