Arachnoid cyst MRI: Difference between revisions

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Revision as of 21:19, 26 June 2020

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: José Eduardo Riceto Loyola Junior, M.D.[2]

Overview

On brain/spine MRI, arachnoid cysts are characterized by cystic images with similar density to CSF and non-enhancing borders, mostly found in the middle cranial fossa while they only rarely occur in the spinal cord. MRIs are more adequate than CT scans for evaluating arachnoid cysts.

MRI

MRIs are better to diagnose and evaluate the extent of the arachnoid cyst than the CT Scan
Demonstrate the exact location, extent, and relationship of the cyst;
Can differentiate arachnoid from epidermoid cysts (arachnoid cysts are identical to CSF, while epidermoid present a higher signal with FLAIR and reduced diffusion with DWI, making them appear brighter than CSF).
CSF signal is seen within the cyst;
Eventually, arachnoid cysts may contain proteinaceous fluid or blood, which can cause diagnostic confusion.^[1]

Differential Diagnosis

Arachnoid cysts differential diagnosis^[2]
Intraventricularly:	Colloid cysts
Intraparenchymally:	Parasitic infections, cystic metastases
Porencephalic cysts
Craniopharyngiomas
Holoprosencephalies
Agenesis of corpus callosum
Defect in the hemispheral cleavage
Dandy-Walker complex (posterior fossa cysts)

MRI Images

(Images courtesy of RadsWiki)

Patient #1: Left middle cranial fossa arachnoid cyst

Cor T2
Sag T1
Axial T1 FLAIR
Axial T2

Patient #2: CT and MR images demonstrate a hemorrhagic arachnoid cyst

CT
Sag T1
Ax T1
Ax FLAIR
Ax T2
Ax T1 with GAD

References

↑ "Arachnoid Cysts". MedPix. 06/26/2020. Check date values in: |date= (help)
↑ Cincu, Rafael, Amit Agrawal, and Jose Eiras. "Intracranial arachnoid cysts: current concepts and treatment alternatives." Clinical neurology and neurosurgery 109.10 (2007): 837-843.

[1] "Arachnoid Cysts". MedPix. 06/26/2020. Check date values in: |date= (help)

[2] Cincu, Rafael, Amit Agrawal, and Jose Eiras. "Intracranial arachnoid cysts: current concepts and treatment alternatives." Clinical neurology and neurosurgery 109.10 (2007): 837-843.

[1]

[2]

@@ Line 4: / Line 4: @@
 ==Overview==
-Diagnosis is principally by [[Magnetic resonance imaging|MRI]].  Frequently, arachnoid cysts are incidental findings on MRI scans performed for other clinical reasons.  In practice, diagnosis of symptomatic arachnoid cysts requires symptoms to be present, and many with the disorder never develop symptoms.
+On brain/spine MRI, arachnoid cysts are characterized by cystic images with similar density to CSF and non-enhancing borders, mostly found in the middle cranial fossa while they only rarely occur in the spinal cord. MRIs are more adequate than CT scans for evaluating arachnoid cysts.
 ==MRI==
-MRI can demonstrate the exact location, extent, and relationship of the cyst, as well as differentiate arachnoid from epidermoid cysts. CSF signal is seen within the well-defined cyst on all sequences. Epidermoids also may have a signal identical or very similar to that of arachnoid cyst on T1-weighted and T2-weighted images. To differentiate this from arachnoid cysts FLAIR as well as diffusion weighted sequences are used. On the FLAIR sequence, , an arachnoid cysts follow the CSF signal, so no signal seen, while there is a higher signal with FLAIR in epidermoid cysts. With DWI, diffusion is reduced within epidermoids, which then appear brighter than CSF, but for arachnoid cysts the signal intensity is low. In some instances though, arachnoid cysts may contain proteinaceous fluid or blood, and signal loss on DWIs may not be marked, which can cause diagnostic confusion. Plain radiographic findings are nonspecific and are not valuable offer in the diagnosis of arachnoid cysts, except for changes in skull contour due to large cysts. Large arachnoid cysts should be considered for serial scans because they may show progressive enlargement, and patients may become candidates for surgical consideration. Indications for surgical intervention include hydrocephalus and increased intracranial pressure. Surgery for asymptomatic cysts is controversial.
+* MRIs are better to diagnose and evaluate the extent of the arachnoid cyst than the CT Scan
+* Demonstrate the exact location, extent, and relationship of the cyst;
+* Can differentiate arachnoid from epidermoid cysts (arachnoid cysts are identical to CSF, while epidermoid present a higher signal with FLAIR and reduced diffusion with DWI, making them appear brighter than CSF).
+* CSF signal is seen within the cyst;
+* Eventually, arachnoid cysts may contain proteinaceous fluid or blood, which can cause diagnostic confusion.<ref>{{Cite web|url=https://medpix.nlm.nih.gov/case?id=9c946ba2-4e56-458a-a20b-bd3092a4704e|title=Arachnoid Cysts|last=|first=|date=06/26/2020|website=MedPix|archive-url=|archive-date=|dead-url=|access-date=}}</ref>
+<br />
 === Differential Diagnosis ===
 {| class="wikitable"