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Background and Purpose: Craniopharyngiomas are intra-cranial tumors, relatively frequent in children, expanding in the pituitary stalk axis, from the third ventricle to the sphenoid body. Plain films and CT scan generally show a calcified lesion, deforming the sella turcica. MRI improves tumor description and topographic and structural analysis of the lesion. The aim of this study is to analyze the MRI aspect of craniopharyngiomas in a pediatric population and to correlate findings with surgical data., Methods: MR and CT studies of 43 pediatric cases of histology-proven craniopharyngiomas were reviewed retrospectively. Tumor emergence, extensions and signal on different sequences were recorded. We searched for radio-surgical correlations., Results: Craniopharyngiomas can be classified into two groups: intra-sellar tumors and third ventricle floor tumors (infundibulum and tuber cinereum). Preferential routes of extension are observed in each group correlated with consistency (cystic and/or solid). Surgical data confirmed these results., Conclusions: MRI is crucial for the pre-therapeutic evaluation of craniopharyngiomas allowing not only a detailed description of the tumor but also guiding therapeutic decisions. This series demonstrated that craniopharyngiomas exhibit two different types of localization and behavior. Embryonic development of the tumor explains the topographical differences.

Background and Purpose: Microsurgical resection have the advantage to be immediately effective according to bleeding risk and is the reference treatment for cerebral arteriovenous malformations. For cerebral arteriovenous malformations located in the brainstem gamma-knife radiosurgery due to its low invasivity is classically a first line treatment. We reviewed the Marseilles experience to assess the efficacy and safety of gamma-knife radiosurgery for brain stem arteriovenous malformations., Methods: We analyzed retrospectively data of 45 patients with an arteriovenous malformation located in the brain stem treated in Marseilles by gamma-knife radiosurgery by between 07/92 and 12/99. Mean age was 42 years, there were 5 children. Arteriovenous malformations were located in the pons or midbrain for the majority of the patients. Intraaxial lesion was found in 82% of patients. Hemorrhage prior to radiosurgery occurred in 75% of the patients. Gamma-knife procedure was the first treatment of the arteriovenous malformations for 29 patients (65%); previous surgery was performed in 34 patients (15%). Mean nidus volume was 550 mm(3) (32-14 196 mm(3)). Mean margin dose was of 23 Gy (range 15-30 Gy). Follow up was available for 25 patients (mean 18 months)., Results: One patient presented a transient worsening of his neurological status, and 2 patients developed a fixed deficit. Two patients underwent rebleeding at an interval of 12 to 36 months after the gamma-knife procedure. At last angiographic follow-up (13 patients), the obliteration rate was 82% of the arteriovenous malformations. A second procedure was proposed to a patient with only partial occlusion at 3 years., Conclusions: Gamma-knife radiosurgery can achieve good obliteration rate of brain stem arteriovenous malformations with low morbidity and may be a valuable first-choice therapy for such arteriovenous malformations. A larger population and longer follow up are mandatory in order to confirm these preliminary results.

Historically, angiography was one of the first diagnostic methods to allow for visualization of neurovascular structures. It has been and still is very useful for precise evaluation of vascular pathology and is one of the main elements in treatment planning for radiosurgical targets. It is the only imaging method that gives insight into the angioarchitecture of a cerebral arteriovenous malformation, possibly reducing the target volume. Construction of frames (Leksell, Fisher) that are compatible with cross-sectional imaging methods, such as CT and MRI allowed there use for planning of stereotactical treatment for brain cerebral arteriovenous malformations. The advantages of these methods are given by the fact, that they are less invasive and that they allow visualization of neurovascular structures and surrounding cerebral structures. Further evolution of the cross-sectional imaging techniques allowed reconstruction of the image data in different planes and segmentation of structures such as vessels. Use of special algorithms allow visualization of the image data, i.e. surface rendering with 3D images of vascular structures. However, such images allow no detailed insight into the angioarchitecture of a cerebral arteriovenous malformation and give rather a view of the whole volume, i.e. a "tumor" aspect of the cerebral arteriovenous malformation. Similar images are currently also obtained with digital substraction angiography using rotational image acquisitions and image postprocessing allowing 3D reconstruction of angiographical image data. The different image evaluation methods are thus complementary all giving useful information for treatment planning. Therefore it would be useful to develop the possibility to integrate the information obtained by these modalities. Image fusion require identification of fiducial marks, what can be performed with application of external marks or by using internal anatomical marks. Recent developments allow now use of vascular structures as fidiucial marks to obtain image fusion. This paper reports on the evolution of stereotactical planning, performed on 541 patients over a period of eight years.

Between July 1992 and August 1995, 11 patients with pineal region tumors (PRTs) were treated at our center. Ages ranged from 8 to 72 years (median 21). Diagnosis was confirmed by histological examination in 7 patients. The remaining cases had strong neuroradiological and marker evidence of the diagnosis, so that a stereotactic biopsy could be avoided. The pathological diagnoses were pinealocytoma (n = 1), tectal astrocytoma (n = 1), germinoma (n = 2), pinealoblastoma (n = 2), and meningioma (n = 3). The marginal dose of these tumors ranged from 12 to 18-20 Gy. Conventional external radiotherapy was never used in this series. With a median follow-up of 12.3 months (range 2-34), all tumors responded to treatment and disappeared or ceased growing. We observed no mortality or major morbidity. One patient (tectal astrocytoma) had a mild radiation-induced reaction, with headache and transient worsening of an abducent nerve palsy, which were controlled with steroids. In germinomas and pinealoblastomas, recovery of normal cerebrospinal fluid circulation was observed in less than 7 days, in parallel with major tumor shrinkage. In this study we confirm that radiosurgery can be an effective and safe alternative for the treatment of pinealocytomas and low-grade tectal gliomas. Moreover, we consider that the characteristics of the radiosurgery technique suggest the method should be evaluated for the treatment of malignant PRTs.

A case of bacterial endocarditis complicated by paralytic pontine exotropia is reported. Magnetic resonance imaging clearly showed a rostral lesion of the paramedial pontine reticular formation and the medial longitudinal fasciculus. The occurrence of paralytic pontine exotropia is suggestive of ischaemia, and patients with this so-called "one-and-a-half syndrome" associated with signs of infection should be investigated for endocarditis.

The detection or suspicion of a tumoral expansive process in the third ventricule is usually performed by MRI. The contribution of MRI to the diagnosis is unquestionable in view of its accuracy in the topographical characterization of these lesions and in the detection of small formations. The great histological variety of tumours in that region may result in different treatments which can be associated. MRI, therefore, plays an important role in pretherapeutic morphological evaluation. Fifteen patients with tumour of the third ventricle were examined by MRI before treatment. The results of these examinations were compared with the pathological data and the therapeutic procedures: ventricular shunting, stereotactic needle biopsy, radio- or chemotherapy and surgery. MRI cannot provide a formal histological characterization, but it can individualise some categories of tumours, give details on the walls of the third ventricle (notably in the case of bifocal pineal and suprassellar lesions), visualize the paths of CSF flow and predict the need for cisternoventriculostomy, and detect venous structures in the vicinity of the great cerebral vein which might result in post-biopsy and post-surgery complications.

Three HIV seropositive patients presented with cerebral toxoplasmosis which was treated by anti-infectious agents. After partial improvement, they developed hemichorea related to striatal infectious lesions. In AIDS patients with cerebral toxoplasmosis, autopsy series have reported a high incidence of basal ganglia abscesses, explaining the occurrence of involuntary movements such as hemichorea.

The authors report their experience with Colloid Cysts of the third ventricle (9 cases treated between 1983 and 1989). Eight of them were punctured using stereotactic approach; five cysts were completely evacuated and the patients are free of recurrence. In three cases, tapping was impossible or the cyst insufficiently evacuated and the patients were secondary operated on (open microsurgical approach). The last case was directly operated on. Colloid cysts cured by stereotactic puncture were all hypo or iso-dense at C.T. scan and had a diameter of more than 1 cm. All these cases have had a M.R.I. exploration and the image of the cyst was always the same increased T1 and T2 signal. Unfortunately, we did not have the opportunity to realize M.R.I. in colloid cysts of a small size and hyperdense at C.T. scan. These results can help to the indication of a stereotactic puncture at the first attempt in some well defined colloid cysts.

On the basis of their experience, the autors report the results obtained after 1500 examinations in the study of space occupying hemispheric lesions and in the study of cerebral atrophy.