Clinical added value of magnetic source imaging in the presurgical evaluation of refractory focal epilepsy

OBJECTIVE

This prospective, bicentre, blinded, intention to treat study assessed the clinical added value of magnetic source imaging (MSI) in the presurgical evaluation of patients with refractory focal epilepsy (RFE).

METHODS

70 consecutive patients with RFE (42 men; mean age 31.5 years, range 3-63) from two Belgian centres were prospectively included. All patients underwent conventional non-invasive presurgical evaluation (CNIPE) and a whole head magnetoencephalography recording (Elekta Neuromag). Equivalent current dipoles corresponding to interictal epileptiform discharges (IED) were fitted in the patients' spherical head model and coregistered on their MRI to produce MSI results. Results of CNIPE were first discussed blinded to the MSI results in respective multidisciplinary epilepsy surgery meetings to determine the presumed localisation of the epileptogenic zone and to set surgical or additional presurgical plans. MSI results were then discussed multidisciplinarily. MSI influence on the initial management plan was assessed.

RESULTS

Based on CNIPE, 21 patients had presumed extratemporal epilepsy, 38 had presumed temporal epilepsy and 11 had undetermined localisation epilepsy. MSI showed IED in 52 patients (74.5%) and changed the initial management in 15 patients (21%). MSI related changes were significantly more frequent in patients with presumed extratemporal or undetermined localisation epilepsy compared with patients with presumed temporal epilepsy (p≤0.001). These changes had a clear impact on clinical management in 13% of all patients.

CONCLUSION

MSI is a clinically relevant, non-invasive neuroimaging technique for the presurgical evaluation of patients with refractory focal epilepsy and, particularly, in patients with presumed extratemporal and undetermined localisation epilepsy.

Collective regulatory stock management and spatiotemporal dynamics of the food flow in ants

The organization of complex societies requires constant information flow between individuals. The shape of the food web organizes itself according to the spatial distribution of the individuals and of the stocks. To understand how the spatial organization of the food stocks changes with the colony needs, we monitored the flow of radiolabeled sugar solution inside an ant nest at different degrees of starvation. The spatial dynamics of the food flow revealed stable patterns and fine-tuning regulation of the feeding process. The complex collective regulatory stock management task can be reproduced by a surprising simple model that integrates a positive and a negative feedback proportional to the number of ants that already received food. Spatial analysis of the food distribution showed that sucrose is heterogeneously stocked among individuals and also heterogeneously consumed. Furthermore, we observed a regular spatial structure, leading to centralization of the stocks: heavily loaded individuals being at the center of the cluster and weakly loaded individuals at its periphery. The centralization of both resources and information in self-organized systems might be a widespread phenomenon that deserves further studies.

¹⁸F-FDG PET/CT and MRI in the follow-up of head and neck squamous cell carcinoma

We evaluated the diagnostic performance of (18)F-FDG PET/CT and MRI for the assessment of head and neck squamous cell carcinoma (HNSCC) relapse. Since early treatment might prevent inoperable relapse, we also evaluated THE performance of early unenhanced (18)F-FDG PET/CT in residual tumor detection. The study was prospectively performed on 32 patients who underwent (18)F-FDG PET/CT and MRI before treatment and at 4 and 12 months after treatment. (18)F-FDG PET/CT was also performed 2 weeks after the end of radiotherapy. Histopathology or a minimum of 18 months follow-up were used as gold standard. Before treatment (18)F-FDG PET/CT and MRI detected all primary tumors except for two limited vocal fold lesions (sensitivity 94%). MRI was more sensitive than (18)F-FDG PET/CT for the detection of local extension sites (sensitivity 75 vs 58%), but at the cost of a higher rate of false positive results (positive predictive value 74 vs 86%). For relapse detection at 4 months, sensitivity was significantly higher for (18)F-FDG PET/CT (92%) than for MRI (70%), but the diagnostic performances were not significantly different at 12 months. For the detection of residual malignant tissue 2 weeks post-radiotherapy, sensitivity and specificity of (18)F-FDG PET/CT were respectively 86 and 85% (SUV cut-off value 5.8). (18)F-FDG PET/CT is effective in the differentiation between residual tumor and radiation-induced changes, as early as 2 weeks after treatment of a primary HNSCC. For follow-up, performance of (18)F-FDG PET/CT and MRI are similar except for a higher sensitivity of (18)F-FDG PET/CT at 4 months.

The pace of prosodic phrasing couples the listener's cortex to the reader's voice

We studied online coupling between a reader's voice and a listener's cortical activity using a novel, ecologically valid continuous listening paradigm. Whole-scalp magnetoencephalographic (MEG) signals were recorded from 10 right-handed, native French-speaking listeners in four conditions: a female (Exp1f) and a male (Exp1m) reading the same text in French; a male reading a text in Finnish (Exp 2), a language incomprehensible for the subjects, and a male humming Exp1 text (Exp 3). The fundamental frequency (f0) of the reader's voice was recorded with an accelerometer attached to the throat, and coherence was computed between f0 time-course and listener's MEG. Similar levels of right-hemisphere-predominant coherence were found at ˜0.5 Hz in Exps 1-3. Dynamic imaging of coherent sources revealed that the most coherent brain regions were located in the right posterior superior temporal sulcus (pSTS) and posterior superior temporal gyrus (pSTG) in Exps 1-2 and in the right supratemporal auditory cortex in Exp 3. Comparison between speech rhythm and phrasing suggested a connection of the observed coherence to pauses at the sentence level both in the spoken and hummed text. These results demonstrate significant coupling at ∼0.5 Hz between reader's voice and listener's cortical signals during listening to natural continuous voice. The observed coupling suggests that voice envelope fluctuations, due to prosodic rhythmicity at the phrasal and sentence levels, are reflected in the listener's cortex as rhythmicity of about 2-s cycles. The predominance of the coherence in the right pSTS and pSTG suggests hemispherical asymmetry in processing of speech sounds at subsentence time scales.

MR imaging versus PET/CT for evaluation of pancreatic lesions

PURPOSE

To retrospectively determine the diagnostic accuracy of magnetic resonance imaging (MRI) and combined positron emission tomography/computed tomography (PET/CT) in the differential diagnosis of benign and malignant pancreatic lesions.

MATERIALS AND METHODS

Twenty-seven patients (15 women/12 men, mean age 56.5 years) with MR imaging and PET/CT studies performed to differentiate benign and malignant pancreatic lesions were identified between October 2008 and October 2010. Both MR and PET/CT data sets were retrospectively and blindly evaluated by two independent readers (4 readers total) with different degrees of experience, using a visual five-point score system. The results were correlated with final diagnosis obtained by histopathology.

RESULTS

17 patients had malignant diseases and 10 patients had benign diseases. Depending on the observer, the sensitivity, specificity, positive predictive value and negative predictive value of MRI varied between 88-94%, 50-80%, 75-89% and 71-89% respectively. Sensitivities, specificities, positive predictive values and negative predictive values of PET/CT were 73%, 56%, 73% and 56% respectively. The diagnostic accuracy of MR for the differential diagnosis of pancreatic lesions was 74-89%, compared with 67% for PET/CT. The weighted Cohen's kappa coefficient was 0.47 at MR and 0.53 at PET/CT.

CONCLUSION

MRI achieved higher sensitivity and specificity in the differential diagnosis of pancreatic lesions.

Advances in PET imaging of brain tumors: a referring physician's perspective

PURPOSE OF REVIEW

To highlight the most recent advances in PET imaging of brain tumors, aiming at expanding the referring physician's knowledge in the field, the sine qua non for translating PET into the practice of neuro-oncology.

RECENT FINDINGS

The role of PET with amino acid tracers in the setting of brain lesions of unknown significance has been better defined, reducing the need for invasive procedures. The impact of PET-guided resection of high-grade glioma using ¹¹C-methionine (¹¹C-MET) has been strongly documented. [¹⁸F]Fluoroethyl-L-tyrosine is currently available for glioma management; advances in targeting glial tumor biopsy and monitoring response to standard chemoradiation of malignant glioma have been remarkable. 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-penta-fluoropropyl)-acetamide is a rationally designed radiotracer with potential for imaging hypoxia in glioblastoma. New insights regarding the predictive value of 3-deoxy-3-[¹⁸F]fluorothymidine in outcome of recurrent malignant glioma treated with bevacizumab/irinotecan have been provided. First steps are being made toward apoptosis PET imaging for early assessment of radiotherapy response in brain metastases.

SUMMARY

The use of ¹¹C-MET and ¹⁸F-labeled PET tracers is getting a more precise position in the management of brain tumors. Advances hold promises in routine decision-making and in the design and conduct of clinical trials.

Comparative pharmacoscintigraphic and pharmacokinetic evaluation of two new formulations of inhaled insulin in type 1 diabetic patients

In this open, single-dose study, we compared the lung deposition and bioavailability of two newly developed insulin formulations for pulmonary delivery. Twelve type 1 diabetic patients were administered the two insulin products (2 U/kg b.w.), which had been radiolabelled with (99m)Tc. The formulations were either microparticles of insulin without excipients (F1) or lipid-coated insulin microparticles (F2). Lung deposition was assessed by γ-scintigraphy imaging performed immediately after administration. Bioavailability was evaluated by quantifying serum insulin levels over a period of 6 h. Lung deposition was found to be 50 ± 9% and 24 ± 8% for the F1 and F2 formulations, respectively. The insulin AUC₀₋₃₆₀ ratio of F1/F2 was 188%, which was consistent with scintigraphic imaging. The concordance between imaging and biological results suggests that the lower bioavailability of F2 is due to its lower lung deposition and not to a reduced absorption into the blood stream. Additional in vitro experiments indicated that the lower performance of F2 was most probably related to a lower disaggregation efficiency of the powder when administered at a sub-optimal flow rate. The two formulations showed interesting pharmacokinetic profiles (T(max) of 26 and 16 min for F1 and F2, respectively) that mimic the physiological insulin secretion pattern. The bioavailability of the developed formulations was within the range of other DPI insulin formulations that have reached the final stages of clinical development.

Metabolic evidence for episodic memory plasticity in the nonepileptic temporal lobe of patients with mesial temporal epilepsy

PURPOSE

Metabolic changes have been described in the nonepileptic temporal lobe of patients with unilateral mesiotemporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS). To better understand the functional correlate of this metabolic finding, we have sought to characterize brain regions in patients with MTLE that show correlation between unilateral episodic memory performances, as assessed by intracarotid amobarbital test (IAT), and interictal regional cerebral metabolism measured by [(18) F]-fluorodeoxyglucose positron emission tomography (FDG-PET).

METHODS

Resting FDG-PET was performed interictally in 26 patients with unilateral MTLE caused by HS (16 female, mean age: 36 years; 16 left HS). Using statistical parametric mapping (SPM8), we performed a group comparison analysis comparing brain metabolism in the patients and in 54 adult controls (27 female, mean age: 32 years), with FDG-PET data of right HS patients being flipped. IAT scores of nonepileptic hemisphere functions (amobarbital injection ipsilateral to HS) were used as covariates of interest in a correlation analysis with regional brain metabolism.

KEY FINDINGS

The group comparison analysis revealed significant hypometabolic areas in a widespread temporofrontal network ipsilateral to HS. In addition, a significant increase in metabolism was found in mesial and lateral temporal regions contralateral to HS. Significant positive correlations were found between IAT scores of nonepileptic hemisphere functions and mesial temporal metabolism in this hemisphere.

SIGNIFICANCE

This study demonstrates the existence of significant increase in relative regional cerebral glucose metabolism in mesial and lateral temporal regions contralateral to the epileptic focus in patients with unilateral MTLE associated with HS. The positive correlation in these brain regions between IAT scores and metabolism supports the role of disease-induced plasticity mechanisms contralateral to HS in the preservation of episodic memory processes.

Diffuse pancreatic lesion mimicking autoimmune pancreatitis in an HIV-infected patient: successful treatment by antiretroviral therapy

CONTEXT

Pancreatitis is a common complication of acquired immunodeficiency syndrome. The most common causes of acute pancreatitis in an HIV population are medication and opportunistic infections.

CASE REPORT

We report the case of a young, untreated, HIV-infected female who presented with acute pancreatitis of unknown origin. Unique to this case are the autoimmune pancreatitis-like features on imaging studies associated with renal mass-like lesions and lymph node involvement as well as the favorable outcome using highly active antiretroviral therapy alone.

CONCLUSION

In HIV-infected patients, acute pancreatitis may present on imaging studies as autoimmune pancreatitis. In patients with uncontrolled HIV infection and imaging studies suggestive of autoimmune pancreatitis, direct HIV-related inflammation should be considered after exclusion of all other causes of pancreatitis.

Brain tumors

For most cancers, PET is essentially a diagnostic tool. For brain tumors, PET has got its main contribution at the level of the therapeutic management. Indeed, specific reasons render the therapeutic management of brain tumors, especially gliomas, a real challenge. Although some gliomas may appear well-delineated on conventional neuroimaging such as CT and MRI, they are by nature infiltrating neoplasms and the interface between tumor and normal brain tissue may not be accurately defined. Moreover, gliomas may present as ill-defined lesions for which various MRI sequences combination does not provide a unique contour for tumor delineation. Also, gliomas are often histologically heterogeneous with anaplastic areas evolving within a low-grade tumor, and contrast-enhancement on CT or MRI does not represent a good marker for anaplastic tissue detection. Finally, assessment of tumor residue, recurrence, or progression, may be altered by different signals related to inflammation or adjuvant therapies, and contrast enhancement on CT and MRI is not an appropriate marker at the postoperative or posttherapeutic stage. These limitations of conventional neuroimaging in detecting tumor tissue, delineating tumor extent and evidencing anaplastic changes, lead to potential inaccuracy in lesion targeting at different steps of the management (diagnostic, surgical, postoperative, and posttherapeutic stages). Molecular information provided by PET has proved helpful to supplement morphological imaging data in this context. F-18 FDG and amino-acid tracers such as C-11 methionine (C-11 MET) provide complementary metabolic data that are independent from the anatomical MR information. These tracers help in the definition of glioma extension, detection of anaplastic areas, and postoperative follow-up. Additionally, PET data have a prognostic value independently of histology. To take advantage of PET data in glioma treatment, PET might be integrated in the planning of image-guided biopsy, resection, and radiosurgery.

Functional motor-cortex mapping using corticokinematic coherence

We present a novel method, corticokinematic coherence (CKC), for functional mapping of the motor cortex by computing coherence between cortical magnetoencephalographic (MEG) signals and the kinematics of voluntary movements. Ten subjects performed self-paced flexion-extensions of the right-hand fingers at about 3 Hz, with a three-axis accelerometer attached to the index finger. Cross-correlogram and coherence spectra were computed between 306 MEG channels and the accelerometer signals. In all subjects, accelerometer and coherence spectra showed peaks around 3-5 Hz and 6-10 Hz, corresponding to the movement frequencies. The coherence was statistically significant (P<0.05) in all subjects, with sources at the hand area of the primary motor cortex contralateral to the movement. CKC appears to be a promising and robust method for reliable and convenient functional mapping of the human motor cortex.

Phase I trial of pegylated interferon-alpha-2b in young patients with plexiform neurofibromas

OBJECTIVE

Interferon has antiproliferative and antiangiogenic properties. We sought to evaluate preliminary efficacy and determine the recommended phase II dose (RP2D) for pegylated interferon-α-2b (PI) in patients with unresectable progressive or symptomatic plexiform neurofibromas (PN).

METHODS

PI was administered weekly in cohorts of 3-6 patients during the dose-finding phase and continued for up to 2 years. Twelve patients were treated at the RP2D to further evaluate toxicity and activity.

RESULTS

Thirty patients (median age 9.3 years, range 1.9-34.7 years) were enrolled. No dose-limiting toxicity (DLT) was seen in patients treated at the 3 μg/kg dose level (DL) during the first 4 weeks. All 5 patients treated at the 4.5 μg/kg DL came off study or required dose reductions for behavioral toxicity or fatigue. Similar DLT on the 3 μg/kg DL became apparent over time. There was 1 DLT (myoclonus) in 12 patients enrolled at the 1.0 μg/kg DL. Eleven of 16 patients with pain showed improvement and 13 of 14 patients with a palpable mass had a decrease in size. Five of 17 patients (29%) who underwent volumetric analysis had a 15%-22% decrease in volume. Three of 4 patients with documented radiographic progression prior to enrollment showed stabilization or shrinkage.

CONCLUSIONS

The RP2D of PI for pediatric patients with PN is 1 μg/kg/wk. Clinical and radiographic improvement and cessation of growth can occur.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that pegylated interferon-α-2b in patients with unresectable, progressive, symptomatic, or life-threatening PNs results in radiographic reduction or stabilization of PN size.

External globus pallidus stimulation modulates brain connectivity in Huntington's disease

Positron emission tomography with O-15-labeled water was used to study at rest the neurophysiological effects of bilateral external globus pallidus (GPe) deep brain stimulation in patients with Huntington's disease (HD). Five patients were compared with a control group in the on and off states of the stimulator. External globus pallidus stimulation decreased neuronal activity and modulated cerebral connectivity within the basal ganglia-thalamocortical circuitry, the sensorimotor, and the default-mode networks. These data indicate that GPe stimulation modulates functional integration in HD patients in accordance with the basal ganglia-thalamocortical circuit model.