An unusual vermiform giant arachnoid granulation

Abstract

Arachnoid granulations are outpouchings of arachnoid membrane which extend into the dural sinuses or calvarium, surrounded by a capsule of dense connective tissue. Within dural sinuses, these appear as well-defined, nodular, rounded, or ovoid structures of focal localization. However, it is important to be aware of their variability in presentation in order to correctly identify them and distinguish them from other dural sinus pathology, especially a misdiagnosis of venous sinus thrombosis with risks of unnecessary anticoagulation, intravascular thrombolysis/thrombectomy, or invasive intracranial pressure monitoring. Here we demonstrate a case of a previously unreported giant intrasinus arachnoid granulation of an unusual vermiform morphology, unduly elongated up to 6 cm in length, involving a significant segment of the superior sagittal sinus. The proof of this diagnosis was the radiologic appearance on multiple modalities and an unchanged appearance over the long-term.

Giant Arachnoid Granulations: A Systematic Literature Review

“…The published literature from 1973 to 2023 yielded 41 publications describing GAGs in 169 persons [ 3 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] ( Table S1 ). This incorporated reports of 146 persons each with a single GAG; 21 persons with at least two GAGs [ 7 , 8 , 9 , 10 , 11 ]; and 2 persons who each exhibited “multiple” GAGs, with three [ 12 ] or four [ 8 ] GAGs being discernible on presented imaging.…”

“…Analyses among these cases revealed no statistically significant difference in mean age across male versus female individuals (females, 38 years; males, 45 years). However, a statistically significant difference was noted for GAG diameter across sex (females, 1.78 cm; males, 3.39 cm; p < 0.05) [ 3 , 13 , 15 , 16 , 20 , 23 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. GAGs also varied in shape.…”

“…GAGs also varied in shape. Typically, GAGs were well-defined, nodular, round-to-ovoid structures, but others were irregular and a discrete, oblong vermiform shape was also characterized in one person (1%) [ 31 ].…”

Supracerebellar infratentorial resection of a torcular lesion causing fulminant intracranial hypertension: illustrative case

“… 14 One report has described a large vermiform arachnoid granulation 6 cm in length, although this was an incidental finding. 9 A second report described a patient with symptoms of IIH who had an arachnoid granulation causing a large sinus pressure gradient (16 cmH 2 O). Venous stenting of this lesion led to symptomatic improvement.…”

Non-neoplastic intracranial cystic lesions: not everything is an arachnoid cyst

“…They often have a parasagittal location, at the confluence of the sinuses. The absence of contrast filling can erroneously be interpreted as a possible cerebral venous thrombosis ( 17 ) ( Figure 13 ).…”