Browse

You are looking at 1 - 10 of 11 items for

  • By Author: Kalani, M. Yashar S. x
  • By Author: Preul, Mark C. x
Clear All
Restricted access

Kaan Yağmurlu, Hasan A. Zaidi, M. Yashar S. Kalani, Albert L. Rhoton Jr., Mark C. Preul and Robert F. Spetzler

Pineal region tumors are challenging to access because they are centrally located within the calvaria and surrounded by critical neurovascular structures. The goal of this work is to describe a new surgical trajectory, the anterior interhemispheric transsplenial approach, to the pineal region and falcotentorial junction area. To demonstrate this approach, the authors examined 7 adult formalin-fixed silicone-injected cadaveric heads and 2 fresh human brain specimens. One representative case of falcotentorial meningioma treated through an anterior interhemispheric transsplenial approach is also described. Among the interhemispheric approaches to the pineal region, the anterior interhemispheric transsplenial approach has several advantages. 1) There are few or no bridging veins at the level of the pericoronal suture. 2) The parietal and occipital lobes are not retracted, which reduces the chances of approach-related morbidity, especially in the dominant hemisphere. 3) The risk of damage to the deep venous structures is low because the tumor surface reached first is relatively vein free. 4) The internal cerebral veins can be manipulated and dissected away laterally through the anterior interhemispheric route but not via the posterior interhemispheric route. 5) Early control of medial posterior choroidal arteries is obtained. The anterior interhemispheric transsplenial approach provides a safe and effective surgical corridor for patients with supratentorial pineal region tumors that 1) extend superiorly, involve the splenium of the corpus callosum, and push the deep venous system in a posterosuperior or an anteroinferior direction; 2) are tentorial and displace the deep venous system inferiorly; or 3) originate from the splenium of the corpus callosum.

Restricted access

Kaan Yagmurlu, M. Yashar S. Kalani, Mark C. Preul and Robert F. Spetzler

The authors describe a safe entry zone, the superior fovea triangle, on the floor of the fourth ventricle for resection of deep dorsal pontine lesions at the level of the facial colliculus. Clinical data from a patient undergoing a suboccipital telovelar transsuperior fovea triangle approach to a deep pontine cavernous malformation were reviewed and supplemented with 6 formalin-fixed adult human brainstem and 2 silicone-injected adult human cadaveric heads using the fiber dissection technique to illustrate the utility of this novel safe entry zone. The superior fovea has a triangular shape that is an important landmark for the motor nucleus of the trigeminal, abducens, and facial nerves. The inferior half of the superior fovea triangle may be incised to remove deep dorsal pontine lesions through the floor of the fourth ventricle. The superior fovea triangle may be used as a safe entry zone for dorsally located lesions at the level of the facial colliculus.

Free access

Kaan Yagmurlu, Sam Safavi-Abbasi, Evgenii Belykh, M. Yashar S. Kalani, Peter Nakaji, Albert L. Rhoton Jr., Robert F. Spetzler and Mark C. Preul

OBJECTIVE

The aim of this investigation was to modify the mini-pterional and mini-orbitozygomatic (mini-OZ) approaches in order to reduce the amount of tissue traumatization caused and to compare the use of the 2 approaches in the removal of circle of Willis aneurysms based on the authors' clinical experience and quantitative analysis.

METHODS

Three formalin-fixed adult cadaveric heads injected with colored silicone were examined. Surgical freedom and angle of attack of the mini-pterional and mini-OZ approaches were measured at 9 anatomical points, and the measurements were compared. The authors also retrospectively reviewed the cases of 396 patients with ruptured and unruptured single aneurysms in the circle of Willis treated by microsurgical techniques at their institution between January 2006 and November 2014.

RESULTS

A significant difference in surgical freedom was found in favor of the mini-pterional approach for access to the ipsilateral internal carotid artery (ICA) and middle cerebral artery (MCA) bifurcations, the most distal point of the ipsilateral posterior cerebral artery (PCA), and the basilar artery (BA) tip. No statistically significant differences were found between the mini-pterional and mini-OZ approaches for access to the posterior clinoid process, the most distal point of the superior cerebellar artery (SCA), the anterior communicating artery (ACoA), the contralateral ICA bifurcation, and the most distal point of the contralateral MCA. A trend toward increasing surgical freedom was found for the mini-OZ approach to the ACoA and the contralateral ICA bifurcation. The lengths exposed through the mini-OZ approach were longer than those exposed by the mini-pterional approach for the ipsilateral PCA segment (11.5 ± 1.9 mm) between the BA and the most distal point of the P2 segment of the PCA, for the ipsilateral SCA (10.5 ± 1.1 mm) between the BA and the most distal point of the SCA, and for the contralateral anterior cerebral artery (ACA) (21 ± 6.1 mm) between the ICA bifurcation and the most distal point of the A2 segment of the ACA. The exposed length of the contralateral MCA (24.2 ± 8.6 mm) between the contralateral ICA bifurcation and the most distal point of the MCA segment was longer through the mini-pterional approach. The vertical angle of attack (anteroposterior direction) was significantly greater with the mini-pterional approach than with the mini-OZ approach, except in the ACoA and contralateral ICA bifurcation. The horizontal angle of attack (mediolateral direction) was similar with both approaches, except in the ACoA, contralateral ICA bifurcation, and contralateral MCA bifurcation, where the angle was significantly increased in the mini-OZ approach.

CONCLUSIONS

The mini-pterional and mini-OZ approaches, as currently performed in select patients, provide less tissue traumatization (i.e., less temporal muscle manipulation, less brain parenchyma retraction) from the skin to the aneurysm than standard approaches. Anatomical quantitative analysis showed that the mini-OZ approach provides better exposure to the contralateral side for controlling the contralateral parent arteries and multiple aneurysms. The mini-pterional approach has greater surgical freedom (maneuverability) for ipsilateral circle of Willis aneurysms.

Free access

Daniel D. Cavalcanti, Mark C. Preul, M. Yashar S. Kalani and Robert F. Spetzler

OBJECT

The aim of this study was to enhance the planning and use of microsurgical resection techniques for intrinsic brainstem lesions by better defining anatomical safe entry zones.

METHODS

Five cadaveric heads were dissected using 10 surgical approaches per head. Stepwise dissections focused on the actual areas of brainstem surface that were exposed through each approach and an analysis of the structures found, as well as which safe entry zones were accessible via each of the 10 surgical windows.

RESULTS

Thirteen safe entry zones have been reported and validated for approaching lesions in the brainstem, including the anterior mesencephalic zone, lateral mesencephalic sulcus, intercollicular region, peritrigeminal zone, supratrigeminal zone, lateral pontine zone, supracollicularzone, infracollicularzone, median sulcus of the fourth ventricle, anterolateral and posterior median sulci of the medulla, olivary zone, and lateral medullary zone. A discussion of the approaches, anatomy, and limitations of these entry zones is included.

CONCLUSIONS

A detailed understanding of the anatomy, area of exposure, and safe entry zones for each major approach allows for improved surgical planning and dissemination of the techniques required to successfully resect intrinsic brainstem lesions.

Free access

Nikolay L. Martirosyan, Jennifer M. Eschbacher, M. Yashar S. Kalani, Jay D. Turner, Evgenii Belykh, Robert F. Spetzler, Peter Nakaji and Mark C. Preul

OBJECTIVE

This study evaluated the utility, specificity, and sensitivity of intraoperative confocal laser endomicroscopy (CLE) to provide diagnostic information during resection of human brain tumors.

METHODS

CLE imaging was used in the resection of intracranial neoplasms in 74 consecutive patients (31 male; mean age 47.5 years; sequential 10-month study period). Intraoperative in vivo and ex vivo CLE was performed after intravenous injection of fluorescein sodium (FNa). Tissue samples from CLE imaging–matched areas were acquired for comparison with routine histological analysis (frozen and permanent sections). CLE images were classified as diagnostic or nondiagnostic. The specificities and sensitivities of CLE and frozen sections for gliomas and meningiomas were calculated using permanent histological sections as the standard.

RESULTS

CLE images were obtained for each patient. The mean duration of intraoperative CLE system use was 15.7 minutes (range 3–73 minutes). A total of 20,734 CLE images were correlated with 267 biopsy specimens (mean number of images/biopsy location, in vivo 84, ex vivo 70). CLE images were diagnostic for 45.98% in vivo and 52.97% ex vivo specimens. After initiation of CLE, an average of 14 in vivo images and 7 ex vivo images were acquired before identification of a first diagnostic image. CLE specificity and sensitivity were, respectively, 94% and 91% for gliomas and 93% and 97% for meningiomas.

CONCLUSIONS

CLE with FNa provided intraoperative histological information during brain tumor removal. Specificities and sensitivities of CLE for gliomas and meningiomas were comparable to those for frozen sections. These data suggest that CLE could allow the interactive identification of tumor areas, substantially improving intraoperative decisions during the resection of brain tumors.

Full access

Nikolay L. Martirosyan, M. Yashar S. Kalani, G. Michael Lemole Jr., Robert F. Spetzler, Mark C. Preul and Nicholas Theodore

OBJECT

The arterial basket of the conus medullaris (ABCM) consists of 1 or 2 arteries arising from the anterior spinal artery (ASA) and circumferentially connecting the ASA and the posterior spinal arteries (PSAs). The arterial basket can be involved in arteriovenous fistulas and arteriovenous malformations of the conus. In this article, the authors describe the microsurgical anatomy of the ABCM with emphasis on its morphometric parameters and important role in the intrinsic blood supply of the conus medullaris.

METHODS

The authors performed microsurgical dissections on 16 formalin-fixed human spinal cords harvested within 24 hours of death. The course, diameter, and branching angles of the arteries comprising the ABCM were then identified and measured. In addition, histological sections were obtained to identify perforating vessels arising from the ABCM.

RESULTS

The ASA tapers as it nears the conus medullaris (mean preconus diameter 0.7 ± 0.12 mm vs mean conus diameter 0.38 ± 0.08 mm). The ASA forms an anastomotic basket with the posterior spinal artery (PSA) via anastomotic branches. In most of the specimens (n= 13, 81.3%), bilateral arteries formed connections between the ASA and PSA. However, in the remaining specimens (n= 3, 18.7%), a unilateral right-sided anastomotic artery was identified. The mean diameter of the right ABCM branch was 0.49 ± 0.13 mm, and the mean diameter of the left branch was 0.53 ± 0.14 mm. The mean branching angles of the arteries forming the anastomotic basket were 95.9° ± 36.6° and 90° ± 34.3° for the right- and left-sided arteries, respectively. In cases of bilateral arterial anastomoses between the ASA and PSA, the mean distance between the origins of the arteries was 4.5 ± 3.3 mm. Histological analysis revealed numerous perforating vessels supplying tissue of the conus medullaris.

CONCLUSIONS

The ABCM is a critical anastomotic connection between the ASA and PSA, which play an important role in the intrinsic blood supply of the conus medullaris. The ABCM provides an important compensatory function in the blood supply of the spinal cord. Its involvement in conus medullaris vascular malformations makes it a critical anatomical structure.

Free access

Joseph Georges, Aqib Zehri, Elizabeth Carlson, Joshua Nichols, Michael A. Mooney, Nikolay L. Martirosyan, Layla Ghaffari, M. Yashar S. Kalani, Jennifer Eschbacher, Burt Feuerstein, Trent Anderson, Mark C. Preul, Kendall Van Keuren-Jensen and Peter Nakaji

Glioblastoma is the most common primary brain tumor with a median 12- to 15-month patient survival. Improving patient survival involves better understanding the biological mechanisms of glioblastoma tumorigenesis and seeking targeted molecular therapies. Central to furthering these advances is the collection and storage of surgical biopsies (biobanking) for research. This paper addresses an imaging modality, confocal reflectance microscopy (CRM), for safely screening glioblastoma biopsy samples prior to biobanking to increase the quality of tissue provided for research and clinical trials. These data indicate that CRM can immediately identify cellularity of tissue biopsies from animal models of glioblastoma. When screening fresh human biopsy samples, CRM can differentiate a cellular glioblastoma biopsy from a necrotic biopsy without altering DNA, RNA, or protein expression of sampled tissue. These data illustrate CRM's potential for rapidly and safely screening clinical biopsy samples prior to biobanking, which demonstrates its potential as an effective screening technique that can improve the quality of tissue biobanked for patients with glioblastoma.

Restricted access

Daniel D. Cavalcanti, M. Yashar S. Kalani, Nikolay L. Martirosyan, Justin Eales, Robert F. Spetzler and Mark C. Preul

Over the past half century molecular biology has led to great advances in our understanding of angio- and vasculogenesis and in the treatment of malformations resulting from these processes gone awry. Given their sporadic and familial distribution, their developmental and pathological link to capillary telangiectasias, and their observed chromosomal abnormalities, cerebral cavernous malformations (CCMs) are regarded as akin to cancerous growths. Although the exact pathological mechanisms involved in the formation of CCMs are still not well understood, the identification of 3 genetic loci has begun to shed light on key developmental pathways involved in CCM pathogenesis. Cavernous malformations can occur sporadically or in an autosomal dominant fashion. Familial forms of CCMs have been attributed to mutations at 3 different loci implicated in regulating important processes such as proliferation and differentiation of angiogenic precursors and members of the apoptotic machinery. These processes are important for the generation, maintenance, and pruning of every vessel in the body. In this review the authors highlight the latest discoveries pertaining to the molecular genetics of CCMs, highlighting potential new therapeutic targets for the treatment of these lesions.