Defects may be congenital or due to aberrant
arachnoid granulations [3, 8].
[14] described a focal brain herniation into a giant
arachnoid granulation located in a DVS which may have developed spontaneously or was induced by elevated intracranial pressure and cerebral edema resulting from prior head trauma.
* According to the other theory,
arachnoid granulations that do not get a venous drain during embryonic development come to lie in a blind end against the inner bony surface of the skull.
Transverse sinus, sigmoid sinus and jugular bulb can normally show asymmetric signal intensity and enhancement and is more frequent on left due to compressive effect of left brachiocephalic vein during respiratory cycle.21
Arachnoid granulations are normal structures that protrude into the dural sinus lumen or lateral lacunae.
postulated that blood clots play the initial role in triggering hypersecretion of CSF and fibrosis of
arachnoid granulations, leading to long-term communicating HCP rather than merely aqueduct obstruction or stenosis [19].
Arachnoid granulations, especially large ones within the transverse and sigmoid sinuses, are also calcified in middle-aged and older people with characteristic appearances.
Communicating hydrocephalus is caused by diminished resorption of CSF at the
arachnoid granulations, leading to an expansion of both the ventricular system and the subarachnoid space.
Transependymal drainage of CSF, followed by medullary venous drainage, supervenes as
arachnoid granulations are not fully matured in the neonate.
Acquired encephaloceles occur as a result of chronic ear disease, aberrant
arachnoid granulations, trauma, and iatrogenic causes.
Arachnoid granulations simulating osteolytic lesions of the calvarium.
Spontaneous CSF temporal bone leakage might occur as a result of an encephalocele or secondary to the development of
arachnoid granulations along the tegmen of the middle ear or mastoid.