The Role of 3T Magnetic Resonance Imaging for Targeting the Human Subthalamic Nucleus in Deep Brain Stimulation for Parkinson Disease.

BACKGROUND: Chronic stimulation of the human subthalamic nucleus (STN) is gradually becoming accepted as a long-term therapeutic option for patients with advanced Parkinson disease (PD). 3Tesla (T) magnetic resonance imaging (MRI) improves contrast resolution in basal ganglia nuclei containing high levels of iron, because of magnetic susceptibility effects that increase significantly as the magnetic field gets higher. This phenomenon can be used for better visualization of the STN and may reduce the time necessary for detailed microrecording (MER) mapping, increasing surgery efficacy and lowering morbidity. OBJECTIVE: The objective of this retrospective study is to analyze a population of 20 deep brain stimulation (DBS) electrode implanted patients with PD divided into two groups in which different targeting methods were used. METHODS: Mean age was 56 years (range 37 to 69 years). Mean disease duration was 11.6 years. Mean follow-up was 12 months (range 6 to 36 months). Patients were divided into two groups: Group A contained 6 patients who underwent STN targeting using 1T stereotactic (T1w + T2w) MRI plus STN indirect atlas derived targeting. Group B consisted of 14 patients who underwent STN targeting using 3T nonstereotactic (T2w) MRI fused with 1T T1w stereotactic MRI and STN direct targeting. For statistical analysis, we compared (five different parameters in both (matched) groups: Unified Parkinson's disease rating scale (UPDRS) score reduction (medication off before surgery against stimulation on/medication off after surgery), postoperative drug reduction, duration of surgery, the "central preoperative track" chosen as final implantation track during surgery, and correspondence between the targeted STN and the intraoperative neurophysiologic data. RESULTS: Mean UPDRS III score reduction (medication off/stimulation on versus preoperative medication off) was 69% in Group A and 74% in Group B (p = 0.015, log-rank test) respectively. Postoperatively, antiparkinsonian treatment was reduced by 66% in Group A and 75% in Group B (p = 0.006, log-rank test). The preoperative "central" track (which corresponds to ideal STN targeting) proved to be the most clinically effective in 2/12 leads for Group A versus 21/28 for Group B (p < 0.001).Neurophysiologic data confirmed these results; the hypothetical target was confirmed by MER data in 76% of tracks in Group A, and in 75% of tracks in Group B (p < 0.001, univariate and multivariate analysis). CONCLUSION: 3T MRI appears to be a useful tool in STN-DBS preoperative targeting. Neurophysiologic testing remains fundamental to determine lead deepness (and prevent clinical side effects.

Radiosurgical options in neuro-oncology: a review on current tenets and future opportunities. Part II: adjuvant radiobiological tools.

Stereotactic radiosurgery (SRS) is currently a well-established, minimally invasive treatment for many primary and secondary tumors, especially deep-sited lesions for which traditional neurosurgical procedures were poorly satisfactory or not effective at all. The initial evolution of SRS was cautious, relying on more than 30 years of experimental and clinical work that preceded its introduction into the worldwide medical community. This path enabled a brilliant present, and the continuous pace of technological advancement holds promise for a brighter future. Part II of this review article will cover the impact of multimodal adjuvant technologies on SRS, and their input to the crucial role played by neurosurgeons, radiation oncologists and medical physicists in the management and care of fragile neuro-oncological patients.

Radiosurgical options in neuro-oncology: a review on current tenets and future opportunities. Part I: therapeutic strategies.

Stereotactic radiosurgery can nowadays be considered not only as a potential adjuvant to surgical treatment of several neuro-oncological pathologies, including primary tumors and metastatic lesions, but in some cases also as a valuable alternative tailored option. In Part I of the review, we propose a dissertation focused on the different irradiation stereotactic radiosurgery techniques to date available for clinical indications more relevant to oncologists and oncologic surgeons, such as high-grade and low-grade gliomas, metastases and meningiomas. It is noteworthy that the most recent body of literature correlated with this topic shows that the therapeutic results presently achievable are revolutionizing the way patients are diagnosed and managed worldwide. As we sought to shed light on the current potentialities of stereotactic radiosurgery, we must consider that to exploit all the benefits provided by this shift in clinical practice, a profound awareness by all practitioners involved in the care of neoplastic patients is certainly warranted.

Significant prevalence of antibodies reacting with simian virus 40 mimotopes in sera from patients affected by glioblastoma multiforme.

BACKGROUND: Glioblastoma multiforme (GBM) is a rare tumor, which affects 1/100 000 individuals, but it represents 30% of central nervous system malignancies. GBM is a severe tumor responsible for 2% of all cancer-related deaths. Although characterized by genotypic and phenotypic heterogeneities, GBM invariably resists conventional chemo- and radiotherapies. Several chromosome alterations and gene mutations were detected in GBM. Simian virus 40 (SV40), a small DNA tumor virus, has been found in GBM specimens by some studies, while other investigations have not confirmed the association. METHODS: An indirect enzyme-linked immunosorbent assay with 2 synthetic peptides mimicking SV40 antigens of viral capsid proteins 1-3 was employed to detect specific antibodies against SV40 in serum samples from GBM-affected patients, together with controls represented by patients affected by breast cancer and normal subjects of the same median age. RESULTS: Our data indicate that in serum samples from GBM-affected patients (n = 44), the prevalence of antibodies against SV40 viral capsid protein antigens is statistically significantly higher (34%, P = .016 and P = .03) than in the control groups (15%), represented by healthy subjects (n = 101) and patients affected by breast cancer (n = 78), respectively. CONCLUSION: Our data indicate that SV40, or a closely related yet undiscovered human polyomavirus, is associated with a subset of GBM and circulates in humans. Our study can be transferred to the clinical oncology application to discriminate different types of heterogeneous GBM, which in turn may address an innovative therapeutic approach to this fatal cancer.

Pleomorphic xanthoastrocytoma: long-term results of surgical treatment and analysis of prognostic factors.

BACKGROUND: Pleomorphic Xanthoastrocytoma (PXA) is a rare brain tumour, most commonly affecting children and young adults. To date, only few data regarding the long-term follow-up of these patients after surgery are available. The aim of this study is to describe our single-institution experience in the surgical management of this particular glioma over a period of over 18 years. METHODS: We performed a retrospective review of all cases of PXA (40 patients) operated upon at the Department of Neurosurgery of Verona, Italy, between 1990 and 2008. The impact of clinical, radiological, surgical and histological factors on overall survival (OS) and progression-free survival (PFS) was analysed by means of univariate and multivariate models. FINDINGS: We achieved a gross total resection (GTR) in 65% of patients. Histological diagnosis was of grade II in 80%; anaplastic features were present in the remaining 20%. Adjuvant treatment, radiotherapy or chemo-radiotherapy, was administered in 40% of the cases. Median follow-up was 74 months. OS at 5- and 10 years was 76.32% and 68.24%, respectively. PFS at 5- and 10 years was 71% and 58%, respectively. In the multivariate model, histological grade, extent of resection and age at diagnosis (≤ 30 years vs > 30 years) were the only independent prognostic factors for both OS and PFS. CONCLUSIONS: Our retrospective long-term study confirms the relatively favourable prognosis associated with PXA. Young patients with a low-grade tumour (WHO grade II) who underwent GTR carry the longest OS and PFS.

Interhemispheric approach to tumors of the posterior gyrus cinguli.

OBJECTIVE: Posterior gyrus cinguli tumors are a well-defined group of tumors that pose considerable challenges in creating surgical access and manipulating adjacent eloquent areas (visual and motor). Here we report our 5-year experience in the surgical treatment of these tumors and describe tumor characteristics, surgical steps, critical aspects, and prognostic factors. METHODS: This series comprises 37 patients operated on for glioma (high-grade in 28, low-grade in 9), often presenting with motor impairment (n=20), intracranial hypertension (n=15), seizures (n=11), and/or hemianopia (n=9). Preoperative assessment was performed with magnetic resonance imaging. Half of the tumors were more than 4 cm in size, and the majority presented secondary extension into the fronto-parieto-occipital area, the temporo-mesial area, and/or the corpus callosum. Positioning and assisted surgery were optimized in each patient based on preoperative planning. RESULTS: The ipsilateral interhemispheric approach was elected in all cases. Tumor size and extension were significantly associated with the degree of tumor removal. Total removal was achieved in 25 patients (65%); 4 (10%) had persistent morbidity (visual or motor deficits). The occurrence of local and systemic complications was negligible. CONCLUSIONS: Surgical treatment of posterior gyrus cinguli tumors can be safely approached via the interhemispheric route as it permits several beneficial operative maneuvers in selected cases.

Surgical treatment of parasagittal and falcine meningiomas of the posterior third.

BACKGROUND: To the authors' knowledge, meningiomas of the posterior third of the falx and the parasagittal sinus have never been specifically described to date and correlated visual outcome remains unclear. With this retrospective study we describe the clinical characteristics of these tumours, their surgical management, and the improvement in visual disturbances after surgery. METHODS: Twenty-six consecutive patients (22 females, 4 males; mean age, 54 years) operated on for parasagittal (n = 22) and falcine (n = 4) meningioma between 1990 and 2010 were analysed retrospectively. Preoperative planning included magnetic resonance imaging (MRI) and magnetic resonance venography (MRV) or angiography. Sinus invasion was classified as normal, stenotic or occluded from the imaging findings and according to the Sindou classification from the intraoperative notes. RESULTS: Visual disturbances and headache (in 21 and 14 cases, respectively) were the most commonly referred symptoms; visual field deficit was present in 19 patients. Simpson grade I was obtained in four patients, grade II in 15, grade III in three, and grade IV in four. The main limiting factor for total removal was sinus involvement. No perioperative deaths or relevant postoperative complications occurred. The mean follow-up was 107 months. Visual field deficit improved or resolved in almost half of the patients during the follow-up period. Three (12%) patients relapsed, two were treated with Gamma Knife surgery (stable at current writing) and the third died of disease progression. CONCLUSIONS: Outcome after surgery compares favourably with other parasagittal meningioma localisations and overall morbidity is negligible. Visual function is crucial for clinical outcome. Since an improvement of the deficit might still be possible, every effort should be undertaken to preserve the visual cortex.

Cystic dilation of the ventriculus terminalis.

OBJECT: The ventriculus terminalis, an embryological remnant consisting of the ependymal-lined space of the conus medullaris, can occasionally become symptomatic after cystic dilation. In the existing literature, consisting of 32 cases, the preferred type of management (conservative vs surgical) is still debated. The object of this study was to report the surgical results in a consecutive series of 10 adult patients with cystic dilation of the ventriculus terminalis (CDVT), to match them with data retrieved from the relevant literature, and specifically to validate a new recent clinical classification. METHODS: The authors reported 13 new cases of CDVT treated in the Department of Neurosurgery at University Hospital in Verona, Italy. Treatment modalities and clinical and radiological outcomes, both early and at follow-up, were analyzed and compared with a preoperative classification of clinical presentation, as established by de Moura Batista and colleagues (2008). RESULTS: Surgical treatment seemed to guarantee the resolution of CDVT. Dorsolumbar laminotomy, myelotomy, and cystic drainage were performed in 10 patients. Patients with Type I symptoms (nonspecific complaints) often presented with comorbidities (herniated disc or facet hypertrophy) confusing their clinical status. The surgical treatment of patients with Type I symptoms promoted good results only if the diagnosis of CDVT was definitive and symptoms had rapidly evolved. In patients with Type II (focal neurological deficits) and III (sphincter disturbances) symptoms, surgical treatment sustained improvement even at the late follow-up. CONCLUSIONS: While confirming the usefulness of de Moura Batista and colleagues' classification in its impact on prognosis, the authors propose a revision of the classification with subgroups Type Ia (nonspecific symptoms without clear relation to CDVT), which is best treated conservatively, and Type Ib (rapid onset and invalidating unspecific complaints without comorbidities), which may benefit from surgical evacuation.

Eligibility criteria and psychological profiles in patient candidates for awake craniotomy: a pilot study.

BACKGROUND: Although generally well tolerated, awake craniotomy is burdened by non-negligible failure rates. The aim of this pilot study was to verify the feasibility of a wider research scope to define objective criteria for patient exclusion and the risk of intraoperative mapping failures. METHODS: Twenty-one patients with brain tumors were subjected to a procedure in 3 steps: neuropsychological criteria for both cognition and language; psychological questionnaires for anxiety, attitude to pain and depression, and psychophysiological monitoring for the candidate's capacity for self-control; and an intraoperative interview for the patient's perception during awake procedure. Outcome measures were as follows: (1) patient compliance, defined as patient response to the intraoperative procedure and measured by psychological scale scores for fear and pain, and (2) failure, defined as the impossibility to complete brain mapping (minor) or conversion to general anesthesia (major). Data analysis included the description of preoperative and intraoperative assessments and their evaluation (Spearman ρ test), and the prognostic factors for intraoperative compliance and procedure failure (Mann-Whitney test). RESULTS: Three patients were considered ineligible after the first step. In the remaining 18, the responses of 10 patients fell within the normal range and 8 showed some degree of impairment on at least 1 preoperative evaluation, but not enough to be excluded from awake surgery. The data analysis also showed that fear of pain correlated with pain felt during the operation and preoperatively with depression and psychophysiological changes, the latter of which was associated with fear felt during craniotomy. Minor failures occurred in 2 patients. CONCLUSIONS: From these preliminary results, we observed that warning signs for minor failure were fear of pain and anxiety, as revealed by psychological questionnaire responses, and the incapability of self-control at psychophysiological monitoring. This assessment may serve to fit mapping modality to the single patient and to avoid complications.

Pre- and post-operative assessment of visuo-spatial functions in right hemisphere tumour patients: a pilot study.

Patients with neglect fail to report, respond to, or orient to stimuli presented on the opposite side of the brain lesion. Spatial neglect is a multi-componential syndrome and many of its symptoms and signs need specific testing to detect their different clinical manifestations. Given that neglect has a dramatic effect on the outcome of these patients, it is of paramount importance for accurate assessment all its manifestations. Thus, the purpose of this study is to assess visuo-spatial functions with a newly-built neuropsychological battery to determine the incidence of visuo-spatial disorders and spatial neglect in patients with right brain tumour. We tested 14 patients undergoing tumour resection, both pre-operatively and post-operatively. Pre-operatively, we found an incidence of 42.86% for visuo-spatial deficits and of 14.29% specifically for spatial neglect. This incidence increases post-operatively to 57.14% for visuo-spatial deficits and to 42.86% specifically for spatial neglect. The present study has important implications for a better knowledge of the spatial disorders in patients with right-brain tumour, thus providing a clearer picture on the everyday life problems faced by these patients, both within the family and in working contexts.

Intraoperative neurophysiological monitoring during surgery for Chiari malformations.

Reports on the use of intraoperative neurophysiological monitoring (INM) techniques during surgery for Chiari malformations are anecdotal. There are almost no data on significant intraoperative worsening in either somatosensory-evoked potentials (SEPs) or brainstem auditory-evoked potentials (BAEPs) during surgery that would have alerted the surgeon to modify the surgical strategy. Yet, a few reports suggest that INM may play a role in preventing spinal cord injury during positioning of the patient. Overall, the use of INM in this type of surgery can be considered only as an option. More speculatively, INM adds information to the ongoing discussion on the most appropriate surgical technique for posterior fossa decompression in Chiari malformations. This debate applies especially to children where a more conservative approach is advisable to reduce the complications. Studies on the conduction time of BAEPs provide some evidence that, from a merely neurophysiological perspective, most of the improvement occurs after bony decompression and removal of the dural band at the level of the atlanto-occipital membrane, not after duraplasty.

Expanding cerebrospinal fluid cyst in the operative cavity: an unusual postoperative complication.

We present two cases of expanding cerebrospinal fluid (CSF) cyst formation appearing as a local complication after supratentorial craniotomy for complete brain tumour removal. Surgical treatment was simple and effective. Diagnosis was less obvious due to apparently normal radiological patterns and the absence of an expanding mass. CSF cysts should be included in the differential diagnosis of postoperative complications, particularly when neuroradiographic findings are inconclusive.

Hyperostosing meningiomas of the cranial vault with and without tumor mass.

OBJECTIVE: This study represents the first clinical series in the reported literature exclusively concentrating on the clinicoradiological features of non-sphenoidal hyperostosing meningiomas. It attempts to identify the factors that may have an impact on the surgical strategy and results of this unique subgroup of meningiomas. METHODS: In the vault, we distinguished between meningiomas with and without tumor mass according to their thickness (<1.5 vs ≥ 1.5 cm) and between convexity (lateral) and calvarial (midline) meningiomas according to their location. The clinical, radiological, surgical and prognostic characteristics of the tumors were examined. RESULTS: Over a 10-year period, we observed 24 cases, 18 of which in the convexity (nine without and nine with tumor mass) and six calvarial (one without and five with tumor mass). Six patients presented with neurological signs, while the majority showed bony hyperostosis (n = 19). Brain edema (n = 7) was found only in cases with tumor mass, in all neurologically impaired patients, and only in one intact patient. Total removal was obtained in 92% patients. Small residual tumors attached to the superior sagittal sinus and perisinusal dura were coagulated in situ and not excised. Morbidity occurred in three symptomatic patients with tumor mass and brain edema (mental confusion in one case and hemiparesis in two cases). Mortality was nil. After a mean follow-up of 4.8 years, three cases relapsed, all of which had initially presented with atypical meningiomas. CONCLUSIONS: The rare hyperostosing cranial vault meningiomas may be classified as being with and without tumor mass. A number of categorical differences exist in their distribution, pattern of hyperostosis, surrounding arachnoidal plane, and their prognosis. Careful preoperative planning aimed at tailoring the extent of tumor removal and reconstruction in the neighboring infiltrated structures enables a good outcome to be achieved.

Cognitive effects of tumour and surgical treatment in glioma patients.

Quality of life in brain tumour patients is an emerging issue and has prompted neurosurgeons to reconsider the need for cognitive assessment in the course of treatment. In particular, to date there has been a lack of comprehensive neuropsychological assessment performed preoperatively and in the acute postoperative period. We examined 29 patients with glioma, analysing several functional domains-intelligence, executive functions, memory, language, praxis, gnosis and mood state-in order to establish the effect of tumour and surgery on cognition. At baseline, using test- and domain-based criteria, 79% and 38% of patients, respectively, were impaired, the former related to tumour factors such as oedema (P < 0.05), larger size (P < 0.05) and higher grade (P = 0.001). Verbal memory, visuospatial memory and word fluency were the most frequently affected functions, partly associated with depression. Postoperatively, again using test- and domain-based criteria, 38% and 55% of patients, respectively, were unchanged, 24% and 21% improved, and 38% and 24% worsened; 24% and 62% of patients were intact, respectively. The extent of removal did not influence the outcome. Improvement involved previously impaired functions and was correlated with high-grade tumours. Worsening regarded executive functions was related to tumour size and was partly explained by radiological findings on postoperative magnetic resonance imaging (MRI). This preliminary study, focussing on the effects of tumour and surgery, showed that tumour significantly affects cognitive functions, mainly due to the mass effect and higher grading. Surgical treatment improved the functions most frequently affected preoperatively and caused worsening of executive functions soon after operation, leaving the overall cognitive burden unchanged and capable of improvement prospectively.

Gamma Knife surgery in vestibular schwannomas: impact on the anterior and posterior labyrinth.

OBJECT: During the past decades, in small-to-medium size vestibular schwannomas, Gamma Knife surgery (GKS) has become a reliable therapeutic option because of either excellent local tumor control or minimal morbidity, with cranial neuropathy becoming increasingly rare. Although still insufficiently analyzed in larger cohorts of patients with long-term follow-ups, adequate chances of hearing preservation and vestibular sparing seem clinically guaranteed. However, deeper investigations are needed in this regard, expanding the number of cases and the follow-up period. METHODS: A small group of patients with vestibular schwannomas (74 patients, including 41 men and 33 women) treated between 2003 and 2009 using GKS at the authors' institution were analyzed--both before and after GKS--with computerized static stabilometry and electronystagmography for balance disorders, vertigo, and ataxia on 1 side and pure tone average, vocal speech discrimination score, auditory brainstem response, and so forth for hearing impairment and tinnitus on the other side. Eligibility criteria for this prospective study included previously untreated unilateral lesions and a Gardner-Robertson hearing class of I-III. Dosimetry plans had been programmed at the lower effective dosages for these tumors (median surface dose 12.4 Gy, range 10-13 Gy), carefully avoiding even minimal toxic dosages on the most vulnerable targets: the cochlea (never > 6 Gy) and the vestibular canals (< 7.5 Gy). RESULTS: To date, tumor growth control rates remain satisfactory; at a mean follow-up of 50 months, the rate was 96%. The overall level of hearing preservation was 72%, with 81% having Gardner-Robertson Class I hearing. Tinnitus decreased, from 52% to 28% of patients (p < 0.01). Significant improvements were also observed in vestibular symptoms, with computerized static stabilometry abnormalities decreasing from 62% to 32% (p < 0.001) and electronystagmography abnormalities reducing from 48% to 14% (p < 0.001). CONCLUSIONS: Using appropriate radiodosimetry planning, GKS seems to guarantee not only adequate tumor growth control rates, but also better levels of hearing preservation, with a documented, long-lasting improvement in vestibular functions.

Surgical approaches to tumors of the anterior gyrus cinguli.

BACKGROUND: Tumors of the gyrus cinguli are deep-seated, and may require a variety of surgical options. We focused on anterior tumors, which have specific anatomic and surgical features. OBJECTIVE: To evaluate different approaches and indications through detailed description and a review of our experience. METHODS: These approaches include unilateral interhemispheric or combined: bilateral interhemispheric, unilateral plus superior frontal gyrectomy, or unilateral plus frontal polectomy. The relevance of this retrospective analysis is stressed by the extremely limited literature in this regard. RESULTS: In the past 5 years we operated on 38 patients with gliomas. We compared the following variables: location (perigenual, prerolandic), pathology (glioblastoma, other gliomas), size (<4 cm, > or =4 cm), extension (unilateral, bilateral), and approach (unilateral interhemispheric, combined). The only significant association we found was between tumor location (perigenual) and bilateral extension (P < .01). However, combined approaches were adopted only slightly more frequently in this region than in the prerolandic area, and this resulted in a lower rate of total removal (33% vs 76%, P < .01). Gross total removal was achieved in 28 cases (66%) and was significantly associated with combined approaches (77% vs 50%, P < .05). CONCLUSIONS: The choice of a combined approach to anterior gyrus cinguli tumors is critical to improving the quality of resection in selected cases. We recommend a combined approach in the surgical treatment of large tumors of the perigenual area.

Surgical treatment of high-grade gliomas in motor areas. The impact of different supportive technologies: a 171-patient series.

In the last few years much has been published to validate new technology in brain mapping for clinical purposes, but there have been few clinical results. In this report we describe our five-year experience in the surgical management of malignant gliomas around motor areas with an evaluation of the impact of functional magnetic resonance imaging (fMRI) plus navigator and intraoperative neurophysiology (IN). End-points were extent of removal, morbidity, and survival. Variables describing patient and tumor characteristics and treatment modalities were statistically weighted in relation to treatment outcome. Tumor depth (P = 0.01), midline shift ≥1 cm. (P = 0.05), and insular location (P = 0.001) negatively affected extent of removal, whereas IN (P < 0.001) and fMRI plus navigator (P = 0.02) contributed to increasing the rate of total removal (73%, 71% vs. 40%). Postoperative motor impairment was mild and transient in a minority of cases (20%). General complications, as defined by the Glioma Outcome Project, occurred in 23% of cases. IN was the only factor associated with acute postoperative motor deterioration (P < 0.001). IN and age >65 years (P = 0.01) were associated with the occurrence of complications. Overall survival was significantly higher in patients operated with IN or fMRI plus navigator (P < 0.01). Comparing different surgical strategies used in the same period, we observed that supportive technologies in glioma surgery have their primary impact on the quality of resection and survival. IN led to transient motor impairment and some additional complications which did not affect functional outcome.

Recovery from hemianopsia after surgical removal of spontaneous occipital haemorrhage.

In cases of spontaneous haemorrhage without severe impairment of consciousness, indications for surgical treatment remain controversial and the effect of surgery on focal deficits is unclear. We report the case of a young man operated for left occipital spontaneous haemorrhage (28 cm(3)) who had presented with right lateral hemianopsia without impaired consciousness. The visual field defect improved soon after the operation and resolved over the following months. The rationale for this approach is discussed.

Intraoperative neurophysiology of the motor system in children: a tailored approach.

INTRODUCTION: Intraoperative neurophysiology has moved giant steps forward over the past 15 years thanks to the advent of techniques aimed to reliably assess the functional integrity of motor areas and pathways. INTRAOPERATIVE NEUROPHYSIOLOGICAL TECHNIQUES: Motor evoked potentials recorded from the muscles and/or the spinal cord (D-wave) after transcranial electrical stimulation allow to preserve the integrity of descending pathways, especially the corticospinal tract (CT), during brain and spinal cord surgery. Mapping techniques allow to identify the motor cortex through direct cortical stimulation and to localize the CT at subcortical levels during brain and brainstem surgery. These techniques are extensively used in adult neurosurgery and, in their principles, can be applied to children. However, especially in younger children, the motor system is still under development, making both mapping and monitoring techniques more challenging. In this paper, we review intraoperative neurophysiological techniques commonly used in adult neurosurgery and discuss their application to pediatric neurosurgery, in the light of preliminary experience from our and other centers. The principles of development and maturation of the motor system, and especially of the CT, are reviewed focusing on clinical studies with transcranial magnetical stimulation.

Gamma knife radiosurgery for trigeminal neuralgia: results and potentially predictive parameters--part I: Idiopathic trigeminal neuralgia.

OBJECTIVE: Gamma knife radiosurgery (GKR) is an increasingly used, minimally invasive treatment option for patients with trigeminal neuralgia (TN) refractory to medical therapy. This retrospective study evaluates the long-term results and side effects of GKR in the treatment of TN focusing on potentially predictive factors. METHODS: One hundred sixty patients with TN were included in this study (minimum follow-up, >6 mo; mean, 37.4 mo; range, 6-144 mo). In 92 patients, GKR represented the first nonmedical option ("primary GKR"). In 68 patients, invasive treatments had been previously attempted. All patients were treated using a single 4-mm collimator shot targeting the pontine trigeminal root entry zone with a maximal dose of 75 to 95 Gy. Brainstem dose exposure never exceeded 15 Gy. Treatment outcome results were classified as Grade I (pain-free with no pharmacological treatment), Grade II (pain-free with pharmacological treatment), and Grade III (no result). Data were analyzed using the log-rank test for univariate analysis and the ordered logit model for multivariate analysis. RESULTS: In the overall series, 98 (61%) out of 160 patients reached a Grade I outcome, 45 (29%) reached a Grade II outcome, and 17 (10%) patients had no results from GKR. These results were encouraging for patients with typical facial pain features and for patients treated by a "primary" gamma knife. Considering the global outcome, the most effective and safest dose was found to be in the 80 to 90 Gy range. CONCLUSION: According to our experience, GKR represents a reliable second-line therapeutic approach for TN after pharmacological failure. Favorable prognostic factors include "primary GKR" and maximal GKR dose ranging between 80 and 90 Gy.