Microsurgically induced aneurysm models in rats, part I: techniques and histological examination.

INTRODUCTION: The percentage of aneurysms treated surgically has steadily decreased since the results of the ISAT study were published in 2002. The aim of this study was to develop different reliable and reproducible aneurysm models for microsurgical training and further research to guarantee effective instruction in microsurgery for young neurosurgeons with comparable aneurysms like in humans. METHODS: Arterial and venous pouch aneurysm models were created microsurgically using 22 Wistar rats. The femoral and the proximal iliac vessels and the bifurcation of the common carotid artery were exposed for induction. For histological examination every aneurysm was dissected out and analysed. RESULTS: A total of 39 microaneurysms was created in three different regions. During the creation four complications occurred: 4 bleedings and 1 defect were observed and immediately treated. Linear regression curves of the microsurgical evaluation showed a significant advancement in the course of the study. The volumes of the different models were: 2.58+/-1.01 mm (3) for the carotid, 6.49+/-3.36 mm (3) for the iliac and 10.41+/-4.13 mm (3) for the femoral aneurysms. The aspect ratios were 1.86+/-0.45 at the iliac, 1.62+/-0.3 at the femoral and 1.21+/-0.29 for the carotid aneurysms. In 89.7% of the cases the aneurysm sac was thrombosed accentuated at the aneurysm tip while the central zone of blood inflow revealed no thrombus formation. The proportion of endothelial cells displayed a reduction in relation to the total number per cross-section in all aneurysm types. CONCLUSIONS: The presented aneurysm models in rats are reliably and immediately available for further training or scientific histological investigations. Despite the fact that these are not bifurcation aneurysms, basic techniques such as suturing and microtechniques used for the dissection and repair of vessels can be taught.

Microsurgically induced aneurysm models in rats, Part II: clipping, shrinking and micro-Doppler sonography.

INTRODUCTION: To adapt to the changed approach in the treatment of aneurysms, the authors have developed three different experimental aneurysm models for teaching clipping, microvascular Doppler sonography and shrinking. METHODS: 39 microaneurysms were created in 22 animals in three different locations at the carotid, femoral and iliac arteries and treated by neurosurgical clipping. Additionally, shrinking was accomplished in selected cases. Microvascular Doppler sonography with a 20-MHz microprobe was performed prior to and after clipping to assess the achieved result of the clipping manoeuvre. Multiple clip applications in different techniques were performed for optimisation of clip placement and additional training. RESULTS: All created aneurysms could be clipped successfully. The mean duration for clipping and control of clipping results by the micro-Doppler was 8:51+/-4:41 minutes at all aneurysms. The aneurysm clip was repositioned in 16 of 39 (41%) cases, on the basis of the Doppler findings in 14 aneurysms (36%). A relevant stenosis was detected in 10 (25.7%) and incomplete occlusion in 4 (10.2%) attempts. In one aneurysm vasospasm was detected at the distal part of the parent artery. Complete clipping was achieved in all cases. During the entire procedure three unexpected complications involving rupture and bleeding impeded the training. CONCLUSION: Surgically induced aneurysms in rats allow the possibility of multiple clipping, shrinking and micro-Doppler sonography for the simulation of aneurysm treatment.

An optical evaluation of the phenomenon of red out in neuroendoscopic surgery: what is the physical background?

BACKGROUND: The loss of visualization in neuroendoscopy due to intraoperative bleeding is called "red out". Although red out is a well-known problem during endoscopy, clear physical descriptions of this phenomenon are lacking. OBJECTIVE: The aim of this study was to investigate the optical properties of red out. In particular, the attenuation coefficient, comprising scattering, and absorption, of various blood/Ringer solutions was quantified and measured spectrally resolved. Small amounts of blood virtually preclude neuroendoscopic visualization. In blood/Ringer solutions with a dilution of 1:101, it was not possible to distinguish characters (font size 10, Arial) at a distance of 5 mm. We have concluded, from our physical investigations, that the problem of red out is dominated by scattering rather than by absorption. Accordingly, technical developments aimed at increasing information acquisition under red out conditions should be based on optical measurement concepts for scattering media.

Lhermitte-Duclos disease as a component of Cowden's syndrome. Case report and review of the literature.

In recent years, 16 cases involving the association between Lhermitte-Duclos disease (LDD), which is a hamartomatous overgrowth of cerebellar tissue, and Cowden's syndrome (CS), an autosomal-dominant condition characterized by multiple hamartomas and neoplasias, have been reported. LDD may be one of the manifestations of CS. Recently, mutations of the PTEN/MMAC 1 gene, a tumor suppressor gene, have been found in families with CS, including four patients in whom LDD was diagnosed. The authors present a case of LDD in a 53-year-old woman who also had the typical mucocutaneous lesions found in CS, as well as goiter and intestinal polyposis. In this case, CS had never been suspected until the diagnosis of LDD was made. The mutation detected in the PTEN/MMAC 1 gene as well as neuropathological results are described.

Development of an endoscopic navigation system based on digital image processing.

We developed a new system to couple the endoscope to an optical position measurement system (OPMS) so that the image frames from the endoscope camera can be labeled with the accurate endoscopic position. This OPMS is part of the EasyGuide Neuro navigation system, which is used for microsurgery and neuroendoscopy. Using standard camera calibration techniques and a newly developed system calibration, any 3-dimensional (3-D) world point can be mapped onto the view from the endoscope. In particular, we can display the coordinates of any anatomical landmark of the patient as it is viewed from the current position of the camera. This and other image-processing techniques are applied to the labeled frame sequence in order to offer the neurosurgeon a variety of control modules that increase the safety and flexibility of neuroendoscopic operations. Several modules, including a new motion alarm system and the "tracking" and "virtual map" modules, were tested in a human cadaveric model using the frontal and occipital approaches. A failure rate of 8.6% was experienced during testing of the first version of the software, but the second version was 100% successful. Thus, an endoscopic navigation system based on digital image processing has been developed that could be a revolutionary advance in image-guided surgery.

MIN-biopsy of brain tumors: operative technique and histomorphological results.

MIN-biopsy is defined as an open minimal invasive biopsy, performed by microsurgical principles over a small osteoplastic trepanation or bore hole. Localization of the lesion is performed by exact calculation using the CT-topogram. Between 1993 and 1995 ten patients with unknown intracranial lesions were operated using the MIN-biopsy approach. Age ranged between 36 to 84 years (median age 57.8 years). Patients included five females and five males. Histomorphological diagnosis was possible in all cases. Histological diagnoses were glioblastoma multiforme in three patients and B-cell malignant lymphoma in four cases. Anaplastic astrocytoma was found in one case and the diagnosis of metastatic adenocarcinoma was observed in two patients. Complications or neurological deterioration were not observed. MIN-biopsy seems to be a safe procedure to arrive at exact neuropathological diagnosis of brain tumors. The procedure is compared with the established method of stereotactic biopsy by review of the literature.

Fornix damage and memory. A case report.

The role of the fornix for episodic memory processing is still a matter of controversy. A juvenile patient of average post-surgical intelligence with fornical damage due to tumor removal is described. The fornix was damaged bilaterally at the level of the fornical columns. The patient thereafter suffered major anterograde amnesia which was most pronounced in tests using long delays (e.g., in the delayed recall index of the revised Wechsler Memory Scale). Amnesia was a prominent on the verbal as on the nonverbal level. Attention, concentration and short term memory abilities were preserved. Cognitive flexibility, procedural memory and priming were principally unimpaired. There was no evidence of retrograde amnesia. It is concluded that the fornix constitutes a major link between the three memory interfaces (medial diencephalon, medial temporal lobe, basal forebrain) and that its bilateral rupture anterior to the thalamic level may lead to lasting anterograde amnesia.

Primary eosinophilic granuloma of the oculomotor nerve. Case report.

The authors report the occurrence of primary eosinophilic granuloma of the oculomotor nerve without osseous involvement in a 68-year-old man. Histopathological and neuroradiological findings are discussed. This case demonstrates that eosinophilic granuloma should be included in the differential diagnosis of tumor in which cranial nerves are involved.

A transcranial Doppler study of blood flow velocity in the middle cerebral arteries performed at rest and during mental activities.

While changes in blood velocity in the middle cerebral artery relative to rest were assessed by transcranial Doppler sonography, 70 volunteers with no sign of cerebrovascular disease performed two (left and right middle cerebral artery) series of six cognitive tasks. The tasks are assumed to be processed predominantly by either the left (verbal and mathematical tests performed aloud) or the right hemisphere (dot/distance estimation, spatial perception, and face recognition performed silently). All tasks were shown to increase middle cerebral artery blood flow velocity on both sides, by 1.6-10.6%. After an initial maximum at approximately 8 seconds, velocity decreased then increased again. A steady state was reached after approximately 24-42 seconds. The initial minimum during the following rest phase was reached some seconds later, followed by a slow increase to the reference rest steady state. A difference according to side could be determined only during the three right-hemispheric tasks (right greater than left, 2.5-2.9%). Left-handedness/ambidexterity, familial sinistrality, and profession seemed to have no influence on the results. The middle cerebral artery blood flow velocity increase on both sides was higher in women than in men during the dot/distance estimation and was also higher bilaterally in older than in younger subjects during the dot/distance and the spatial perception tasks. Habituation in performing the tasks was an important factor associated with a decrease of blood flow velocity, especially in the right middle cerebral artery. The habituation more pronounced on the right side possibly reflects the role of the right hemisphere in attention and arousal. The absolute blood velocities at rest decreased bilaterally with age.

Brain activity and blood flow velocity changes: a transcranial Doppler study.

Seventy volunteers with no sign of cerebral vascular disease performed two series of 6 cognitive tasks, 3 of which are assumed to be processed predominantly by the left and 3 by the right hemisphere. During the tasks, blood flow velocity changes in the middle cerebral artery were recorded every 3 seconds by the transcranial Doppler method (TCD). All tasks increased blood flow velocities in both MCAs, but only the "right hemispheric" tasks resulted in a statistically significantly higher increase than the left MCA. The time course of velocity changes reflects the increase in blood flow caused by increased brain metabolism during brain activity. During stimulation of the right and/or left visual field, blood flow velocity changes were recorded in the P2-segment of the corresponding hemisphere. In 76 volunteers, the study was performed. The time course of velocity changes was similar to that in the MCA study. Velocity rose as a result of increasing complexity of the visual stimulus. The velocity changes are similar to blood flow increases reported in the literature and rose by as much 2 to 25%. Assuming that the diameter of the large branches of the circle of Willis does not change during mental activity, blood flow velocity changes reflect blood flow volume changes. With the TCD method the close relationship among brain activity, metabolism, and blood flow can be reliably investigated. The high spatial resolution enables information to be given about the onset of autoregulation.

Possibilities and results of the preoperative and postoperative application of transcranial doppler sonography

The non-invasive, repeatable method of measuring blood flow velocities in the arterial circle of Willis by transcranial Doppler sonography is a method for assessing the hemodynamics of neurovascular diseases. For aneurysm surgery it provides information on the severity and extent of the vasospasms, as well as on the possible effect of therapy. The flow velocity, which is the hemodynamic measuring parameter, is used to judge whether the cerebral circulation is raised (arteriovenous angioma), lowered, or unchanged (hemodynamic effective stenoses, cerebral circulatory cessation). Knowledge of the intracranial hemodynamics is a prerequisite for the accurate interpretation of the Doppler findings

Microvascular and transcranial Doppler sonographic evaluation of cerebral aneurysm flow pattern.

Ninety percent of cerebral aneurysms were diagnosed after their first rupture with consecutive subarachnoid haemorrhage. In order to detect the aneurysms before rupture investigation by transcranial Doppler sonography was used on the basis of intra-operative evaluation of the normal aneurysmal flow pattern. In 34 patients the directly registered aneurysmal flow pattern was characterized by mean velocities slower than in parent arteries, by low diastolic flow velocities and by additional peaks superimposed on the normal pulse curve. The transcranial investigation with a large sample volume which includes aneurysm and parent artery was not able to distinguish this aneurysmal flow pattern from the normal one. Only in large to giant aneurysms a pathological flow pattern could be recorded transcranially.

Two transcranial Doppler studies on blood flow velocity in both middle cerebral arteries during rest and the performance of cognitive tasks.

While the middle cerebral artery (MCA) blood flow velocity changes relative to rest were assessed with transcranial Doppler sonography (TCD), 28 right-handed subjects with no sign of cerebrovascular disease performed two series of 6 cognitive tasks (two series = right and left MCA). The tasks included "reading", "finding nouns with a given first letter", and "multiplication" in four comparable versions to be performed aloud and silently in each of the two series. All of the tasks increased the MCA blood flow velocity bilaterally (2.7-12.1%). A significant left-right difference was present during "noun finding aloud" (left greater than right by 4.7%). A statistically insignificant tendency in the same direction was also present for the five other tasks. During loud reading the increase was higher bilaterally than during silent reading. Blood flow velocity changes in the right MCA for the three tasks performed aloud were lower in older than in younger people. It is posited that older people perform the tasks more slowly and under less stress requiring less right-hemispheric participation. Averaging the results for each of the four subjects involved leads to the conclusion that future TCD-lateralization studies should be done bilaterally at the same time to assess lateralization in a single person.

Morbidity and mortality after early aneurysm surgery--a prospective study with nimodipine prevention.

Based on the outcome in 116 consecutive patients who were subjected to early aneurysm operation combined with additional nimodipine treatment, and who were controlled by transcranial Doppler (TCD) sonography, a morbidity and mortality analysis was performed. Of the 84 patients who preoperatively were in Hunt & Hess grades III, 79 patients (94%) were considered to show a favourable (good-fair) late recovery, while one patient (1%) had a poor outcome, and four patients (5%) died. Of the 32 poor condition patients (H & H IV-V), 17 (53%) showed a favourable recovery, while seven (22%) had a poor outcome, and eight patients (25%) died. Altogether, 20 patients (17%) had an unfavourable (poor-dead) outcome. Only two of these patients showed delayed ischaemic deterioration, one as a consequence of a secondary occlusion of perforating branches from the basilar artery and one with decompensated vasospasm after the evacuation of an epidural haematoma and a longlasting severe systemic hypotension; both these patients died. In another six of the patients with an unfavourable outcome, this was mainly related to a complicated surgery. The unfavourable outcome was related to primary brain damage produced by the subarachnoid haemorrhage (SAH) in ten patients and in two patients to internal medical complications. In addition to the two patients who died following delayed deterioration, secondary neurological dysfunction occurred in 11 patients. In 10 of these patients transient neurological dysfunction was attributed to vasospasm or to a combination of vasospasm with intraoperative or postoperative complications. One further case of delayed deterioration was attributed to secondary occlusion of the internal carotid artery after a complicated operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Early aneurysm surgery: a 7 year clinical practice report.

One hundred and fifty patients with intracranial aneurysms, operated on consecutively in the early stage in our department, were re-evaluated retrospectively. Seven surgeons operated on 159 aneurysms in 150 patients. Seventy-nine percent of the patients were in grades I-III (scale of Hunt and Hess), 21% in grades IV-V. Seventy-one percent had a severe haemorrhage (classification of Fisher et al.), 21% had an intracerebral haematoma. Intraoperative CSF drainage was an almost indispensable tool while postoperative external drainage did not prove to be helpful in preventing vasospasm and/or hydrocephalus. Induced hypotension was abandoned in favour of temporary clipping. Thirteen percent of the patients suffered a permanent or fatal immediate postoperative deterioration, while 11% developed delayed neurological deficits. Five percent were related to vasospasms alone, they were all transient. Five percent had vasospasm combined with other complications. One of them had permanent and the other one fatal deficits. One percent deteriorated due to embolism or occluded vessels. The results improved with the introduction of the calcium channel blocker nimodipine, induced hypertension and transcranial Doppler sonographic control of the vasospasm. Patients in good preoperative condition had a good early outcome in 69%. The result was fair in 21% and poor in 4%, while 6% of the patients died. In the poor condition group 22% of the patients made a good, 13% a fair, and 59% a poor recovery, 16% of whom died.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of blood velocity changes related to vasospasm in the circle of Willis measured by transcranial Doppler ultrasound.

Fifty patients with ruptured aneurysms were operated on within 72 hours after the first subarachnoid hemorrhage (SAH). To prevent symptomatic vasospasm, the patients were given the calcium channel blocker, nimodipine, intravenously (2 mg/hr) for 14 days and orally (60 mg four times daily) for another 7 days. At short intervals (at least every 3rd day) the blood flow velocity in the different segments of the circle of Willis was measured with a noninvasive transcranial Doppler ultrasonography method. Within the first 72 hours after SAH, the velocity was normal in the large branches of the circle of Willis and angiography revealed no signs of vasospasm. The Doppler frequency changes that relate to blood flow accelerated between Days 3 and 10, and maximum blood flow velocities were recorded between Days 11 and 20, with normalization occurring within the following 4 weeks. The changes showed a significant relationship to the source of SAH, the side of the operative approach, and the method of nimodipine administration. A comparison between the angiographically proven diameter of spastic arteries and the Doppler-measured blood flow velocity showed an inverse relationship in flow of the middle cerebral artery and the internal carotid artery that was statistically highly significant (p less than 0.001) while this correlation was only slightly significant in the A1 segment of the anterior cerebral artery (p = 0.054). Seven patients (14%) developed delayed ischemic deficits (DID's), which were all functionally reversible. One patient (2%) died as a result of decompensated vasospasm. Based on the information provided by Doppler measurement of the individual blood flow velocity changes due to vasospasm, preventive hypertensive treatment was introduced to improve the perfusion pressure while patients were still in an asymptomatic stage. Among the last 40 patients who were treated according to this regimen, reversible DID's were observed in only three patients (7.5%) and postoperative angiography to detect vasospasm was not necessary.