Stereolithographic (SL) biomodeling is a new technology that allows three-dimensional (3D) imaging data to be used in the manufacture of accurate solid plastic replicas of anatomical structures. The authors describe their experience with a patient series in which this relatively new visualization method was used in surgery for cerebral aneurysms. Using the rapid prototyping technology of stereolithography, 13 solid anatomical biomodels of cerebral aneurysms with parent and surrounding vessels were manufactured based on 3D computerized tomography scans (three cases) or 3D rotational angiography (10 cases). The biomodels were used for diagnosis, operative planning, surgical simulation, instruction for less experienced neurosurgeons, and patient education. The correspondence between the biomodel and the intraoperative findings was verified in every case by comparison with the intraoperative video. The utility of the biomodels was judged by three experienced and two less experienced neurosurgeons specializing in microsurgery. A prospective comparison of SL biomodels with intraoperative findings proved that the biomodels replicated the anatomical structures precisely. Even the first models, which were rather rough, corresponded to the intraoperative findings. Advances in imaging resolution and postprocessing methods helped overcome the initial limitations of the image threshold. The major advantage of this technology is that the surgeon can closely study complex cerebrovascular anatomy from any perspective by using a haptic, "real reality" biomodel, which can be held, allowing simulation of intraoperative situations and anticipation of surgical challenges. One drawback of SL biomodeling is the time it takes for the model to be manufactured and delivered. Another is that the synthetic resin of the biomodel is too rigid to use in dissecting exercises. Further development and refinement of the method is necessary before the model can demonstrate a mural thrombus or calcification or the relationship of the aneurysm to nonvascular structures. This series of 3D SL biomodels demonstrates the feasibility and clinical utility of this new visualization medium for cerebrovascular surgery. This medium, which elicits the intuitive imagination of the surgeon, can be effectively added to conventional imaging techniques. Overcoming the present limitations posed by material properties, visualization of intramural particularities, and representation of the relationship of the lesion to parenchymal and skeletal structures are the focus in an ongoing trial.

We describe the case of a 16-year-old boy with idiopathic hydrocephalus, who developed cranial subdural hygromas and subsequent cranial subdural hemorrhage after a shunting procedure. Sciatica and radicular lumbar pain initially seemed to be unrelated to the proceeding implantation of a ventriculoatrial shunt. CT scan revealed a sharply demarcated hyperdensity in the lumbar subdural space with compression of the cauda equina. Differential diagnosis considerations included vascular malformations, vascular tumors, benign tumors of meninges or nerve sheets, ependymoma, lymphoma, and metastases. MR investigation did, in fact, clearly recognize this hyperintense space-occupying lesion as blood in the subdural space which outlined the cauda equina. We believe that the spinal subdural hematoma in our case represented an extension of intracranial subdural haemorrhage fluid into the spinal subdural space.

BACKGROUND: Endovascular coiling has become a standard technique in the treatment of cerebral aneurysms. The mechanisms of recurrence are incompletely understood. METHODS: In our clinical investigations we present three uncommon cases where the pathology at the base might has been underestimated in digital subtraction or magnetic resonance angiography. RESULTS: In the fi rst clinical study rehemorrhage occurred 11 years after endovascular coiling. Before rehemorrhage occurred, serial magnetic resonance angiographies had revealed a stable situation with only a small base remnant after initial endovascular treatment. In the second clinical study, intraprocedural rupture during endovascular coiling occurred and a residual angiographic occult lesion was detected only during microsurgical clipping. In the third clinical study, we again found a residual lesion during microsurgical clipping. CONCLUSION: We present three clinical studies were the pathology at the base might has been underestimated in digital subtraction angiography or magnetic resonance angiography. The incidence of angiographic occult residuals is unknown, but their clinical relevance may be important. Beside other mechanisms, these lesions might be the source of aneurysmal regrowth and hemorrhage (Fig. 4, Ref. 27). Text in PDF www.elis.sk.

We present a case involving a microsurgical approach to solving the problem of a medial cerebral artery (MCA) occlusion occurring after GDC coiling of an internal cerebral artery (ICA) bifurcation aneurysm in a 40 year old woman. We describe the clinical course of the case and discuss technical possibilities and risks of clipping a coiled aneurysm. One key to success is awareness of changes in the aneurysm's properties after coiling. With loss of elasticity the aneurysm had the effect of a tumor fixed on the vessel. The apposition of the aneurysm to the wall of the vessel, as well as the aneurysm's rigidity and increase of intracranial pressure after subarachnoideal hemorrhage (SAH), may lead to occlusion of the vessel. In cases of an mandatory operation due to the occlusion of a main arterial stem after coiling, it is primarily crucial to perforate the aneurysm's fundus, remove the coils, and, finally, to clip the slack neck of the aneurysm. An attempt to precisely prepare and clip the aneurysmal neck without removing the coils could result in the rupture of the aneurysm's neck.

The authors present a case report on rebleeding of a medial cerebral aneurysm (MCA) eight years after complete endovascular coiling. The primarily successfully coiled MCA aneurysm showed a local regrowth which, however, was not the source of the rebleeding. The angiogram demonstrated no evidence of contrast filling of the coiled segment, but according to intraoperative findings (haematoma location, displacement of coils, evident place of rupture) there is no doubt that the coiled segment of the aneurysm was responsible for the haemorrhage.