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Topic: Arachnoid membrane

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	NursingCenter (Site not responding. Last check: 2007-11-07)
		Spinal arachnoiditis is a disease characterized by inflammation and scarring of the arachnoid membrane of the spinal cord.
		Arachnoiditis symptoms are difficult to distinguish from other types of neural compressive diseases, because many of the symptoms are similar and the disease onset can be months to years from the initial injury.
		Visual diagnosis of arachnoiditis is most commonly made using CAT scan (using intravenous contrast dye) and MRI, thus a trend toward noninvasive diagnosis without the potential exacerbation or further irritation of the arachnoid membrane secondary to the direct introduction of dyes to the spinal membranes (i.e., myelograms).
	www.nursingcenter.com /prodev/cearticleprint.asp?CE_ID=414141 (3367 words)

	Arachnoid Cysts
		Arachnoid cysts are cerebrospinal fluid-filled sacs that may develop between the surface of the brain and the cranial base or on the arachnoid membrane--one of the 3 membranes that cover the brain and the spinal cord.
		Symptoms of an arachnoid cyst are related to the cyst size and location.
		Untreated, arachnoid cysts may cause permanent severe neurological damage due to the progressive expansion of the cyst(s) or hemorrhage (bleeding).
	healthlink.mcw.edu /article/921384364.html (218 words)

	BRAIN - LoveToKnow Article on BRAIN (Site not responding. Last check: 2007-11-07)
		Between the dura mater and the subjacent arachnoid membrane is a fine space containing a minute quantity of limpid serum, which moistens the smooth inner surface of the dora and the corresponding smooth outer surface of the arachnoid.
		Arachnoid Mater.The arachnoid is a membrane of great delicacy and transparency, which loosely envelops both the brain and spinal cord.
		The cell which conducts impulses to the brain from the olfactory membrane in the nose resembles cells in the skin of the earthworm, in that its cell-body lies actually amid the epithelium of the skin-surface and is not deeply buried near or in the central nervous organ.
	www.1911encyclopedia.org /B/BR/BRAIN.htm (20541 words)

	eMedicine - Arachnoid Cyst : Article Excerpt by: Ali Nawaz Khan, MBBS, FRCP, FRCR (Site not responding. Last check: 2007-11-07)
		Arachnoid cysts also occur within the spinal canal, in which arachnoid cysts or arachnoid diverticula may be located subdurally or in the epidural space, respectively.
		Microscopic examination of arachnoid cysts shows that the walls are formed from a splitting of the arachnoid membrane, with an inner and outer leaflet surrounding the cyst cavity.
		Arachnoid cysts usually occur in association with normal arachnoid cisterns, and such cysts are congenital, arising from arachnoid clefts and arachnoid duplications.
	www.emedicine.com /radio/byname/arachnoid-cyst.htm (584 words)

	Bioline International Official Site (site up-dated regularly)
		The purpose of this study was to clarify the rearrangement of the arachnoid membrane on the tumour surface during its growth in relation to adjacent neural structures.
		The arachnoid fold seen near the porus between the tumour and the surgeon during surgery at Stage 3 and 4 is an artifact caused by retraction of the cerebellum.
		Consequently, the arachnoid on the lateral surface of the cerebellar hemisphere is stretched, causing the arachnoidal duplication around the lateral pole of the tumour near the porus with the invaginated arachnoid membrane and the stretched arachnoid membrane originally covering the lateral surface of the cerebellar hemisphere.
	www.bioline.org.br /request?jp02089 (3608 words)

	IX. Neurology. 4g. The Meninges of the Brain and Medulla Spinalis. Gray, Henry. 1918. Anatomy of the Human Body. (Site not responding. Last check: 2007-11-07)
		The spinal dura mater is attached to the circumference of the foramen magnum, and to the second and third cervical vertebræ; it is also connected to the posterior longitudinal ligament, especially near the lower end of the vertebral canal, by fibrous slips.
		The Arachnoid—The arachnoid is a delicate membrane enveloping the brain and medulla spinalis and lying between the pia mater internally and the dura mater externally; it is separated from the pia mater by the subarachnoid cavity, which is filled with cerebrospinal fluid.
		On the upper surface of the brain the arachnoid is thin and transparent; at the base it is thicker, and slightly opaque toward the central part, where it extends across between the two temporal lobes in front of the pons, so as to leave a considerable interval between it and the brain.
	www.bartleby.com /107/193.html (3158 words)

	MENINGES - Definition
		[n] a membrane (one of 3) that envelops the brain and spinal cord
		?, ?, a membrane.] (Anat.) The three membranes that envelop the brain and spinal cord; the pia mater, dura mater, and arachnoid membrane.
		The three membranes that cover the brain and spinal cord; going from skull to the brain, the membranes are the dura mater (the toughest of the three, a.k.a the pachymennix), the arachnoid (so called because it resembles a web) and the pia mater (delicate and highly vascular).
	www.hyperdictionary.com /dictionary/meninges (109 words)

	Developmental Disorders
		Arachnoid cysts, also known as intra-arachnoid cysts, meningeal cysts, leptomeningeal cysts, and arachnoid diverticula, have been reported with increasing frequency over the past few years in dogs and cats [1-13].
		Ultrastructurally, the cyst is formed by splitting of the arachnoid membrane and the wall of the cyst is independent of the inner layer of the dura mater [16].
		Spina bifida manifesta, cystica, and operta are synonymous subclassifications indicating presence of meningocele cyst (protrusion of the spinal cord membranes through a defect in the spinal column), myelocele (protrusion of the spinal cord) or meningomyelocele (protrusion of the spinal cord and its membranes through a defect in the spinal column) [247].
	www.ivis.org /special_books/Braund/braund16/chapter_frm.asp?LA=1 (13098 words)

	Glossary of terms (Site not responding. Last check: 2007-11-07)
		Arachnoid: lies within the vertebral canal and surrounds the spinal cord and the vertebral portion of the subarachnoid space.
		Since the spinal cord ends at the L-2 vertebral level, a wide separation occurs between the arachnoid and pia mater, the lumbar cistern, filled with cerebrospinal fluid in which the cauda equina is suspended.
		Arachnoid cyst A fluid-filled cyst lined with arachnoid membrane, frequently situated near the lateral aspect of the fissure of Sylvius; usually congenital in origin.
	www.arachnoiditisonline.org.uk /Glossary.htm (1619 words)

	causes (Site not responding. Last check: 2007-11-07)
		Arachnoid cysts are fluid-filled sacs that occur on the arachnoid membrane that covers the brain (intracranial) and the spinal cord (spinal).
		Arachnoid cysts appear on the arachnoid membrane, and they may also expand into the space between the pia mater and arachnoid membranes (subarachnoid space).
		Because many cases of arachnoid cysts have no symptoms, it is difficult to determine the true frequency of this disorder in the general population.
	arachnoidcyst.org /technical/causes.htm (186 words)

	Arachnoid Cysts
		Spinal arachnoid cysts may be associated with progressive weakness of the legs, abnormal side-to-side curvature of the spine (scoliosis), back pain, and involuntary muscle spasms (spasticity) that result in slow, stiff movements of the legs.
		Researchers believe that most cases of arachnoid cysts are developmental malformations that arise from the unexplained splitting or tearing of the arachnoid membrane.
		Arachnoid cysts of the middle cranial fossa and traumatic complications.
	hw.healthdialog.com /kbase/nord/nord989.htm (2298 words)

	6-5-9
		The authors present the case of a patient in whom progressive thoracic myelopathy was caused by the extensive ossification of the arachnoid membrane and associated intramedullary syrinx.
		The third type is the least common, consisting of diffuse ossification of the arachnoid membrane at one or several segments of the spinal cord and may be associated with larger ossified masses such as those encountered in the second type.
		Lubin AJ: Adhesive spinal arachnoiditis as a cause of intramedullary cavitation.
	www.aans.org /education/journal/neurosurgical/may99/6-5-9.html (3527 words)

	cysts (Site not responding. Last check: 2007-11-07)
		It is postulated that, during the process of the complex folding of the primitive neural tube and the formation of normal subarachnoid cisterns, an anomalous splitting of the arachnoid membrane occurs.
		Cysts of the sellar region (supra, para and intrasellar) are considered to be an extension of the Lillequist membrane, which divides the chiasmatic cistern of the interpeduncular cistern, being associated with alterations of the normal CSF flow.
		The cyst membrane may also be composed of arachnoid, but in addition, inflammatory cells and hemosiderin deposits may be present and it is difficult to fenestrate these cysts.
	www.thamburaj.com /cysts.htm (4251 words)

	GlobalSpine - Advanced Anatomy - Spinal Cord
		Between the two is the arachnoid membrane, a non-vascular membrane, which envelops the cord and is connected to the pia mater by slender filaments of connective tissue.
		It is a thin, delicate, tubular membrane, which invests the surface of the cord, and is connected to the pia mater by slender filaments of connective tissue.
		In addition to this it is partially subdivided by a longitudinal membranous partition, the septum posticum, which serves to connect the arachnoid with the pia mater, opposite the posterior median fissure of the spinal cord, a partition which is incomplete and cribriform in structure, consisting of bundles of white fibrous tissue interlacing with each other.
	www.globalspine.net /spinal_cord_advanced.html (4217 words)

	Arachnoiditis
		Arachnoiditis is a general term for several progressive regional disorders all of which result in the inflammation of parts of the middle membrane surrounding the spinal cord and brain (arachnoid membrane) and the space defined by this membrane (subarachnoid space).
		Epiduritis is characterized by inflammation of the outer tough fibrous membrane surrounding the brain and spinal cord known as the dura mater.
		Bilgen IG, et al., Adhesive arachnoiditis causing cauda equina syndrome in ankylosing spondylitis: CT and MRI demonstration of dural calcification and a dorsal dural diverticulum.
	hw.healthdialog.com /kbase/nord/nord444.htm (980 words)

	Relevant anatomy
		The arachnoid membrane or the middle meningeal layer is an extremely thin and delicate layer that loosely encloses the brain.
		Arachnoid villi within the subarachnoid space absorb CSF continuously into the venous layers of the brain.
		The subarachnoid space is a layer lying between the arachnoid membrane and the pia mater.
	www.rnceus.com /sah/sahanat.html (176 words)

	CONGENITAL ABNORMALITIES (Site not responding. Last check: 2007-11-07)
		Arachnoid cysts are congenital lesions containing clear fluids similar to the cerebro-spinal fluid in composition.
		Arachnoids cysts are a benign condition, which occurs throughout the cerebral spinal axis in relation to arachnoid membrane.
		The intra-cranial arachnoid cysts are invariably intra-dural while the spinal cyst may be either intra or extra dural.
	www.health.adelaide.edu.au /paed-neuro/congenital.html (760 words)

	INTRACRANIAL ARACHNOID CYSTS: TREATMENT ALTERNATIVES
		True arachnoid cysts are, however, widely accepted to be developmental anomalies in which splitting or duplication of the primitive arachnoid membrane in the early embryonal life leads to intra-arachnoid fluid collection.
		Arachnoid cysts of the middle cranial fossa, surgical considerations.
		Arachnoid cysts of the middle fossa: surgical considerations.
	www.kfshrc.edu.sa /annals/173/96-352.html (3241 words)

	Radiology, University of Rochester Medical Center
		Arachnoid cysts are usually sporadic and non-syndromic, though rare familial cases have been described in the literature [3].
		Arachnoid cysts are found in several syndromes but data are not sufficient to indicate whether the association is typical or fortuitous.
		Arachnoid cysts associated with tumors develop as a consequence of CSF loculation surrounded by arachnoid scarring, with expansion of osmotic filtration or via a ball-valve mechanism.
	www.urmc.rochester.edu /smd/Rad/neurocases/Neurocase103.htm (1606 words)

	eMedicine - Arachnoid Cyst : Article by Ali Nawaz Khan, MBBS, FRCP, FRCR (Site not responding. Last check: 2007-11-07)
		Arachnoid cysts are associated with myelodysplasia in spinal dysraphism.
		Arachnoid cysts typically show compression of the subarachnoid space by a cystic structure that may be unilocular or septate and of variable size, although the septa may not always be visible.
		On CT scans, arachnoid cysts are characterized by sharp nonenhancing borders and are isodense to CSF.
	www.emedicine.com /radio/topic48.htm (3695 words)

	ICP monitors
		It is postulated that arachnoid cysts develop because of a minor aberration in the flow of CSF in the primordial stage of the development of the subarachnoid pathways resulting in the sequestration of an enclosed chamber or diverticulum within the perimedullary mesh.
		The involved cisterns are the cistern of the Sylvian fissure, the CP angle, the ambient cistern, the cisterna magna, the prepontine and interpeduncular cistern, and the chiasmatic cistern.
		There is splitting of the arachnoid membrane at the margin of the cyst.
	www.ucsf.edu /nreview/11-Pediatrics/ArachnoidCysts.html (1159 words)

	Adhes Arach Nomenclature
		In this illustration the arachnoid membrane is shown with the red dot.
		The arachnoid and the very fine and filamentous pia mater (which covers the nerve structures directly) are referred to as the "leptomeninges" (the fine membranes) while the dura mater shown with the green dot is referred to as the "pachymeninges" (the thick membrane).
		It can be appreciated that the term "arachnoiditis" is very non-specific as all known meningitis entities (acute and chronic) involve the arachnoid membrane.
	www.burtonreport.com /InfSpine/ArachNomenclature.htm (835 words)

	Meninges (Site not responding. Last check: 2007-11-07)
		There is no connection between the dural sheath and the vertebrae that form the canal there is a cavity called the epidural space which is highly vascular and contains loose and adipose tissue which forms a protective pad around the spinal cord.
		The arachnoid membrane is the middle of the meningeal layers and as its name implies, appears spider-like or more specifically, has the appearance of a spider web.
		The subarachnoid space, located between the arachnoid membrane and the pia mater is maintained by delicate, web-like strands that connect the arachnoid membrane and the pia mater.
	www.innerbody.com /text/nerv146.html (223 words)

	This is the Title/Header
		The subarachnoid space (SAS), which lies between the arachnoid membrane externally and the pia mater internally, carries the flow from the cerebral ventricles to its points of absorption.
		The inner surface of the arachnoid and the outer surface of the pia are covered with flattened mesothelial cells; these also cover the numerous trabeculae, which bridge the SAS, and the nerves and blood vessels which pass across it.
		Large molecules fail to enter the CSF from the blood because of the interposition of the vascular endothelium (the blood CSF barrier) but there is a rapid exchange of small molecular weight substances between the CSF and the extracellular fluid of the brain and cord.
	www.angelfire.com /wa/wafshaf50/CSF.html (638 words)

	Chapter 3
		The subarachnoid space beneath the arachnoid membrane is filled with cerebrospinal fluid, which cushions the brain.
		The fluid-filled space between the arachnoid membrane and the pia mater.
		Small projections of the arachnoid membrane through the dura mater into the superior sagittal sinus; CSF flows through them to be reabsorbed into the blood supply.
	www.albany.edu /faculty/cafrye/apsy601/Ch03terms.html (1962 words)

	Blood Brain Barrier CSF Anatomy and Physiology (Site not responding. Last check: 2007-11-07)
		The choroid plexus and the arachnoid membrane act together at the barriers between the blood and CSF.
		Passage of substances from the blood through the arachnoid membrane is prevented by tight junctions (Nabeshima et al., 1975).
		The arachnoid membrane is generally impermeable to hydrophilic substances, and its role is forming the Blood-CSF barrier is largely passive.
	users.ahsc.arizona.edu /davis/csfanatomy.htm (407 words)

	MEMBRANE - Definition
		{Adventitious membrane}, a membrane connecting parts not usually connected, or of a different texture from the ordinary connection; as, the membrane of a cicatrix.
		{Mucous membranes} (Anat.), the membranes lining passages and cavities which communicate with the exterior, as well as ducts and receptacles of secretion, and habitually secreting mucus.
		{Serous membranes} (Anat.), the membranes, like the peritoneum and pleura, which line, or lie in, cavities having no obvious outlet, and secrete a serous fluid.
	www.hyperdictionary.com /dictionary/membrane (166 words)

	Arachoiditis, Help Needed:
		The arachnoid membrane lies is the middle membrane.
		Immediately beneath the arachnoid membrane is the subarachnoid space where the spinal fluid is located, which bathes the brain and spinal cord..
		In arachnoiditis, there is proliferation of connective tissue resulting in thickening of the arachnoidal membranes and adhesions between the arachnoid and the dura (which is the outer membrane).
	www.medhelp.org /forums/neuro/archive/604.html (850 words)

	What are Meninges?
		The membranes of the craniosacral system include the dura mater (the "tough mother"), the arachnoid membrane, and the pia mater.
		The outer layer of these membranes, the dura mater, is a tough relatively inelastic connective tissue which adheres to the inside surface of the skull bones.
		The pia mater is the innermost layer of membrane which is highly vascularized, follows the convolutions or folds of the brain and spinal cord, and delivers blood supply to these tissues.
	www.10ac.com /meninges.htm (320 words)

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