Pretherapeutic functional neuroimaging predicts tremor arrest after thalamotomy.

OBJECTIVE: Essential tremor (ET) represents the most common movement disorder. Drug-resistant ET can benefit from standard stereotactic procedures (deep brain stimulation or radiofrequency thalamotomy) or alternatively minimally invasive high-focused ultrasound or radiosurgery. All aim at same target, thalamic ventro-intermediate nucleus (Vim). METHODS: The study included a cohort of 17 consecutive patients, with ET, treated only with left unilateral stereotactic radiosurgical thalamotomy (SRS-T) between September 2014 and August 2015. The mean time to tremor improvement was 3.32 months (SD 2.7, 0.5-10). Neuroimaging data were collected at baseline (n = 17). Standard tremor scores, including activities of daily living (ADL) and tremor score on treated hand (TSTH), were completed pretherapeutically and 1 year later. We further correlate these scores with baseline inter-connectivity in twenty major large-scale brain networks. RESULTS: We report as predictive three networks, with the interconnected statistically significant clusters: primary motor cortex interconnected with inferior olivary nucleus, bilateral thalamus interconnected with motor cerebellum lobule V2 (ADL), and anterior default-mode network interconnected with Brodmann area 103 (TSTH). For all, more positive pretherapeutic interconnectivity correlated with higher drop in points on the respective scores. Age, disease duration, or time-to-response after SRS-T were not statistically correlated with pretherapeutic brain connectivity measures (P > .05). The same applied to pretherapeutic tremor scores, after using the same methodology described above. CONCLUSIONS: Our findings have clinical implications for predicting clinical response after SRS-T. Here, using pretherapeutic magnetic resonance imaging and data processing without prior hypothesis, we show that pretherapeutic network(s) interconnectivity strength predicts tremor arrest in drug-naïve ET, following stereotactic radiosurgical thalamotomy.

Primary pituitary lymphoma: an update of the literature.

Primary intracranial lymphomas (Weller et al. in Neuro Oncol 14(12):1481-1484, 2012) are an emerging disease and an isolated localization in the pituitary gland i.e. primary pituitary lymphoma (PPL) represents a rare condition. We present an update of the most recent evidence for PPL through a systematic review of the literature. A systematic literature review was conducted using PubMed database up to October 2015. The population was defined as immunocompetent patients with a pathologically confirmed diagnosis of PPL. Patients' characteristics, clinical presentation, radiological features, pathology reports, adjuvant treatment and follow-up data were analyzed. We reported one case of PPL and included our data in this analysis. A total of 33 cases of PPL were identified, including ours. A slight not significant female prevalence was evident, with a mean age of 59 years at diagnosis. Visual troubles and headaches were the most common presenting symptoms. About 80 % of patients presented a cranial nerve (CN) deficit. The most frequently involved were the II and III CN. Anterior hypopituitarism was present in 70 % of cases and a diabetes insipidus in 36 % of cases. PPL was rarely limited to the sella and most often extended to the suprasellar and parasellar space. 70 % of cases underwent resection, 21 % a biopsy. A B-cell lymphoma was isolated in 82 % of cases, a T-cell lymphoma in 15 % and a NK/T cell lymphoma in one case. Overall mean survival rate was 14.4 months (95 % confidence interval 9.0-19.8 months) and there was no difference in terms of survival rates when patients were stratified according to the treatment they received. PPL is an emerging clinical entity. Literature data are too scarce to allow the definition of specific protocols of treatment and the management is based on the guidelines present for PCNSL. The role of surgery aiming at a complete resection of PPL should be reevaluated in wider studies including only this category of patients, to establish the real role of each therapeutic strategy.

Sympathetic activity and early mobilization in patients in intensive and intermediate care with severe brain injuries: a preliminary prospective randomized study.

BACKGROUND: Patients who experience severe brain injuries are at risk of secondary brain damage, because of delayed vasospasm and edema. Traditionally, many of these patients are kept on prolonged bed rest in order to maintain adequate cerebral blood flow, especially in the case of subarachnoid hemorrhage. On the other hand, prolonged bed rest carries important morbidity. There may be a clinical benefit in early mobilization and our hypothesis is that early gradual mobilization is safe in these patients. The aim of this study was to observe and quantify the changes in sympathetic activity, mainly related to stress, and blood pressure in gradual postural changes by the verticalization robot (Erigo®) and after training by a lower body ergometer (MOTOmed-letto®), after prolonged bed rest of minimum 7 days. METHODS: Thirty patients with severe neurological injuries were randomized into 3 groups with different protocols of mobilization: Standard, MOTOmed-letto® or Erigo® protocol. We measured plasma catecholamines, metanephrines and blood pressure before, during and after mobilization. RESULTS: Blood pressure does not show any significant difference between the 3 groups. The analysis of the catecholamines suggests a significant increase in catecholamine production during Standard mobilization with physiotherapists and with MOTOmed-letto® and no changes with Erigo®. CONCLUSIONS: This preliminary prospective randomized study shows that the mobilization of patients with severe brain injuries by means of Erigo® does not increase the production of catecholamines. It means that Erigo® is a well-tolerated method of mobilization and can be considered a safe system of early mobilization of these patients. Further studies are required to validate our conclusions. TRIAL REGISTRATION: The study was registered in the ISRCTN registry with the trial registration number ISRCTN56402432 . Date of registration: 08.03.2016. Retrospectively registered.

[Early neurorehabilitation in an acute university hospital: from dream to reality]. / Neurorééducation précoce au Centre hospitalier universitaire vaudois: du rêve à la réalité.

The need for an early neurorehabilitation pathway was identified in an acute university hospital. A team was formed to draw up and implement it. A neuro-sensorial, interdisciplinary and coordinated therapy program was developed, focused on tracheostomised patients as soon as they were admitted to the intermediate care in neurology and neurosurgery. The impact of this care plan was evaluated by comparing the results obtained with that pertaining to patients treated previously in the same services. The comparison showed a reduction of 48% of the mean duration of tracheostomy, of 39% in the time to inscription in a neurorehabilitation centre and of 20% in the length of stay in the intermediate care. An early neurorehabilitation care program, with an interdisciplinary and coordinated team, reduces complications and lengths of stay.

[Periinsular hemispherotomy: surgical technique, intraoperative EEG monitoring and results on seizure outcome]. / L'hémisphérotomie péri-insulaire: technique chirurgicale, monitoring EEG intraopératoire et résultats sur le contrôle de l'épilepsie.

Peri-insular hemispherotomy is a surgical technique used in the treatment of drug-resistant epilepsy of hemispheric origin. It is based on the exposure of insula and semi-circular sulci, providing access to the lateral ventricle through a supra- and infra-insular window. From inside the ventricle, a parasagittal callosotomy is performed. The basal and medial portion of the frontal lobe is isolated. Projections to the anterior commissure are interrupted at the time of amygdala resection. The hippocampal tail and fimbria-fornix are disrupted posteriorly. We report our experience of 18 cases treated with this approach. More than half of them presented with congenital epilepsy. Neuronavigation was useful in precisely determining the center and extent of the craniotomy, as well as the direction of tractotomies and callosotomy, allowing minimal exposure and blood loss. Intra-operative monitoring by scalp EEG on the contralateral hemisphere was used to follow the progression of the number of interictal spikes during the disconnection procedure. Approximately 90% of patients were in Engel's Class I. We observed one case who presented with transient postoperative neurological deterioration probably due to CSF overdrainage and documented one case of incomplete disconnection in a patient presenting with hemimegalencephaly who needed a second operation. We observed a good correlation between a significant decrease in the number of spikes at the end of the procedure and seizure outcome. Peri-insular hemispherotomy provides a functional disconnection of the hemisphere with minimal resection of cerebral tissue. It is an efficient technique with a low complication rate. Intra-operative EEG monitoring might be used as a predictive factor of completeness of the disconnection and consequently, seizure outcome.

[Intraoperative MRI and epilepsy surgery]. / IRM opératoire et chirurgie de l'épilepsie.

Intraoperative imaging, in particular intraoperative MRI, is a developing area in neurosurgery and its role is currently being evaluated. Its role in epilepsy surgery has not been defined yet and its use has been limited. In our experience with a compact and mobile low-field intraoperative MRI system, a few epilepsy surgeries have been performed using this technique. As the integration of imaging and functional data plays an important role in the planning of epilepsy surgery, intraoperative verification of the surgical result may be highly valuable. Therefore, teams that have access to intraoperative MRI should be encouraged to use this technique prospectively to evaluate its current relevance in epilepsy surgery.

Sixty-four-row multisection CT angiography for detection and evaluation of ruptured intracranial aneurysms: interobserver and intertechnique reproducibility.

BACKGROUND AND PURPOSE: The purpose of this work was to assess intertechnique and interobserver reproducibility of 64-row multisection CT angiography (CTA) used to detect and evaluate intracranial aneurysms. MATERIALS AND METHODS: From October 2005 to November 2006, 54 consecutive patients with nontraumatic subarachnoid hemorrhage (SAH) underwent both CTA and digital substraction angiography (DSA). Four radiologists independently reviewed CT images, and 2 other radiologists reviewed DSA images. Aneurysm diameter (D), neck width (N), and the presence of a branch arising from the sac were assessed. RESULTS: DSA revealed 67 aneurysms in 48 patients and no aneurysm in 6 patients. Mean sensitivity and specificity of CTA for the detection of intracranial aneurysms were, respectively, 94% and 90.2%. For aneurysms less than 3 mm, CTA had a mean sensitivity of 70.4%. Intertechnique and interobserver agreements were good for the detection of aneurysms (mean kappa = 0.673 and 0.732, respectively) and for the measurement of their necks (mean kappa = 0.753 and 0.779, respectively). Intertechnique and interobserver agreements were excellent for the measurement of aneurysm diameters (mean kappa = 0.847 and 0.876, respectively). In addition, CTA was accurate in determining the N/D ratio of aneurysms and adjacent arterial branches. However, the N/D ratio was overestimated by all of the readers at CTA. CONCLUSION: Sixty-four-row multisection CTA is an imaging method with a good interobserver reproducibility and a high sensitivity and specificity for the detection and the morphologic evaluation of ruptured intracranial aneurysms. It may be used as an alternative to DSA as a first-intention imaging technique in patients with SAH.

Stereotactic comparison among cerebral blood volume, methionine uptake, and histopathology in brain glioma.

BACKGROUND AND PURPOSE: Vascularity, metabolism, and histologic grade are related in gliomas but the exact determinants of these relationships are not fully defined. We used image coregistration and stereotactic biopsies to regionally compare cerebral blood volume (CBV) and (11)C-methionine (MET) uptake measurements in brain gliomas and to assess their relationship by histopathologic examination. MATERIALS AND METHODS: Fourteen patients with brain gliomas underwent MR imaging, including dynamic susceptibility contrast-enhanced MR and positron-emission tomography (PET) using MET acquired in identical stereotactic conditions before biopsy. MR-based CBV maps were calculated and both CBV maps and PET images were coregistered to anatomic images. Sixty-five biopsy samples were obtained on trajectories targeted toward high MET uptake area. The following histopathologic features were semiquantified in each sample: mitotic activity, endothelial proliferation, cellular pleomorphism, and tumor necrosis. CBV and MET uptake values were measured in the biopsy area and normalized to contralateral white matter. CBV ratios were compared with MET uptake ratios, and both measurements were compared with histologic features of each sample. RESULTS: CBV ratios ranged from 0.08 to 10.24 (median = 1.73), and MET uptake ratios ranged from 0.30 to 4.91 (median = 1.67). There was a positive correlation between CBV ratios and MET uptake ratios (r = 0.65, P < .001). Both CBV and MET uptake ratios were found to be significantly related to endothelial proliferation and mitotic activity (P < .01). CONCLUSION: Within glial tumors, there is a local relationship between CBV and MET uptake measurements. Both provide indices of focal malignant activity.

Overexpression of mouse IsK protein fused to green fluorescent protein induces apoptosis of human astroglioma cells.

Intracellular K(+) plays an important role in controlling ion homeostasis for maintaining cell volume and inhibiting activity of pro-apoptotic enzymes. Cytoplasmic K(+) concentration is regulated by K(+) uptake via Na(+) -K(+) -ATPase and K(+) efflux through K(+) channels in the plasma membrane. The IsK (KCNE1) protein is known to co-assemble with KCNQ1 (KvLQT1) protein to form a K(+) channel underlying the slowly activating delayed rectifier K(+) outward current which delays voltage activation. In order to further study the activity and cellular localization of IsK protein, we constructed a C-terminal fusion of IsK with EGFP (enhanced green fluorescent protein). Expression of the fusion protein appeared as clusters located in the plasma membrane and induced degeneration of both transiently or stably transfected cells.

Anatomical and physiological basis, clinical and surgical considerations, mechanisms underlying efficacy and future prospects of cortical stimulation for pain.

The analgesic efficacy of cortical stimulation on refractory neuropathic pain has been established. Although it offers pain relief to 45-75% of the patients, this technique remains under evaluation and the definitive protocol for its application has not been established yet. The mechanisms underlying the analgesic efficacy of cortical stimulation are still largely unknown. Successive technical adaptations have been proposed and tried in order to reduce the number of non-responding patients. In this chapter, we summarize the limited amount of crucial information that has been acquired so far on pain processing in the central nervous system, on the functional pathophysiology of neuropathic pain and on the mechanisms underlying the efficacy of cortical stimulation. We also discuss key issues that could help to increase the success rate and enhance the future prospects of the technique.

Endovascular treatment of intracranial aneurysms as the first thérapeutic option.

BACKGROUND AND PURPOSE: To prospectively evaluate the results of endovascular treatment (EVT) of intracranial aneurysms when it is considered as first-intention treatment. METHODS: From April 2004-October 2006, 167 consecutive patients with 202 aneurysms were treated in our institution. Five patients with a ruptured aneurysm with an associated haematoma were excluded. In 162 patients with 197 aneurysms, EVT was considered as first-intention treatment. RESULTS: Surgical clipping was performed in 25 aneurysms (25/197=12.7%) including 22 aneurysms excluded from EVT and three EVT failures. EVT was thus attempted in 144 patients with 175 aneurysms and successfully performed in 141 patients with 172 aneurysms (172/197=87.3%). EVT failure rate was 1.7%. Clinical outcome according to the modified Glasgow Outcome Scale was: Excellent, 81.5%; Good, 7%; Poor or Fair, 3.5%; Death, 8%. Procedural complications occurred in 17 cases (10%). Balloon- or stent-assisted techniques were used in 60 cases (34.9%) and were not associated with higher complication rate. Overall procedural morbidity and mortality rates were 4.2 and 2.1%. Initially, complete occlusion was obtained in 68%, neck remnant in 23%, and incomplete occlusion in 9% of aneurysms. Follow-up (mean 11 months) was obtained in 119 aneurysms and showed major recanalisation--that required re-treatment--in 13 cases (11%) and minor recanalisation in 17 cases (14.3%). CONCLUSION: Our findings suggest that new endovascular techniques allow proposing EVT as first-intention treatment in 87.3% of patients with intracranial aneurysms. This therapeutic strategy is associated with good clinical results. However, anatomical results are not improved and remain the EVT limiting factor.

Immediate intracranial aneurysm occlusion after embolization with detachable coils: a comparison between MR angiography and intra-arterial digital subtraction angiography.

BACKGROUND AND PURPOSE: To prospectively compare the effectiveness of time-of-flight (TOF) and contrast-enhanced (CE) MR angiography (MRA) with that of digital subtraction angiography (DSA) to assess immediate intracranial aneurysm occlusion after selective embolization. METHODS: From August 2006 to March 2007, 33 consecutive patients with 40 aneurysms were included. Thirty aneurysms were treated by endosaccular coils (group 1). Ten aneurysms were treated by stent placement and subsequent endosaccular coils (group 2). All patients underwent MRA within 24 h after treatment. One senior and one fellow radiologist independently reviewed the MR images, and another senior radiologist reviewed the DSA images. RESULTS: DSA showed 22 complete occlusions, ten residual necks, and eight residual aneurysms. For residual neck detection, there was no difference between TOF-MRA (sensitivity, 80%-80%; specificity, 93.8%-100%, according to both readers) and CE-MRA (sensitivity, 80%-80%; specificity, 100%). For residual aneurysm detection, there was a significant difference between TOF-MRA (sensitivity, 50%-62.5%; specificity, 100%) and CE-MRA (sensitivity and specificity, 100%, according to both readers). In group 2, a residual aneurysm was missed by both readers with TOF-MRA in the same 3 aneurysms. Moreover, both readers judged CE-MRA better than TOF-MRA to assess parent-artery patency in group 2. Interobserver agreement was excellent for TOF-MRA and CE-MRA (kappa=0.9 and 1, respectively). CONCLUSIONS: In our study, both TOF-MRA and CE-MRA had high and comparable sensitivity and specificity for the assessment of immediate aneurysm occlusion after selective embolization, except when a stent-assisted technique was used. In such cases, CE-MRA was superior to TOF-MRA to evaluate aneurysm occlusion and parent-artery patency.

[Subthalamic nucleus stimulation using a Fisher ZD stereotactic frame, MR-CT fusion guidance and peroperative orthogonal radiographs, in Parkinson disease]. / Evaluation de la stimulation du noyau sous-thalamique utilisant un cadre de Fischer adapté, un guidage par fusion IRM-scanner et un contrôle radiographique stéréotaxique peropératoire, dans la maladie de Parkinson.

BACKGROUND: We present the method and results of an original technique to implant electrodes in the subthalamic nucleus (STN) to treat Parkinson's disease, based on adaptations of the Fisher ZD stereotactic frame. METHODS: Targets coordinates were calculated after fusion of stereotactic CT-scan and MRI images. STN was localized by its theoretical coordinates according to AC-PC and by its direct visualization on T2 images. Electrodes were implanted after local anesthesia, using peroperative multicanal microrecordings and test stimulation. Electrodes location was checked by peroperative perpendicular radiographs. To avoid projection of the frame arm on the area of interest on anteroposterior and lateral radiographs, the arm was fixed at 45 degrees from the usual 90 degrees position. This original fixation needed a trigonometric transformation of the X and Y stereotactic coordinates. Radiopaque markers, fixed on the frame, were identified on the radiographs, allowing the calculation of the stereotactic coordinates of the electrode tip, which were then entered in the stereotactic MRI, to check its location from the defined target. RESULTS: No problem due to adaptations of the frame occurred in the 60 patients. In all cases, peroperative radiographs allowed to confirm the correct location of electrodes. Six months after surgery, UPDRS III score without medication was decreased by 52% with stimulation "on". UPDRS IV items 32, 33 and 39 scores were decreased by 75,7, 79,5 and 72%. Daily dopa-equivalent dose was decreased by 71%. One asymptomatic thalamic hematoma and two wound infections occurred. CONCLUSION: This method was efficient and safe to implant deep electrodes.

Gamma Knife surgery for a hemangioma of the cavernous sinus in an adult: Case report and short review of the literature.

Cavernous sinus hemangiomas (CSH) are rare benign extra-axial vascular lesions. Both radiological and clinical aspects are important, for deciding a therapeutic modality, including medical treatment, radiation therapy or microsurgery. In the particular case of CSH, a radical removal of the tumor often cannot be achieved and is associated with a considerable risk for intraoperative uncontrollable bleeding. An alternative treatment modality is radiosurgery. Here we report the case of a 45-year-old patient, who presented with diplopia due to left abducens nerve palsy. A left-sided cavernous sinus lesion was found, initially considered to be a meningioma. However, after serial MR acquisitions, a progressive and heterogeneous enhancement was observed. In order to clarify the diagnosis between meningioma and hemangioma, a diagnostic Tc-99m labeled red blood cells (RBC) scintigraphy (Tc-99m RBC scintigraphy) was performed and showed a typical perfusion blood pool mismatch, with accumulation of the RBC at the level of the left CS, which is typical for a hemangioma. The patient underwent Gamma Knife surgery. The CSH showed a significant reduction in size starting 6 months after treatment and a full regression of the left abducens nerve palsy was observed within 1 year. These clinical and radiological results persisted over the next 3 years.

Endovascular treatment of intracranial aneurysms with a branch arising from the sac.

BACKGROUND AND PURPOSE: The endovascular treatment (EVT) of intracranial aneurysms is no more limited by the presence of a branch at the neck or by the neck width. Saccular aneurysms with a branch arising from the sac, however, are mostly candidates for surgery rather than embolization. We prospectively evaluated the feasibility and safety of the EVT in such cases. METHODS: Between May and November 2004, 9 consecutive patients with a saccular aneurysm that presents a branch arising from the sac were treated by embolization. There were 7 women and 2 men (mean age, 58 years). Six patients presented with a subarachnoid hemorrhage (SAH), and 3 were asymptomatic. All patients were treated by selective coiling with (n = 6) or without (n = 3) the remodeling technique. Clinical outcome was assessed with a modified Glasgow Outcome Scale at 3 months. RESULTS: EVT was successfully performed in all patients and resulted in 7 excellent outcomes and 2 deaths related to SAH complications. The arterial branch could be preserved in 7 cases and intentionally occluded in 2. Neither embolic nor ischemic complication occurred in the vascular territory of the involved branch. Angiographic results showed 5 neck remnants, 2 incomplete occlusions, and 2 complete occlusions. No rebleeding occurred. CONCLUSION: Our study, though limited by its small patient population, suggests that saccular intracranial aneurysms with a branch arising from the sac may be treated by endovascular approach with excellent clinical results; however, larger series with long-term follow-up are mandatory to confirm these preliminary results mostly in terms of anatomic stability.

Extended endoscopic endonasal approach to clival and paraclival tumors: Indications and limits.

OBJECTIVE: To report our experience with the Extended endoscopic endonasal approach (EEEA) for clival and paraclival tumors. DESIGN: Retrospective analysis of a consecutive series of patients. RESULTS: Eleven patients were considered: 3 chordomas, 3 meningiomas, 3 metastatic lesions, one chondroma and one chondrosarcoma. Gross total resection (GTR) was achieved in all chordomas and in chondromas with patients free of disease at the last follow-up. The chondrosarcoma was first operated on using a transfacial approach and endoscopy was performed for local progression with subtotal resection. The meningiomas were treated by a combination of transcranial and endoscopic approach due to their extension. The resection was subtotal and the residue treated by radiosurgery. Two patients with rhinopharyngeal carcinoma underwent palliative debulking. One metastatic melanoma that underwent GTR experienced remission. Two patients had postoperative cranial nerve palsy. No other complications were observed. CONCLUSIONS: EEEA allows a direct access to the skull base. Through a minimal access, it limits the incidence of neurological morbidities. For midline epidural clival tumors, EEEA allows a total excision. It also offers an excellent access to the clival component of intradural lesions. A combined approach permits good tumor control with minimal complications.

Recent advances in the management of atypical meningiomas.

Based on the 2007 WHO classification, the proportion of atypical meningiomas has steeply increased. Complete resection is usually considered curative, however, the recurrence rate remains high. The treatment of more aggressive meningiomas remains problematic. We performed a literature review via the PubMed database with specific attention to radiological, pathological, genetic and molecular aspects particular to WHO grade II meningiomas and current therapeutic strategies. We also reviewed the role of surgery and summarized the results of the principal studies dealing with adjuvant strategies based on the most recent evidence. Adjuvant radiotherapy, administered as stereotactic radiosurgery or conventional external beam irradiation, should be strongly considered in selected cases. Limited data exist regarding the role of hormonal treatment or chemotherapy as adjunct therapy. A target therapy modulating the altered molecular balance may be the key to revolutionize the prognosis of these patients.

[Transsphenoidal approach with low field MRI for pituitary adenoma]. / Apport de la résonance magnétique per-opératoire à bas champs dans la chirurgie de l'adénome hypophysaire.

INTRODUCTION: Appropriate evaluation of resection remains one of the major difficulties of surgical treatment of pituitary adenoma. The transsphenoidal approach does not allow direct visual control. Endoscopy provides useful information but may no distinguish well residual adenoma from the pituitary gland. Intraoperative MRI offers new perspectives for assessing the quality of resection. We report our experience with low field intraoperative MRI in surgical treatment of pituitary adenoma. POPULATION: Intraoperative MRI (Polestar N10, 30 patients and Polestar N20, 17 patients) was performed in 45 consecutive patients undergoing surgery for pituitary adenoma. Thirty-seven patients had a macroadenoma. Patients were in the prone position with the head fixed with a three-pin MRI-compatible headholder. METHOD: Coronal T1 MRI scans with enhancement were acquired pre and per operatively. We compared scans and surgical filling (complete removal). If there was a difference, a surgical control was undertaken. RESULTS: Intraoperative images were unavailable for two patients due to small size of the neck and the pituitary glands which were not in the middle in the field of view. For the others, the pituitary glands were in the field of view and the intraoperative scans could be used for comparison. For four patients, there was a discrepancy between surgeon filling and the intraoperative MRI. A control showed no residual adenoma but hemostatic tissue. CONCLUSION: Low field intraoperative MRI is an excellent technique for controlling the size of pituitary adenoma resection.

Biphasic response of a tecto-mesencephalic pilocytic astrocytoma after Gamma Knife surgery--A case report.

Biphasic response (shrinkage-regrowth-shrinkage) of tumors has never previously been reported in the postoperative course, neither after microsurgery, nor after Gamma Knife surgery (GKS). We present the case of an adult with dorsal midbrain syndrome resulting from a pilocytic astrocytoma centered on the mesencephalic tectum. The tumor extended to the third ventricle and the thalamus. Initially, due to tumor growth, a biopsy was performed and histology established. Later, a ventriculocisternostomy for obstructive hydrocephalus was performed. Finally, GKS was performed, as the tumor continued to grow. After GKS, the lesion exhibited a biphasic response, with a major shrinkage at 3 months, regrowth within the target volume at 6 and 9 months and a second phase of important shrinkage at 12 months, which persisted for the next two years. The possible mechanisms for this particular response pattern are discussed.