Dural sinus filling defect: intrasigmoid encephalocele

Abstract

Filling defects of dural venous sinuses are considered to be a challenging problem especially in case of symptomatic patients. Many lesions have to be ruled out such as sinus thrombosis, arachnoid granulations and tumours. Encephalocele into dural sinus is also a rare cause of these filling defects of dural sinuses. Here, we report an extremely rare case with spontaneous occult invagination of temporal brain tissue into the left sigmoid sinus and accompanying cerebellar ectopia.

Brain Herniation into Arachnoid Granulations: Clinical and Neuroimaging Features

“…Prior to the large systematic study published by Battal et al in 2015, there were only a small number of case series and case reports in the English literature . Battal et al reviewed a total of 6,160 brain MRIs, identifying a total of 21 herniations into the calvarium or dural venous sinuses in 20 patients, establishing a prevalence of 0.32%.…”

“…Arachnoid granulations (AGs) are invaginations of the arachnoid membrane that protrude through gaps in the dura into the dural venous sinuses and occasionally the calvarium. They are functionally and histologically related to arachnoid villi, differing only in size and complexity, providing a route for cerebral spinal fluid (CSF) resorption into the bloodstream . Frequently seen on imaging, AGs are considered normal anatomic structures, though rare cases have been reported that indirectly implicate AGs with symptoms such as headache, tinnitus, CSF otorrhea, and intracranial venous hypertension …”

“…Recently, herniation of brain parenchyma into the dural venous sinuses and calvarium have been reported, sometimes referred to as occult encephaloceles, as the herniation does not extend through the outer cortex of the calvarium or skull base . While it remains to be proven, the association of the herniation with presumed preexisting AGs has been suggested in prior reports.…”

“…Some authors have suggested that the abnormality occurs spontaneously, while others have postulated that intracranial hypertension could be a predisposing condition . Symptoms attributed to these abnormalities are variable and largely anecdotal …”

“…They are functionally and histologically related to arachnoid villi, differing only in size and complexity, providing a route for cerebral spinal fluid (CSF) resorption into the bloodstream. [1][2][3][4] Frequently seen on imaging, AGs are considered normal anatomic structures, though rare cases have been reported that indirectly implicate AGs with symptoms such as headache, tinnitus, CSF otorrhea, and intracranial venous hypertension. [5][6][7][8][9][10][11][12][13][14] Recently, herniation of brain parenchyma into the dural venous sinuses and calvarium have been reported, sometimes referred to as occult encephaloceles, as the herniation does not extend through the outer cortex of the calvarium or skull base.…”