Diffusion tensor imaging in anisotropic tissues: application of reduced gradient vector schemes in peripheral nerves

BACKGROUND

In contrast to the brain, fibers within peripheral nerves have distinct monodirectional structure questioning the necessity of complex multidirectional gradient vector schemes for DTI. This proof-of-concept study investigated the diagnostic utility of reduced gradient vector schemes in peripheral nerve DTI.

METHODS

Three-Tesla magnetic resonance neurography of the tibial nerve using 20-vector DTI (DTI20) was performed in 10 healthy volunteers, 12 patients with type 2 diabetes, and 12 age-matched healthy controls. From the full DTI20 dataset, three reduced datasets including only two or three vectors along the x- and/or y- and z-axes were built to calculate major parameters. The influence of nerve angulation and intraneural connective tissue was assessed. The area under the receiver operating characteristics curve (ROC-AUC) was used for analysis.

RESULTS

Simplified datasets achieved excellent diagnostic accuracy equal to DTI20 (ROC-AUC 0.847-0.868, p ≤ 0.005), but compared to DTI20, the reduced models yielded mostly lower absolute values of DTI scalars: median fractional anisotropy (FA) ≤ 0.12; apparent diffusion coefficient (ADC) ≤ 0.25; axial diffusivity ≤ 0.96, radial diffusivity ≤ 0.07). The precision of FA and ADC with the three-vector model was closest to DTI20. Intraneural connective tissue was negatively correlated with FA and ADC (r ≥ -0.49, p < 0.001). Small deviations of nerve angulation had little effect on FA accuracy.

CONCLUSIONS

In peripheral nerves, bulk tissue DTI metrics can be approximated with only three predefined gradient vectors along the scanner's main axes, yielding similar diagnostic accuracy as a 20-vector DTI, resulting in substantial scan time reduction.

RELEVANCE STATEMENT

DTI bulk tissue parameters of peripheral nerves can be calculated with only three predefined gradient vectors at similar diagnostic performance as a standard DTI but providing a substantial scan time reduction.

KEY POINTS

• In peripheral nerves, DTI parameters can be approximated using only three gradient vectors. • The simplified model achieves a similar diagnostic performance as a standard DTI. • The simplified model allows for a significant acceleration of image acquisition. • This can help to introduce multi-b-value DTI techniques into clinical practice.

Association of Small Fiber Function with Microvascular Perfusion of Peripheral Nerves in Patients with Type 2 Diabetes : Study using Quantitative Sensory Testing and Magnetic Resonance Neurography

INTRODUCTION/AIMS

Diabetic small fiber neuropathy (SFN) is caused by damage to thinly myelinated A‑fibers (δ) and unmyelinated C‑fibers. This study aimed to assess associations between quantitative sensory testing (QST) and parameters of peripheral nerve perfusion obtained from dynamic contrast enhanced (DCE) magnetic resonance neurography (MRN) in type 2 diabetes patients with and without SFN.

METHODS

A total of 18 patients with type 2 diabetes (T2D, 8 with SFN, 10 without SFN) and 10 healthy controls (HC) took part in this cross-sectional single-center study and underwent QST of the right leg and DCE-MRN of the right thigh with subsequent calculation of the sciatic nerve constant of capillary permeability (Ktrans), extravascular extracellular volume fraction (Ve), and plasma volume fraction (Vp).

RESULTS

The Ktrans (HC 0.031 min-1 ± 0.009, T2D 0.043 min-1 ± 0.015; p = 0.033) and Ve (HC 1.2% ± 1.5, T2D: 4.1% ± 5.1; p = 0.027) were lower in T2D patients compared to controls. In T2D patients, compound z‑scores of thermal and mechanical detection correlated with Ktrans (r = 0.73; p = 0.001, and r = 0.57; p = 0.018, respectively) and Ve (r = 0.67; p = 0.002, and r = 0.69; p = 0.003, respectively). Compound z‑scores of thermal pain and Vp (r = -0.57; p = 0.015) correlated negatively.

DISCUSSION

The findings suggest that parameters of peripheral nerve microcirculation are related to different symptoms in SFN: A reduced capillary permeability may result in a loss of function related to insufficient nutritional supply, whereas increased capillary permeability may be accompanied by painful symptoms related to a gain of function.

Microstructural changes of peripheral nerves in early multiple sclerosis: A prospective magnetic resonance neurography study

BACKGROUND AND PURPOSE

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system (CNS). However, there is increasing evidence of peripheral nerve involvement. This study aims to characterize the pattern of peripheral nerve changes in patients with newly diagnosed MS using quantitative magnetic resonance (MR) neurography.

METHODS

In this prospective study, 25 patients first diagnosed with MS according to the revised McDonald criteria (16 female, mean age = 32.8 ± 10.6 years) and 14 healthy controls were examined with high-resolution 3-T MR neurography of the sciatic nerve using diffusion kurtosis imaging (DKI; 20 diffusional directions, b = 0, 700, 1200 s/mm2 ) and magnetization transfer imaging (MTI). In total, 15 quantitative MR biomarkers were analyzed and correlated with clinical symptoms, intrathecal immunoglobulin synthesis, electrophysiology, and lesion load on brain and spine MR imaging.

RESULTS

Patients showed decreased fractional anisotropy (mean = 0.51 ± 0.04 vs. 0.56 ± 0.03, p < 0.001), extra-axonal tortuosity (mean = 2.32 ± 0.17 vs. 2.49 ± 0.17, p = 0.008), and radial kurtosis (mean = 1.40 ± 0.23 vs. 1.62 ± 0.23, p = 0.014) and higher radial diffusivity (mean = 1.09 ∙ 10-3  mm2 /s ± 0.16 vs. 0.98 ± 0.11 ∙ 10-3  mm2 /s, p = 0.036) than controls. Groups did not differ in MTI. No significant association was found between MR neurography markers and clinical/laboratory parameters or CNS lesion load.

CONCLUSIONS

This study provides further evidence of peripheral nerve involvement in MS already at initial diagnosis. The characteristic pattern of DKI parameters indicates predominant demyelination and suggests a primary coaffection of the peripheral nervous system in MS. This first human study using DKI for peripheral nerves shows its potential and clinical feasibility in providing novel biomarkers.

Magnetization transfer ratio of the sciatic nerve differs between patients in type 1 and type 2 diabetes

BACKGROUND

Previous studies on magnetic resonance neurography (MRN) found different patterns of structural nerve damage in type 1 diabetes (T1D) and type 2 diabetes (T2D). Magnetization transfer ratio (MTR) is a quantitative technique to analyze the macromolecular tissue composition. We compared MTR values of the sciatic nerve in patients with T1D, T2D, and healthy controls (HC).

METHODS

3-T MRN of the right sciatic nerve at thigh level was performed in 14 HC, 10 patients with T1D (3 with diabetic neuropathy), and 28 patients with T2D (10 with diabetic neuropathy). Results were subsequently correlated with clinical and electrophysiological data.

RESULTS

The sciatic nerve's MTR was lower in patients with T2D (0.211 ± 0.07, mean ± standard deviation) compared to patients with T1D (T1D 0.285 ± 0.03; p = 0.015) and HC (0.269 ± 0.05; p = 0.039). In patients with T1D, sciatic MTR correlated positively with tibial nerve conduction velocity (NCV; r = 0.71; p = 0.021) and negatively with hemoglobin A1c (r =  - 0.63; p < 0.050). In patients with T2D, we found negative correlations of sciatic nerve's MTR peroneal NCV (r =  - 0.44; p = 0.031) which remained significant after partial correlation analysis controlled for age and body mass index (r = 0.51; p = 0.016).

CONCLUSIONS

Lower MTR values of the sciatic nerve in T2D compared to T1D and HC and diametrical correlations of MTR values with NCV in T1D and T2D indicate that there are different macromolecular changes and pathophysiological pathways underlying the development of neuropathic nerve damage in T1D and T2D.

TRIAL REGISTRATION

https://classic.

CLINICALTRIALS

gov/ct2/show/NCT03022721 . 16 January 2017.

RELEVANCE STATEMENT

Magnetization transfer ratio imaging may serve as a non-invasive imaging method to monitor the diseases progress and to encode the pathophysiology of nerve damage in patients with type 1 and type 2 diabetes.

KEY POINTS

• Magnetization transfer imaging detects distinct macromolecular nerve lesion patterns in diabetes patients. • Magnetization transfer ratio was lower in type 2 diabetes compared to type 1 diabetes. • Different pathophysiological mechanisms drive nerve damage in type 1 and 2 diabetes.

Insulin Resistance Is Associated With Reduced Capillary Permeability of Thigh Muscles in Patients With Type 2 Diabetes

CONTEXT

Insulin-mediated microvascular permeability and blood flow of skeletal muscle appears to be altered in the condition of insulin resistance. Previous studies on this effect used invasive procedures in humans or animals.

OBJECTIVE

The aim of this study was to demonstrate the feasibility of a noninvasive assessment of human muscle microcirculation via dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) of skeletal muscle in patients with type 2 diabetes (T2D).

METHODS

A total of 56 participants (46 with T2D, 10 healthy controls [HC]) underwent DCE-MRI of the right thigh at 3 Tesla. The constant of the musculature's microvascular permeability (Ktrans), extravascular extracellular volume fraction (ve), and plasma volume fraction (vp) were calculated.

RESULTS

In T2D patients, skeletal muscle Ktrans was lower (HC 0.0677 ± 0.002 min-1, T2D 0.0664 ± 0.002 min-1; P = 0.042) while the homeostasis model assessment (HOMA) index was higher in patients with T2D compared to HC (HC 2.72 ± 2.2, T2D 6.11 ± 6.2; P = .011). In T2D, Ktrans correlated negatively with insulin (r = -0.39, P = .018) and HOMA index (r = -0.38, P = .020).

CONCLUSION

The results signify that skeletal muscle DCE-MRI can be employed as a noninvasive technique for the assessment of muscle microcirculation in T2D. Our findings suggest that microvascular permeability of skeletal muscle is lowered in patients with T2D and that a decrease in microvascular permeability is associated with insulin resistance. These results are of interest with regard to the impact of muscle perfusion on diabetic complications such as diabetic sarcopenia.

In vivo nanoparticle-based T cell imaging can predict therapy response towards adoptive T cell therapy in experimental glioma

Rationale: Intrinsic brain tumors, such as gliomas are largely resistant to immunotherapies including immune checkpoint blockade. Adoptive cell therapies (ACT) including chimeric antigen receptor (CAR) or T cell receptor (TCR)-transgenic T cell therapy targeting glioma-associated antigens are an emerging field in glioma immunotherapy. However, imaging techniques for non-invasive monitoring of adoptively transferred T cells homing to the glioma microenvironment are currently lacking. Methods: Ultrasmall iron oxide nanoparticles (NP) can be visualized non-invasively by magnetic resonance imaging (MRI) and dedicated MRI sequences such as T2* mapping. Here, we develop a protocol for efficient ex vivo labeling of murine and human TCR-transgenic and CAR T cells with iron oxide NPs. We assess labeling efficiency and T cell functionality by flow cytometry and transmission electron microscopy (TEM). NP labeled T cells are visualized by MRI at 9.4 T in vivo after adoptive T cell transfer and correlated with 3D models of cleared brains obtained by light sheet microscopy (LSM). Results: NP are incorporated into T cells in subcellular cytoplasmic vesicles with high labeling efficiency without interfering with T cell viability, proliferation and effector function as assessed by cytokine secretion and antigen-specific killing assays in vitro. We further demonstrate that adoptively transferred T cells can be longitudinally monitored intratumorally by high field MRI at 9.4 Tesla in a murine glioma model with high sensitivity. We find that T cell influx and homogenous spatial distribution of T cells within the TME as assessed by T2* imaging predicts tumor response to ACT whereas incomplete T cell coverage results in treatment resistance. Conclusion: This study showcases a rational for monitoring adoptive T cell therapies non-invasively by iron oxide NP in gliomas to track intratumoral T cell influx and ultimately predict treatment outcome.

MR microscopy to assess clot composition following mechanical thrombectomy predicts recanalization and clinical outcome

BACKGROUND

Mechanical thrombectomy (MT) is the standard of care for patients with a stroke and large vessel occlusion. Clot composition is not routinely assessed in clinical practice as no specific diagnostic value is attributed to it, and MT is performed in a standardized 'non-personalized' approach. Whether different clot compositions are associated with intrinsic likelihoods of recanalization success or treatment outcome is unknown.

METHODS

We performed a prospective, non-randomized, single-center study and analyzed the clot composition in 60 consecutive patients with ischemic stroke undergoing MT. Clots were assessed by ex vivo multiparametric MRI at 9.4 T (MR microscopy), cone beam CT, and histopathology. Clot imaging was correlated with preinterventional CT and clinical data.

RESULTS

MR microscopy showed red blood cell (RBC)-rich (21.7%), platelet-rich (white,38.3%) or mixed clots (40.0%) as distinct morphological entities, and MR microscopy had high accuracy of 95.4% to differentiate clots. Clot composition could be further stratified on preinterventional non-contrast head CT by quantification of the hyperdense artery sign. During MT, white clots required more passes to achieve final recanalization and were not amenable to contact aspiration compared with mixed and RBC-rich clots (maneuvers: 4.7 vs 3.1 and 1.2 passes, P<0.05 and P<0.001, respectively), whereas RBC-rich clots showed higher probability of first pass recanalization (76.9%) compared with white clots (17.4%). White clots were associated with poorer clinical outcome at discharge and 90 days after MT.

CONCLUSION

Our study introduces MR microscopy to show that the hyperdense artery sign or MR relaxometry could guide interventional strategy. This could enable a personalized treatment approach to improve outcome of patients undergoing MT.

A Cellular Ground Truth to Develop MRI Signatures in Glioma Models by Correlative Light Sheet Microscopy and Atlas-Based Coregistration

Glioblastoma is the most common malignant primary brain tumor with poor overall survival. Magnetic resonance imaging (MRI) is the main imaging modality for glioblastoma but has inherent shortcomings. The molecular and cellular basis of MR signals is incompletely understood. We established a ground truth-based image analysis platform to coregister MRI and light sheet microscopy (LSM) data to each other and to an anatomic reference atlas for quantification of 20 predefined anatomic subregions. Our pipeline also includes a segmentation and quantification approach for single myeloid cells in entire LSM datasets. This method was applied to three preclinical glioma models in male and female mice (GL261, U87MG, and S24), which exhibit different key features of the human glioma. Multiparametric MR data including T2-weighted sequences, diffusion tensor imaging, T2 and T2* relaxometry were acquired. Following tissue clearing, LSM focused on the analysis of tumor cell density, microvasculature, and innate immune cell infiltration. Correlated analysis revealed differences in quantitative MRI metrics between the tumor-bearing and the contralateral hemisphere. LSM identified tumor subregions that differed in their MRI characteristics, indicating tumor heterogeneity. Interestingly, MRI signatures, defined as unique combinations of different MRI parameters, differed greatly between the models. The direct correlation of MRI and LSM allows an in-depth characterization of preclinical glioma and can be used to decipher the structural, cellular, and, likely, molecular basis of tumoral MRI biomarkers. Our approach may be applied in other preclinical brain tumor or neurologic disease models, and the derived MRI signatures could ultimately inform image interpretation in a clinical setting.SIGNIFICANCE STATEMENT We established a histologic ground truth-based approach for MR image analyses and tested this method in three preclinical glioma models exhibiting different features of glioblastoma. Coregistration of light sheet microscopy to MRI allowed for an evaluation of quantitative MRI data in histologically distinct tumor subregions. Coregistration to a mouse brain atlas enabled a regional comparison of MRI parameters with a histologically informed interpretation of the results. Our approach is transferable to other preclinical models of brain tumors and further neurologic disorders. The method can be used to decipher the structural, cellular, and molecular basis of MRI signal characteristics. Ultimately, information derived from such analyses could strengthen the neuroradiological evaluation of glioblastoma as they enhance the interpretation of MRI data.

T cell-independent eradication of experimental glioma by intravenous TLR7/8-agonist-loaded nanoparticles

Glioblastoma, the most common and aggressive primary brain tumor type, is considered an immunologically "cold" tumor with sparse infiltration by adaptive immune cells. Immunosuppressive tumor-associated myeloid cells are drivers of tumor progression. Therefore, targeting and reprogramming intratumoral myeloid cells is an appealing therapeutic strategy. Here, we investigate a β-cyclodextrin nanoparticle (CDNP) formulation encapsulating the Toll-like receptor 7 and 8 (TLR7/8) agonist R848 (CDNP-R848) to reprogram myeloid cells in the glioma microenvironment. We show that intravenous monotherapy with CDNP-R848 induces regression of established syngeneic experimental glioma, resulting in increased survival rates compared with unloaded CDNP controls. Mechanistically, CDNP-R848 treatment reshapes the immunosuppressive tumor microenvironment and orchestrates tumor clearing by pro-inflammatory tumor-associated myeloid cells, independently of T cells and NK cells. Using serial magnetic resonance imaging, we identify a radiomic signature in response to CDNP-R848 treatment and ultrasmall superparamagnetic iron oxide (USPIO) imaging reveals that immunosuppressive macrophage recruitment is reduced by CDNP-R848. In conclusion, CDNP-R848 induces tumor regression in experimental glioma by targeting blood-borne macrophages without requiring adaptive immunity.

NIMG-41. NON-INVASIVE TRACKING OF T-CELL RECRUITMENT TO THE TUMOR MICROENVIRONMENT IN A MURINE GLIOMA MODEL BY HIGH FIELD CELLULAR MRI

Gliomas are characterized by increased T cell exhaustion and poor T cell infiltration into the tumor as well as an overall highly immunosuppressive tumor microenvironment (TME). Response rates in preclinical glioma models and patients to promising new therapeutic approaches in the field of immunotherapies - such as checkpoint blockade, vaccines and adoptive therapy with chimeric antigen receptor (CAR) or T cell receptor (TCR)-transgenic T cells - remain heterogeneous. This demonstrates the need for non-invasive tracking of T cell recruitment to the TME in order to monitor T cell activating immunotherapies, adapt therapeutic strategies and predict treatment outcome. Iron oxide nanoparticles (NP) can be visualized non-invasively by magnetic resonance imaging (MRI) and dedicated MRI sequences such as T2* mapping. Using isolated murine T cells cultures we show that labeling of T cells with iron oxide NP as contrast agent is feasible and does not impact T cell viability and functionality as assessed by cytokine secretion and antigen-specific killing activity in vitro. We demonstrate that adoptively transferred T cells can be visualized intratumorally in a murine glioma model by high field MRI at 9.4 Tesla with high sensitivity and that T cells can be tracked non-invasively in a time course of over one week. Ongoing work assesses preclinical efficacy of adoptive T cell therapy targeting well characterized model antigens expressed in experimental gliomas using longitudinal MRI to visualize spatial and temporal T-cell dynamics in the TME. Correlative methods include immunohistochemistry, flow cytometry, tissue clearing and ultramicroscopy. We hypothesize that T cell distribution and numbers may predict therapeutic efficacy and correlate with treatment outcome in experimental gliomas.

Diffusion MRI in Peripheral Nerves: Optimized b Values and the Role of Non-Gaussian Diffusion

Background Diffusion-weighted imaging (DWI) provides specific in vivo information about tissue microstructure, which is increasingly recognized for various applications outside the central nervous system. However, standard sequence parameters are commonly adopted from optimized central nervous system protocols, thus potentially neglecting differences in tissue-specific diffusional behavior. Purpose To characterize the optimal tissue-specific diffusion imaging weighting scheme over the b domain in peripheral nerves under physiologic and pathologic conditions. Materials and Methods In this prospective cross-sectional study, 3-T MR neurography of the sciatic nerve was performed in healthy volunteers (n = 16) and participants with type 2 diabetes (n = 12). For DWI, 16 b values in the range of 0-1500 sec/mm² were acquired in axial and radial diffusion directions of the nerve. With a region of interest-based approach, diffusion-weighted signal behavior as a function of b was estimated using standard monoexponential, biexponential, and kurtosis fitting. Goodness of fit was assessed to determine the optimal b value for two-point DWI/diffusion tensor imaging (DTI). Results Non-Gaussian diffusional behavior was observed beyond b values of 600 sec/mm² in the axial and 800 sec/mm² in the radial diffusion direction in both participants with diabetes and healthy volunteers. Accordingly, the biexponential and kurtosis models achieved a better curve fit compared with the standard monoexponential model (Akaike information criterion >99.9% in all models), but the kurtosis model was preferred in the majority of cases. Significant differences between healthy volunteers and participants with diabetes were found in the kurtosis-derived parameters D_k and K. The results suggest an upper bound b value of approximately 700 sec/mm² for optimal standard DWI/DTI in peripheral nerve applications. Conclusion In MR neurography, an ideal standard diffusion-weighted imaging/diffusion tensor imaging protocol with b = 700 sec/mm² is suggested. This is substantially lower than in the central nervous system due to early-occurring non-Gaussian diffusion behavior and emphasizes the need for tissue-specific b value optimization. Including higher b values, kurtosis-derived parameters may represent promising novel imaging markers of peripheral nerve disease. ©RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Jang and Du in this issue.

Characterization of experimental diabetic neuropathy using multicontrast magnetic resonance neurography at ultra high field strength

In light of the limited treatment options of diabetic polyneuropathy (DPN) available, suitable animal models are essential to investigate pathophysiological mechanisms and to identify potential therapeutic targets. In vivo evaluation with current techniques, however, often provides only restricted information about disease evolution. In the study of patients with DPN, magnetic resonance neurography (MRN) has been introduced as an innovative diagnostic tool detecting characteristic lesions within peripheral nerves. We developed a novel multicontrast ultra high field MRN strategy to examine major peripheral nerve segments in diabetic mice non-invasively. It was first validated in a cross-platform approach on human nerve tissue and then applied to the popular streptozotocin(STZ)-induced mouse model of DPN. In the absence of gross morphologic alterations, a distinct MR-signature within the sciatic nerve was observed mirroring subtle changes of the nerves’ fibre composition and ultrastructure, potentially indicating early re-arrangements of DPN. Interestingly, these signal alterations differed from previously reported typical nerve lesions of patients with DPN. The capacity of our approach to non-invasively assess sciatic nerve tissue structure and function within a given mouse model provides a powerful tool for direct translational comparison to human disease hallmarks not only in diabetes but also in other peripheral neuropathic conditions.

Probabilistic mapping of the antidystonic effect of pallidal neurostimulation: a multicentre imaging study

Deep brain stimulation of the internal globus pallidus is a highly effective and established therapy for primary generalized and cervical dystonia, but therapeutic success is compromised by a non-responder rate of up to 25%, even in carefully-selected groups. Variability in electrode placement and inappropriate stimulation settings may account for a large proportion of this outcome variability. Here, we present probabilistic mapping data on a large cohort of patients collected from several European centres to resolve the optimal stimulation volume within the pallidal region. A total of 105 dystonia patients with pallidal deep brain stimulation were enrolled and 87 datasets (43 with cervical dystonia and 44 with generalized dystonia) were included into the subsequent 'normative brain' analysis. The average improvement of dystonia motor score was 50.5 ± 30.9% in cervical and 58.2 ± 48.8% in generalized dystonia, while 19.5% of patients did not respond to treatment (<25% benefit). We defined probabilistic maps of anti-dystonic effects by aggregating individual electrode locations and volumes of tissue activated (VTA) in normative atlas space and ranking voxel-wise for outcome distribution. We found a significant relation between motor outcome and the stimulation volume, but not the electrode location per se. The highest probability of stimulation induced motor benefit was found in a small volume covering the ventroposterior globus pallidus internus and adjacent subpallidal white matter. We then used the aggregated VTA-based outcome maps to rate patient individual VTAs and trained a linear regression model to predict individual outcomes. The prediction model showed robustness between the predicted and observed clinical improvement, with an r2 of 0.294 (P < 0.0001). The predictions deviated on average by 16.9 ± 11.6 % from observed dystonia improvements. For example, if a patient improved by 65%, the model would predict an improvement between 49% and 81%. Results were validated in an independent cohort of 10 dystonia patients, where prediction and observed benefit had a correlation of r2 = 0.52 (P = 0.02) and a mean prediction error of 10.3% (±8.9). These results emphasize the potential of probabilistic outcome brain mapping in refining the optimal therapeutic volume for pallidal neurostimulation and advancing computer-assisted planning and programming of deep brain stimulation.

Carbon analysis of steel using compact spectrometer and passively Q-switched laser for laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is carried out with compact 1064 nm laser and spectrometer components which are suitable for handheld applications. Bursts of ∼0.6 mJ, 5 ns laser pulses are generated by a passively Q-switched laser with a 1 kHz triggered pump diode. The miniature spectrometer with a set wavelength range of ∼188-251 nm has an instrumental broadening at the carbon analyte line, C I 193.09 nm, of less than 36 pm. Analytical calibration curves of C, as well as Cr, Ni, and Si are taken with certified reference samples of iron and steel in an argon purged setup. The net duration of the laser bursts is ∼0.7-1.4 s for a measurement, depending on the number of repetitions on the sample surface. The limit of detection (LOD) is determined to a mass fraction of 34 µg/g for C. High-alloy steels 1.4306 (0.01% C) and 1.4541 (0.035% C) are separated clearly by the LIBS measurement of carbon.

EXTH-17. TREATMENT OF MALIGNANT GLIOMAS WITH DRUG-LOADED MICROBUBBLES: CONCEPTION OF A PROMISING FUTURE THERAPEUTIC STRATEGY

The major obstacles for an effective chemotherapy of glioblastomas (GBM) are the blood-brain barrier (BBB) and serious systemic side effects of the cytotoxic drugs. A new promising strategy could be the delivery of the chemotherapeutics across the BBB to the tumor site encapsulated in microbubbles. The microbubbles will shield the drug from detrimental systemic effects. Low intensity focused ultrasound (LIFU) allows opening of the BBB and a targeted release of the drugs within the brain tumor. We synthesized microbubbles ≤ 2 µm in diameter by thin-film hydration of lipids, which could be disintegrated applying LIFU. The toxicity was tested on GBM cell lines and neither the intact bubbles nor the lipids alone showed any toxic effects. Additionally, these cells were treated with 6 platinum(II) and palladium(II) complexes conjugated to lipophilic side chains of different length (C1, C8, C10) for 72 h. Cell viability was evaluated with MTT assay and in real-time utilizing the impedance-based xCELLigence DP-System. EC50 values were calculated from both assays and all six drugs were highly effective. Especially the palladium(II) compound with the C1-chain had a very low EC50 value (< 10 µM), while the longer chains and the platinum(II) compounds were less effective (EC50 10 - 30 µM). The real time proliferation assay of the drugs revealed an early and concentration-dependent onset of the cytotoxic effect, about 30 h after application. The lipophilic side chains of the drugs should allow encapsulating them into the microbubbles to develop an effective drug-delivery system for the treatment of GBM.

P11.44 Conception of a promising future therapy: Drug loaded-microbubbles against glioblastoma

BACKGROUND

Major obstacles for an effective chemotherapy of glioblastomas (GBM) are the blood-brain-barrier (BBB) and serious systemic side effects of the cytotoxic drugs. A new promising strategy could be the delivery of microbubbles, encapsulating the chemotherapeutics, across the BBB to the tumor site. This will shield the drug from detrimental systemic effects. Low intensity focused ultrasound (LIFU) is able to open the BBB and triggers targeted release of the drugs within the tumor. First data on the synthesis of microbubbles, specifically designed new drugs and the targeted rupture of microbubbles by LIFU are presented.

MATERIAL AND METHODS

Thin-film hydration of lipids was utilized to prepare microbubbles, which were tested for toxicity on the GBM cell lines GaMG, U87, U138 and U343. In addition these cells were treated with 6 platinum(II) and palladium(II) complexes conjugated to lipophilic side chains of different length (C1, C8, C10) for 72h. To evaluate cell viability and calculate EC50 values MTT assays and a real-time proliferation assay using the impedance-based xCELLigence DP-System were executed.

RESULTS

Microbubbles ≤ 2µm in diameter were synthesized and could be disintegrated by applying LIFU. Neither the intact bubbles nor the lipids alone had any toxic effects on the GBM cells. In contrast, all six drugs were highly effective with EC50 values far below those of Temozolomide (67µM) and in the range of the reference drug cisplatin (3µM). Especially the palladium(II) compound with the C1-chain displayed a very low EC50 value (<10µM), while the longer chains and the platinum(II) compounds were less effective (EC50 10–40µM). An early and concentration-dependent onset of the cytotoxic effect of drugs with C1 and C8 side chains was revealed in the real time proliferation assay.

CONCLUSION

All components for a new microbubble-based therapeutic strategy are in place. Microbubbles were synthesized without having toxic effects in cell culture. New highly potent palladium(II) and platinum(II) compounds with low EC50 values were developed. The next step will be their encapsulation into the microbubbles via their lipophilic side chains to develop an effective drug-delivery system for the treatment of GBM in combination with LIFU. This will allow increasing the local concentration of chemotherapeutic agents at the tumor site, irrespectively of their molecular size and BBB penetration capacity.

Open-label trial of anterior limb of internal capsule-nucleus accumbens deep brain stimulation for obsessive-compulsive disorder: insights gained

BACKGROUND

For more than 15 years, deep brain stimulation (DBS) has served as a last-resort treatment for severe treatment-resistant obsessive-compulsive disorder (OCD).

METHODS

From 2010 to 2016, 20 patients with OCD (10 men/10 women) were included in a single-centre trial with a naturalistic open-label design over 1 year to evaluate the effects of DBS in the anterior limb of the internal capsule and nucleus accumbens region (ALIC-NAcc) on OCD symptoms, executive functions, and personality traits.

RESULTS

ALIC-NAcc-DBS significantly decreased OCD symptoms (mean Yale-Brown Obsessive Compulsive Scale reduction 33%, 40% full responders) and improves global functioning without loss of efficacy over 1 year. No significant changes were found in depressive or anxiety symptoms. Our study did not show any effect of ALIC-NAcc-DBS on personality traits or executive functions, and no potential outcome predictors were identified in a post hoc analysis. Other than several individual minor adverse events, ALIC-NAcc-DBS has been shown to be safe, but 35% of patients reported a sudden increase in anxiety and anhedonia after acute cessation of stimulation.

CONCLUSIONS

We conclude that ALIC-NAcc-DBS is a well-tolerated and promising last-resort treatment option for OCD. The cause of variability in the outcome remains unclear, and the aspect of reversibility must be examined critically. The present data from one of the largest samples of patients with OCD treated with DBS thus far support the results of previous studies with smaller samples.

Prä- und intraoperative Volumenbestimmung bei Craniopharyngiomcysten

Die richtige Dosierung des 90Y für die intracavitäre Therapie bei monocystischen Craniopharyngiomen setzt die genaue Bestimmung des Cystenvolumens voraus. Der intraoperativen Volumenbestimmung mittels Radionuklid-Verdünnungsanalyse wurde die präoperative Volumetrie mit Hilfe von Computertomographieaufnahmen gegenübergestellt. Die Ergebnisse beider Verfahren zeigten eine gute übereinstimmung. Zur frühzeitigen Erkennung von Komplikationen werden Aufnahmen mit der Gammakamera als notwendig erachtet.

Neuroanatomical Characteristics Associated With Response to Deep Brain Stimulation of the Nucleus Basalis of Meynert for Alzheimer's Disease

OBJECTIVES

First reports on the application of deep brain stimulation (DBS) of the Nucleus basalis of Meynert (NBM) showed feasibility and safety of the intervention in patients with Alzheimer´s disease. However, clinical effects vary and the mechanisms of actions are still not well understood. The aim of this study was to characterize neuroimaging changes that are associated with the responsiveness to the treatment.

MATERIALS AND METHODS

We examined preoperative T1-weighted MR images of ten patients with Alzheimer's disease (AD) treated with DBS of the NBM and correlated the clinical outcome with volumetric differences of cortical thickness. Subsequently, we sought to identify brain regions that carry out the clinical effects by correlating the outcome with streamlines connected to the volume of activated tissue. Clinical assessments at baseline, 6 and 12 months after the intervention included the AD Assessment Scale as well as the mini mental status examination.

RESULTS

A fronto-parieto-temporal pattern of cortical thickness was found to be associated with beneficial outcome. Modulation of streamlines connected to left parietal and opercular cortices was associated with better response to the intervention.

CONCLUSION

Our results indicate that patients with less advanced atrophy may profit from DBS of the NBM. We conclude that beneficial effects of the intervention are related to preserved fronto-parieto-temporal interplay.

Deep Brain Stimulation of the H Fields of Forel Alleviates Tics in Tourette Syndrome

The current rationale for target selection in Tourette syndrome revolves around the notion of cortico-basal ganglia circuit involvement in the pathophysiology of the disease. However, despite extensive research, the ideal target for deep brain stimulation (DBS) is still under debate, with many structures being neglected and underexplored. Based on clinical observations and taking into account the prevailing hypotheses of network processing in Tourette syndrome, we chose the fields of Forel, namely field H1, as a target for DBS. The fields of Forel constitute the main link between the striatopallidal system and the thalamocortical network, relaying pallidothalamic projections from core anatomical structures to the thalamic ventral nuclear group. In a retrospective study we investigated two patients suffering from chronic, medically intractable Tourette syndrome who underwent bilateral lead implantation in field H1 of Forel. Clinical scales revealed significant alleviation of tics and comorbid symptoms, namely depression and anxiety, in the postoperative course in both patients.

Micro-Multileaf Collimator LINAC Radiosurgery for Vestibular Schwannomas

OBJECTIVE

This study evaluates the efficacy of linear accelerator (LINAC) radiosurgery using micro multi-leaf collimator technique (μMLC) in the treatment of a consecutive series of patients with vestibular schwannomas.

PATIENTS AND METHODS

In this retrospective study, we enrolled 50 patients with non-neurofibromatosis type 2 vestibular schwannoma who were treated with μMLC LINAC-based SRS at University Hospital of Cologne, Germany. A minimum clinical follow-up of 24 months was conducted. Thirty-nine out of the 50 tumors (78 %) were treated with μMLC LINAC as a primary treatment (a newly diagnosed tumor). The remaining 11 vestibular schwannomas (22%) were treated as a salvage treatment (5 patients with a residual tumor; and 6 patients with a recurrent tumor following a microsurgical resection). The median tumor volume was 1.4 ml. The median tumor surface dose, median maximal dose and median therapeutic isodose were 12 Gy, 16 Gy and 77% respectively.

RESULTS

Follow-up MR images showed that a tumor progression-free status was achieved for 95.7% of patients. Partial tumor shrinkage was observed after μMLC LINAC SRS for 21.3% of patients. No change in tumor size (a stable tumor) was noted for 74.5% of patients. Tumor progression was observed for 4.3% of patients. At the end of follow-up, the actuarial 5- year and 10 year progression-free survival after radiosurgery were both 95.7%.

CONCLUSIONS

LINAC radiosurgery using a micro multi-leaf collimator for vestibular schwannomas smaller than 3 cm is effective in yielding a high local tumor control, whereas the treatment-related morbidity remains low.

Deep Brain Stimulation of Medial Dorsal and Ventral Anterior Nucleus of the Thalamus in OCD: A Retrospective Case Series

BACKGROUND

The current notion that cortico-striato-thalamo-cortical circuits are involved in the pathophysiology of obsessive-compulsive disorder (OCD) has instigated the search for the most suitable target for deep brain stimulation (DBS). However, despite extensive research, uncertainty about the ideal target remains with many structures being underexplored. The aim of this report is to address a new target for DBS, the medial dorsal (MD) and the ventral anterior (VA) nucleus of the thalamus, which has thus far received little attention in the treatment of OCD.

METHODS

In this retrospective trial, four patients (three female, one male) aged 31-48 years, suffering from therapy-refractory OCD underwent high-frequency DBS of the MD and VA. In two patients (de novo group) the thalamus was chosen as a primary target for DBS, whereas in two patients (rescue DBS group) lead implantation was performed in a rescue DBS attempt following unsuccessful primary stimulation.

RESULTS

Continuous thalamic stimulation yielded no significant improvement in OCD symptom severity. Over the course of thalamic DBS symptoms improved in only one patient who showed "partial response" on the Yale-Brown Obsessive Compulsive (Y-BOCS) Scale. Beck Depression Inventory scores dropped by around 46% in the de novo group; anxiety symptoms improved by up to 34%. In the de novo DBS group no effect of DBS on anxiety and mood was observable.

CONCLUSION

MD/VA-DBS yielded no adequate alleviation of therapy-refractory OCD, the overall strategy in targeting MD/VA as described in this paper can thus not be recommended in DBS for OCD. The magnocellular portion of MD (MDMC), however, might prove a promising target in the treatment of mood related and anxiety disorders.

[Vision Screening in Zurich]

BACKGROUND

In the city of Zurich, vision screening is performed by school medical services as part of the legally compulsory preventive medical examinations. We retrospectively evaluated the results of the 2011-2012 school year.

PATIENTS AND METHODS

Preventive medical examinations by the school medical services were performed in all kindergartens. The examinations were mandatory for first, second and eighth grade children, whilst those for the fourth grade were voluntary. The basic diagnostic testing consisted of monocular visual acuity (Snellen E chart) for all age groups and the stereopsis test (TNO test) in kindergartens.

RESULTS

Vision screening was performed on 7499 children. 1471 first graders (55 %), 201 fourth graders (11 %) and 211 eighth graders (12.3 %) did not pass the examinations. In 33.7 % of the children who underwent the follow-up examination from an ophthalmologist, amblyogenic potential was found.

CONCLUSIONS

Vision screening by the school medical services enrols most of the children from a single age group. The Snellen E charts used for the monocular distance acuity, together with the TNO stereo test, appear to constitute an effective testing combination. Ophthalmological follow-up examinations of the affected children revealed that one third were afflicted by amblyogenic factors.

Effects of deep brain stimulation on prepulse inhibition in obsessive-compulsive disorder

Owing to a high response rate, deep brain stimulation (DBS) of the ventral striatal area has been approved for treatment-refractory obsessive-compulsive disorder (tr-OCD). Many basic issues regarding DBS for tr-OCD are still not understood, in particular, the mechanisms of action and the origin of side effects. We measured prepulse inhibition (PPI) in treatment-refractory OCD patients undergoing DBS of the nucleus accumbens (NAcc) and matched controls. As PPI has been used in animal DBS studies, it is highly suitable for translational research. Eight patients receiving DBS, eight patients with pharmacological treatment and eight age-matched healthy controls participated in our study. PPI was measured twice in the DBS group: one session with the stimulator switched on and one session with the stimulator switched off. OCD patients in the pharmacologic group took part in a single session. Controls were tested twice, to ensure stability of data. Statistical analysis revealed significant differences between controls and (1) patients with pharmacological treatment and (2) OCD DBS patients when the stimulation was switched off. Switching the stimulator on led to an increase in PPI at a stimulus-onset asynchrony of 200 ms. There was no significant difference in PPI between OCD patients being stimulated and the control group. This study shows that NAcc-DBS leads to an increase in PPI in tr-OCD patients towards a level seen in healthy controls. Assuming that PPI impairments partially reflect the neurobiological substrates of OCD, our results show that DBS of the NAcc may improve sensorimotor gating via correction of dysfunctional neural substrates. Bearing in mind that PPI is based on a complex and multilayered network, our data confirm that DBS most likely takes effect via network modulation.

Changes in Nutritional Status after Deep Brain Stimulation of the Nucleus Basalis of Meynert in Alzheimer's Disease--Results of a Phase I Study

OBJECTIVE

The progression of Alzheimer's disease (AD) is associated with impaired nutritional status. New methods, such as deep brain stimulation (DBS), are currently being tested to decrease the progression of AD. DBS is an approved method in the treatment of Parkinson's disease, and its suitability for the treatment of AD patients is currently under experimental investigation. To evaluate the advantages and disadvantages of this new treatment, it is important to assess potential side effects of DBS regarding the nucleus basalis of Meynert; this new treatment is thought to positively affect cognition and might counteract the deterioration of nutritional status and progressive weight loss observed in AD. This study aims to assess the nutritional status of patients with AD before receiving DBS of the nucleus basalis of Meynert and after 1 year, and to analyze potential associations between changes in cognition and nutritional status.

DESIGN

A 1-year phase I proof-of-concept study.

SETTING

The Department of Psychiatry and Psychotherapy at the University of Cologne.

PARTICIPANTS

We assessed a consecutive sample of patients with mild to moderate AD (n=6) who fulfilled the inclusion criteria and provided written informed consent.

INTERVENTION

Bilateral low-frequency DBS of the nucleus basalis of Meynert.

MEASUREMENTS

Nutritional status was assessed using a modified Mini Nutritional Assessment, bioelectrical impedance analysis, a completed 3-day food diary, and analysis of serum levels of vitamin B12 and folate.

RESULTS

With a normal body mass index (BMI) at baseline (mean 23.75 kg/m²) and after 1 year (mean 24.59 kg/m²), all but one patient gained body weight during the period of the pilot study (mean 2.38 kg, 3.81% of body weight). This was reflected in a mainly stable or improved body composition, assessed by bioelectrical impedance analysis, in five of the six patients. Mean energy intake increased from 1534 kcal/day (min 1037, max 2370) at baseline to 1736 kcal/day (min 1010, max 2663) after 1 year, leading to the improved fulfillment of energy needs in four patients. The only nutritional factors that were associated with changes in cognition were vitamin B12 level at baseline (Spearman's rho = 0.943, p = 0.005) and changes in vitamin B12 level (Spearman's rho = -0.829, p = 0.042).

CONCLUSION

Patients with AD that received DBS of the nucleus basalis of Meynert demonstrated a mainly stable nutritional status within a 1-year period. Whether DBS is causative regarding these observations must be investigated in additional studies.

Stereotactic LINAC radiosurgery for the treatment of typical intracranial meningiomas. Efficacy and safety after a follow-up of over 12 years

PURPOSE

The efficacy and safety of stereotactic radiosurgery (SRS) for treatment of intracranial meningiomas has been demonstrated in numerous studies with short- and intermediate-term follow-up. In this retrospective single-center study, we present long-term outcomes of SRS performed with a linear accelerator (LINAC) for typical intracranial meningiomas.

PATIENTS AND METHODS

Between August 1990 and December 2007, 148 patients with 168 typical intracranial meningiomas were treated with stereotactic LINAC-SRS, either as primary treatment or after microsurgical resection. A median tumor surface dose of 12 Gy (range 7-20 Gy) and a median maximum dose of 24.1 Gy (range 11.3-58.6 Gy) was applied. The median target volume was 4.7 ml (range 0.2-32.8 ml, SD ± 4.8 ml).

RESULTS

Overall mean radiological follow-up was 12.6 years. Tumor shrinkage was seen in 75 (44.6 %) and stable disease in 85 (50.6 %) cases. Eight of 168 meningiomas (4.8 %) showed local tumor progression. The tumor control rate (TCR) after 5, 10, and 15 years was 93.6 % at each time point, and the progression-free survival (PSF) rates were 92, 89, and 89 %, respectively. The neurological symptoms existing prior to LINAC-SRS improved in 77 patients (59.7 %), remained unchanged in 42 (32.6 %), and deteriorated in 10 (7.8 %) patients.

CONCLUSION

Our study emphasizes the efficacy of LINAC-SRS for de novo, residual and recurrent typical intracranial meningiomas. A high long-term local TCR with a low morbidity rate could be achieved. LINAC-SRS should thus be considered as a primary treatment option, as one arm of a combined treatment approach for incompletely resected meningiomas, or as a salvage therapy for recurrences.

Stereotactic LINAC-Radiosurgery for Glomus Jugulare Tumors: A Long-Term Follow-Up of 27 Patients

BACKGROUND

The optimal treatment of glomus jugulare tumors (GJTs) remains controversial. Due to the critical location, microsurgery still provides high treatment-related morbidity and a decreased quality of life. Thus, we performed stereotactical radiosurgery (SRS) for the treatment of GJTs and evaluated the long-term outcome.

METHODS

Between 1991 and 2011, 32 patients with GJTs underwent SRS using a linear accelerator (LINAC) either as primary or salvage therapy. Twenty-seven patients (median age 59.9 years, range 28.7-79.9 years) with a follow-up greater than five years (median 11 years, range 5.3-22.1 years) were selected for retrospective analysis. The median therapeutic single dose applied to the tumor surface was 15 Gy (range 11-20 Gy) and the median tumor volume was 9.5 ml (range 2.8-51 ml).

RESULTS

Following LINAC-SRS, 10 of 27 patients showed a significant improvement of their previous neurological complaints, whereas 12 patients remained unchanged. Five patients died during follow-up due to old age or other, not treatment-related reasons. MR-imaging showed a partial remission in 12 and a stable disease in 15 patients. No tumor progression was observed. The actuarial overall survival rates after five, ten and 20 years were 100%, 95.2% and 79.4%, respectively.

CONCLUSIONS

Stereotactic LINAC-Radiosurgery can achieve an excellent long-term tumor control beside a low rate of morbidity in the treatment of GJTs. It should be considered as an alternative therapy regime to surgical resection or fractionated external beam radiation either as primary, adjuvant or salvage therapy.

[Three horizontal muscle surgery for infantile esotropia and decompensated microtropia]

BACKGROUND

Surgical management of large-angle infantile esotropia and decompensated microtropia has been controversially debated. There seems to be a relative bias against surgery on more than two horizontal muscles to avoid overcorrections. In our study we report on the sensory and motor outcomes after three horizontal muscle surgery. Furthermore we aim to suggest a table to guide surgery amounts.

PATIENTS AND METHODS

This study was a retrospective interventional cohort of 27 patients (16 female, 11 male; mean age 7.9 [years], ranging from 1 to 27 [years]) with infantile esotropia and decompensated microtropia who underwent three horizontal muscle surgery (bilateral medial rectus muscle recession and lateral rectus muscle plication) between 2005 and 2013.

RESULTS

Preoperative deviation in primary position measured 30.2 [°] (mean; range 21.9 to 48.0). Postoperatively esotropia was significantly reduced to 2.6 [°] (mean; range -16.7 to 16.7). After six months deviation measured 5.5 [°] (mean, range -14.1 to 21.9). An effect of 1.63°/mm was calculated for the combined three muscle surgery.

CONCLUSIONS

For the correction of large-angle infantile esotropia and decompensated microtropia three horizontal muscle surgery is associated with a high success rate. Only a very low rate of consecutive exotropia does occur.

Deep brain stimulation of the nucleus basalis of Meynert in Alzheimer's dementia

Cholinergic neurons of the medial forebrain are considered important contributors to brain plasticity and neuromodulation. A reduction of cholinergic innervation can lead to pathophysiological changes of neurotransmission and is observed in Alzheimer's disease. Here we report on six patients with mild to moderate Alzheimer's disease (AD) treated with bilateral low-frequency deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM). During a four-week double-blind sham-controlled phase and a subsequent 11-month follow-up open label period, clinical outcome was assessed by neuropsychological examination using the Alzheimer's Disease Assessment Scale-cognitive subscale as the primary outcome measure. Electroencephalography and [(18)F]-fluoro-desoxyglucose positron emission tomography were, besides others, secondary endpoints. On the basis of stable or improved primary outcome parameters twelve months after surgery, four of the six patients were considered responders. No severe or non-transitional side effects related to the stimulation were observed. Taking into account all limitations of a pilot study, we conclude that DBS of the NBM is both technically feasible and well tolerated.

Coordinated reset neuromodulation for Parkinson's disease: proof-of-concept study

Background

The discovery of abnormal synchronization of neuronal activity in the basal ganglia in Parkinson's disease (PD) has prompted the development of novel neuromodulation paradigms. Coordinated reset neuromodulation intends to specifically counteract excessive synchronization and to induce cumulative unlearning of pathological synaptic connectivity and neuronal synchrony.

Methods

In this prospective case series, six PD patients were evaluated before and after coordinated reset neuromodulation according to a standardized protocol that included both electrophysiological recordings and clinical assessments.

Results

Coordinated reset neuromodulation of the subthalamic nucleus (STN) applied to six PD patients in an externalized setting during three stimulation days induced a significant and cumulative reduction of beta band activity that correlated with a significant improvement of motor function.

Conclusions

These results highlight the potential effects of coordinated reset neuromodulation of the STN in PD patients and encourage further development of this approach as an alternative to conventional high-frequency deep brain stimulation in PD. © 2014 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Inferior oblique muscle anteriorization in congenital superior oblique palsy

BACKGROUND

Inferior oblique muscle overaction of variable amounts is usually present with congenital superior oblique palsy. Inferior oblique muscle anteriorization has been described as a suitable surgical procedure in this entity. The aim of this study was to investigate the effect of inferior oblique muscle anteriorization in patients with congenital superior oblique palsy on vertical, torsional and horizontal alignment.

PATIENTS AND METHODS

The study was designed as an institutional retrospective cohort study. 45 patients with congenital superior oblique palsy (15 female, 30 male; mean age 36 years ± 19.2 SD, ranging from 6 to 75 years) underwent inferior oblique muscle anteriorization between 2000 and 2010. Preoperative amounts of vertical, torsional and horizontal deviation (using Harms tangent screen), measurements of Bielschowsky head tilt phenomenon as well as stereopsis (Lang test) were compared with findings three months and one year postoperatively.

RESULTS

Preoperative vertical deviation in primary position measured 10.1° (mean; range 0-19). Three months postoperatively vertical deviation was significantly reduced (p<0.001) to 4° (mean; range 0-20). After one year vertical deviation measured 3.5° (mean; range 0-15). The values three months postoperatively did not significantly differ from those one year postoperatively (p=0.46).

CONCLUSIONS

Inferior oblique muscle anteriorization leads to a significant and sustained improvement of ocular alignment in patients with congenital superior oblique palsy of various degrees of severity. Thus the procedure is recommendable as a first line treatment in this clinical situation.

Intracranial ganglioglioma WHO I: results in a series of eight patients treated with stereotactic interstitial brachytherapy

In this retrospective study we evaluated the efficacy of interstitial brachytherapy (IBT) using (125)Iodine seeds ((125)I) for intracranial ganglioglioma WHO I. Between October 1994 and March 2010, eight patients (m/f = 5/3, median age 30.4 years, age range 7-42.5 years) with intracranial ganglioglioma WHO I were treated with IBT using stereotactically implanted (125)I seeds. The median follow-up time was 41.5 months (range 16.7-140.1 months). Prior to interstitial brachytherapy one patient underwent microsurgical resection for three times; seven patients were treated with IBT primarily. In all patients we implanted the (125)I seeds stereotactically guided. The cumulative tumor surface dose ranged between 50 and 65 Gy (permanent implantation) and the median tumor volume was 5.6 ml (range 0.9-26 ml). After brachytherapy, follow-up MR imaging revealed complete remission in one patient, partial remission in three and stable disease in the remaining four patients. Five of eight patients presented with seizures were either seizure-free (1/5) or improved (4/5). Temporary treatment-related morbidity occurred in one patient only (headache, nausea/vomiting) and resolved completely under steroid medication after 4 weeks. No treatment-related mortality was observed. This study indicates that interstitial brachytherapy for the treatment of intracranial ganglioglioma WHO I is safe and provides a high rate of local tumor control. Due to the limited number of cases, it is not possible to conduct a rigorous statistical evaluation. Thus, larger numbers of patients are required.

Stereotactic iodine-125 brachytherapy for the treatment of WHO grades II and III gliomas located in the central sulcus region

BACKGROUND

Resection of gliomas located in eloquent brain areas remains a neurosurgical challenge. The reported incidence of transient or permanent neurological deficits after microsurgery in eloquent brain ranges 20%-100%, or 0%-47% among contemporary neurosurgical series. The aim of this study was to assess the feasibility of stereotactic brachytherapy (SBT) as a local treatment alternative to microsurgical resection for patients with gliomas in highly eloquent areas, located in the central sulcus region (CSR).

METHOD

Between 1997 and 2010, 60 patients with World Health Organization (WHO) grades II and III gliomas located in the CSR were treated with SBT (iodine-125 seeds; cumulative therapeutic dose, 50-65 Gy). Following SBT, WHO grade III glioma patients additionally received percutaneous radiotherapy (median boost dose, 25.2 Gy). We evaluated procedure-related complications, clinical outcome, and progression-free survival.

RESULTS

Procedure-related mortality was zero. Within 30 days of SBT, 3 patients (5%) had transient neurological deficits, and 8 patients (13%) had temporarily increased seizure activity. One patient (1.6%) deteriorated permanently. Space-occupying cysts (6 patients) and radiation necrosis (1 patient) developed after a median of 38 months and required surgical intervention. Seizure activity, rated 12 months following SBT, decreased in 82% of patients (Engel classes I-III). Median progression-free survivals were 62.2 ± 19.7 months (grade II gliomas) and 26.1 ± 17.9 months (grade III gliomas).

CONCLUSIONS

Compared with microsurgical resection, SBT harbors a low risk of procedural complications, is minimally invasive, and seems to be an effective local treatment option for patients with inoperable, eloquent WHO grade II and III gliomas in the CSR. However, the value of SBT for treating gliomas still needs to be determined in prospective, randomized studies.

Tractography-guided stimulation of somatosensory fibers for thalamic pain relief

BACKGROUND

The spinothalamocortical tract (STC) is seen as a neural tract responsible for or involved in the generation or transmission of thalamic pain. Either the thalamus itself or the posterior limb of the internal capsule (PLIC) are targets for deep brain stimulation (DBS) in patients with thalamic pain, but due to its low contrast, conventional MRI cannot visualize the STC directly.

OBJECTIVES

To show the feasibility of integrating diffusion tensor imaging-based tractography into the stereotactic treatment planning for identification of an object-oriented lead trajectory that allows STC-DBS with multiple electrode contacts.

METHODS

Diffusion tensor imaging was performed in 4 patients with thalamic pain. The STC was modeled and integrated into the stereotactic treatment planning for DBS. DBS-lead implantation was done according to trajectory planning along the modeled STC at the level of the PLIC.

RESULTS

After implantation, electrode stimulation was possible over a length of more than 20 mm with a tractography-based trajectory along the PLIC part of the STC. After a follow-up of 12 months, pain relief of more than 40% was achieved in 3 of 4 patients with rating on a visual analogue scale. In 1 patient, stimulation failed to reach any long-lasting positive effects.

CONCLUSIONS

Integrating tractography data into stereotactic planning of DBS in thalamic pain is technically feasible. It can be used to identify a lead trajectory that allows for multiple contact stimulation along the STC at the level of the PLIC. Due to long-lasting positive stimulation effect, tractography-guided stimulation of sensory fibers seems to be beneficial for thalamic pain relief.