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Erratum

Editorial. Personal considerations on the history of microneurosurgery

M. Gazi Yaşargil

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Editorial

Personal considerations on the history of microneurosurgery

M. Gazi Yaşargil

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John L. Fox and M. Gazi Yasargil

✓ Direct electrical current (DC) was applied to the basilar artery of 20 dogs and the circle of Willis of five monkeys. The artery was in contact with microsurgical forceps acting as the monopolar electrode. The DC currents from 0 to 1 mA were used at voltages of 0 to 3 V with observable effect noted at levels above 0.5 mA at 1 V. Neither negative (−) nor positive (+) DC caused vasoconstriction unless the initial and terminal current change occurred too rapidly causing a stimulus pulse. Both − and + DC caused focal vasodilatation of the artery made spastic by needle puncture or topical 10% barium chloride (BaCl2). This dilatation was more rapid (30 to 60 sec) and more pronounced with −DC current. Angiography confirmed extreme focal dilatation lasting at least 4 days after −DC application. This appears to be secondary to the known production of hydroxyl (OH) ions at the cathode and possibly hydrogen (H+ or H3O+) ions at the anode during electrolysis. We hypothesize that smooth muscle protein bonds are affected. The effects of DC on the systemic arteries also are described.

Also studied were the effects of similar DC on brain cortical microvasculature of 10 dogs and on the systemic arteries of 50 rats. It was discovered that not only did + DC cause the well-known local coagulation phenomena but also both − and + DC caused formation of micro-emboli with resulting occlusion of arterioles. These phenomena, which could be seen only under the operating microscope, occurred after a decomposition potential of about 1 V was reached. We theorize this was due to the formation of denatured protein and alkali-hematin at the − pole secondary to the formation of OH ions during electrolytic reduction and due to formation of denatured protein and acid-hematin at the + pole secondary to the formation of H+ ions during electrolytic oxidation. For reasons not yet clear there was an acute breakdown in the blood-brain barrier to fluorescein around the negative pole but not around the positive pole.

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M. Gazi Yaşargil and L. Philip Carter

✓ A series of 13 patients with saccular aneurysms of the distal anterior cerebral artery, operated on by the same surgeon with microtechniques, is reviewed. The incidence of aneurysms in this location was 3.4%, the median age of the patients 44 years, and the median time from most recent hemorrhage to surgery 13 days. There were five cases of multiple aneurysms. No operative mortality occurred; the operative morbidity was 15%. Because of their multiplicity, characteristic broad base, and the small subarachnoid space in the interhemispheric fissure, these aneurysms are judged technically difficult.

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S. John Peerless and M. Gazi Yasargil

✓ The Hillarp technique of fluorescent staining of monoamines was used to examine the adrenergic fibers in the cerebral vessels of rabbit brains. These fibers were found to lie wholly within the deeper layers of the adventitia and not within muscle layers. Varicosities were interpreted as representing neural transmitter substance. The basilar artery had a sparse innervation; the anterior cerebral, carotid, and middle cerebral arteries were more richly supplied by adrenergic terminals, with the most dense innervation in the superficial vessels between 100 and 300 µ in diameter. Mild trauma to the basilar artery, as well as subarachnoid blood without trauma, caused the catecholamine reaction to disappear. A marked depletion of adrenergic fibers was also noted after administration of alpha methyl tyrosine and subjection of the animals to extremes of blood pressure.

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M. Gazi Yaşargil, Uğur Türe and Dianne C. H. Yaşargil ¸

Object

In this paper the authors correlate the surgical aspects of deep median and paramedian supratentorial lesions with the connective fiber systems of the white matter of the brain.

Methods

The cerebral hemispheres of 10 cadaveric brains were dissected in a mediolateral direction by using the fiber dissection technique, corresponding to the surgical approach.

Conclusions

This study illuminates the delicacy of the intertwined and stratified fiber laminae of the white matter, and establishes that these structures can be preserved at surgical exploration in patients.

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Uğur Türe, Dianne C. H. Yaşargil, Ossama Al-Mefty and M. Gazi Yaşargil

Object. The insula is one of the paralimbic structures and constitutes the invaginated portion of the cerebral cortex, forming the base of the sylvian fissure. The authors provide a detailed anatomical study of the insular region to assist in the process of conceptualizing a reliable surgical approach to allow for a successful course of surgery.

Methods. The topographic anatomy of the insular region was studied in 25 formalin-fixed brain specimens (50 hemispheres). The periinsular sulci (anterior, superior, and inferior) define the limits of the frontoorbital, frontoparietal, and temporal opercula, respectively. The opercula cover and enclose the insula. The limen insula is located in the depths of the sylvian fissure and constitutes the anterobasal portion of the insula. A central insular sulcus divides the insula into two portions, the anterior insula (larger) and the posterior insula (smaller). The anterior insula is composed of three principal short insular gyri (anterior, middle, and posterior) as well as the accessory and transverse insular gyri. All five gyri converge at the insular apex, which represents the most superficial aspect of the insula. The posterior insula is composed of the anterior and posterior long insular gyri and the postcentral insular sulcus, which separates them. The anterior insula was found to be connected exclusively to the frontal lobe, whereas the posterior insula was connected to both the parietal and temporal lobes. Opercular gyri and sulci were observed to interdigitate within the opercula and to interdigitate the gyri and sulci of the insula. Using the fiber dissection technique, various unique anatomical features and relationships of the insula were determined.

Conclusions. The topographic anatomy of the insular region is described in this article, and a practical terminology for gyral and sulcal patterns of surgical significance is presented. This study clarifies and supplements the information presently available to help develop a more coherent surgical concept.

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Uğur Türe, M. Gazi Yaşargil, Ossama Al-Mefty and Dianne C. H. Yaşargil

Object. The insula is located at the base of the sylvian fissure and is a potential site for pathological processes such as tumors and vascular malformations. Knowledge of insular anatomy and vascularization is essential to perform accurate microsurgical procedures in this region.

Methods. Arterial vascularization of the insula was studied in 20 human cadaver brains (40 hemispheres). The cerebral arteries were perfused with red latex to enhance their visibility, and they were dissected with the aid of an operating microscope.

Arteries supplying the insula numbered an average of 96 (range 77–112). Their mean diameter measured 0.23 mm (range 0.1–0.8 mm), and the origin of each artery could be traced to the middle cerebral artery (MCA), predominantly the M2 segment. In 22 hemispheres (55%), one to six insular arteries arose from the M1 segment of the MCA and supplied the region of the limen insulae. In an additional 10 hemispheres (25%), one or two insular arteries arose from the M3 segment of the MCA and supplied the region of either the superior or inferior periinsular sulcus. The insular arteries primarily supply the insular cortex, extreme capsule, and, occasionally, the claustrum and external capsule, but not the putamen, globus pallidus, or internal capsule, which are vascularized by the lateral lenticulostriate arteries (LLAs). However, an average of 9.9 (range four–14) insular arteries in each hemisphere, mostly in the posterior insular region, were similar to perforating arteries and some of these supplied the corona radiata. Larger, more prominent insular arteries (insuloopercular arteries) were also observed (an average of 3.5 per hemisphere, range one–seven). These coursed across the surface of the insula and then looped laterally, extending branches to the medial surfaces of the opercula.

Conclusions. Complete comprehension of the intricate vascularization patterns associated with the insula, as well as proficiency in insular anatomy, are prerequisites to accomplishing appropriate surgical planning and, ultimately, to completing successful exploration and removal of pathological lesions in this region.