Glioblastoma: does the pre-treatment geometry matter? A postcontrast T1 MRI-based study.

BACKGROUND: The potential of a tumour's volumetric measures obtained from pretreatment MRI sequences of glioblastoma (GBM) patients as predictors of clinical outcome has been controversial. Mathematical models of GBM growth have suggested a relation between a tumour's geometry and its aggressiveness. METHODS: A multicenter retrospective clinical study was designed to study volumetric and geometrical measures on pretreatment postcontrast T1 MRIs of 117 GBM patients. Clinical variables were collected, tumours segmented, and measures computed including: contrast enhancing (CE), necrotic, and total volumes; maximal tumour diameter; equivalent spherical CE width and several geometric measures of the CE "rim". The significance of the measures was studied using proportional hazards analysis and Kaplan-Meier curves. RESULTS: Kaplan-Meier and univariate Cox survival analysis showed that total volume [p = 0.034, Hazard ratio (HR) = 1.574], CE volume (p = 0.017, HR = 1.659), spherical rim width (p = 0.007, HR = 1.749), and geometric heterogeneity (p = 0.015, HR = 1.646) were significant parameters in terms of overall survival (OS). Multivariable Cox analysis for OS provided the later two parameters as age-adjusted predictors of OS (p = 0.043, HR = 1.536 and p = 0.032, HR = 1.570, respectively). CONCLUSION: Patients with tumours having small geometric heterogeneity and/or spherical rim widths had significantly better prognosis. These novel imaging biomarkers have a strong individual and combined prognostic value for GBM patients. KEY POINTS: • Three-dimensional segmentation on magnetic resonance images allows the study of geometric measures. • Patients with small width of contrast enhancing areas have better prognosis. • The irregularity of contrast enhancing areas predicts survival in glioblastoma patients.

Dynamic risk control by human nucleus accumbens.

Real-world decisions about reward often involve a complex counterbalance of risk and value. Although the nucleus accumbens has been implicated in the underlying neural substrate, its criticality to human behaviour remains an open question, best addressed with interventional methodology that probes the behavioural consequences of focal neural modulation. Combining a psychometric index of risky decision-making with transient electrical modulation of the nucleus accumbens, here we reveal profound, highly dynamic alteration of the relation between probability of reward and choice during therapeutic deep brain stimulation in four patients with treatment-resistant psychiatric disease. Short-lived phasic electrical stimulation of the region of the nucleus accumbens dynamically altered risk behaviour, transiently shifting the psychometric function towards more risky decisions only for the duration of stimulation. A critical, on-line role of human nucleus accumbens in dynamic risk control is thereby established.

Deep brain stimulation for obsessive-compulsive disorder: is the side relevant?

BACKGROUND: Deep brain stimulation for obsessive-compulsive disorder (OCD) has targeted several subcortical nuclei, including the subthalamic nucleus (STN) and the nucleus accumbens. While the most appropriate target is still being looked for, little attention has been given to the side of the stimulated hemisphere in relationship to outcome. METHODS: We report 2 patients diagnosed with OCD, one having symmetry obsessions and the other one with sexual-religious obsessive thoughts. They were implanted bilaterally with deep electrodes located at both STN and nuclei accumbens. The effectiveness of the stimulation was tested for every possible paired combination of electrodes guided by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score reduction. RESULTS: In both cases, the combination of electrodes which best relieved the OCD symptoms was both the left STN and left accumbens. In case 1, the preoperative Y-BOCS score was 33, and 1 month after stimulation it was 16. In case 2, the Y-BOCS scores were 33 and 3, respectively, with the patient being free of obsessions. CONCLUSION: Some reports suggest that lesion stimulation or stimulation of only the right side relieves OCD symptoms. However, anatomical and functional studies are not conclusive as to which side is most affected in OCD. Possibly, each OCD patient has an individualized optimal side to stimulate.