Manuel Dujovny

Pericyte endothelial gap junctions in human cerebral capillaries.

SummaryHuman cerebral tissue has been ultrastructurally studied and gap junctions have been visualized between endothelial cells and pericytes that permit ion exchange. We propose that the functional interrelationship between endothelium and pericytes may play a role in the alteration of capillary diameter for the control of local cerebral blood flow.

Anomalies and variations of the middle cerebral artery: a microanatomical study.

The microvascular anatomy of the main trunk and divisions of the middle cerebral artery was studied in 104 unfixed brain hemispheres injected with polyester resin and dissected under the operating microscope. The following anomalies and variations of the middle cerebral artery were found: fenestration (1 case; 1%), located on the first 4 mm of the main trunk of the middle cerebral artery; duplication (1 case; 1%), with vessels arising from the internal carotid artery; accessory middle cerebral artery (2 cases; 2%), originating on the A1 segment of the anterior cerebral artery; single-trunk type of middle cerebral artery (4 cases; 4%), with no division of its main trunk; quadrifurcation (4 cases; 4%), in which the main trunk of the middle cerebral artery divided into four secondary trunks. The clinical implications of these anatomical findings are discussed, and photographs of representative specimens illustrate the anomalies.

Microanatomy of the anterior cerebral artery

The microanatomic features of the anterior cerebral artery were studied in 30 unfixed human brains which were injected with tinted polyester resin via cannulation of the internal carotid arteries under microscopic dissection. The outer diameter, length, and number of perforating branches were measured for each of the following vessels: anterior cerebral artery (proximal A1 segment, distal A2 segment), anterior communicating artery, and recurrent artery of Heubner. The perforating branches of the proximal segment of the anterior cerebral artery penetrated the brain at the anterior perforated substance, lateral chiasm, and optic tracts. The perforating branches of the anterior communicating artery penetrated the brain at the lamina terminalis, anterior perforated substance, and medial chiasm. The first 5 mm of the distal anterior cerebral artery (A2) had perforating branches penetrating the brain at the gyrus rectus and olfactory sulcus. The recurrent artery of Heubner originated from the A2 segment of the anterior cerebral artery in 57% of the cases, from the anterior cerebral artery-anterior communicating artery junction in 35%, and from the A1 segment in 8%. The depth of the interhemispheric fissure at the genu was 36.0 +/- 0.5 mm and at the midbody of the corpus callosum, 35.0 +/- 0.5 mm. Extension of the dissection to approach the anterior communicating artery from the genu of the corpus callosum using the anterior interhemispheric route was an additional 31.7 +/- 0.7 mm. The callosal arterial supply from the anterior cerebral artery showed short callosal branches in all brain specimens and long callosal vessels in 10% of the specimens.

Microanatomy of the posterior communicating artery.

Fifty unfixed cerebral hemispheres were injected with polyester resin and dissected under the operating microscope to show the anatomy of the posterior communicating artery (PCoA). There was a single PCoA in every hemisphere. Eleven (22%) were of fetal origin, and 17 (34%) were hypoplastic. Infundibular dilatations were found in 5 (10%) of the arteries. The outer diameter (OD) of the PCoA at its origin was 1.5 +/- 0.8 mm on the right and 1.6 +/- 0.6 mm on the left. At the junction of the PCoA with the P1 segment of the posterior cerebral artery, the PCoA had an OD of 1.4 +/- 0.7 mm on the right side and 1.6 +/- 0.6 mm on the left. The total length of the PCoA was 12.7 +/- 3.2 mm on the right and 12.5 +/- 1.7 mm on the left side. PCoA branches originated from the superior (36%) or lateral (64%) surface of the PCoA and coursed superiorly, posteriorly, or laterally. These vessels supplied the paramedian perforated substance (21%), the tuber cinereum (16.8%), the sulcus between the optic tract and the tuber cinereum (14.4%), the circuminfundibular anastomosis (11.5%), the mamillary bodies (8.4%), the sulcus between the optic tract and the cerebral peduncles (7.6%), and the cerebral peduncles (5.7%). The largest and most constant branch of the PCoA was the premamillary artery. The number and size of the branches from the PCoA were independent of the size of the parent artery.

Three-Quarter Prone Approach to the Pineal-Tentorial Region

A three-quarter prone, operative approach to the pineal region is described: the three-quarter prone, operated-side-down position. This approach avoids the disadvantages of the approaches from other directions to this region and provides a comfortable position for the surgeon and assistant, minimal retraction of the parietal-occipital lobe, and access to the third ventricle, pineal region, midbrain, and superior vermis.

Aneurysm Clip Motion during Magnetic Resonance Imaging: In Vivo Experimental Study with Metallurgical Factor Analysis

Because of various mechanical, metallurgical, and commercial constraints, aneurysm clips are manufactured from different alloys, including several stainless steel and cobalt alloys. Some of the steels contain volume fractions of the crystal phase known as martensite. Martensitic alloys have body-centered cubic structure, are prone to stress corrosion failure, and are ferromagnetic. Martensitic steel can be displaced like a compass needle when exposed to a magnetic field such as that generated during magnetic resonance imaging (MRI). The force exerted by the magnetic field is proportional to the volume fraction of the magnetic phase. We investigated the martensitic content and magnetic field-induced displacement of 12 common aneurysm clips. Four clips of each of the following types were examined: Sugita, Sundt-Kees Multi-Angle, Heifetz (two types), Vari-Angle McFadden, Yasargil (two types), Scoville, Mayfield, Vari-Angle, Pivot, and Kapp. Phase homogeneity and crystal structure were analyzed by x-ray diffraction using a Phillips x-ray diffractometer. Clip deflection in an Oxford Research Systems MRI spectrometer was measured in our in vivo rat abdominal aortic aneurysm model. Results showed that the volume fraction of the martensitic phase in the various clips correlated with the magnitude of the deflection. Among the clips examined, the Yasargil, Sugita, Heifetz Elgiloy, and Vari-Angle McFadden had a nonmartensitic composition and did not deflect in the magnetic field. The Scoville contained 5% martensite and deflected only marginally. Martensite comprised 35% of the Mayfield clip, which deflected 45 degrees, and 90% of the Heifetz, Vari-Angle, Pivot, and Sundt-Kees Multi-Angle clips, which deflected approximately 70 degrees or slipped off the aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereotactic Endoscopic Interventions in Cystic and Intraventricular Brain Lesions

Image guided stereotaxis is an accurate and safe method of directing therapy to target volumes defined in two-dimensional (2D) multiplanes or three-dimensional (3D) perspectives using computer reconstruction of image data. The major limitations of stereotactic techniques are related to a lack of intraoperative visualization and direct monitoring of the procedures and to changes of intracranial coordinates after decompression of cystic lesions or aspiration of cerebrospinal fluid in the management of intraventricular lesions. Endoscopic laser stereotaxis (ELS) involves integration of rigid-flexible endoscopy and Nd-YAG laser to 3D-2D multiplanar image-guided stereotactic procedures. The major advantages of ELS include: direct intraoperative visualization, hemostasis, evacuation or resection assessment, and wide exploration of intracranial cavities or ventricles. The technique allows safe aspiration, biopsy, and resection or internal decompression of deep and subcortical intracranial lesions. ELS has proved to be safe and effective in the management of 76 clinical cases and appears to be a promising technique in the management of cystic and intraventricular lesions.

Use of experimental aneurysms to evaluate wrapping materials

Experimental venous pouch aneurysms in rats were wrapped with muscle, bovine collagen, muslin, cotton, or polyvinyl alcohol. The rats were killed 6 or 12 weeks later, and the aneurysms were compared with control aneurysms. Bovine collagen and muscle were reabsorbed and the aneurysms were similar to the control group. Cotton, muslin, and polyvinyl alcohol caused fibrosis around the aneurysm. However, giant aneurysms were found in the muslin and polyvinyl alcohol group. Cotton appears to be the most suitable material for wrapping aneurysms. The experimental venous pouch aneurysm model in rats can be used to evaluate wrapping materials.

Intracranial Clips: An Examination of the Devices Used for Aneurysm Surgery

A properly functioning aneurysm clip is of paramount importance in the surgical ablation of intracranial aneurysms. An appropriate match between the closing force needed to ablate an aneurysm and the force exerted by the aneurysm clip must be achieved. In this study, the opening and closing forces exerted by several commonly used aneurysm clips were tested. There was a strong correlation between the classification of the clips, according to the Dujovny system, and their mechanical behavior. Minimal variability among different lots of the same clip type and minimal hysteresis were generally exhibited by the alpha mobile fulcrum class clips, such as the Yasargil, Vari-Angle McFadden, Scoville, and Mayfield clips. Significant exceptions included several types of Mayfield and Drake clips. In contrast, pivot class clips generally showed twice as much lot variability among different lots, as well as a significant amount of hysteresis. Clips of this class include the Vari-Angle, Heifetz, and Pivot clips. Because significant variations in clip force exist and because several other factors can compound these differences, it is suggested that aneurysm clips be individually tested for their closing forces before they are used in an operation.

Measurement of regional cerebrovascular haemoglobin oxygen saturation in cats using optical spectroscopy

We describe the use of optical spectroscopy in the near infra-red light range to non-invasively measure regional cerebral haemoglobin oxygen saturation (rSHbO2) in cats during progressive cerebral hypoxia. This technique differs from spectroscopic techniques previously described in that the concentration ratio--percentage haemoglobin: oxygen saturation--is quantified. This saturation is the weighted summation of saturation in the cerebrovascular system: arterial, venous, and capillary beds. In a cat model of progressive cerebral hypoxia, a positive linear correlation between this regional measurement of cerebral saturation and actual saturation, calculated from cerebral arterial and mixed venous blood, was noted (n = 20, r = 0.88, p less than 0.01). The spectroscopic measurement rSHbO2 is also used to index cerebral oxygen extraction. During hypoxia spectroscopic indexed oxygen extraction (iOE) and cerebral arterial-venous difference in oxygen content were simultaneously measured. A least-squares positive linear correlation between these two parameters was noted [AVDO2 = iOE (0.05) + 4.4] (n = 40, r = 0.6, s = 1.2). Objective measurement of regional cerebrovascular haemoglobin saturation and an index of cerebral oxygen extraction are possible using optical spectroscopy.