IU Indianapolis ScholarWorks :: Browsing by Author "Loukas, Marios"

Browsing by Author "Loukas, Marios"

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Blood Supply to the Human Spinal Cord. I. Anatomy and Hemodynamics
(Wiley, 2015-01) Bosmia, Anand N.; Hogan, Elizabeth; Loukas, Marios; Tubbs, R. Shane; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
The arterial network that supplies the human spinal cord, which was once thought to be similar to that of the brain, is in fact much different and more extensive. In this article, the authors attempt to provide a comprehensive review of the literature regarding the anatomy and known hemodynamics of the blood supply to the human spinal cord. Additionally, as the medical literature often fails to provide accurate terminology for the arteries that supply the cord, the authors attempt to categorize and clarify this nomenclature. A complete understanding of the morphology of the arterial blood supply to the human spinal cord is important to anatomists and clinicians alike.
Blood Supply to the Human Spinal Cord. II. Imaging and Pathology
(Wiley, 2015-01) Bosmia, Anand N.; Tubbs, R. Shane; Hogan, Elizabeth; Bohnstedt, Bradley N.; DeNardo, Andrew J.; Loukas, Marios; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
The blood supply of the spinal cord is a complex system based on multilevel sources and anastomoses. Diseases often affect this vascular supply and imaging has been developed that better investigates these structures. The authors review the literature regarding pathology and imaging modalities for the blood supply of the spinal cord. Knowledge of the disease processes and imaging modalities used to investigate these arterial lesions of the spinal cord will assist the clinician when treating patients with spinal cord lesions.
Choroid Plexus of the Fourth Ventricle: Review and Anatomic Study Highlighting Anatomical Variations
(Elsevier, 2016-04) Tubbs, R. Shane; Shoja, Mohammadali M.; Aggarwal, Anjali; Gupta, Tulika; Loukas, Marios; Sahni, Daisy; Ansari, Shaheryar F.; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
Relatively few studies have been performed that analyze the morphology of the choroid plexus of the fourth ventricle. Due to the importance of this tissue as a landmark on imaging and during surgical intervention of the fourth ventricle, the authors performed a cadaveric study to better characterize this important structure. The choroid plexus of the fourth ventricle of 60 formalin fixed adult human brains was examined and measured. The horizontal distance from the midline to the lateral most point of the protruding tip of the horizontal limbs was measured. In the majority of the 60 brain specimens, right and left horizontal limbs of the choroid plexus were seen extending from the midline and protruding out of their respective lateral apertures of the fourth ventricle and into the subarachnoid space. However, on 3.3% of sides, there was absence of an extension into the foramen of Luschka and in one specimen, this lack of extension into the foramen of Luschka was bilateral. On two sides, there was discontinuity between the midline choroid plexus and the tuft of choroid just outside the foramen of Luschka. For specimens in which the choroid plexus did protrude through the foramen of Luschka (96.7%), these tufts were located anterior to the flocculus and inferolateral to the facial/vestibulocochlear nerve complex and posterosuperior to the glossopharyngeal/vagal/accessory complex. A thorough understanding of the normal and variant anatomy of the fourth ventricular choroid plexus is necessary for those who operate in, or interpret imaging of, this region.
Dural Septation on the Inner Surface of the Jugular Foramen: An Anatomical Study
(Thieme Publishing Group, 2015-06) Tubbs, R. Shane; Griessenauer, Christoph J.; Bilal, Muhammad; Raborn, Joel; Loukas, Marios; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
Introduction Preserving cranial nerve (CN) function during tumor removal at the jugular foramen is challenging. No anatomical study has better defined the relevant dural septations on the inner surface of the jugular foramen. This study was undertaken to elucidate this anatomy. Methods Fourteen cadaveric heads (28 sides) were dissected, and relationships of the meningeal coverings of the jugular foramen and adjacent CNs documented. A classification scheme was created to better describe the dural septations of the inner surface of the jugular foramen. Results Four types of dural septations were noted. Type I: 10 sides (36%) where a dural septation was seen between CNs IX anteriorly and X and XI posteriorly. Of these, the septum was ossified in 20%. Type II (32%) was defined as a jugular foramen with no dural septation. Type III (7%) was defined as septation between CNs IX and X anteriorly and XI posteriorly. Type IV (7 sides, 25%) or the chaotic form was defined as multiple septations within the jugular foramen that housed and divided CN rootlets. Conclusions The dural septations defined here can be used in future studies to help correlate operative strategy to meningeal morphology within the jugular foramen.
External cortical landmarks and measurements for the temporal horn: Anatomic study with application to surgery of the temporal lobe
(Wolters Kluwer, 2015-02-03) Tubbs, R. Shane; Sharma, Amit; Loukas, Marios; Cohen-Gadol, Aaron; Department of Neurological Surgery, IU School of Medicine
BACKGROUND: The location of the temporal horn is important to neurosurgeons during procedures such as amygdalohippocampectomy and intraventricular electrode placement for temporal lobe seizure monitoring. However, sometimes the temporal horn is difficult to localize, especially without neuronavigation. The authors aimed to better localize this structure using superficial anatomic landmarks. METHODS: Twenty-two brain halves were dissected from the midline, and the fornix identified and followed toward the left and right temporal horns. Once the temporal horn was isolated from a mesial approach, 6-cm long needles were placed into its anterior and posterior walls of the temporal horn and passed laterally from the axial plane to the cortical surface. Pin exit sites were marked externally and measurements taken between the outer temporal lobe cortex and the underlying temporal horn. RESULTS: No statistical differences were noted between left and right sides. The temporal horn was generally directed anteroinferiorly and best marked externally by the inferior temporal sulcus. The mean length of the temporal horn was 4.4 cm. Mean distance from anterior temporal tip to anterior wall of the temporal horn was 3.3 cm. The mean distance from the anterior temporal tip to the posterior wall of the temporal horn was 7 cm. The anterior wall of the temporal horn was a mean of 3 mm superior to the inferior temporal sulcus. The posterior wall was a mean of 1.2 cm superior to the inferior temporal sulcus. CONCLUSIONS: These landmarks and measurements may help neurosurgeons better localize this part of the lateral ventricular system.
External cortical landmarks for localization of the hippocampus: Application for temporal lobectomy and amygdalohippocampectomy
(Scientific Scholar, 2018-08-22) Tubbs, R. Shane; Loukas, Marios; Barbaro, Nicholas M.; Shah, Kushal J.; Cohen-Gadol, Aaron A.; Neurological Surgery, School of Medicine
Background: Accessing the hippocampus for amygdalohippocampectomy and minimally invasive procedures, such as depth electrode placement, require an accurate knowledge regarding the location of the hippocampus. Methods: The authors removed 10 human cadaveric brains from the cranium and observed the relationships between the lateral temporal neocortex and the underlying hippocampus. They then measured the distance between the hippocampus and superficial landmarks. The authors also validated their study using magnetic resonance imaging (MRI) scans of 10 patients suffering from medial temporal lobe sclerosis where the distance from the hippocampal head to the anterior temporal tip was measured. Results: In general, the length of the hippocampus was along the inferior temporal sulcus and inferior aspect of the middle temporal gyrus. Although the hippocampus tended to be more superiorly located in female specimens and on the left side, this did not reach statistical significance. The length of the hippocampus tended to be shorter in females, but this too failed to reach statistical significance. The mean distance from the anterior temporal tip to the hippocampal head was identical in the cadavers and MRIs of patients with medial temporal lobe sclerosis. Conclusions: Additional landmarks for localizing the underlying hippocampus may be helpful in temporal lobe surgery. Based on this study, there are relatively constant anatomical landmarks between the hippocampus and overlying temporal cortex. Such landmarks may be used in localizing the hippocampus during amygdalohippocampectomy and depth electrode implantation in verifying the accuracy of image-guided methods and as adjuvant methodologies when these latter technologies are not used or are unavailable.
The Intramuscular Course of the Greater Occipital Nerve: Novel Findings with Potential Implications for Operative Interventions and Occipital Neuralgia
(2014-10) Tubbs, R. Shane; Watanabe, Koichi; Loukas, Marios; Cohen-Gadol, Aaron A.; Department of Neurology, IU School of Medicine
Background: A better understanding of the etiologies of occipital neuralgia would help the clinician treat patients with this debilitating condition. Since few studies have examined the muscular course of the greater occipital nerve (GON), this study was performed. Methods: Thirty adult cadaveric sides underwent dissection of the posterior occiput with special attention to the intramuscular course of the GON. Nerves were typed based on their muscular course. Results: The GON traveled through the trapezius (type I; n = 5, 16.7%) or its aponeurosis (type II; n = 15, 83.3%) to become subcutaneous. Variations in the subtrapezius muscular course were found in 10 (33%) sides. In two (6.7%) sides, the GON traveled through the lower edge of the inferior capitis oblique muscle (subtype a). On five (16.7%) sides, the GON coursed through a tendinous band of the semispinalis capitis, not through its muscular fibers (subtype b). On three (10%) sides the GON bypassed the semispinalis capitis muscle to travel between its most medial fibers and the nuchal ligament (subtype c). For subtypes, eight were type II courses (through the aponeurosis of the trapezius), and two were type I courses (through the trapezius muscle). The authors identified two type IIa courses, four type IIb courses, and two type IIc courses. Type I courses included one type Ib and one type Ic courses. Conclusions: Variations in the muscular course of the GON were common. Future studies correlating these findings with the anatomy in patients with occipital neuralgia may elucidate nerve courses vulnerable to nerve compression. This enhanced classification scheme describes the morphology in this region and allows more specific communications about GON variations.
Neural Connections between the Nervus Intermedius and the Facial and Vestibulocochlear Nerves in the Cerebellopontine Angle: An Anatomic Study
(Springer, 2015) Tubbs, R. Shane; Hose, Nicole; Loukas, Marios; De Caro, Raffaele; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
Purpose Unexpected clinical outcomes following transection of single nerves of the internal acoustic meatus have been reported. Therefore, this study aimed to investigate interneural connections between the nervus intermedius and the adjacent nerves in the cerebellopontine angle. Methods On 100 cadaveric sides, dissections were made of the facial/vestibulocochlear complex in the cerebellopontine angle with special attention to the nervus intermedius and potential connections between this nerve and the adjacent facial or vestibulocochlear nerves. Results A nervus intermedius was identified on all but ten sides. Histologically confirmed neural connections were found between the nervus intermedius and either the facial or vestibulocochlear nerves on 34 % of sides. The mean diameter of these small interconnecting nerves was 0.1 mm. The fiber orientation of these nerves was usually oblique (anteromedial or posterolateral) in nature, but 13 connections traveled anteroposteriorly. Connecting fibers were single on 81 % of sides, doubled on 16 %, and tripled on 3 %, six sides had connections both with the facial nerve anteriorly and the vestibular nerves posteriorly. On 6.5 % of sides, a connection was between the nervus intermedius and cochlear nerve. For vestibular nerve connections with the nervus intermedius, 76 % were with the superior vestibular nerve and 24 % with the inferior vestibular nerve. Conclusions Knowledge of the possible neural interconnections found between the nervus intermedius and surrounding nerves may prove useful to surgeons who operate in these regions so that inadvertent traction or transection is avoided. Additionally, unanticipated clinical presentations and exams following surgery may be due to such neural interconnections.
A new segment of the trochlear nerve: cadaveric study with application to skull base surgery
(Thieme, 2014-02) Tubbs, R. Shane; Veith, Philip; Griessenauer, Christoph J.; Loukas, Marios; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
Objectives The trochlear nerve is important to preserve during approaches to the skull base. Traditionally, this nerve has been divided into cisternal, cavernous, and orbital segments. However, the authors anecdotally observed an additional segment during routine cadaveric dissections. Therefore, they performed this study to better elucidate this anatomy. Design Twenty latex-injected cadaveric sides (10 adult cadavers) were dissected with the aid of an operating microscope. Standard microdissection techniques were used to examine the course of the distal cisternal and precavernous segments of the trochlear nerve. Setting Cadaver laboratory. Main Outcome Measures Measurements were made using a microcaliper. Digital images were made of the dissections. Results The authors identified a previously undescribed segment of the trochlear nerve in all specimens. This part of the nerve coursed between the entrance of the trochlear nerve into the posterior corner of the oculomotor trigone to the posterior wall of the cavernous sinus. This segment of trochlear nerve was, on average, 4 mm in length. Conclusions The authors have identified a new segment of the trochlear nerve not previously described. They propose that this be referred to as the trigonal segment. Knowledge of the microanatomy of the trochlear nerve is useful to skull base surgeons.
A novel method for sciatic nerve decompression: Cadaveric feasibility study with potential application to patients with piriformis syndrome
(Elsevier, 2015-12) Tubbs, Richard Isaiah; Barton, James C., III; Watson, Caroline C.; Kollias, Theofanis; Ward, Robert J.; Loukas, Marios; Barbaro, Nicholas M.; Cohen-Gadol, Aaron A.; Department of Neurological Surgery, IU School of Medicine
Introduction Approaches for proximal sciatic nerve decompression use a transgluteal route, but are associated with morbidity and complications. An alternative anterior approach to the sciatic nerve was designed. Methods Five adult human cadavers (10 sides) were used. In the supine position and with lower limbs abducted, an incision was made 3-cm inferolateral to the pubic tubercle of each specimen. With blunt dissection, a muscle-splitting approach through the obturator foramen was performed through the underlying adductor muscles and deeper obturator muscles that traversed the obturator foramen. Within the pelvis, a laparoscope was inserted in the surgical corridor, which was extraperitoneal. The obturator neurovascular bundle was identified medially and followed posterolaterally toward the greater sciatic foramen. The sciatic nerve was identified. The piriformis muscle was identified as it exited the greater sciatic foramen. Microscissors were inserted and under visualization with the laparoscope, the piriformis muscle was transected near the spine. Results The piriformis was well visualized and transected. The muscle was best visualized inferolateral to the sciatic nerve. No gross damage to the sciatic nerve or surrounding neurovascular structures occurred. Mean distance from the superomedial edge of the obturator foramen to the ischial spine was 7.2 cm for left sides and 7.3 cm for right sides. Conclusions Use of a laparoscope to approach the piriformis muscle from an anterior intrapelvic, extraperitoneal approach via the obturator foramen is feasible. Clinical use of this method is in order to demonstrate use in patients with suspected compression of the sciatic nerve by the piriformis muscle.

Browsing by Author "Loukas, Marios"

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