B. Wowra

3d tof mr angiography of cerebral arteriovenous malformations after radiosurgery

To investigate the potential of three-dimensional time-of-flight MR angiography (MRA) to complement SE imaging, 18 patients with intracerebral arteriovenous malformations were prospectively followed after undergoing radiosurgery. Vessel occlusion after stereotaxic single high dose radiotherapy develops slowly. The MRA detected signs of nidus obliteration earlier and with a higher sensitivity than did SE imaging. Six months after radiosurgery, MRA showed a reduction of the nidus flow signals in nine patients and after 1 year it showed reduction in 15 of the 18 patients. As shown by MRA, the loss of flow signals was related to a reduction of the nidus size in 4 patients after 6 months and in 11 after 1 year. The SE imaging revealed a reduction of the nidus size in only two patients after 6 months and in eight after 1 year. The signal intensity of the feeding arteries was reduced in nine patients and that of the draining veins was reduced in six. The T2-weighted images exhibited white matter lesions in eight patients after 1 year. For complete follow-up, SE imaging should be performed together with MRA.

Incidence of late radiation necrosis with transient mass effect after interstitial low dose rate radiotherapy for cerebral gliomas

SummaryLate radiation necroses constitute a hazard in low dose rate interstitial irradiation for inoperable gliomas. An incidence of 40% (8/20 patients) was found after permanent implantation of Iodine-125 seeds. This finding may even underestimate the real frequency, because follow-up of unaffected patients was shorter than in patients with radiation necrosis. The necrotic reactions caused a transient mass effect, which lead to a significant deterioration of performance scores. Further manifestations of late delayed radiation damage were observed in two patients.The occurrence of radiation necrosis was correlated with total radiation dose, amount of implanted radioactivity, and with velocity of tumour shrinkage. A mechanism underlying the development of radiation necrosis is proposed: A rapid shrinkage of tumour after interstitial Iodine-125 implantation may cause a significant irradiation of surrounding brain tissue, which was initially lying outside the target volume. Since most patients affected by radiation necrosis were children or adolescents, the risk of radiation damage should be minimized. This could probably be achieved either by reduction of irradiation dose, or by using temporary implants of Iodine-125.

Titanium Riechert head ring for MR stereotaxy : technical note

SummaryMagnetic Resonance has become the preferred neuro-imaging modality. To fully take advantage of the high anatomical resolution the Riechert stereotactic system was adapted for use in Magnetic Resonance Stereotaxy. The head ring which until recently was made of an aluminum alloy has been replaced by an unsegmented head ring of pure titanium without changing the dimensions and fixation mode. No significant misregistration due to eddy currents has been noticed. Minor distortion induced by the titanium head ring can be corrected mathematically. Thus the geometric information is limited only by the pixel resolution of the MR image.

Microsurgery of Malignant Gliomas of the Temporal Lobes: Cognitive Deficits Depend on the Extent of Lost Tissue

The neuropsychological evaluation of neurosurgical treatment methods has a long tradition. The treatment for genuine epilepsy, or infantile hemiplegia, for example, has shown that even complete removals of one temporal lobe or one hemisphere may be followed by surprisingly little psychological deficit, provided that the contralateral hemisphere has an entirely normal function [6, 9]. However, in most of these cases, the brain had a lifelong opportunity to adapt to the disease, a fact completely missing in patients with malignant gliomas. Today, the neurosurgical treatment of malignant tumors is performed less radically than earlier: The availability and continuous improvement of radiation therapy and chemotherapy enables the neurosurgeon to extirpate gliomas within the solid tumor margins. However, radiotherapy may cause dementia in long-term survivors with glioblastoma [5]. Therefore, it still seems justified to decide about the extent of the neurosurgical approach on the basis of the assumed psychological importance of the region under treatment and the costs and benefits of its radical extirpation.

Neuropsychological Abnormalities in Patients with Cerebral Arteriovenous Malformations: A Pilot Study

Stereotactic irradiation is the treatment of choice for inoperable cerebral arteriovenous malformations. At the University of Heidelberg a device for stereotactic radiotherapy using a modified linear accelerator has been developed and used for therapy of nearly 100 patients since 1984 [6, 11, 16].

Magnetic Resonance Imaging and Magnetic Resonance Angiography in Treatment Planning and Response Monitoring of Single High-Dose Radiotherapy in Intracerebral Arteriovenous Malformations

Arteriovenous malformations (AVM) are regarded as congenital anomalies consisting of a racemose convolution of pathological vessels which predispose to intercerebral bleeding. The bleeding risk is about 4% per year, with a combined rate of major morbidity and mortality of 2.7% per year (Ondra et al. 1990). Cerebral AVM can be graded according to Spetzler et al. (1986). This system is based on the size of the AVM, localization of draining veins, and eloquence of adjacent brain tissue. It is derived from the potential postoperative complications, such as neurological deficits and mortality. AVMs of grade I or II are easily resectable, while those of grade IV or V are correlated with a high risk of major postoperative neurological deficits. This grading allows comparison with other therapeutic approaches: (a) embolization is very helpful preoperatively in preventing excessive bleeding but does not obliterate a large AVM alone (Fox et al. 1990); (b) stereotactic single high-dose radiotherapy, or “radiosurgery,” shows good results for complete occlusion of the AVM after a latency of approximately 2 years (Engenhart et al. 1989).