Biomedical subjects

Albert L Rhoton

Publications and source records attributed to Albert L Rhoton.

At least 19 recordsLinked to original sources

PubMed2006

Surgical approaches to the atrium of the lateral ventricle: microsurgical anatomy.

BACKGROUND: Managing lesions situated in the atrium of the lateral ventricle remains a challenging neurosurgical problem. The purposes of this study were to examine the microsurgical anatomy of the atrium of the lateral ventricle and the optic radiation and to define the differences in the exposure obtained by various surgical approaches. METHODS: Fifteen adult cadaveric specimens were studied using magnification x3 to x40 after perfusion of the arteries and veins with colored silicone. The microsurgical anatomy of the atrium of the lateral ventricle was examined. The relationship between the optic radiation and the atrium was studied using the white matter fiber dissection technique. Surgical approaches to the atrium of the lateral ventricle were examined in stepwise dissection. RESULTS: The medial and inferior walls of the atrium were free from optic radiation fibers. Surgical approaches to the atrium of the lateral ventricle are divided into 3 routes: (1) anterior approach: transsylvian approach, (2) posterior approaches: posterior transcortical, posterior transcallosal, occipital, and supracerebellar transtentorial approaches, and (3) lateral approaches: transtemporal and subtemporal approaches. CONCLUSION: Knowledge of the microsurgical anatomy of the atrium of the lateral ventricle and surrounding vital structures and the choice of an appropriate surgical approach will help surgeons perform safe and minimally invasive surgery.

Adult↗

PubMed2006

Scalp to meningeal arterial anastomosis in the parietal foramen.

OBJECTIVE: The purpose of this study was to examine the parietal foramen and to determine whether it is the site of an anastomosis between the meningeal and scalp arteries. METHODS: Forty parietal regions from 20 adult cadavers, in which the arteries were perfused with colored latex, were examined for this study. The scalp was separated from the parietal foramen, and the vasculature in the foramen and adjacent scalp and dura were examined using x3 magnification. The scalp arteries that anastomosed with the meningeal arteries through the parietal foramen were followed into the dura after craniotomy. RESULTS: Parietal foramen was found in 20 of the 40 (50%) parietal regions. They were present bilaterally in eight heads and unilaterally in four. Every parietal foramen transmitted an anastomosis between the middle meningeal and scalp arteries. In 11 (55%) of the 20 foramina found in this study, the superficial temporal and occipital artery formed an anastomosis in the galea and pericranial layer that sent a branch through the parietal foramen to anastomose with parietal branches of the middle meningeal artery. In the remaining nine (45%) sides, the middle meningeal artery had a connection through the foramen with a small pericranial artery. CONCLUSION: Every parietal foramen was the site of a connection between the middle meningeal and scalp arteries. The scalp end of the anastomosis most commonly arose in an anastomosis between the superficial temporal and occipital arteries. This anastomosis may be involved in several pathologies.

Arteriovenous Anastomosis↗

PubMed2006

Microsurgical anatomy of the oculomotor cistern.

OBJECTIVE: To define the characteristics of the arachnoidal sleeve and cistern that accompany the oculomotor nerve through the cavernous sinus roof. METHODS: Forty cavernous sinuses were examined using 3 to 40x magnification. Information was obtained about the size of the oculomotor cistern and its relationship to the roof of the cavernous sinus and anterior clinoid process. RESULTS: An arachnoidal sleeve and cistern, referred to as the oculomotor cistern, accompanied the oculomotor nerve into the roof of all the cavernous sinuses examined. The oculomotor cistern extends from the oculomotor porus, where the nerve enters the roof of the cavernous sinus, to the area below the tip or the adjacent part of the lower margin of the anterior clinoid process. From the porus, the nerve passes forward and downward to the depth of the cistern where it becomes incorporated into the fibrous lateral wall of the cavernous sinus. The width of the cistern was maximal at the oculomotor porus averaged 5.5 mm (range, 3.0-9.2 mm), and tapered slightly towards the midpoint and deep end of the cistern. The cistern's average length was 6.5 mm (range, 3.0-11.0 mm). The oculomotor nerve usually coursed closer to the anterior than the posterior wall of the cistern at the level of the oculomotor porus. CONCLUSION: The oculomotor cistern, an arachnoidal and dural cuff, accompanies the oculomotor nerve through the cavernous sinus roof to the area just below or anterior to the lower edge of the tip of the anterior clinoid process. The segment of the nerve inside the oculomotor cistern is interposed between its free portion in the interpeduncular cistern and the part of its course where it is incorporated into the fibrous lateral wall of the cavernous sinus. The cistern can be opened to aid in the exposure and mobilization of the nerve in dealing with pathology in the area.

Carotid Artery, Internal↗

PubMed2006

Microsurgical anatomy of the cochlear nuclei.

OBJECTIVE: The dorsal and ventral cochlear nuclei are exposed when treating lesions involving the fourth ventricle and the cerebellopontine angle. Precisely locating the nuclei is important in the placement of the auditory brainstem implantation and in intraoperative monitoring of auditory evoked potentials. This study examined the microsurgical anatomy of the cochlear nuclei. METHODS: The relationships and the surgical approaches to the nuclei were examined in 20 formalin-fixed specimens with the aid of an operating microscope. RESULTS: The dorsal cochlear nucleus is located in the floor of the lateral recess of the fourth ventricle on the posterior surface of the inferior cerebellar peduncle where it produces a prominence, the auditory tubercle. The ventral cochlear nucleus is positioned on the lateral surface of the inferior cerebellar peduncle where it often straddles the anterior edge of the foramen of Luschka at the junction of the lateral recess and cerebellopontine angle and produces less of a prominence on the surface of the brainstem than on the dorsal nucleus. CONCLUSION: Both the dorsal and ventral cochlear nuclei can be exposed after opening the foramen of Luschka and the lateral recess of the fourth ventricle by the retrosigmoid or translabyrinthine approach. The dorsal cochlear nucleus is positioned so that it would be damaged by a tumor within or approaches to the floor of the lateral recess. The ventral cochlear nucleus is positioned so that it would be vulnerable to damage by tumors within or operative approaches to the cerebellopontine angle. The dorsal cochlear nucleus and the adjacent intraventricular part of the ventral cochlear nucleus have anatomic characteristics that make them the preferable site of placement for the auditory brain stem implant.

Cochlear Nucleus↗

PubMed2006

One-piece versus two-piece orbitozygomatic craniotomy: quantitative and qualitative considerations.

OBJECTIVE: The orbitozygomatic (OZ) craniotomy minimizes brain retraction and improves cranial base exposure by providing a multidirectional view, increased operative angles and working space. The two main variations of the approach include the one-piece and the two-piece types. The microsurgical anatomy of the one- and two-piece OZ craniotomies are presented with the goal of comparing the extent of orbital roof removal between these two craniotomies and the effect of orbital roof removal on operative exposure. METHODS: Ten two-piece and 11 one-piece OZ craniotomies were performed in a stepwise manner simulating the approaches on formalin fixed specimens. The orbital surface area removed above the frontozygomatic suture extending medially over the orbital roof was measured from each bone flap. The two-sided unpaired t test using STATA 7.0 software was used to compare the amount of orbital roof removed using the two approaches. RESULTS: The two-piece OZ craniotomy allowed for the removal of a larger portion of the roof and lateral wall of the orbit than the one-piece. The total orbitotomy, including the orbital roof plus the part of the lateral wall above the frontozygomatic suture, had an average surface area of 996 +/- 229 mm for the two piece and 372 +/- 103 mm for the one-piece. The orbital roof made up 27 +/- 18% of the orbital osteotomy for the one-piece craniotomies and 67 +/- 10% of the osteotomy for the two-piece craniotomies (P < 0.001). CONCLUSION: The two-piece OZ craniotomy allows for more extensive orbital roof removal and better visualization of the basal frontal lobe. Therefore, the two-piece may result in a lower incidence of enophtalmus and poor cosmetic outcomes, particularly if the remaining orbital roof must be removed piecemeal during the one-piece OZ craniotomy in order to obtain satisfactory exposure.

Craniotomy↗

PubMed2006

Anatomic dissection and classic three-dimensional documentation: a unit of education for neurosurgical anatomy revisited.

OBJECTIVE AND IMPORTANCE: Despite development of computer-assisted neurosurgical navigation, learning by dissecting anatomic specimens is still important. CLINICAL PRESENTATION: We describe the processes from preparation of specimens for cranial dissection to documentation of three-dimensional (3-D) stereoscopic pictures, particularly focusing on the latter, which has been initiated in the Microneuroanatomy Laboratory, Department of Neurological Surgery, University of Florida. INTERVENTION: Preparation consists of irrigation of the major vessels and injection of colored silicone. The 3-D documentation, obtaining two pictures corresponding to each eye's view, is obtained by the shoot-shift-shoot method using a single camera mounted on a slide bar. The key of this method is correct shifting of the camera without alignment error to get exact 3-D effects. Observation of 3-D image can be made with free viewing, a 3-D viewer, or projection. Tips concerning all of the processes involved are described. CONCLUSION: The presented method of dissection and obtaining 3-D images is beneficial for accomplishing studies of anatomy and for providing teaching method.

Dissection↗

PubMed2006

Speculum opening in transsphenoidal surgery.

OBJECTIVE: To assess the extent to which the transsphenoidal speculum can be safely opened at the face of and within the sphenoid sinus without risking damage to the optic nerves in the optic canals and at the orbital apex and the nerves coursing adjacent the walls of the sphenoid sinus. METHODS: The distance was measured between the optic nerves at the level of the anterior wall of the sphenoid sinus and 0.5 and 1.0 cm within the sinus. In addition, the distance between the middle turbinates and the contralateral optic canals was assessed because this turbinate is the largest structure blocking access to the sphenoid sinus in the transsphenoidal approach and tends to force the speculum away from the midline and toward the optic nerve in the contralateral side of the approach. RESULTS: Opening the transsphenoidal speculum at the anterior wall of the sphenoid sinus beyond 2.5 centimeters carries some risk of damaging the optic nerves and this distance narrows when the speculum opening is positioned inside the sphenoid sinus. Displacement of the speculum to one side by the middle turbinate places the speculum near the contralateral optic nerve and may be associated with optic nerve injury with lesser degrees of speculum opening. CONCLUSIONS: Careful attention should be directed to avoiding excessive opening of the transsphenoidal speculum at the anterior face of the sphenoid or within the sphenoid sinus.

Anthropometry↗

PubMed2006

Gray matter overlying anterior basal temporal sulci as an intraoperative landmark for locating the temporal horn in amygdalohippocampectomies.

OBJECTIVE: Use of the gray matter overlying the anterior portions of the occipitotemporal and rhinal sulci as an intraoperative landmark for locating the temporal horn during amygdalohippocampectomies approached by the superior or lateral surface of the temporal lobe. METHODS: The presence of occipitotemporal and rhinal sulci was analyzed in the magnetic resonance imaging scans of 165 patients who subsequently underwent mesial temporal resections, focusing on coronal slices up to 4 cm from the temporal pole. These sulci were used during surgery to locate the temporal horn in 150 surgeries. Five adult cadaveric heads whose vessels were perfused with colored silicone were used for photography. RESULTS: These sulci are the principal sulci of the anterior basal temporal lobe. They were present in 154 out of 165 and 165 out of 165 patients, respectively. When approaching mesial temporal structures from the superior or lateral surface of the temporal lobe, dissection is initially performed through the white matter toward the floor of the middle fossa until the gray matter overlying an anterior basal sulcus is encountered. Dissection continues medially and superiorly from the top of the gray matter until the temporal horn is entered. CONCLUSION: Gray matter overlying these sulci leads toward the anterior portion of the floor of the temporal horn and constitutes a landmark for locating the temporal horn. However, only the rhinal sulcus was always present. When both are present, the gray matter overlying the occipitotemporal sulcus is a reliable landmark. These landmarks are most suitable for mesial temporal resections without significant displacement of the temporal horn.

Amygdala↗

PubMed2006

Meyer's loop and the optic radiations in the transsylvian approach to the mediobasal temporal lobe.

OBJECTIVE: In the transsylvian approach to the mediobasal temporal structures, the temporal horn is approached through the floor of the sylvian fissure. The anterior bundle of the optic radiations (Meyer's loop) courses between the floor of the sylvian fissure and roof of the temporal horn and could be damaged in this approach. This study was designed to define the route through the floor of the sylvian fissure least likely to damage the optic pathways. METHODS: Meyer's loop was dissected by applying Klingler's fiber dissection technique in 10 formalin-fixed human hemispheres. Several measurements quantified the relationship of the Meyer's loop to surgically important structures. RESULTS: This study identified a triangular safe area below the floor of the sylvian fissure through which the temporal horn could be accessed in the transsylvian approach with a low risk of damaging the optic radiations. An incision in the floor of the sylvian fissure directed downward at the level of limen insula and the adjacent 5 mm of the inferior insular sulcus would avoid the optic radiations. An incision directed straight downward 10, 15, and 20 mm behind the limen in the inferior insular sulcus would cross Meyer's loop and would need to be directed downward and medially as much as 80 degrees from the sagittal plane to avoid Meyer's loop. CONCLUSION: In the transsylvian approach to the temporal horn, incisions at the level of the limen, or adjacent 5 mm of the inferior insular sulcus, are less likely to damage Meyer's loop and the optic radiations than more posterior incisions along the inferior insular sulcus. Incision at this safe level commonly opens into the amygdala, a portion of which is removed to provide entry into the temporal horn for removal of the mediobasal structures.

Cadaver↗

PubMed2006

Microsurgical approaches to the medial temporal region: an anatomical study.

OBJECTIVE: To describe the surgical anatomy of the anterior, middle, and posterior portions of the medial temporal region and to present an anatomic-based classification of the approaches to this area. METHODS: Twenty formalin-fixed, adult cadaveric specimens were studied. Ten brains provided measurements to compare different surgical strategies. Approaches were demonstrated using 10 silicon-injected cadaveric heads. Surgical cases were used to illustrate the results by the different approaches. Transverse lines at the level of the inferior choroidal point and quadrigeminal plate were used to divide the medial temporal region into anterior, middle, and posterior portions. Surgical approaches to the medial temporal region were classified into four groups: superior, lateral, basal, and medial, based on the surface of the lobe through which the approach was directed. The approaches through the medial group were subdivided further into an anterior approach, the transsylvian transcisternal approach, and two posterior approaches, the occipital interhemispheric and supracerebellar transtentorial approaches. RESULTS: The anterior portion of the medial temporal region can be reached through the superior, lateral, and basal surfaces of the lobe and the anterior variant of the approach through the medial surface. The posterior group of approaches directed through the medial surface are useful for lesions located in the posterior portion. The middle part of the medial temporal region is the most challenging area to expose, where the approach must be tailored according to the nature of the lesion and its extension to other medial temporal areas. CONCLUSION: Each approach to medial temporal lesions has technical or functional drawbacks that should be considered when selecting a surgical treatment for a given patient. Dividing the medial temporal region into smaller areas allows for a more precise analysis, not only of the expected anatomic relationships, but also of the possible choices for the safe resection of the lesion. The systematization used here also provides the basis for selection of a combination of approaches.

Cadaver↗

PubMed2006

Microsurgical anatomy of the central retinal artery.

OBJECTIVE: To define the microsurgical anatomy of the central retinal artery (CRA) and to provide a guide to avoiding damage to it during surgery. METHODS: The anatomic characteristics of the CRA and small arteries distributed to the optic sheath were examined in 109 orbits. The origin, course, and site of entry of the artery into the optic sheath and the distance between the orbital apex and the site of entry into the sheath were examined. RESULTS: The CRAs originated directly from the intraorbital ophthalmic artery or in a common trunk with a posterior ciliary or a muscular branch. The CRAs most commonly originated on the inferomedial side of the ophthalmic artery an average of 8.4 mm distal to the orbital end of the optic canal. They penetrated the optic sheath near the junction of the middle and anterior thirds of the length of the intraorbital optic nerve an average of 18.6 mm distal to the optic canal. More than 70% of CRAs penetrated near the midline of the lower surface of the optic sheath, 21% entered the inferomedial surface, and 7% the inferolateral or lateral surface of the optic sheath. Only one CRA gave off a branch before penetrating the nerve. CONCLUSION: The CRA is at risk of being damaged or occluded during procedures involving a large part of the orbit. Procedures directed along the lower half of the proximal two-thirds of the optic sheath have the greatest risk of interrupting the artery.

Cadaver↗

PubMed2005

Suboccipital burr holes and craniectomies.

OBJECT: The goal of this study was to delimit the external cranial projection of the transverse and sigmoid sinuses, and to establish initial strategic systematized burr hole sites for lateral infratentorial suboccipital approaches based on external cranial landmarks particularly related to the lambdoid, occipitomastoid, and parietomastoid sutures. METHODS: The external cranial projection of the transverse and sigmoid sinuses was studied through their external outlining obtained with the aid of multiple small perforations made from inside to outside along the inner margins of the sinuses of 50 paired temporoparietooccipital regions in 25 dried adult human skulls. The burr hole placement was studied by evaluating the supratentorial, over-the-sinuses, and infratentorial components of 1-cm-diameter openings made at strategic sites identified in the initial part of the study, which was performed in another 50 paired temporoparietooccipital regions. The asterion and the midpoint of the inion-asterion line were found to be particularly related to the inferior half of the transverse sinus; the transverse and sigmoid sinuses' transition occurs 1 cm anteriorly to the asterion across the parietomastoid suture, and the most superior part of the sigmoid sinus is located anteriorly to the occipitomastoid suture, with its posterior margin crossing this suture posteriorly to the most superior aspect of the mastoid process, which is located at the most superior level of the mastoid notch. Burr holes made at the midpoint of the inion-asterion line, at the asterion, 1 cm anterior to the asterion, just inferiorly to the parietomastoid suture, and over the occipitomastoid suture at the most superior level of the mastoid notch are appropriate to expose the inferior half of the transverse sinus at its midpoint, the inferior half of the transverse sinus at its most lateral aspect, the transverse and sigmoid sinuses' transition, and the posterior margin of the basal aspect of the sigmoid sinus, respectively. CONCLUSIONS: These findings allow an estimation of the transverse and sigmoid sinuses' external cranial projection. The asterion and the most posterior part of the parietomastoid suture constitute a suitable initial burr hole site at which to perform an upper or asterional suboccipital craniectomy to expose the superior aspect of the cerebellopontine angle (CPA). The occipitomastoid suture at the most superior aspect of the mastoid notch constitutes an adequate initial burr hole site at which to perform a basal suboccipital craniectomy to expose the lower portion of the CPA. The sites can be used together as initial burr hole sites to perform wide suboccipital exposures, because they already constitute natural infratentorial lateral limits.

Adolescent↗

PubMed2005

Microsurgical anatomy and approaches to the cavernous sinus.

OBJECTIVE: The aim of this article is to describe the anatomy of the cavernous sinus and to provide a guide for use when performing surgery in this complex area. Clinical cases are used to illustrate routes to the cavernous sinus and its contents and to demonstrate how the cavernous sinus can be used as a pathway for exposure of deeper structures. METHODS: Thirty cadaveric cavernous sinuses were examined using x3 to x40 magnification after the arteries and veins were injected with colored silicone. Distances between the entrance of the oculomotor and trochlear nerves and the posterior clinoid process were recorded. Stepwise dissections of the cavernous sinuses, performed to demonstrate the intradural and extradural routes, are accompanied by intraoperative photographs of those approaches. RESULTS: The anatomy of the cavernous sinus is complex because of the high density of critically important neural and vascular structures. Selective cases demonstrate how a detailed knowledge of cavernous sinus anatomy can provide for safer surgery with low morbidity. CONCLUSION: A precise understanding of the bony relationships and neurovascular contents of the cavernous sinus, together with the use of cranial base and microsurgical techniques, has allowed neurosurgeons to approach the cavernous sinus with reduced morbidity and mortality, changing the natural history of selected lesions in this region. Complete resection of cavernous sinus meningiomas has proven to be difficult and, in many cases, impossible without causing significant morbidity. However, surgical reduction of such lesions enhances the chances for success of subsequent therapy.

Adult↗

PubMed2005

Vascular anatomy of the anteriorly based pericranial flap.

OBJECTIVE: The purpose of this study was to examine the vascular supply of the anteriorly based frontal pericranial flap to determine whether separating the pericranium from the galea above the orbital rim would devascularize the pericranial flap. METHODS: The arteries supplying and the veins draining the frontal pericranial flap were examined in 17 adult cadavers using x3 to x30 magnification. The arteries were examined on 25 sides and the veins on 16 sides. RESULTS: The main trunk and superficial branches of the supraorbital and supratrochlear arteries, which course in the galea-frontalis muscle layer, give rise to the deep branches that supply the pericranium. These pericranial branches may arise in the orbit or at the level of or above the orbital rim. Pericranial arteries that arose above the level of the orbital rim and would be divided in separating the galea and pericranium were found in 28% of the sides examined. Pericranial veins that coursed above the orbital rim and would be divided in separating the galea-frontalis muscle layer from the pericranial layer were found in 43.8% of the sides examined. CONCLUSION: In preparing a pericranial flap based anteriorly on the supraorbital rim, the separation of the galea-frontalis muscle layer from the pericranium layer should not extend into the 10 mm above the supraorbital rim if the arterial and venous pedicle of the pericranial flap is to be preserved.

Arteries↗

PubMed2005

MacCarty keyhole and inferior orbital fissure in orbitozygomatic craniotomy.

OBJECTIVE: This study had two objectives. The first was to define the ideal position of the MacCarty keyhole, a commonly used craniotomy entry site into which three of the bone cuts in orbitozygomatic craniotomy extend. The second objective was to examine the relationships in the inferior orbital fissure, a site into which two of the bone cuts in orbitozygomatic craniotomy extend. METHODS: Twenty frontotemporal regions from adult skulls were examined to delineate the relationships between the surface anatomy of the fronto-orbitozygomatic region and the underlying frontal fossa and orbit. Drill holes placed along, above, and below the frontosphenoid suture were made beginning anteriorly at an area referred to as the three-suture junction, located at the junction of the frontozygomatic, sphenozygomatic, and frontosphenoid sutures. The site of the deep end of each hole was recorded to clarify the ideal position of the keyhole. The relationships in the inferior orbital fissure, the site of the lower end of the bone cut that begins in the orbital portion of the keyhole and extends along the lateral orbital wall, were also examined. CONCLUSION: Placing the MacCarty keyhole on the frontosphenoid suture 5 to 6 mm behind the three-suture junction results in greater preservation of the lateral wall and roof of the orbit than when the hole is placed at a more anterior site, as previously recommended. The anterolateral part of the inferior orbital fissure, which faces the temporal fossa and into which the bone cuts in the orbitozygomatic craniotomy extend, has a lower density of vascular and neural structures than the middle and posteromedial parts, which are related to the infratemporal and pterygopalatine fossa.

Cadaver↗

PubMed2005

The anteroinferior cerebellar artery embedded in the subarcuate fossa: a rare anomaly and its clinical significance.

OBJECTIVE: The purpose of this study is to call attention to an anomaly in which a segment of the anteroinferior cerebellar artery (AICA) is embedded in the dura or bone surrounding the subarcuate fossa, a small depression in the bone posterior to the internal acoustic meatus (IAM), through which the subarcuate artery enters the bone. This anomaly places the artery at risk in removing the posterior wall of the IAM. METHODS: An anomalous AICA having a segment that was embedded in the dura covering on the bone surrounding the subarcuate fossa was found during a microsurgical dissection course. The senior author (ALR) has observed this anomaly in four patients during surgery for acoustic neuromas and in three specimens in microsurgery dissection courses. To define the microsurgical anatomy of the anomalous artery further, the latex-injected specimen was dissected in a stepwise manner using x3 to x40 magnification. RESULTS: The anomalous AICA described in this report bifurcated into a rostral trunk and a caudal trunk near the facial-vestibulocochlear nerve complex. The caudal trunk formed a sharp lateral loop that was embedded in the dura covering the subarcuate fossa. The involved trunk continued to supply the suboccipital area normally supplied by the posteroinferior cerebellar artery, which was hypoplastic. The dura surrounding the anomalous loop was opened, and the adjacent bone was removed to free the anomalous loop from the subarcuate fossa so that the artery could be displaced medially to remove the posterior wall of the IAM. Although it has been reported that the AICA may occasionally be adherent to the dura over the subarcuate fossa, this study is the first to demonstrate an AICA that is embedded in the dura and bone of the subarcuate fossa. CONCLUSION: Mobilizing the AICA loop that is embedded in the subarcuate fossa posterior to the IAM places the involved AICA at significant risk in exposing the contents of the IAM.

Cerebral Arteries↗

PubMed2005

Three-dimensional relationships of the optic radiation.

OBJECTIVE: This study examined the relationship of the optic radiation to the landmarks important in temporal lobe surgery. METHODS: The optic radiation was dissected by applying Klingler's fiber dissection technique to 20 formalin-fixed human hemispheres. The dissections were performed with the operating microscope and imaged in three-dimensional photographs. Several measures quantified the relationship of the radiation to reliable surgical landmarks. RESULTS: In all specimens, the anterior loop of the radiation extended to the anterior tip of the roof of the temporal horn. The anterior edge of the optic radiation was located an average of 25 mm (range, 22-30 mm) behind the temporal pole. The optic radiation extended an average of 5 mm (range, 3-6 mm) anterior to the hippocampus head and 22 mm (range, 20-25 mm) anterior to the anterior edge of the lateral geniculate body. The optic radiation also extended an average of 2 mm (range, 1-3 mm) anterior to the tip of the temporal horn. The relationships of the optic radiation to important surgical landmarks are discussed. CONCLUSION: The optic radiation reached the anterior tip of the temporal horn. Resections that extend through the roof of the temporal horn more than 3 cm behind the temporal pole cross the anterior loop of the optic radiation.

Dissection↗

PubMed2005

Microsurgical anatomy of cerebral revascularization. Part I: anterior circulation.

OBJECT: Revascularization is an important component of treatment for complex aneurysms that require parent vessel occlusion, skull base tumors that involve major vessels, and certain ischemic diseases. In this study, the authors examined the microsurgical anatomy of cerebral revascularization in the anterior circulation by demonstrating various procedures for bypass surgery. METHODS: Twenty-five adult cadaveric specimens were studied, using 3 to 40 magnification, after the arteries and veins had been perfused with colored silicone. The microsurgical anatomy of cerebral revascularization in the anterior circulation was examined with the focus on the donor, recipient, and graft vessels. The techniques discussed in this paper include the superficial temporal artery (STA)-middle cerebral artery (MCA), middle meningeal artery (MMA)-MCA, and side-to-side anastomoses; short arterial and venous interposition grafting; and external carotid artery/internal carotid artery (ICA)-M2 and ICA-ICA bypasses. Bypass procedures for cerebral revascularization are divided into two categories depending on their flow volume: low-flow and high-flow bypasses. A low-flow bypass, such as the STA-MCA anastomosis, is used to cover a relatively small area, whereas a high-flow bypass, such as the ICA-ICA anastomosis, is used for larger areas. Cerebral revascularization techniques are also divided into two types depending on the graft materials: pedicled arterial grafts, such as STA and occipital artery grafts, and free venous or arterial grafts, which are usually saphenous vein and radial artery grafts. Pedicled arterial grafts are mainly used for low-flow bypasses, whereas venous or arterial grafts are used for high-flow bypasses. CONCLUSIONS: It is important to understand the methods of bypass procedures and to consider indications in which cerebral revascularization is needed.

Anastomosis, Surgical↗