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Editorial

Personal considerations on the history of microneurosurgery

M. Gazi Yaşargil

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Erratum

Editorial. Personal considerations on the history of microneurosurgery

M. Gazi Yaşargil

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Pascal O. Zinn, Oliver Bozinov, Jan-Karl Burkhardt, Robert Reisch, M. Gazi Yaşargil and Helmut Bertalanffy

Mechanical obstruction is a severe complication of ventricular catheter use. Its incidence was shown to be high in the 1960s and 1970s, with up to 41% of the catheters becoming obstructed within 10 years after surgery. The authors present what is to their knowledge the first reported case of a patient with failure of a Torkildsen shunt after 50 years of functioning. A 60-year-old woman presented with increasing gait ataxia, decline in cognitive functions (including short-term memory loss), and slight urinary incontinence. The diagnosis of hydrocephalus and thus malfunction of the Torkildsen shunt implanted 50 years previously was confirmed by MR images, which revealed a prominent triventricular hydrocephalus. The patient subsequently underwent endoscopic third ventriculostomy (ETV), the current surgical treatment of choice, resulting in total resolution of her neurological symptoms and amelioration of cerebral tissue distension. Decrease in ventricle dilation and success of the ETV were confirmed on postoperative follow-up MR images.

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M. Gazi Yaşargil, Niklaus Krayenbühl, Peter Roth, Sanford P. C. Hsu and Dianne C. H. Yaşargil

Object

The proximal (anterior) transsylvian approach through a pterional craniotomy was developed by the senior author (M.G.Y.) in 1967 for the microsurgical treatment of saccular aneurysms of the circle of Willis, frontoorbital and temporobasal arteriovenous malformations, cavernomas, and extrinsic and intrinsic tumors. The acquired positive surgical experiences on this large series enabled the senior author, in 1973, to apply this approach for the selective amygdalohippocampectomy in patients with intractable mesial temporal lobe epilepsy.

Methods

The proximal (anterior) transsylvian-transamygdala approach to the mesial temporal structures permits the selective two-thirds resection of the amygdala and hippocampus-parahippocampus in an anteroinferior to posteroinferior exploration axis along the base of the semicircular temporal horn. This strategy ensures preservation of the overlying neopallial temporal convolutions such as the T1, T2, T3, and T4 gyri as well as the related subcortical connective fiber systems and other essential components of the temporal white matter.

The application of rigid brain self-retaining retractor systems was strictly avoided during the entire procedure. Computer-assisted navigation was never used. On routine postoperative CT scanning and MR imaging studies, infarction was not observed in any patient. The availability of tractography technology has proven that the connective fiber system around the resected mesial temporal area remains intact.

Results

The surgical outcome and results on neoplastic and vascular lesions of the mesiobasal temporal region have been presented in Volumes II, IIIB, and IVB of Microneurosurgery. The surgical outcomes and results in 102 patients with mesial temporal seizures who underwent surgery performed by the senior author in Zürich have been previously published.

In this paper, 73 patients who underwent surgery between 1994 and September 2006 in Little Rock, Arkansas, are presented, and 13 other patients are excluded who underwent surgery after September 2006. Altogether, among 188 patients who underwent surgery, there was no surgical mortality or morbidity, and no neurological deficits, new neurocognitive dysfunction, or impairments of the preoperative incapacities.

Conclusions

The surgical outcome in terms of seizures was rewarding in the majority of patients, particularly in those who exhibited the following irregularities on preoperative investigations: regular local dysfunctions on electroencephalography, dysmorphic changes in the mesiobasal temporal parenchyma on MR imaging studies, and hypometabolism in the anterior third of the temporal lobe on PET studies.

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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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M. Gazi Yaşargil, Ugur Türe and Dianne C. H. Yaşargil

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Christoph Burkhard, Pier-Luigi Di Patre, Danielle Schüler, Georges Schüler, M. Gazi Yaşargil, Yasuhiro Yonekawa, Urs M. Lütolf, Paul Kleihues and Hiroko Ohgaki

Object. The incidence of pilocytic astrocytomas and the rate of patient survival were analyzed in a population-based study in the canton of Zürich, Switzerland.

Methods. Between 1980 and 1994, 987 astrocytic and oligodendroglial tumors were diagnosed, of which 55 (5.5%) were pilocytic astrocytomas. The incidence rate, adjusted to the World Standard Population, was 4.8 per 1 million per year. The mean age at clinical diagnosis was 19.6 ± 12.7 years, and the male/female ratio was 1.12. The most frequent tumor sites were the cerebellum (40%), followed by supratentorial locations (35%), the optic pathway and hypothalamus (11%), and the brainstem (9%). The mean follow-up period was 12 years. Observed survival rates were 100% at 5 years and 95.8% at 10 years after diagnosis (relative survival rate at 10 years: 96.8%). Seven patients (13%) received postoperative radiotherapy, but this did not significantly affect survival. In all patients the tumors were histologically classified as WHO Grade I, except in two patients who had anaplastic pilocytic astrocytoma (Grade III), one of whom died after 7 years, whereas the other was still alive after 10 years.

Conclusions. This population-based study shows that, because of the benign biological behavior of pilocytic astrocytomas and advances in microneurosurgery, the survival rates for patients with these tumors are excellent, regardless of postoperative radiotherapy.

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Emad Aboud, Ossama Al-Mefty and M. Gazi Yaşargil

Object. Laboratory training models are essential for developing and refining surgical skills, especially for microsurgery. The closer to live surgery the model is, the greater the benefit. In this paper the authors introduce a cadaver model with unique characteristics: dynamic filling of the cerebral vasculature with colored liquid and clear fluid filling of the arachnoid cisterns. This model is distinctive and has great practical value for training in a wide range of surgical procedures.

Methods. Cadaveric heads were prepared for surgical procedures in the following manner: the carotid arteries (CAs) and vertebral arteries (VAs) in the neck were cannulated, as were the internal jugular veins (JVs) on both sides. Two tubes were introduced into the spinal canal and each one was advanced into one of the cerebellopontine angle cisterns. A CA, VA, or both were then connected to a reservoir containing light red fluid and a pressure of 80 to 120 mm Hg and a pulse rate of 60 beats/minute were established using a pump. The JV on the side currently being dissected was connected to a reservoir containing dark red fluid and kept at a pressure between 20 and 40 mm Hg. The remaining vessels were clamped in the neck. The cisternal tubes were connected to a reservoir of clear fluid that was regulated by an adjustable flow. Nine trainees have tested this model on eight specimens by practicing a variety of surgical procedures and maneuvers, including craniotomies; hemostasis; cisternal and vascular dissection; vascular anastomosis and repair; establishment of arterial bypasses; aneurysm creation, dissection, and clipping; management of an aneurysm rupture; intraparenchymal resection such as amygdalohippocampectomy; ventricular endoscopy and third ventriculostomy; cavernous sinus and skull base approaches; and resection of artificial tumors in the basal cisterns.

Conclusions. This model mimics the normal human anatomy and dynamic vascular filling found in real surgery and presents it from the training perspective, allowing a wide range of skill development and repeated practice. It provides an alternative model to laboratory animals. It is inexpensive and readily available, and has great value for the acquisition and refinement of surgical skills that are not only specific to neurosurgery, but are applicable to other surgical disciplines.

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M. Gazi Yaşargil

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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.