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PubMed1998

Role of ultrasound biomicroscopy in the differentiation of block glaucomas.

Ultrasound biomicroscopy has allowed us to elucidate the anatomic variations and underlying mechanisms in angle-closure glaucoma. Four levels of anatomic block can be distinguished, and a specific approach to treatment exists for each level to correct the abnormal forces leading to closure of the angle. As more quantitative approaches are developed, our understanding of these disorders will become increasingly sophisticated.

Anterior Eye Segment↗

PubMed1998

The architecture of the atrial musculature between the orifice of the inferior caval vein and the tricuspid valve: the anatomy of the isthmus.

INTRODUCTION: Electrophysiologists recognize a so-called "isthmus" in the right atrium through which passes the reentrant circuit of common atrial flutter. Ablative lesions placed in this narrow channel have proved effective in breaking the circuit. To the best of our knowledge, however, no study has been performed to establish the arrangement and orientation of the atrial myocardial fibers in this crucial area. METHODS AND RESULTS: We examined 28 normal heart specimens, identifying a quadrilateral area composed of three morphologic sectors between the inferior caval vein and the tricuspid valve confluent superiorly with the triangle of Koch. Within this quadrilateral, there are constant recesses, or sinuses, inferior and lateral to the orifice of the coronary sinus. The inferior isthmus measured an average of 31+/-4 mm (range 19 to 40). Gross examination identified marked differences in the atrial wall forming the quadrilateral. A smooth anterior component forming the vestibule of the tricuspid valve was found in all the hearts, but variations in the remaining sectors were seen in ten specimens. The usually membranous posterior sector was noticeably muscular in three specimens, while the middle, trabecular sector was more membranous in five specimens. We demonstrated the orientation of the subendocardial atrial fibers by dissection in 14 specimens, revealing a relatively constant overall pattern in eight specimens and variations in fiber orientation in the remaining specimens. CONCLUSION: There are considerable anatomic variations in the atrial wall that comprises the so-called isthmus. The presence of recesses and membranous areas in some hearts and the variations in arrangement of the subendocardial fibers are relevant in improving understanding of conduction in this area.

Data Interpretation, Statistical↗

PubMed2005

Surgical anatomy of the ophthalmic artery: its origin and proximal course.

OBJECTIVE: We examined the surgical anatomy of the ophthalmic artery (OA) by dissection of cadaver heads, evaluating the anatomic relationships between the origin of the OA and both its proximal course and surrounding structures. In addition, we demonstrated the surgical application of these anatomic features for safe surgical exploration of this region. METHODS: Through anatomic dissection, the origin of the OA was examined in both sides of 25 formalin-fixed and 10 fresh cadaver specimens. The following parameters were evaluated: the location of the origin of the OA in relation to the dural rings, the topographic relationship of the paraclinoid region, and the location of the dural penetrating point of the OA in the optic canal. RESULTS: The OA originated from the internal carotid artery within the intradural space in 49% of cases, just above the upper dural ring in 37%, at the clinoid segment in 7%, and within the cavernous sinus in 6%. The dural penetrating point of the OA was anterior to the falciform ligament, and thereby in the optic canal, in 74% of cases, ventral to the falciform ligament in 19%, and posterior to the falciform ligament in 7%. The anterior circumference point of the upper dural ring, the point at which the upper dural ring intersects the anterior edge of the internal carotid artery, was more anterior to the falciform ligament in 40% of cases and ventral and posterior to the falciform ligament in 16.4% and 43.6%, respectively. CONCLUSION: Our anatomic findings demonstrate anatomic variation of the OA in terms of its region of origin. Several anatomic points that were noteworthy during surgical exploration of this region are discussed.

Cadaver↗

PubMed1999

[Right aortic arches: anatomic and embryologic classification].

Right aortic arches are rare but non exceptional abnormalities of embryonic aortic system. Sometimes responsible for tracheal or esophageal compression, they may be totally asymptomatic and fortuitously discovered. They have to be preoperatively identified in order to modify the procedure of an eventual mediastinal surgery. In this review, we describe the embryonic events which lead to these anatomical variations and the anatomosurgical classification used to precisely define their type. This anatomical definition is indispensable to adjust the surgical procedure to the consequent modification of anatomical relationships.

Aorta, Thoracic↗

PubMed2006

Safety of carpal tunnel release with a short incision. A cadaver study.

The standard long incision technique for carpal tunnel release causes inevitable damage to skin sensation, the inter-thenar plexus and especially the distal branches of the palmar cutaneous branch of the median nerve (PCM), and may cause long-term disabling pain and scar tenderness. There are many variations in the distal branches of the median nerve at the wrist. Anatomic studies of this region also have important clinical implications to prevent injury to important anatomic structures. The purpose of this study was to evaluate the short-incision carpal tunnel release in cadavers. Several important anatomic structures, with possible anatomic variations, pass through the carpal tunnel, and blind percutaneous transection of the transverse ligament seems to be a high risk procedure. Sixty hands from 40 fresh cadavers were evaluated. Both the transverse ligament and the distal third of the deep forearm fascia were released using a Smillie knife. At the end of each procedure, the hand was explored for injury to tendinous and neurovascular structures of the wrist. In all cases the release of the carpal tunnel and the distal third of the forearm fascia was found to be complete. The superficial palmar arterial arch, flexor tendons, ulnar nerve and vessels, digital nerves, median nerve and its recurrent accessory branches, the flexor tendons, and even the subcutaneous tissue over the transverse ligament were damaged in no instance. Guyon's canal was entered in 6 (10%) hands without damage to its components. The distal branches from the ulnar side of the palmar cutaneous branch of the median nerve (PCM) were injured in 8 (13.6%) hands, an injury that is almost unavoidable with the classic open technique.

Adult↗

PubMed1997

Donor biliary variations: an overlooked problem?

Documented causes of biliary complications following orthotopic liver transplantation have been related to technical imperfections or insufficient arterial supply. Although anatomical variations of the extrahepatic biliary system are not infrequent, neither their incidence, surgical management nor possible association with complications have been reported in liver transplantation. At our institution, the global incidence of biliary complications following 357 consecutive liver transplants performed in 324 patients over a 2-yr period was 15.4% (55/357). Anomalous donor extrahepatic ducts were verified in 10 cases (2.8%) and they were recognized intraoperatively, prior to biliary reconstruction, in 7 cases. Technical complications occurred in 1 of these 7 and in 3 other cases where the anomalous ducts were not identified until later in the postoperative period when serious clinical problems ensued. We herein present a description of these 10 cases, with reference to the techniques employed to manage the anatomical anomalies and to treat complications. As in any hepatobiliary procedure, awareness of possible variations of the extrahepatic biliary system, intraoperative identification of the anomalous ducts and appropriate tailoring of the surgical technique are advisable in order to avoid serious postoperative complications in liver transplantation.

Adult↗

PubMed1992

Application of magnetic resonance imaging in functional stereotactic thalamotomy for the evaluation of individual variations of the thalamus.

An application of MRI in functional stereotactic thalamotomy is presented. To estimate the individual anatomic variations of the thalamus prior to stereotactic thalamotomy, a special study using a proton density image that shows myeloarchitectonic features of the thalamus was performed. The proton density MRI was demonstrated to be very useful to determine the safest trajectory and tentative target point. However, as a detailed functional localization of the thalamic subnuclei cannot be yet obtained by MRI, the final target should be decided on the basis of electrophysiological findings.

Adult↗

PubMed2006

Evidence of altered prefrontal-thalamic circuitry in schizophrenia: an optimized diffusion MRI study.

MRI diffusion tensor imaging (DTI), optimized for measuring the trace of the diffusion tensor, was used to investigate microstructural changes in the brains of 12 individuals with schizophrenia compared with 12 matched control subjects. To control for the effects of anatomic variation between subject groups, all participants' diffusion images were nonlinearly registered to standard anatomical space. Significant statistical differences in mean diffusivity (MD) measures between the two groups were determined on a pixel-by-pixel basis, using Gaussian random field theory. We found significantly elevated MD measures within temporal, parietal and prefrontal cortical regions in the schizophrenia group (P > 0.001), especially within the medial frontal gyrus and anterior cingulate. The dorsal medial and anterior nucleus of the thalamus, including the caudate, also exhibited significantly increased MD in the schizophrenia group (P > 0.001). This study has shown for the first time that MD measures offer an alternative strategy for investigating altered prefrontal-thalamic circuitry in schizophrenia.

Brain↗

PubMedDate not supplied

Clinically challenging mammographic artifacts: a pictorial guide.

Artifacts on mammographic images detract from the overall quality of the images and often present clinical and technical troubleshooting difficulties for the interpreting radiologist, technologist, and medical physicist and for the equipment and processor service personnel. This presentation demonstrates several types of mammographic artifacts that may pose a clinical challenge. They are arranged in the following categories: (1) particularly dangerous artifacts, (2) masses, (3) calcifications, (4) density variations, and (5) miscellaneous artifacts. Examples of such findings as summation shadows, normal anatomic variations, and incorrect positioning are also demonstrated as artifacts in this guide, because they may affect image quality or patient radiation dose. Under the Mammography Quality Standards Act, the lead interpreting physician has the responsibility for ensuring that the facility meets quality assurance requirements and is required to follow up with the technologist on poor-quality images. It is vital to recognize and correct for artifacts, whether they simulate non-existent lesions or obscure real pathology, because misinterpretation can lead to undesirable consequences.

Artifacts↗

PubMed2004

The anatomy of the greater occipital nerve: implications for the etiology of migraine headaches.

An interest in pursuing new theories of the underlying etiology of migraine headaches has been sparked by previously published reports of an association between amelioration of migraine headache symptoms and corrugator resection during endoscopic brow lift. This theory has further been reinforced by recent publications documenting improvement in migraine headaches following injection of botulinum A toxin. There are thought to be four major "trigger points" along the course of several peripheral nerves that may cause migraine headaches. Among these peripheral nerves is the greater occipital nerve. For this reason, the authors have undertaken an anatomic study of this nerve to determine its usual course, potential anatomic variations, and possible points of potential entrapment or compression. The results of this anatomic study have enhanced further development of techniques designed to address these points of entrapment/compression and potentially lead to relief of migraine headaches caused by this mechanism. Twenty cadaver heads from patients with an unknown history of migraine headaches were dissected to trace the normal course of the greater occipital nerve from the semispinalis muscle penetration to the superior nuchal line. Standardized measurements were performed on 14 specimens to determine the location of the emergence of the nerve using the midline and occipital protuberance as landmarks. On the basis of this information, the location of emergence was determined to be at a point centered approximately 3 cm below the occipital protuberance and 1.5 cm lateral to the midline. This location can, in turn, be used to guide the practitioner performing chemodenervation of the semispinalis capitis muscle in an attempt to provide migraine symptom relief.

Humans↗

PubMed1996

The variations of lenticulostriate arteries in the middle cerebral artery aneurysms.

This study attempts to analyse the intra-operative anatomical findings of the lenticulostriate artery (LSA) in 60 patients with middle cerebral artery (MCA) aneurysms who were operated on at the Neurosurgical Department of Atatürk University Medical School, Erzurum, Türkiye. All patients underwent radical surgery for aneurysm by the right or left pterional approach. The findings were recorded during surgical intervention using slides and videotapes of the operations. On average there were 4 (range, 1-14, total number = 240) LSAs, in one hemisphere, per case with MCA aneurysm. Twenty percent of LSAs (n = 48) arise from the prebifurcation part of the M1 segment, 65% (n = 156) arise from the postbifurcation part of the M1 segment, and 15% (n = 36) arise from the proximal part of the M2 segment. The great majority of the LSAs (85%, n = 204) originated along the proximal part of the MCA. Of a total of 240 LSAs, 125 (52%) originated from one single large vessel, a stem artery which then divided after 2-10 mm into many branches, 85 (35%) originated as two large proximal trunks, and 30 (13%) originated as multiple small arteries arising along the whole infero-medial wall of the M1 segment of MCA. We concluded that recognition of the anatomical variations of the LSA and detailed knowledge of the microvascular relationships of the MCA aneurysms, will allow neurosurgeons to construct a better and safer microdissection plan, to save time, and to prevent postoperative neurological deficits.

Adolescent↗

PubMed2003

Venous variations in the region of the third ventricle: the role of MR venography.

In this study, we examined the anatomical variations of the subependymal veins in the region of the foramen of Monro and the third ventricle by MR time of flight (TOF) venography. Fifty healthy subjects, ten patients with third-ventricle tumors, and four patients with lateral-ventricle tumors were included in the study. The courses of the anterior septal vein (ASV), thalamostriate vein (TSV), and internal cerebral vein (ICV) were studied. The proximity of the venous angle, the false venous angle, and the ASV-ICV junction to the posterior margin of the foramen of Monro was measured. In 69 (53.9%) sides, the ASV-ICV junction was located at the venous angle and at the posterior margin of the foramen of Monro. In 59 (46.1%) sides, the ASV-ICV junction was located beyond the foramen of Monro. Our study shows the high incidence of posteriorly located ASV-ICV junctions, which can be crucial in the planning of a better surgical approach. We strongly recommend that MR venography, which is a short radiological examination, be used before one operates on third-ventricle and lateral-ventricle tumors.

Cerebral Veins↗

PubMed2006

Multiple variations of the hepatobiliary vasculature including double cystic arteries, accessory left hepatic artery and hepatosplenic trunk: a case report.

Anatomical variations in the origins and branching patterns of the hepatobiliary arterial system may be encountered during both conventional surgical and laparoscopic cholecystectomy. We report a rare case of double cystic arteries arising from both the right hepatic artery and the proximal part of the posterior superior pancreaticoduodenal artery. Additional variations consisting of an accessory left hepatic artery arising from a left gastric which in turn arose from the descending aorta superior to the origin of the celiac trunk and a small left hepatic artery arising from the hepatic proper artery were also noted. The celiac trunk bifurcated into the splenic artery and the common hepatic artery forming a hepatosplenic or lienohepatic trunk. The possible clinical implications are discussed.

Cadaver↗

PubMed1989

[Variations of division of the extrahepatic bile ducts: significance and origin, surgical implications].

As opposed to congenital anomalies, the anatomical variations, as well as the modal type, are issued from a normal morphological development. The variations of division of extra-hepatic biliary ducts are very frequent. They are clearly explained by the sequence of embryological development in man, and also by compared anatomy. Lots of variations occur, some of them being more frequently encountered than others during cholecystectomy for gallbladder lithiasis. A cysto-hepatic duct draining a large hepatic territory is the most dangerous variation. As a matter of fact, it can look as if the junction between the cystic duct and the common biliary duct was of the modal type. In surgical practice, the dissection of cystic duct must never go over the right side of the common biliary duct in order for it never to be injured. Radiological exploration of biliary tree during cholecystectomy for gallbladder lithiasis has to be routine, in order to discover the obviously unpredictable individual variations of division of extra-hepatic biliary ducts.

Animals↗

PubMedDate not supplied

The effect of variations in temporal bone structure upon the caloric response.

A high degree of inter-subject variability reduces the clinical usefulness of the caloric test. Both anatomical and physiological factors are responsible for this problem, but the proportion of variability caused by either factor has not been determined. This study sets a quantitative estimate on the amount of caloric test variability which can be ascribed to anatomical variations in the study population. Polytome radiographs of 48 "normal' subjects were studied do determine how individual variations in the intensity of caloric-induced nystagmus might be related to anatomical features of the temporal bone. A statistical analysis showed that pneumatization in the petrous and "buttress' areas, and the dimensions of the internal auditory canal were significantly correlated with caloric response intensity. Furthermore, about 23% of caloric response variability in this population could be accounted for by a combination of anatomical characteristics. However, neither the extent of mastoid pneumatization nor the dimensions of the external auditory canal were found to be significantly related to caloric responsiveness.

Adolescent↗

PubMed1978

Anatomical analysis of the developmental effects of aneuploidy in man--the 18-trisomy syndrome: II. Anomalies of the upper and lower limbs.

We report the anatomical variations of the limbs in eight infants with the trisomy-18 syndrome that were dissected and studied in detail. In each case, the upper limbs showed defects which further define the specific influence of this aneuploidy on the development of its preaxial (radial) component, and the tendency towards reduction defects. Abnormalities included muscle variations concentrated along the radial margin of the forearm and hand, the absence of the definitive musculocutaneous nerve in all of the limbs, and reductions of the radial artery in four of the bodies. Pathogenetic mechanisms explaining the observed defects are discussed, and include: 1) a defect in peripheral nerve development; or 2) tissue necrosis. The characteristic flexion deformities of the fingers seem to be due to a displacement of the tendons of extensors digitorum and digiti minimi. The lower limbs did not show a consistent pattern of defects, except for the absence of some muscles (psoas minor, the tendon of flexor digitorum brevis to digit V), and the presence of several supernumerary muscles. These variations are discussed as possible nonspecific effects of 18-trisomy on development. The additional anatomical data from this and the first paper in this series [Bersu and Ramirez-Castro, 1977] provide a more detailed picture of the trisomy-18 phenotype which may be useful in corroborating an unconfirmed clinical diagnosis of the syndrome.

Abnormalities, Multiple↗

PubMed1985

Occipital distribution of foveal half-field responses.

Foveal left and right half-field responses were recorded in six subjects (12 half-fields) and compared with wide half-field responses. In the foveal responses a general trend was seen for the negative-positive-negative (NPN) complex to extend to the contralateral channels, replacing the contralateral positive-negative-positive (PNP) complex found with wide half-field stimulation. Many individual variations in foveal response morphology were seen, which may be understood in terms of anatomical variation. Individual differences between foveal half-fields in the same subject may be as great as those between subjects.

Evoked Potentials, Visual↗

PubMed1990

Renal vein anatomy and its implications for retroperitoneal surgery.

Because of its complicated embryological development, the anatomy of the renal veins shows extensive variability. A full understanding of the potential anatomical variations is imperative for retroperitoneal operations. Based on 4,520 retroperitoneal computerized tomography scans, anatomical studies of autopsy material of 354 unselected cases and intraoperative observations made during 215 major retroperitoneal procedures, an attempt was made to define the most common renal vein variants and retrace their development during embryogenesis. Awareness of rare anomalies in urological and general surgery is crucial to prevent severe damage to the venous drainage of the left kidney, and because troublesome bleeding may occur during vascular and retroperitoneal oncological procedures in patients with unknown venous anomalies. We found the incidence of these variants to be 0.8 versus 1.7 versus 3.7%, respectively.

Humans↗