Angioarchitectures and Hemodynamic Characteristics of Posterior Communicating Artery Aneurysms and Their Association with Rupture Status.

BACKGROUND AND PURPOSE: Intracranial aneurysms originating at the posterior communicating artery are known to have high rupture risk compared with other locations. We tested the hypothesis that different angioarchitectures (ie, branch point configuration) of posterior communicating artery aneurysms are associated with aneurysm hemodynamics, which in turn predisposes aneurysms to rupture. MATERIALS AND METHODS: A total of 313 posterior communicating artery aneurysms (145 ruptured, 168 unruptured) were studied with image-based computational fluid dynamics. Aneurysms were classified into different angioarchitecture types depending on the location of the aneurysm with respect to parent artery bifurcation. Hemodynamic characteristics were compared between ruptured and unruptured aneurysms, as well as among aneurysms with different angioarchitectures. RESULTS: Angioarchitecture was associated with rupture (P = .003). Ruptured aneurysms had higher, more concentrated, and more oscillatory wall shear stress distributions (maximum wall shear stress, P < .001; shear concentration index, P < .001; mean oscillatory shear index, P < .001), stronger and more concentrated inflow jets (represented as Q, P = .01; inflow concentration index, P < .001), and more complex and unstable flow patterns (vortex core length, P < .001; proper orthogonal decomposition entropy, P < .001) compared with unruptured aneurysms. These adverse conditions were more common in aneurysms with bifurcation-type angioarchitectures compared with those with lateral or sidewall angioarchitectures. Interestingly, ruptured aneurysms also had lower normalized mean wall shear stress (P = .02) and minimum wall shear stress (P = .002) than unruptured aneurysms. CONCLUSIONS: High-flow intrasaccular hemodynamic characteristics, commonly found in bifurcation-type angioarchitectures, are associated with the posterior communicating artery aneurysm rupture status. These characteristics include strong and concentrated inflow jets, concentrated regions of elevated wall shear stress, oscillatory wall shear stress, lower normalized wall shear stress, and complex and unstable flow patterns.

Thalamic reticular nucleus in Caiman crocodilus: Relationship with the dorsal thalamus.

The thalamic reticular nucleus was investigated in one group of crocodilians, Caiman crocodilus. This neuronal aggregate is composed of two parts: a compact portion and a diffuse region made up of scattered cells within the forebrain bundles. In Caiman, both the lateral and medial forebrain bundles project to the telencephalon and the thalamic reticular nucleus is associated with each fiber tract. In the lateral forebrain bundle, the compact area is termed the nucleus of the dorsal peduncle (dorsal peduncular nucleus) while the diffuse part is called the perireticular area. In the medial forebrain bundle, the interstitial nucleus comprises one part of the compact area while another region without a specific neuronal label is also present. Similar to the perireticular cells of the lateral forebrain bundle, scattered cells are also present in the medial forebrain bundle. Morphological features of the thalamic reticular nucleus are revealed with stains for the following: fibers; cells; succinic acid dehydrogenase; and acetylcholinesterase. Regardless of which dorsal thalamic nucleus was injected, a localized region of the thalamic reticular nucleus contained retrogradely labeled cells and anterogradely labeled axons and terminals. This grouping was termed clusters and was felt to represent the densest interconnection between the dorsal thalamus and the reticular nucleus. Using clusters as an index of interconnections, the reticular nucleus was divided into sectors, each of which was associated with a specific dorsal thalamic nucleus. An organization similar to that found in Caiman is present in other sauropsids as well as in mammals. These data suggest that a thalamic reticular nucleus is present in all amniotes and has morphological properties similar to those described in this analysis. Lastly, a hypothesis is presented to explain how the external shape of the reticular nucleus in Caiman might be transformed into the homologous area in a representative bird and mammal.

Calcium binding protein expression in the optic tectum of Alligator during development.

The onset and distribution of the calcium binding proteins, calretinin, calbindin, and parvalbumin, were examined in the optic tectum of Alligator mississipiensis embryos between Stages 18 and 26-28. The immunoreactivity of each calcium binding protein correlated well with the results from the Western blot experiments. In terms of onset and distribution, calretinin expressison was the most widespread of the three calcium binding proteins that were examined, and was also the earliest to be visualized. Calbindin expression occurred next, whereas parvalbumin expression was the most limited and appeared last. For small calretinin (+) neurons, the pattern of immunoreactivity during development was from inside to outside, whereas for the larger cells, it was from outside to inside. For calbindin immunoreactive cells in the superficial zone, the pattern was from outside to inside. The distribution of the parvalbumin immunopositive neurons did not change significantly over the time period examined. Similar data on other amniotes is limited. However, the pattern in Alligator shares some similarities with kittens in regards to the distribution of calbindin and parvalbumin in the developing superior colliculus.

Acoustic communication in crocodilians: from behaviour to brain.

Crocodilians and birds are the modern representatives of Phylum Archosauria. Although there have been recent advances in our understanding of the phylogeny and ecology of ancient archosaurs like dinosaurs, it still remains a challenge to obtain reliable information about their behaviour. The comparative study of birds and crocodiles represents one approach to this interesting problem. One of their shared behavioural features is the use of acoustic communication, especially in the context of parental care. Although considerable data are available for birds, information concerning crocodilians is limited. The aim of this review is to summarize current knowledge about acoustic communication in crocodilians, from sound production to hearing processes, and to stimulate research in this field. Juvenile crocodilians utter a variety of communication sounds that can be classified into various functional categories: (1) "hatching calls", solicit the parents at hatching and fine-tune hatching synchrony among siblings; (2) "contact calls", thought to maintain cohesion among juveniles; (3) "distress calls", induce parental protection; and (4) "threat and disturbance calls", which perhaps function in defence. Adult calls can likewise be classified as follows: (1) "bellows", emitted by both sexes and believed to function during courtship and territorial defence; (2) "maternal growls", might maintain cohesion among offspring; and (3) "hisses", may function in defence. However, further experiments are needed to identify the role of each call more accurately as well as systematic studies concerning the acoustic structure of vocalizations. The mechanism of sound production and its control are also poorly understood. No specialized vocal apparatus has been described in detail and the motor neural circuitry remains to be elucidated. The hearing capabilities of crocodilians appear to be adapted to sound detection in both air and water. The ear functional anatomy and the auditory sensitivity of these reptiles are similar in many respects to those of birds. The crocodilian nervous system likewise shares many features with that of birds, especially regarding the neuroanatomy of the auditory pathways. However, the functional anatomy of the telencephalic auditory areas is less well understood in crocodilians compared to birds.

PAX6 immunoreactivity in the diencephalon and midbrain of alligator during early development.

PAX6 expression was examined during early development of the diencephalon and midbrain of Alligator using an immunocytochemical methodology. These observations focused on the basal plate to determine whether diencephalic prosomere organization in this region followed a pattern previously identified for alar plate areas. PAX6 expression was also described in alar diencephalic regions and the adjacent midbrain. PAX6 (+) cells in the basal plate were first seen in prosomere 1 at stage 7, in the midbrain at stage 10, and lastly in prosomeres 2 and 3 at stage 11. By stage 12, a nearly continuous column of PAX6 (+) cells extended from the midbrain basal plate through the entire diencephalon. In the diencephalon, PAX6 (+) cells in the basal plate were of greatest number in prosomere 1, least in prosomere 2, and intermediate in prosomere 3. This pattern of PAX6 expression distinguished these individual basal plate prosomeres. These results indicate that basal plate prosomeres follow a pattern similar to alar plate prosomereric organization during the later stages of early diencephalon development. Over a comparable time period of early diencephalon development, similar observations have been made in chick basal plate. In Alligator and chick, PAX6 expression in the basal plate is similar in the midbrain and prosomere 1 but different in prosomeres 2 and 3: present in Alligator and absent in chick. In alar plate areas of the Alligator diencephalon, PAX6 expression follows a similar pattern to that described for chick and mouse. These similarities in PAX6 expression in alar diencephalic prosomeres suggest that this is a common feature of amniotes. Differential PAX6 expression in alar prosomere 1 and the midbrain in Alligator is similar to that described for a wide range of species which suggests that these features are common to all vertebrates.

Intra-osseous meningioma of the orbit: an unusual presentation (2007: 5b).

Primary calvarial or intra-osseous meningiomas are uncommon lesions often confused preoperatively with other primary or secondary bone tumors of the skull. We present details of a patient with a primary calvarial meningioma involving the frontal, zygomatic, sphenoid and temporal bones that was radiographically diagnosed as fibrous dysplasia and initially treated conservatively for many years. Progressive vision loss and significant proptosis, with difficulty of eye closure, prompted surgical removal with cranioplasty and a 3D reconstructed prosthetic flap. Histological examination revealed intra-osseous meningioma. The clinical and radiological findings of intra-osseous meningiomas are discussed, together with a review of the literature.

Teflon granuloma with midbrain cysts after microvascular decompression of the trigeminal nerve.

Granuloma formation is a known complication after microvascular decompression using Teflon fibers. Such granulomas commonly present with recurrent neuralgia whereas other symptoms are exceedingly rare. We report the first case of a multicystic lesion due to a Teflon granuloma that is also uncommon for the lack of recurrent neuralgia.

Usefulness of color Doppler ultrasound in the management of a spinal arteriovenous fistula.

BACKGROUND: While color Doppler ultrasonography and microvascular Doppler recordings have been used intraoperatively for spinal cord vascular malformations, they have not been employed for similar spinal cord lesions preoperatively. CASE DESCRIPTION: We report the usefulness of color Doppler ultrasonography through a lumbar laminectomy defect in the management of a spinal arteriovenous fistula. CONCLUSION: Color Doppler ultrasonography should be considered for spinal lesions in which a laminectomy defect is present.

Moyamoya: Indiana University Medical Center experience.

BACKGROUND: Moyamoya usually presents with cerebral ischemia in children and intracranial hemorrhage in adults. Treatment remains controversial. DESIGN AND OBJECTIVE: We reviewed our experience from June 1995 to August 1999 of 20 adult and pediatric angiographically diagnosed patients with moyamoya to report their clinical presentation, radiological findings, management, and clinical outcomes. RESULTS: The mean age of patients at symptom onset was 17 years (range, 2-54 years). Patients were divided into 2 age groups (group 1, <18 years; group 2, > or =18 years). There were 13 patients in group 1 and 7 patients in group 2. Ischemic strokes or transient ischemic attacks were the predominant initial presentations in both groups. One patient in group 2 had an intraparenchymal brain hemorrhage. Five patients received medical treatment, and 15 had surgical revascularization. The mean time from symptom onset to surgical procedure was significantly longer for patients in group 1 than for those in group 2 (P =.03). The mean follow-up time was 36 months. One patient in group 1 had an ischemic stroke. There was no difference in stroke recurrence, mortality, or modified Rankin scale score among medically or surgically treated patients. CONCLUSIONS: Moyamoya disease may have a different presentation and more benign natural history in our population than in Asian populations. Our findings emphasize the need to better understand the natural history of patients with moyamoya as well as the clinical benefit of different treatment modalities. Structured multicenter randomized clinical trials are needed to further assess the best treatment modalities for patients with moyamoya in the United States.

External carotid artery reconstruction performed using an autologous internal carotid artery patch. Technical note.

The reconstruction of the external carotid artery (ECA) and obliteration of an occluded stump or atretic internal carotid artery (ICA) are described. In this method the occluded ICA is used as an autologous patch graft. Satisfactory ICA obliteration and expanded, smooth common carotid artery-ECA contour were obtained in three patients. Advantages of this procedure include ICA obliteration and precise patch placement by using an ideal, autologous, arterial graft.

Ruptured middle cerebral artery aneurysm and bilateral chronic subdural hematomas.

BACKGROUND: While rupture of a cerebral aneurysm into the subdural space is rare, aneurysmal subarachnoid hemorrhage in the presence of subdural hematoma(s) is much more uncommon. Such a patient requires changes in routine perioperative management. CASE DESCRIPTION: A patient with a ruptured middle cerebral artery bifurcation aneurysm and bilateral subdural hematomas is presented. He underwent successful aneurysm clipping and subdural hematoma evacuations. At the time of surgery, measures commonly used to obtain brain relaxation were avoided. The patient was kept normovolemic, normocarbic, and normotensive. He recovered completely and resumed his prior occupation. CONCLUSIONS: Changes in standard techniques for a patient undergoing a pterional craniotomy for a ruptured cerebral aneurysm are required when bilateral extra-axial mass lesions are present.

Myocardial stunning secondary to aneurysmal subarachnoid hemorrhage.

BACKGROUND: Although subarachnoid hemorrhage (SAH) is often associated with electrocardiographic abnormalities, profound effects on cardiac performance are rare. CASE DESCRIPTION: A 57-year-old woman who developed loss of consciousness, respiratory distress, severe hypotension, and left ventricular hypokinesis with minimal coronary artery disease is described. Despite normal appearance of the coronary arteries on angiography, left ventricle function was so severely depressed that she required intra-aortic balloon pump support for 24 hours. Mental status changes prompted a head computed tomographic (CT) scan, which showed severe SAH and an intraventricular hemorrhage (IVH). Cerebral angiography demonstrated a basilar apex aneurysm. An echocardiogram done on hospital day 6 was normal. A left frontal ventriculostomy catheter was placed. This was later changed to a lumbar subarachnoid (SA) drain. The patient underwent an orbito-zygomatic craniotomy and aneurysm clipping. Although several serious medical problems occurred during her hospitalization, at follow-up, her sole neurological impairment was a minimal and resolving oculomotor paresis. CONCLUSION: This patient's respiratory failure and severe hypotension were initially thought to be due to a chemical pneumonitis or a cardiomyopathy. However, her symptoms ultimately proved to be secondary to a ruptured basilar apex aneurysm. The complex relationship of SAH to myocardial stunning, as illustrated by this patient, is discussed.

Glial fibrillary acidic protein-immunopositive structures in the brain of a Crocodilian, Caiman crocodilus, and its bearing on the evolution of astroglia.

Caiman crocodilus, as a representative of the order Crocodilia, was used in immunohistochemical studies. Immunohistochemical procedures were performed on free-floating sections using a monoclonal antibody against porcine glial fibrillary acidic protein (GFAP) and employing standard avidin-biotin complex methodology. The astroglia of Caiman exhibited robust immunoreactivity to the antibodies raised against mammalian GFAP. In Caiman, the predominant GFAP-immunopositive elements are the radial ependymoglia, similar to other reptiles. The regional variability of glial architecture in Caiman, however, seems greater than in other reptiles so far examined, although it is less compared with chickens. We suggest that this finding corresponds to a more advanced "regional adaptation" of the glial structure in Caiman compared with other reptiles. The main feature that distinguishes the astroglia of Caiman from those of other reptiles is the widespread occurrence of GFAP-immunopositive astrocytes. These cells are limited in lizards and snakes, are not present in turtles, but are found in every major brain area in Caiman. However, even in Caiman, astrocytes are only intermingled with radial glia and are not the predominant glial element of any brain area. The occurrence of astrocytes does not correlate with brain wall thickness. Despite their origin from different ancestral groups of stem reptiles (synapsid or diapsid), mammals and birds exhibit some common general features in their glial architecture and GFAP distribution: 1) predominance of astrocytes and 2) absent or limited GFAP immunopositivity of several brain areas. The present study demonstrates that, even in Caiman, a representative of the reptilian group most closely related to birds, these features are present only in part, suggesting that, in mammals and birds, they have evolved independently.

Cervical hemilaminectomy reconstruction: technical note.

STUDY DESIGN: A technique for posterior cervical hemilaminectomy reconstruction is described. OBJECTIVE: To describe a technique for reconstruction of cervical hemilaminae in an adult that resulted in osseous fusion and to suggest modifications for use in children. SUMMARY OF BACKGROUND DATA: Although uncommon, cervical hemilaminectomy can result in spine deformity. Re-establishment of the osseous and ligamentous structures should minimize this problem. METHOD: After excision of an intraspinal neurenteric cyst, removed cervical hemilaminae at C2 and C3 were reconstructed with metal plates, and posterior ligaments were reapproximated with suture. RESULTS: Radiologic evidence of osseous fusion was present at 1 year after surgery. CONCLUSIONS: The advantages of this technique are restoration of normal anatomy, technical ease, and simplicity. A modification of this technique in children by using absorbable rather than metal plates should allow for normal spine growth.

Craniofacial resection of a nasoseptal chondrosarcoma: case report and review of the literature.

BACKGROUND: Chondrosarcoma of the nasal septum is a rare, malignant neoplasm. A case is presented that illustrates the evaluation and treatment of this malignancy, reviews the relevant literature, discusses surgical approaches, and assesses adjuvant, nonsurgical therapy. METHODS: A craniofacial approach using an extended, bifrontal craniotomy and lateral rhinotomy with medial maxillectomy resulted in gross total resection at surgery. Because permanent sections of bone margins after decalcification were positive, conformal external beam radiation was used. RESULTS: The patient made a complete recovery, returned to work, and is disease-free 26 months after treatment. CONCLUSIONS: Surgical therapy using an anterior craniofacial resection is the preferred approach. External beam radiation therapy is potentially indicated for the following: positive or close surgical margins on permanent histopathology, extensive tumor with known residual at operation, or local recurrence not amenable to resection. Because of late local recurrence, lifelong follow-up is required.

Calcium binding protein immunoreactivity in nucleus rotundus in a reptile, Caiman crocodilus.

Nucleus rotundus is a prominent nucleus in the dorsal thalamus of nonmammalian amniotes. In one group of reptiles, Caiman crocodilus, previous studies have identified three parts of this neuronal aggregate. The central portion, the rotundal core, which receives visual input from the midbrain and projects to a restricted portion of the telencephalon, contains relay cells only. Previous examinations using Nissl morphology indicated that neurons of the rotundal core were not a homogeneous population of cells. The present investigation utilized another methodology to examine cell populations within the rotundal core, immunoreactivity to the calcium binding proteins, calbindin/calretinin and parvalbumin. Light microscopic observations revealed the following features. First, calbindin/calretinin immunoreactive neurons and parvalbumin immunoreactive neurons were present in the rotundal core. Of these two antibodies, immunoreactivity to calbindin/calretinin was much more robust and calbindin/calretinin immunoreactive neurons were more numerous than parvalbumin cells. Second, neurons immunoreactive to either calbindin/calretinin or parvalbumin were not homogeneous but comprised several populations based on perikaryal shape and size and neuronal process morphology. These results are compared with similar data in other amniotes.

Rhombomere development in a reptilian embryo.

Rhombomere development was investigated in a reptile, Alligator mississippiensis, using a variety of methodologies: cytoarchitecture (cresyl violet), histochemistry (peanut agglutinin), immunocytochemistry (antibodies to acetylated tubulin, vimentin, calretinin, and acetylcholinesterase), and external and internal morphology of wholemount embryos. Rhombomere boundaries form sequentially until 8 rhombomeres are present at stage 8. From stage 11 onwards, rhombomere borders fade. When present, boundaries of rhombomeres 2 through 5 were distinct. In all embryos, except the earliest stages, neural tissue was divided between the caudal end of the mesencephalon and the rostral end of the rhombencephalon. This area of transection was designated as the isthmus. For these technical reasons, a distinct border between the midbrain and the first rhombomere was not seen and the isthmic rhombomere could not be identified. The interrhombomeric boundary between rhombomere 7 and rhombomere 8 and between the most caudal rhombomere and the spinal cord was not nearly as clear as were the boundaries of rhombomeres 2 through 5. Development of rhombomeres 2 through 5 was investigated in wholemount preparations between stages 5/6 and 11. Qualitative and quantitative observations were made. In these rhombomeres, r2 through r5, rostrocaudal caudal expansion occurs at a slower rate than mediolateral development. This differential growth sculpts the morphology of rhombomeres 2 through 5. Rhombomere development in Alligator shares several features in common with hindbrain segmentation in chick. The identification of rhombomeres in a multitude of vertebrates from a variety of classes suggests that segmentation is a feature common to hindbrain development in all vertebrates.

Suboccipital resection of a medial acoustic neuroma with hearing preservation.

BACKGROUND: Many reports indicate that acoustic neuromas greater than 2.0 cm should be removed without hearing preservation attempted, even if hearing is present preoperatively. These studies advocate a translabyrinthine approach because the likelihood of hearing preservation is low. Medial acoustic neuromas, unlike the more common lateral tumors that involve the internal auditory canal, originate medial to that portion of the eighth nerve complex where the cochlear and vestibular nerves are fused. This anatomical feature suggests that these tumors may be amenable to resection with hearing preservation. METHODS: A patient with a 3.5 cm medial acoustic neuroma and useful preoperative hearing is presented. RESULTS: Gross total tumor removal with functional hearing was achieved after a two-stage procedure using a suboccipital approach. CONCLUSION: Based on the anatomico-pathologic features in this case, we believe that, if a patient has reasonable preoperative hearing (speech discrimination score > 70%) and a medial acoustic neuroma, an approach to preserve hearing should be considered regardless of tumor size.