Anatomical location of the abducens nerves (VI) in the ventral approach of clival tumors.

The aim of this work was to determine reliable anatomical landmarks for locating and preserving the abducens nerves (6th cranial nerves) during trans-facial or trans-nasal endoscopic approaches of skull base tumors involving the clivus and the petrous apex. In order to describe this specific anatomy, we carefully dissected 10 cadaveric heads under optic magnification. Several measurements were taken between the two petro-sphénoidal foramina, from the bottom of the sella and the dorsum sellae. The close relationship between the nerves and the internal carotid artery were taken into account. We defined a trapezoid area that allowed drilling the clivus safely, preserving the 6th cranial nerve while being attentive to the internal carotid artery. The caudal part of this trapezium is, on average, 20 mm long at mi-distance between the two petro-sphenoidal foramina. The cranial part is at the sella level, a line between both paraclival internal carotid arteries. Oblique lateral edges between the cranial and caudal parts completed the trapezium.

Sella turcica morphometry using computed tomography

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Sellar lesions and visual loss: key concepts in neuro-ophthalmology.

The pituitary gland serves an essential role in the activity and regulation of the endocrine system. Mass lesions within the pituitary gland account for approximately 10-15% of intracranial neoplasms. Patients with pituitary adenomas may present with endocrine dysfunction or neuro-ophthalmic pathology, resulting from compression of surrounding structures, most notably the optic chiasm. Visual deficits from chiasmal tumors may manifest as visual field defects, visual loss, diplopia, nystagmus and visual hallucinations. Visual field defects are the most commonly reported presenting visual symptom. The specific visual field defect usually results from the anatomic compression of the tumor upon the optic chiasm. It is important to recognize characteristic visual deficits in the diagnosis and treatment of chiasmal tumors.

Imaging features of sellar cysticercosis.

Cases of sellar involvement of neurocysticercosis (NCC) are rare. Little is known about the mechanisms by which the parasite can compromise the pituitary gland. Although NCC damages sellar structures with direct compression by large cysts, extension through the basal cisterns and third ventricle with focal arachnoiditis can result as an inflammatory response. Evaluation for hypophyseal lesions in patients with NCC may allow for the diagnosis of unexplained loss of visual acuity and hormonal disturbances.

The lateral sellar nerve plexus and its connections in humans.

OBJECT: The aim of the present study was to elucidate the systematic topography of the lateral sellar (cavernous sinus [CS]) nerve plexus and its connections in humans. METHODS: Seven specimens of human CS and adjacent regions were dissected in steps and stained as whole-mount preparations by using a sensitive acetylcholinesterase method. Another specimen was frozen, cut on a frontal plane, and stained for acetylcholinesterase. The human CS contains an extensive nerve plexus with small ganglia. The plexus is composed of a main part, the lateral sellar plexus proper, which is located around the abducent nerve and medial to the ophthalmic nerve, and a lateral extension just underneath the outermost layer of the lateral CS wall, which is located lateral to the trochlear and ophthalmic nerves. The lateral sellar plexus is connected to the internal carotid nerve, the pterygopalatine ganglion, and the trigeminal ganglion. From the lateral sellar plexus, nerve branches run along the oculomotor, trochlear, ophthalmic, and abducent nerves into the orbit. In addition, the lateral sellar plexus has multiple connections with nerves located around the internal carotid artery. The presence of connections between the lateral sellar plexus and functionally defined neural structures suggests that the plexus receives sympathetic, parasympathetic, and sensory contributions. CONCLUSIONS: The plexus may distribute nerve subpopulations to several targets, including cerebral arteries and orbital structures. The presence of a mixed nerve plexus that projects to a variety of targets indicates that injury or disease in the CS may result in a variety of symptoms.

Microanatomy of the hypophyseal fossa boundaries.

OBJECT: The authors studied the heads of 17 adult cadavers and one fetus to clarify the anatomy of the sellar region, particularly the lateral boundaries of the hypophyseal fossa. METHODS: Vascular injections and microdissection or histological techniques were used in this study. The roof of the cavernous sinuses and diaphragma sellae were part of a single horizontal dural layer that joined the two anterior petroclinoid folds. Laterally, the direction of this layer changed; it became the lateral wall of the cavernous sinus and joined the dura mater of the middle cerebral fossa. On the midline, this layer ballooned toward the sella through the diaphragmatic foramina, created a dural bag containing the hypophysis, and attached to the inferior aspect of the diaphragma sellae. As a consequence, no straight sagittal dural wall existed between the pituitary gland and cavernous sinus; the lateral border of the hypophyseal fossa was part of this anteroposterior and superoinferior convex bag. The authors stress the importance of the venous elements of the region and discuss the structure of the cavernous and coronary sinuses. CONCLUSIONS: Invasion of the cavernous sinus makes surgery more risky and difficult and may necessitate modification of the surgical treatment plan. The preoperative diagnosis of cavernous sinus invasion is thus of great interest, but the possibility of normal lateral expansions of the pituitary gland must be kept in mind. A lateral expansion of this gland into the cavernous sinus was encountered in 29% of the specimens, and an adenoma that developed in such an expansion could easily mimic cavernous sinus invasion.

The sympathetic nerves of the parasellar region: pathways to the orbit and the brain.

Sympathetic nerves innervate targets in the orbit and the brain. They issue from the superior cervical ganglion and reach the parasellar region via the internal carotid nerve. Information on their further parasellar course and distribution is scant and contradictory. In this study the parasellar sympathetic pathways of 30 human infants and 6 human fetuses were investigated by microdissection and histologically. A common parasellar sympathetic trunk, which reunites all the nerve fibers emanating from the lateral and medial internal carotid plexus, is described as well as its further divisions. It was found that the posterior knee of the infant carotid siphon is free of large sympathetic nerve bundles. In addition a ganglion is described, which is situated in the parasellar adipose body. It is reached by nerve fibers coming from the parasellar sympathetic pathways. Fibers that issue from this ganglion join the periorbita and the orbital muscle of Müller. These anatomical facts are of immediate importance for preventing nerve damage during cavernous sinus surgery. Furthermore, the study improves the anatomical knowledge of the parasellar region and suggests a new concept for the innervation of the orbital muscle.

[The parasellar osteo-dural chamber and the vascular and neural elements that traverse it. An anatomical concept that would replace the cavernous sinus of classical anatomy]. / La loge ostéo-durale parasellaire et les éléments vasculaires et nerveux qui la traversent. Une conception anatomique qui doit remplacer celle du sinus caverneux des classiques.

On each side of the sella turcica, because of the existence of vascular and nervous elements, the two aspects of the parasellar segment of the tentorium cerebelli diverge and with the wall of the sphenoid bone form an extradural lodge. In this space are included a venous pathway (the cavernous sinus of the classics), the internal carotid artery and the three oculo-motor cranial nerves. The venous pathway is a plexus of small sized veins, mainly draining the orbital blood, and has neighborhood relations with the carotid. The morphology of the region and the relations of the internal carotid artery and the cranial nerves with the dura propria are the result of the embryonnic development of the brain and the formation of the anterior and middle cerebral fossae. In the parasellar space the cranial nerves have a dural sheath as well as a leptomeningeal one. Nerves III and IV are very close to the lateral wall explaining its multilayered aspect. The internal carotid artery, extradural in its parasellar segment, at the level of the anterior clinoid process, is involved by dura propria to become intradural (the artery does not pierce the dura). Because of the adhesion of the dura propria to the intracranial periosteum the artery is attached to the bone whereas in its extradural and intradural segments it has some mobility. Recent studies have confirmed and completed this topographical concept, first presented in 1949, allowing successful approaches to vascular and tumorous lesions considered inoperable.