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Objectives: As most reports on the gamma knife have related only to short or mid-term results, we decided to evaluate the effectiveness and toxicity of radiosurgical treatment for benign skull base meningiomas in 200 patients with a follow up of 5–12 years to define the role of gamma knife radiosurgery (GKRS) for basal meningiomas and to provide further data for comparison with other treatment options. Methods: In total, 99 patients were treated with a combination of microsurgical resection and GKRS. In 101 patients, GKRS was performed as the sole treatment option. Tumour volumes ranged from 0.38 to 89.8 cm3 (median 6.5 cm3), and doses of 7–25 Gy (median 12 Gy) were given to the tumour borders at covering isodose volume curves (range 20–80%, median 45%). Results: The actuarial progression free survival rate was 98.5% at 5 years and 97.2% at 10 years. Passing radiation induced oedema occurred in two patients (1%). The neurological status improved in 83 cases (41.5%), remained unaltered in 108 (54%), and deteriorated in 9 (4.5%). Worsening was transient in seven patients (3.5%) and unrelated to tumour or treatment in one (0.5%). Repeated microsurgical resection was performed in five patients following GKRS (2.5%). Conclusions: GKRS has proved to be an effective alternative to microsurgical resection, radiotherapy, and Linac based radiosurgery for adjunctive and primary treatment of selected patients with basal meningiomas. Because of the excellent long term tumour control rate and low morbidity associated with GKRS, this treatment option should be used more frequently in the therapeutic management of benign skull base meningiomas.

Objectives: Anatomical evidence and lesion studies, as well as functional magnetic resonance imaging (fMRI) studies, indicate that the cerebellum contributes to higher cognitive functions. Cerebellar posterior lateral regions seem to be relevant for cognition, while vermal lesions seem to be associated with changes in affect. However, the results remain controversial. Deficits of patients are sometimes still attributed to motor impairment. Methods: We present data from a detailed neuropsychological examination of 21 patients with cerebellar lesions due to tumour or haematoma, and 21 controls matched for age, sex, and years of education. Results: Patients showed deficits in executive function, and in attentional processes such as working memory and divided attention. Further analysis revealed that patients with right-sided lesions were in general more impaired than those with left-sided lesions. Conclusions: Those hypotheses that suggest that lesions of the right cerebellar hemisphere lead to verbal deficits, while those of the left lead to non-verbal deficits, have in part been confirmed. The generally greater impairment of those patients with a right-sided lesion has been interpreted as resulting from the connection of the right cerebellum to the left cerebral hemisphere, which is dominant for language functions and crucial for right hand movements. Motor impairment was correlated with less than half of the cognitive measures, with no stronger tendency for correlation with cognitive tests that require motor responses discernible. The results are discussed on the basis of an assumption that the cerebellum has a predicting and preparing function, indicating that cerebellar lesions lead to a "dysmetria of thought."

Objective: To evaluate the safety and efficacy of removing large acoustic neurinomas (⩾3 cm) by the retrosigmoid approach. Methods: Large acoustic neurinomas (mean (SD), 4.1 (0.6) cm) were removed from 50 consecutive patients by the retrosigmoid suboccipital approach while monitoring the facial nerve using a facial stimulator-monitor. Excision began with the large extrameatal portion of the tumour, followed by removal of the intrameatal tumour, and then removal of the residual tumour in the extrameatal region just outside the porus acusticus. The last pieces of tumour were removed by sharp dissection from the facial nerve bidirectionally, and resected cautiously in a piecemeal fashion. Results: There were no postoperative deaths. The tumour was removed completely in 43 of 50 patients (86%). The facial nerve was anatomically preserved in 92% of the patients and 84% had excellent facial nerve function (House-Brackmann grade 1/2). One patient recovered useful hearing after tumour removal. Cerebrospinal fluid leak occurred in 4%, but there were no cases of meningitis. All but two patients (96%) had a good functional outcome. Conclusions: The method resulted in a high rate of functional facial nerve preservation, a low incidence of complications, and good functional outcomes, with no mortality and minimal morbidity. Very favourable results can be obtained using the retrosigmoid approach for the removal of large acoustic neurinomas.

Objectives: To analyse the results of gamma knife radiosurgery (GKS) for the trreatment of intracranial meningiomas and to assess possible factors related to the outcome and complications of such treatment. Methods: The authors retrospectively reviewed the clinical and radiological data of 179 patients (194 lesions) treated with GKS for meningiomas between May 1992 and October 2000. The mean follow up duration was 37.3 months (range 6.4 to 86.3 months). The study determined the correlation between radiosurgical outcome including imaging changes after GKS and multiple factors such as tumour location and size, patient characteristics, venous sinus status, pre-GKS degree of oedema, other treatment modalities, and radiosurgical parameters. Results: The radiological control rate was 97.1%. Magnetic resonance imaging (MRI) showed complications after GKS in 35 lesions (25.0%) among the 140 lesions followed up with MRI. Complications were divided into peritumorous imaging changes (33 lesions; 23.6%) and transient cranial nerve dysfunction (two lesions; 1.4%). Radiation induced imaging changes were seen mostly in convexity, parasagittal, and falx meningiomas that were deeply embedded in the cortex. About 60% of these were asymptomatic and the overall rate of symptomatic imaging changes was 9.3%. Neurological deficit related to imaging changes developed in only three patients, and all the symptoms were transient. Conclusion: GKS for intracranial meningiomas seems to be a safe and effective treatment. However, meningiomas of the convexity, parasagittal region, or falx cerebri have a higher incidence of peritumorous imaging changes after GKS than those of the skull base. Therefore, the use of GKS needs to be considered very cautiously in cerebral hemispheric meningiomas, taking into consideration patient age and general condition, tumour size and location, pattern of cortical embedding, relation between the tumour and venous sinuses, presenting symptoms, and patient preference.

Objective: To undertake a prospective study of the long term neuropsychological outcome in patients with late onset idiopathic aqueduct stenosis (LIAS) after endoscopic third ventriculostomy. Methods: Six patients with LIAS were evaluated pre- and postoperatively using magnetic resonance imaging (MRI) and standardised psychometric testing procedures. Endoscopic third ventriculostomy was done using standard surgical techniques. The mean long term follow up was 81.2 weeks. Results: Preoperatively, all patients had cognitive impairment, four of them showing deficits in several cognitive domains. After endoscopic third ventriculostomy, all patients improved clinically and had ventricular size reduction on MRI. Postoperative neuropsychological testing showed that five patients achieved normal or near normal cognitive functions, and one improved moderately. Conclusions: Endoscopic third ventriculostomy caused a substantial improvement in the neuropsychological deficit of LIAS patients. This was also true for patients with enlarged ventricles that might be diagnosed radiologically as "arrested hydrocephalus."

Objectives: Advances in neuroimaging studies have recently improved the understanding of the functional anatomy of the calculation processes, having in particular underlined the central role of the angular gyrus (AG). In this study, the authors applied this knowledge to the surgical resection of a glioma invading the left AG, by localising and sparing the cortical areas involved in two different components of calculation (multiplication and subtraction), using direct electrical stimulations. Methods: A calculation mapping was performed in a patient without deficit except a slightly impaired performance for serial arithmetic subtraction, during the resection under local anaesthesia of a left parieto-occipital glioma invading the dominant AG. After somatosensory and language mappings, cortical areas involved in single digit multiplications and subtractions of seven were mapped using the method of electrostimulation, before glioma removal. Results: Distinct sites specifically involved in multiplication or subtraction were detected within the left AG, with a precise spatial distribution and overlapping. All the eloquent (somatosensory, language, and calculation) areas were surgically spared. Postoperatively, the patient had a transient complete deficit for arithmetic subtraction, without either multiplication or language disturbance. The tumour removal was complete. Conclusions: These findings suggest: firstly, the usefulness of an intraoperative calculation mapping during the removal of a lesion involving the left dominant AG, to avoid permanent postoperative deficit of arithmetic processes while optimising the quality of tumour resection; secondly, the possible existence of a well ordered and dynamic anatomo-functional organisation for different components of calculation within the left AG.

Objectives: This study was undertaken to review the indications for surgical treatment of brain stem cavernomas and to develop strategies to minimise the complications of surgery. Patients and results: Twelve patients underwent surgical resection of a brain stem cavernoma due to symptoms caused by one or more haemorrhages. Age ranged from 18 to 47 years (mean 29.2 years). Long term follow up (mean 3.7 years) included a complete neurological examination and annual MRI studies. The annual haemorrhage rate was 6.8 %/patient/year and a rate of 1.9 rehaemorrhages/patient/year was found. Surgery was performed under microsurgical conditions with endoscopic assistance, use of neuronavigation, and neurophysiological monitoring. Navigation proved to be reliable when applied in an early stage of operative procedure with minimal brain retraction. Endoscopy was a useful tool in some cases to confirm complete resection of the lesion and to ascertain haemostasis. Ten patients had a new neurological deficit in the early postoperative period, nine of these were transient. At the last follow up the neurological state was improved in five patients, unchanged in six, and worse in one compared with the preoperative conditions. The preoperative average Rankin score was 2.2 points and had improved at the last follow up by 0.6 points to 1.6 points. Conclusions: Symptomatic brain stem cavernomas should be considered for surgical treatment after the first bleeding. Careful selection of the optimal operative approach and a meticulous microsurgical technique are mandatory. The additional use of modern tools such as neuronavigation, endoscopic assistance, and monitoring can contribute to the safety of the procedure.