arachnoid

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arachnoid

 [ah-rak´noid]
1. resembling a spider's web.
2. the delicate membrane interposed between the dura mater and the pia mater, and with them constituting the meninges.

a·rach·noid mat·er

[TA]
a delicate fibrous membrane forming the middle of the three coverings of the central nervous system. In life, the arachnoid (specifically the arachnoid barrier cell layer) is tenuously attached to the externally adjacent dura mater (specifically the dural border cell layer), and no natural space occurs at the dura-arachnoid interface. Thus, in a spinal puncture, dura mater and arachnoid are penetrated simultaneously as if a single layer. Separation of the arachnoid mater from the dura mater (usually through the dural-border cell layer) may result from traumatic or pathologic processes creating what is commonly, but incorrectly, called a subdural hematoma. The arachnoid mater is named for the delicate, spiderweblike filaments that extend from its deep surface, through the cerebrospinal fluid of the subarachnoid space, to the pia mater. See: cranial arachnoid mater, spinal arachnoid mater.
See also: leptomeninx.

arachnoid

/arach·noid/ (ah-rak´noid)
1. resembling a spider's web.
2. a delicate membrane interposed between the dura mater and the pia mater, separated from the latter by the subarachnoid space.

arachnoid

(ə-răk′noid′)
n.
A delicate fibrous membrane forming the middle of the three coverings of the brain and spinal cord, closely attached to the dura mater.

a·rach′noid′al adj.

arachnoid

(ə-răk′noid′)
adj.
1. Anatomy Of or relating to a delicate membrane enclosing the spinal cord and brain.
2. Of, relating to, or resembling arachnids.
3. Covered with or consisting of thin, soft, entangled hairs or fibers resembling those of a cobweb or spider's web.
n.
1. An arachnid.
2. Anatomy A delicate membrane that encloses the spinal cord and brain and lies between the pia mater and dura mater.

arachnoid

[ərak′noid]
Etymology: Gk, arachne, spider, eidos, form
resembling a cobweb or spiderweb, such as the arachnoid membrane. arachnoidal, adj.

arachnoid

adjective
(1) Spider-like in appearance
(2) Cobweb-like; covered with or consisting of entangled soft fibres or hair-like material.
 
noun A member of the arachnid family.

arachnoid

adjective Like a cobweb, covered with or consisting of entangled soft fibers or hair-like material noun A member of the arachnoid family

a·rach·noid mat·er

(ă-rak'noyd mā'tĕr) [TA]
A delicate fibrous membrane forming the middle of the three coverings of the central nervous system. In life the arachnoid (specifically the arachnoid barrier cell layer) is tenuously attached to the externally adjacent dura mater (specifically the dural border cells) and there is no naturally occurring space at the dura-arachnoid interface. Thus, in a spinal puncture, dura mater and arachnoid are penetrated simultaneously as if a single layer. Separation of the arachnoid mater from the dura mater (usually through the dural border cell layer) may result from traumatic or pathologic processes creating what is commonly, but quite incorrectly, called a subdural hematoma. The arachnoid mater is named for the delicate, spiderweblike filaments that extend from its deep surface, through the cerebrospinal fluid of the subarachnoid space, to the pia mater.
Synonym(s): arachnoidea mater [TA] , arachnoid membrane, arachnoidea, arachnoides.
[G. arachnē, spider, cobweb, + eidos, resemblance]

arachnoid

The delicate middle layer of the three MENINGES covering the spinal cord and brain, lying between the pia mater and dura mater. Unlike the pia mater, the arachnoid bridges over the grooves (sulci) on the surface of the brain and covers many large blood vessels lying in the sulci. Bleeding from any of these vessels causes a subarachnoid haemorrhage. From the Greek arachne , a spider.

arachnoid

  1. the middle of the three membranes (see MENINGES that cover the brain and spinal cord.
  2. see ARACHNID.

Arachnoid

One of the membranes that sheathes the spinal cord and brain; the arachnoid is the second-layer membrane.

meninges

three-layered vascular membrane covering brain and spinal cord
  • arachnoid middle meningeal layer

  • dura mater outer meningeal layer

  • pia mater inner meningeal layer

  • subarachnoid space space between arachnoid and pia mater

  • subdural space space between dura mater and arachnoid layers

arachnoid 

The middle member of the three meninges covering the brain, the spinal cord and the optic nerve. From the optic nerve it becomes continuous with the sclera. See sclera.

arachnoid

1. resembling a spider's web.
2. the delicate membrane interposed between the dura mater and the pia mater, and with them constituting the meninges. Called also arachnoidea.

cerebral arachnoid, arachnoidea cerebri
the arachnoid investing the brain.
arachnoid cyst
cysts of the pia and arachnoid containing cerebrospinal fluid; may cause gradually increasing pressure on nervous tissue, especially spinal cord, causing ataxia, paresis.
arachnoid fibroblastoma
arachnoid granulations
villous enlargements of the arachnoid that protrude into dural sinuses or diploic veins and serve to drain cerebrospinal fluid. They are conspicuous in the dorsal sagittal sinus of the horse.
arachnoid membrane
arachnoid; middle layer of the meninges.
spinal arachnoid
the arachnoid investing the spinal cord.

Patient discussion about arachnoid

Q. What is the treatment for an arachnoid cyst? My 15 year old son has just been diagnosed with an arachnoid cyst. What is the treatment? Is an operation necessary?

A. An operation is not always necessary, it depends on the size and location of the cyst. I suggest you take your son to a neurologist or a neurosurgeon for further consult.

Q. info on arachnoid cyst in the right posterior fossa

A. Basically it's like a small sac filled with fluid. The problem is that the skull is a rigid closed space, which means that if there's something other than the brain, it'll occupy space, usually on expense of the brains' space. These kinds of problems are often referred to as "space occupying lesion".

It's usually congenital (i.e. develops during pregnancy), and even when it cause symptoms they develop slowly.

YOu can read more here (http://en.wikipedia.org/wiki/Arachnoid_cyst)

Q. Is there any problem, if an arachnoid cyst ,2cmx1.5cm size, rostral to cerebellar region left untreated? symptoms: repeated headaches, twitching of muscles, tiredness

A. An arachnoid cyst that leads to symptoms usually needs treatment. Mild symptoms as you suggested are ok to left untreated however gradual onset of new symptoms may arise such as seizures, paralysis and other complications, therefore once symptoms occur one should consider treatment.

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