The Geometry of the Circle of Willis Anatomical Variants as a Potential Cerebrovascular Risk Factor.

AIM: To correlate the anatomical variants of the circle of Willis with their effects on the hemodynamic and geometrical parameters responsible for the pathogenesis of neurological diseases. MATERIAL AND METHODS: The circle of Willis and the proximal segments of the main arteries were dissected and measured on ten formalin-fixed human brains. The anatomical variants were systematized using descriptive statistics. The mathematical models for brain perfusion and wall shear stress were developed by optimally approximating resistance to flow, vascular conductance, and branching. RESULTS: Eighty percent of the brains presented asymmetries, especially in the posterior communicating (70%) and anterior cerebral (40%) arteries. The posterior circulation had more variations (65.21%). Nine hypoplastic vessels were found in 7 brains. Atypical origins were observed in eight specimens. According to the mathematical models, which integrated each anatomical change in the global circle of Willis anatomy, the circle of Willis' geometry could represent a risk factor for intracranial aneurysms and atherosclerosis, mostly when hypoplastic arteries are present, due to high resistance to flow and imbalanced bifurcation geometry. Accessory vessels are less associated with cerebrovascular risk. CONCLUSION: We described anatomical variants of both the anterior and posterior circulations and their specific effects on the hemodynamic balance of cerebral blood flow.

Morphometric study of the human brainstem and its neurovascular relations.

AIM: The brainstem is a very complex segment of the central nervous system because it has a high density of nuclei and tracts with vital functional roles. This explains the considerable difficulty of surgery for lesions located in or around the brainstem. Our paper aims to provide a concise description of the external configuration, its internal correspondence and the neurovascular relations of the brainstem with morphometric data that can be useful in surgical planning. MATERIAL AND METHODS: The study was conducted on formalin fixed brainstem specimens, which were harvested with respect to the topographic anatomy. Macroscopic measurements were performed with a Vernier caliper. RESULTS: The anatomical structures on the ventral and dorsal aspects of the brainstem are described and illustrated schematically. Their dimensions are also graphically represented using the mean values. Serial axial sections through the brainstem demonstrate the internal correspondence of its external features. Then there are presented the apparent origins and the proximal diameters of the cranial nerves and the arteries of the posterior circulation as well as their anatomical relations. CONCLUSION: The external morphometry of the brainstem correlated with the position of the internal structures provides landmarks with aplicability in neurosurgery especially in the fields of intrinsic brainstem lesions, posterior fossa and fourth ventricle surgery.

Solitary Langerhans histiocytosis of the orbit: case report and review of the literature.

Langerhans cell histiocytosis (LCH), previously known as "histiocytosis X", is a clinical entity characterized by abnormal proliferation of Langerhans cells, which exert a mass effect. Orbital involvement due to LCH is rare as a unifocal disease, seldom occurring outside the pediatric population. We report a case of a 21-year-old man with solitary LCH of the orbit depicted by magnetic resonance imaging (MRI) and diagnosed by histopathological examination.

Keratoacanthoma of the conjunctiva - case report and review of the literature.

INTRODUCTION: Keratoacanthoma (KA) is a relatively common, benign, rapidly growing and self-limiting squamous proliferation, which appears most frequently on the sun-exposed skin. The nature of KA and its relationship to squamous cell carcinoma (SCC) still represent one of the major debates in dermatopathology, as it is the truthfulness of such a diagnosis outside the skin. However, the tumor is now known to originate from the pilosebaceous units of the skin or from ectopic sebaceous glands of squamous mucous membranes, and to differentiate onto follicular isthmus÷infundibulum-like epithelium. CASE PRESENTATION: A 71-year-old man presented with a sore and red right eye, which on slit-lamp biomicroscopical examination revealed a dome-shaped lesion at the temporal inferior conjunctival limbus. After a thorough histopathological examination, a diagnosis of KA has been made, both after the initial tumor excision and after the relatively rapid recurrence. After the second intervention, no recurrence was observed over five years of follow-up, confirming the diagnosis. CONCLUSIONS: The peculiarity of the case stands in his exceptional rarity, being to our knowledge the first conjunctival KA reported in our country. In the light of current knowledge, the peculiar limbal location of all the conjunctival KAs reported in the literature raised the question of the possible role of limbal stem cells in the histogenesis of these tumors, similar to the pilosebaceous ones. The treatment of conjunctival KA remains the complete excision of the tumor, as it allows histopathological evaluation of the entire tumor and the exclusion of a KA-like SCCs or KAs with SCC component.