Giant Arachnoid Granulations: A Systematic Literature Review

Abstract

Giant arachnoid granulations (GAGs) are minimally investigated. Here, we systematically review the available data in published reports to better understand their etiologies, nomenclature, and clinical significance. In the literature, 195 GAGs have been documented in 169 persons of varied ages (range, 0.33 to 91 years; mean, 43 ± 20 years; 54% female). Prior reports depict intrasinus (i.e., dural venous sinus, DVS) (84%), extrasinus (i.e., diploic or calvarial) (15%), and mixed (1%) GAG types that exhibit pedunculated, sessile, or vermiform morphologies. GAG size ranged from 0.4 to 6 cm in maximum dimension (mean, 1.9 ± 1.1 cm) and encompassed symptomatic or non-symptomatic enlarged arachnoid granulations (≥1 cm) as well as symptomatic subcentimeter arachnoid granulations. A significant difference was identified in mean GAG size between sex (females, 1.78 cm; males, 3.39 cm; p < 0.05). The signs and symptoms associated with GAGs varied and include headache (19%), sensory change(s) (11%), and intracranial hypertension (2%), among diverse and potentially serious sequelae. Notably, brain herniation was present within 38 GAGs (22%). Among treated individuals, subsets were managed medically (19 persons, 11%), surgically (15 persons, 9%), and/or by endovascular DVS stenting (7 persons, 4%). Histologic workup of 53 (27%) GAG cases depicted internal inflammation (3%), cystic change consistent with fluid accumulation (2%), venous thrombosis (1%), hemorrhage (1%), meningothelial hyperplasia (1%), lymphatic vascular proliferation (1%), and lymphatic vessel obliteration (1%). This review emphasizes heterogeneity in GAG subtypes, morphology, composite, location, symptomatology, and imaging presentations. Additional systematic investigations are needed to better elucidate the pathobiology, clinical effects, and optimal diagnostic and management strategies for enlarged and symptomatic arachnoid granulation subtypes, as different strategies and size thresholds are likely applicable for medical, interventional, and/or surgical treatment of these structures in distinct brain locations.

Neuroimaging of Vermiform Giant Arachnoid Granulations in Children

“…Arachnoid granulations (AGs) are membrane outgrowths that play a crucial role in cerebrospinal fluid (CSF) reabsorption [1,3,6,9]. They present in various shapes and sizes and are often incidentally noted in imaging studies of the transverse and superior sagittal sinus [1][2][3][4][5][6][7][8][9]. Giant arachnoid granulations (GAGs), especially their vermiform subtype, pose a unique diagnostic challenge due to their distinctive morphology, often resembling serious pathologies like dural sinus thrombosis, sinus cavernoma, and tumors [1][2][3].…”

“…Arachnoid granulations (AGs) or Pacchionian granulations, named after the Italian physician Antonio Pacchioni (1665-1726) are typically benign, collagen and immune cellrich structures within the subarachnoid space that extend into the dural sinuses and calvarial bone [1][2][3][4][5]. These formations exhibit a wide range of sizes and morphologies and are typically best visualized in MRI studies after 10 years of age [3,6].…”

“…These formations exhibit a wide range of sizes and morphologies and are typically best visualized in MRI studies after 10 years of age [3,6]. Despite a lack of consensus in the literature, they are typically termed 'giant' arachnoid granulations (GAGs) when their size exceeds 1 cm in diameter, or they occupy a significant portion of a dural sinus' lumen [1][2][3][4][5]7]. Within the spectrum of GAGs exist the vermiform giant arachnoid granulations, characterized by their distinctive worm-like appearance [2,3].…”

“…Despite a lack of consensus in the literature, they are typically termed 'giant' arachnoid granulations (GAGs) when their size exceeds 1 cm in diameter, or they occupy a significant portion of a dural sinus' lumen [1][2][3][4][5]7]. Within the spectrum of GAGs exist the vermiform giant arachnoid granulations, characterized by their distinctive worm-like appearance [2,3]. Because of their variability in presentation, AGs and GAGs present a unique diagnostic challenge as they can mimic pathologies such as dural sinus thrombosis, sinus cavernoma, and tumors like meningiomas or metastatic invasions of the sinus [1][2][3]8].…”

“…Within the spectrum of GAGs exist the vermiform giant arachnoid granulations, characterized by their distinctive worm-like appearance [2,3]. Because of their variability in presentation, AGs and GAGs present a unique diagnostic challenge as they can mimic pathologies such as dural sinus thrombosis, sinus cavernoma, and tumors like meningiomas or metastatic invasions of the sinus [1][2][3]8]. This case report aims to present and elucidate the imaging characteristics and differential diagnoses of vermiform GAGs to assist clinicians in accurately identifying these formations and prevent both misdiagnoses and improper management.…”