Andrea Faymonville

Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule

Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery. The integration of functional localizer data into tracking algorithms offers to establish a direct structure–function relationship in DTI data. However, alterations of MRI signals in and adjacent to brain tumours often lead to spurious tracking results. We here compared the impact of subcortical seed regions placed at different positions and the influences of the somatotopic location of the cortical seed and clinical co-factors on fibre tracking plausibility in brain tumour patients. The CST of 32 patients with intracranial tumours was investigated by means of deterministic DTI and neuronavigated transcranial magnetic stimulation (nTMS). The cortical seeds were defined by the nTMS hot spots of the primary motor area (M1) of the hand, the foot and the tongue representation. The CST originating from the contralesional M1 hand area was mapped as intra-individual reference. As subcortical region of interests (ROI), we used the posterior limb of the internal capsule (PLIC) and/or the anterior inferior pontine region (aiP). The plausibility of the fibre trajectories was assessed by a-priori defined anatomical criteria. The following potential co-factors were analysed: Karnofsky Performance Scale (KPS), resting motor threshold (RMT), T1-CE tumour volume, T2 oedema volume, presence of oedema within the PLIC, the fractional anisotropy threshold (FAT) to elicit a minimum amount of fibres and the minimal fibre length. The results showed a higher proportion of plausible fibre tracts for the aiP-ROI compared to the PLIC-ROI. Low FAT values and the presence of peritumoural oedema within the PLIC led to less plausible fibre tracking results. Most plausible results were obtained when the FAT ranged above a cut-off of 0.105. In addition, there was a strong effect of somatotopic location of the seed ROI; best plausibility was obtained for the contralateral hand CST (100%), followed by the ipsilesional hand CST (>95%), the ipsilesional foot (>85%) and tongue (>75%) CST. In summary, we found that the aiP-ROI yielded better tracking results compared to the IC-ROI when using deterministic CST tractography in brain tumour patients, especially when the M1 hand area was tracked. In case of FAT values lower than 0.10, the result of the respective CST tractography should be interpreted with caution with respect to spurious tracking results. Moreover, the presence of oedema within the internal capsule should be considered a negative predictor for plausible CST tracking.

Functional MRI vs. navigated TMS to optimize M1 seed volume delineation for DTI tractography. A prospective study in patients with brain tumours adjacent to the corticospinal tract.

Background DTI-based tractography is an increasingly important tool for planning brain surgery in patients suffering from brain tumours. However, there is an ongoing debate which tracking approaches yield the most valid results. Especially the use of functional localizer data such as navigated transcranial magnetic stimulation (nTMS) or functional magnetic resonance imaging (fMRI) seem to improve fibre tracking data in conditions where anatomical landmarks are less informative due to tumour-induced distortions of the gyral anatomy. We here compared which of the two localizer techniques yields more plausible results with respect to mapping different functional portions of the corticospinal tract (CST) in brain tumour patients. Methods The CSTs of 18 patients with intracranial tumours in the vicinity of the primary motor area (M1) were investigated by means of deterministic DTI. The core zone of the tumour-adjacent hand, foot and/or tongue M1 representation served as cortical regions of interest (ROIs). M1 core zones were defined by both the nTMS hot-spots and the fMRI local activation maxima. In addition, for all patients, a subcortical ROI at the level of the inferior anterior pons was implemented into the tracking algorithm in order to improve the anatomical specificity of CST reconstructions. As intra-individual control, we additionally tracked the CST of the hand motor region of the unaffected, i.e., non-lesional hemisphere, again comparing fMRI and nTMS M1 seeds. The plausibility of the fMRI-ROI- vs. nTMS-ROI-based fibre trajectories was assessed by a-priori defined anatomical criteria. Moreover, the anatomical relationship of different fibre courses was compared regarding their distribution in the anterior-posterior direction as well as their location within the posterior limb of the internal capsule (PLIC). Results Overall, higher plausibility rates were observed for the use of nTMS- as compared to fMRI-defined cortical ROIs (p < 0.05) in tumour vicinity. On the non-lesional hemisphere, however, equally good plausibility rates (100%) were observed for both localizer techniques. fMRI-originated fibres generally followed a more posterior course relative to the nTMS-based tracts (p < 0.01) in both the lesional and non-lesional hemisphere. Conclusion NTMS achieved better tracking results than fMRI in conditions when the cortical tract origin (M1) was located in close vicinity to a brain tumour, probably influencing neurovascular coupling. Hence, especially in situations with altered BOLD signal physiology, nTMS seems to be the method of choice in order to identify seed regions for CST mapping in patients.

The Dual Layer Casper Micromesh Stent: Taking Advantage of Flow-Diverting Capabilities for the Treatment of Extracranial Aneurysms and Pseudoaneurysms

(Microvention, Tustin, CA) is a low-profile closed cell stent with an increased mesh density and reduced pore size compared to commonly utilized stents in carotid artery procedures. We describe our preliminary experience from flow diversion in two iatrogenic ECAP with the Casper stent in a retrospective observational analysis of patients with extracranial aneurysms treated endovascularly with the Casper stent. Patients were followed for up to 6 months (clinical exam and imaging). According to the institutional review board, the current analysis did not require approval. All patients or their legal representatives gave informed consent.

Fully automated detection and segmentation of meningiomas using deep learning on routine multiparametric MRI

ObjectivesMagnetic resonance imaging (MRI) is the method of choice for imaging meningiomas. Volumetric assessment of meningiomas is highly relevant for therapy planning and monitoring. We used a multiparametric deep-learning model (DLM) on routine MRI data including images from diverse referring institutions to investigate DLM performance in automated detection and segmentation of meningiomas in comparison to manual segmentations.MethodsWe included 56 of 136 consecutive preoperative MRI datasets [T1/T2-weighted, T1-weighted contrast-enhanced (T1CE), FLAIR] of meningiomas that were treated surgically at the University Hospital Cologne and graded histologically as tumour grade I (n = 38) or grade II (n = 18). The DLM was trained on an independent dataset of 249 glioma cases and segmented different tumour classes as defined in the brain tumour image segmentation benchmark (BRATS benchmark). The DLM was based on the DeepMedic architecture. Results were compared to manual segmentations by two radiologists in a consensus reading in FLAIR and T1CE.ResultsThe DLM detected meningiomas in 55 of 56 cases. Further, automated segmentations correlated strongly with manual segmentations: average Dice coefficients were 0.81 ± 0.10 (range, 0.46-0.93) for the total tumour volume (union of tumour volume in FLAIR and T1CE) and 0.78 ± 0.19 (range, 0.27-0.95) for contrast-enhancing tumour volume in T1CE.ConclusionsThe DLM yielded accurate automated detection and segmentation of meningioma tissue despite diverse scanner data and thereby may improve and facilitate therapy planning as well as monitoring of this highly frequent tumour entity.Key Points• Deep learning allows for accurate meningioma detection and segmentation• Deep learning helps clinicians to assess patients with meningiomas• Meningioma monitoring and treatment planning can be improved

Bilateral hypoglossal nerve palsy and unilateral recurrent laryngeal nerve palsy following lumbar discectomy: A case report.

Having started with depositing 5 ml of bupivacaine 0.5% around each nerve, the 1 ml per nerve volume was reached by the fifth recruited patient. Successful surgical anaesthesia was accomplished in the next eight consecutive patients with the same volume. No immediate adverse event related to the nerve blocks, that is vascular injury or signs of local anaesthetic toxicity, was noted. Sensory block onset times (median value and interquartile range) for musculocutaneous, median, ulnar and radial nerves were 10 (5–10), 10 (5–20), 10 (5–15) and 10 (5–20) min, whereas motor block onset times were 10 (5–10), 15 (10–15), 10 (10–15) and 10 (5–15) min, respectively. All but one nerve of the entire study group were fully anaesthetised within 45 min of completion of the ABPB block. The outlier was the motor block in the median innervation territory of one patient (who got 1 ml of bupivacaine 0.5%) with an onset time of 55 min. At that point, however, the patient had surgical anaesthesia of the entire forearm and the operation was uneventful under regional anaesthesia alone. The prolonged onset time could have been the consequence of an anatomical variation as branches have been described far away from the most visible main tract. Uneven local anaesthetic distribution could also delay the development of the block. All patients had adequate surgical anaesthesia without any discomfort in the surgical field. No patient requested intraoperative sedation. One patient (1 ml per nerve bupivacaine 0.5% used) experienced slight tourniquet pain 60 min after cuff inflation, which was successfully treated with 100 mcg of intravenous fentanyl. Tourniquet pain is not uncommon with higher doses of local anaesthetic; therefore it is unlikely to be a direct consequence of the low dose of local anaesthetic used.

66‐Year Old Man with Facial Pain

A 66-year-old man with a medical history of metastatic prostate cancer (Stage IV) had undergone systemic chemotherapy until June and received hormone therapy since then. Regular follow-up examinations showed stable disease. A bone scintigraphy 2 weeks prior to presentation showed known diffuse metastases throughout the skeleton, excluding the cranium. In August the patient presented to the emergency room with a 10 day history of progressive right-sided facial pain, diplopia and drooping of his right upper eyelid. On physical examination he was alert and complained about right deep orbital pain, numbness down the right side of his face and horizontal diplopia. Neurological examination showed cranial nerves I-V and VII-XII intact, a severe abducens nerve palsy and a slight ptosis on the right side. The right pupil was slightly dilated but round and reactive to light. Ocular fundi were normal. The right-sided facial pain followed the distribution of the first and second branch of the trigeminal nerve. Hypoand paresthesia was stated along the distribution of all three divisions of the right trigeminal nerve. Complete blood count and the serum examination were within normal ranges except for a slight elevation of the prostate-specific antigen level (35 mg/L). A contrast CT scan including bone windows showed a hyperdense lesion adjacent to the right petrous apex and sphenoid wing and was interpreted as meningioma (Figure 1A). On MRI, a homogenous lesion involving the right petrous apex and the medial sphenoid wing infiltrating the ipsilateral cavernous sinus was revealed (Figure 1B). The mass appeared hypointense in T2weighed images and showed only slight contrast-enhancement in T1-weighed images. The white matter of the right temporal lobe and the amygdala showed signal enhancement in T2WI, suggesting edema. There were no signs of bone metastasis to the skull based on CT and MR imaging. Differential diagnoses based on neuroimaging were meningioma of the petrous-temporal bone, extra-axial metastasis and primary brain tumor. The rapid progression of the patient’s clinical signs was atypical for the clinical presentation of a meningioma. Thus the patient underwent craniotomy for partial resection of the tumor via a pterional/subtemporal approach. Intra-operatively, an extra-axial tumor with soft consistency and mild vascularization was found. The intraoperative tumor morphology was not typical for meningioma; thus smear preparations were initiated, which showed a highly proliferative tumor suspicious for malignant glioma.