arachnoid granulation

Pacchioni-Granulation
im Sinus transversus links: Die typische klar umgrenzte Morphe und die Signalintensität in T1 und T2 wie Liquor lassen eine Sinusthrombose differenzialdiagnostisch ausscheiden. Die Asymmetrie des Sinus transversus (hier links größer rechts) ist ein häufiger Befund, wenngleich meist der rechte Sinus voluminöser ist.
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Spectrum of
lytic lesions of the skull: a pictorial essay. Arachnoid granulations (AGs). Axial computed tomography (CT) images with brain (a) and bone (b) windows showing two well-defined, round-shaped lesions with cerebrospinal fluid (CSF) density, protruding into the calvarium along the right transverse sinus
insightsimaging.springeropen.com • CC-by-4.0
Pacchioni-Granulation
in der Schädelkalotte in der Computertomographie
Wikipedia • CC BY-SA 4.0
editVenous-phase
CT angiography of the head of a 41 year old woman who had cerebral venous sinus thrombosis on previous CT angiographies, but with no remaining thrombosis on the current exam. It shows a pacchionian body in the right transverse sinus.
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Diagrammatic
representation of a section across the top of the skull, showing the membranes of the brain, etc. (Modified from Testut.)
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Arachnoidale
/ Pacchioni"sche Granulation mit (mutmaßlich) kleiner "Enzephalozele": Obere Reihe axial T2, T1 mit Kontrastmittel, 2 Schichten sagittal T1 mit Kontrastmittel. Untere Reihe 2 Ebenen schräg FLAIR (2 mm), koronar T1 ohne und mit Kontrastmittel. Man erkennt die Herniation des Aarachnoidalraums in den Sinus sagittalis superior. Zentral in der Herniation findet sich eine Kontinuität des angrenzenden Cortex wie ein kleiner Zapfen in die Pacchion"sche Granulation hinein. Dies ist eine MR-morphologische Beschreibung und kein histologisch gesicherter Befund.
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Imaging of
skull vault tumors in adults. Calvarial pseudolesions. NECT (a, c–f), T2WI (b), MR venography (g, h). Parasagittal occipital arachnoid granulation (a). Occipital encephalocele (b). Dilated vascular canals and lacunae (c). Hyperostosis frontalis interna (d). Bilateral thinning of the parietal bones (e). Enlarged parietal foramina (f). Congenital sinus pericranii (g). Iatrogenic acquired sinus pericranii from a prior ventricular drainage (h)
insightsimaging.springeropen.com • CC-by-4.0
Radiological
review of skull lesions. Arachnoid granulations. Axial head CT (a) shows well-defined structures along the inner table in the region of the transverse sinus (arrowheads). Axial T1-weighted (b) and axial T2-weighted (c) images demonstrate fluid signal of these structures following CSF along the transverse sinus extending into the occipital bone (arrowheads)
insightsimaging.springeropen.com • Open Access
Diagrammatic
representation of a section across the top of the skull, showing the membranes of the brain, etc.
Wikipedia • Public domain
Arachnoid
granulation • Prominent intraosseous arachnoid granulations (foveolae granulations) - Ganzer Fall bei Radiopaedia
O'Donnell C, Prominent intraosseous arachnoid granulations (foveolae granulations). Case study, Radiopaedia.org (Accessed on 12 Mar 2023) https://doi.org/10.53347/rID-29219 • CC by-nc-sa 3.0 (modified)
Radiopaedia • CC-by-nc-sa 3.0 • de

Arachnoid granulations, also known as Pacchionian granulations, are projections of the arachnoid membrane (villi) into the dural sinuses that allow CSF to pass from the subarachnoid space into the venous system.

Epidemiology

They increase in size and number with age and are seen in approximately two-thirds of patients.

Pathology

Location

They most frequently occur in a parasagittal location with the transverse and superior sagittal sinuses being the most common locations. The granulations typically occur next to the entrance of a superficial draining cortical vein into a sinus (similar to colonic diverticula occurring next to penetrating vessels).

Radiographic features

They are most commonly encountered in radiological practice as incidental osteolytic, sharply circumscribed indolent-appearing lucencies on skull CT or x-rays, or a filling defect in dural venous sinuses, which can be mistaken for dural venous thrombosis.

CT

The granulations are typically of CSF density and protrude into the calvaria or a dural venous sinus causing a filling defect. They may simulate a dural venous sinus thrombosis but are usually easy differentiated given their round well-defined shape and classic location.

MRI

Signal characteristics are generally those of CSF :

  • T1: low signal intensity
  • T2: high signal intensity; iso- or even slightly hyperintense to CSF
  • FLAIR: should attenuate
  • T1 C+ (Gd): no enhancement

Giant granulations (>10 mm) may show atypical MRI signal characteristics, with higher T1 and T2 signal than CSF and incomplete FLAIR signal suppression . Rarely these may cause sinus obstruction .

History and etymology

Arachnoid granulations are named after Antonio Pacchioni (1665-1726), an Italian physician, who wrote extensively on the anatomy of the dura mater, and provided the first written description of his eponymous granulations in 1705 in the Dissertatio Epistolaris de Glandulis Conglobatis Durae Meningis Humanae, one of his monographs .

Differential diagnosis

Considerations include

On CT if there is lytic erosion of the bone also consider

or rarely

See also

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Pacchionische Granulationen:
solitäre
lytische Läsion des Schädels
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Sinusthrombose
 
www.eurorad.org • CC by-nc-sa-4.0
Venae
diploicae
Wikipedia • Public domain
venöse
Kanäle und Lakunen der Kalotte
insightsimaging.springeropen.com • Open Access
Fett in den
intrakranialen venösen Sinus
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