Giant arachnoid granulation in a patient with benign intracranial hypertension

We report magnetic resonance (MR), computed tomography (CT) and angiographic imaging of an unusual giant arachnoid granulation in the superior sagittal sinus in a man with headache and vertigo. Intrasinus pressure measurements revealed a significant pressure gradient across the lesion. MR imaging is useful to identify giant arachnoid granulation and dural sinus thrombosis, whereas dural sinus pressure measurement in certain cases of giant arachnoid granulations can be used to evaluate the lesion as the cause of the patient's symptoms.     

Giant arachnoid granulation in a patient with benign intracranial hypertension (2009: 1b)

We report magnetic resonance (MR), computed tomography (CT) and angiographic imaging of an unusual giant arachnoid granulation 7(GAG) in the superior sagittal sinus in a man with headache and vertigo. Intrasinus pressure measurements revealed a significant pressure gradient across the lesion. MR imaging is useful to identify GAG and dural sinus thrombosis, whereas dural sinus pressure measurement in certain cases of GAGs can be used to evaluate the lesion as the cause of the patient’s symptoms.     

Normal structures in the intracranial dural sinuses: delineation with 3D contrast-enhanced magnetization prepared rapid acquisition gradient-echo imaging sequence

BACKGROUND AND PURPOSE: The potential pitfalls in the diagnosis of dural sinus thrombosis include the presence of arachnoid granulations, intrasinus fibrotic bands (so-called septa), and hypoplasia or aplasia of the dural sinuses. The purpose of this study was to assess the appearance, distribution, and prevalence of arachnoid granulations and septa in the dural sinuses by using a high resolution 3D contrast-enhanced magnetization prepared rapid acquisition gradient-echo (MPRAGE) imaging sequence. METHODS: Conventional MR images and contrast-enhanced MPRAGE images of 100 consecutive patients who had no abnormalities of the dural sinuses were retrospectively reviewed. The incidence, site, number, size, signal intensity, and shape of arachnoid granulations and septa within the sinuses and their relationship with adjacent veins were recorded. RESULTS: With 3D contrast-enhanced MPRAGE imaging, 433 round, oval, or lobulated focal filling defects were found in a total of 90 patients. Curvilinear septa were observed in 92 patients. Sixty-nine patients had round, oval, or lobulated defects in the transverse sinus, 59 had such defects in the superior sagittal sinus, and 47 had such defects in the straight sinus. All except two of the above defects were isointense relative to CSF on all images. These structures were presumed to be arachnoid granulations. Of 431 arachnoid granulations, 233 (53.8%) were located in the superior sagittal sinus, 122 (28.1%) in the transverse sinus, and 76 (17.6%) in the straight sinus. One or more veins were seen to enter arachnoid granulations in 414 (96%) instances. CONCLUSION: The contrast-enhanced 3D MPRAGE imaging sequence showed a much higher prevalence and a different distribution of arachnoid granulations and septa within dural sinuses than have been observed in previous radiologic studies. Arachnoid granulations were closely related spatially to veins.     

MRI of arachnoid granulations within the dural sinuses using a FLAIR pulse sequence

The purpose of the study was to assess the signal intensities of arachnoid granulations within the dural sinuses using the FLAIR sequence for differentiation of space-occupying lesions in and adjacent to the dural sinuses. We retrospectively reviewed MR images of the brain of 1118 consecutive subjects, ranging in age from 0 to 93 years (mean 57.2 years). Nodules within the dural sinuses with signal intensities similar to that of cerebrospinal fluid (CSF) on both T1 and T2 weighted images were defined as arachnoid granulations. The location, signal intensity on T1 weighted spin echo (SE), T2 weighted fast SE and FLAIR images, the impression on the inner table of the skull, and the size of the lesion were assessed. 112 subjects (10.0%), age range 4-89 years old (mean 58.9 years), were found to have 134 arachnoid granulations. The commonest location was the transverse sinus, with 115 granulations (85.8%). The prevalence of the granulations showed a peak in the sixth decade of age. All granulations were isointense relative to CSF on T2 weighted images and almost all lesions were isointense relative to CSF on T1 weighted images. On FLAIR images, 90.3% of the granulations were isointense relative to CSF and the other 9.7% granulations were slightly hyperintense compared with the CSF. 21 (15.7%) subjects showed impressions on the inner table; one case involved the outer table. In conclusion, arachnoid granulations were isointense or slightly hyperintense relative to CSF on FLAIR. FLAIR images are helpful in differentiating arachnoid granulations from other dural sinus lesions or skull lesions which have an intensity similar to that of CSF on T1 weighted and T2 weighted images.     

MR of giant arachnoid granulation,a normal variant presenting as a mass within the dural venous sinus.

We report three cases of masses within the cerebral dural venous sinuses shown with either MR or angiography. The dural venous sinuses of 10 patients without known venous disease were examined at autopsy. In two patients, three giant arachnoid granulations were identified. On the basis of the literature and our limited autopsy series, we suggest that these lesions identified at imaging are giant arachnoid granulations, normal variants of no known clinical significance.     

Anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé: an angiographic study

We studied the anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé in 57 consecutive angiograms. Patients with pathology in intracranial venous structures or with inadequate image quality of the venous system were excluded. Arachnoid granulations were found in 12 of the 57 patients (21.1%), always at the junction of the vein of Labbé and the transverse sinus; the vein of Labbé was present in 55 patients (96.5%), most often without associated arachnoid granulations; the latter, however, were not observed in the absence of a vein of Labbé. This study confirms the close, constant anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbé. This observation may help to differentiate arachnoid granulations from pathologic conditions involving the transverse sinus such as dural sinus thrombosis. The constant character of this relationship suggests a developmental role of afferent veins in the formation of arachnoid granulations.     

Normal appearance of arachnoid granulations on contrast-enhanced CT and MR of the brain: differentiation from dural sinus disease.

PURPOSETo determine the imaging appearance and frequency with which arachnoid granulations are seen on contrast-enhanced CT and MR studies of the brain.METHODSWe retrospectively reviewed 573 contrast-enhanced CT scans and 100 contrast-enhanced MR studies of the brain for the presence of discrete filling defects within the venous sinuses. An anatomic study of the dural sinuses of 29 cadavers was performed, and the location, appearance, and histologic findings of focal protrusions into the dural sinus lumen (arachnoid granulations) were assessed and compared with the imaging findings.RESULTSDiscrete filling defects within the dural sinuses were found on 138 (24%) of the contrast-enhanced CT examinations. A total of 168 defects were found, the majority (92%) within the transverse sinuses. One third were isodense and two thirds were hypodense relative to brain parenchyma. Patients with filling defects were older than patients without filling defects (mean age, 46 years versus 40 years). Discrete intrasinus signal foci were noted on 13 (13%) of the contrast-enhanced MR studies. The foci followed the same distribution as the filling defects seen on CT scans and were isointense to hypointense on T1-weighted images, variable in signal on balanced images, and hyperintense on T2-weighted images. Transverse sinus arachnoid granulations were noted adjacent to venous entrance sites in 62% and 85% of the CT and MR examinations, respectively. Arachnoid granulations were found in 19 (66%) of the cadaveric specimens, in a similar distribution as that seen on the imaging studies.CONCLUSIONDiscrete filling defects, consistent with arachnoid granulations, may be seen in the dural sinuses on 24% of contrast-enhanced CT scans and on 13% of MR studies. They are focal, well-defined, and typically located within the lateral transverse sinuses adjacent to venous entrance sites. They should not be mistaken for sinus thrombosis or intrasinus tumor, but recognized as normal structures.     

Arachnoid granulations in the transverse and sigmoid sinuses: CT,MR, and MR angiographic appearance of a normal anatomic variation.

PURPOSETo investigate the imaging characteristics, prevalence, and clinical significance of arachnoid granulations in the transverse and sigmoid venous sinuses.METHODSWe reviewed the imaging findings, clinical signs and symptoms, final diagnoses, and follow-up studies of 32 patients with 41 probable arachnoid granulations.RESULTSOn CT scans, arachnoid granulations appear as well-defined filling defects, wholly or partly within a venous sinus, with the same density as cerebrospinal fluid. MR images show these entities as largely isointense with cerebrospinal fluid in all sequences. Linear variations of signal intensity within the granulations are thought to be fibrous septa or vessels. Calcification was present in 3 granulations and altered both CT density and MR signal intensity. The granulations appear as filling defects at MR angiography and at digital subtraction angiography. In some oblique MR angiographic projections, they appear elliptical and could be mistaken for thrombus. No clinical significance could be given to the existence of any of these arachnoid granulations. They occur in 0.3 to 1 of 100 adults in the population.CONCLUSIONArachnoid granulations in the transverse and sigmoid venous sinuses are common findings seen with thin-section imaging and are usually of no significance.     

Giant arachnoid granulation mimicking dural sinus thrombosis in a boy with headache: MRI

We report MRI and angiographic findings of an unusual giant arachnoid granulation in the left sigmoid sinus in a boy with headache. Its signal intensity was lower than that of cerebral cortex on T1-weighted images and higher on T2 weighting, mimicking dural sinus thrombosis. Received: 17 February 1997 Accepted: 17 February 1997     

Elimination of metrizamide from the spinal subarachnoid space: a study of patients with abolished intracranial circulation

Two absorptive pathways for contrast media injected into the lumbar subarachnoid space have been postulated: (1) through the intracranial parasagittal arachnoid granulations and (2) direct absorption through the spinal arachnoid villi into the blood. To study the capacity of the spinal absorptive pathway, serial measurements of metrizamide concentrations in blood serum and urine were obtained before and after lumbar intrathecal injection of contrast medium in four patients with arrested intracranial blood circulation ("brain death") and intracranial pressure exceeding systolic blood pressure who had no circulation of cerebrospinal fluid from the spinal subarachnoid space to the parasagittal arachnoid granulations. These measurements indicated a high capacity of the spinal absorptive pathway for metrizamide elimination.     

The postoperative myelogram. Radiographic evaluation of arachnoiditis and dural/arachnoidal tears.

Either arachnoriditis or dural/arachnoidal tears may cause symptoms in the postoperative spinal patient. Surgery and myelography as causes of arachnoiditis are discussed. Intradural arachnoid cyst formation and intramedullary cavitation may present as unusual sequelae of arachnoiditis. Extra-dural cysts and cerebrospinal fluid fistulas resulting from dural/arachnoidal tears are unusual postoperative complications presenting striking myelographic features. Their mechanisms of formation, clinical significance, and radiographic features are discussed.     

颞骨岩锥后壁蛛网膜颗粒的影像学表现

目的:探讨颞骨岩锥后壁蛛网膜颗粒的影像学特征并与其它疾病进行鉴别诊断。方法:回顾性分析5例6耳颞骨岩锥后壁蛛网膜颗粒压迹的HRCT,薄层MRI表现特点。结果:4耳颞骨岩锥后壁蛛网膜颗粒在HRCT上表现为分叶状骨质缺损区,内部均匀低密度,边缘无硬化及钙化,周围无软组织肿块,相邻的前庭导水管及半规管未受累。在薄层MRI上6耳颞骨岩锥后壁蛛网膜颗粒在T1WI、T2WI、FLAIR上表现为与脑脊液相同的信号,并可见其内显示呈放射状分布的细条状的纤维索条影,膜性半规管形态结构未受累。增强后无强化。结论:颞骨岩锥后壁蛛网膜颗粒是见于老年人酷似恶性骨质破坏的正常变异,其特征是所含脑脊液内有纤维分隔,据此能够与此部位的其它病变区别开来。     

Post-dural puncture pseudomeningocele (“arachnoid bleb”): An underrecognized etiology of spontaneous intracranial hypotension symptomatology

Spontaneous intracranial hypotension (SIH) is an important secondary cause of a persistent headache syndrome, classically presenting as sudden onset debilitating positional headaches related to reduced intracranial cerebrospinal fluid (CSF) volume. Current understanding of SIH pathogenesis recognizes three underlying etiologies: dural tear, meningeal diverticulum, and CSF-venous fistula, with a fourth broad category of indeterminate/unknown etiologies. Post-dural puncture headache (PDPH) is a well-known and common complication of dural puncture, typically remitting spontaneously within two weeks of onset or with autologous epidural blood patch, though with some patients developing complex and difficult to manage chronic PDPH. Herein, we present a case of chronic PDPH resulting in SIH symptomatology secondary to a post-dural puncture pseudomeningocele, or “arachnoid bleb,” successfully treated with curative surgical intervention. Increasing awareness of additional potential etiologies of SIH symptomatology will allow for improved detection for targeted definitive therapy, ultimately improving patient outcomes including quality of life in this debilitating and difficult to manage secondary headache syndrome.     

Arachnoid granulations of the posterior temporal bone wall: imaging appearance and differential diagnosis

Arachnoid granulations are rarely seen on high-resolution CT (HRCT) at the posterior temporal bone wall, where they appear as erosions, without bone spicules and often with a lobulated surface. Differential diagnosis includes endolymphatic sac tumor, paraganglioma, chordoma, and chondromatous and metastatic tumors. MR imaging can confirm the diagnosis because arachnoid granulations behave like CSF without gadolinium enhancement. This report aims to illustrate the appearance and differentiation of temporal bone arachnoid granulations on HRCT and MR imaging.     

Abnormal perfusion of the pituitary gland secondary to dural arteriovenous fistulas in the cavernous sinus: dynamic MR findings

BACKGROUND AND PURPOSE: If venous congestion is the primary cause of pituitary gland enlargement in cases of dural arteriovenous fistulas (AVFs), other abnormal pituitary findings may be detectable on MR images. We sought to investigate the perfusion abnormality of the pituitary gland secondary to dural AVFs in the cavernous sinus and to clarify its clinical importance. METHODS: Nine consecutive patients (all female; age range, 50-77 years) with dural AVFs in the cavernous sinus underwent prospective MR examinations, including dynamic studies, before and after therapy. Their clinical signs and symptoms were recorded. Two radiologists visually evaluated the enhancement patterns of the anterior pituitary gland. Dynamic MR curves were obtained by locating regions of interest at the center and bilateral peripheral areas of the anterior pituitary gland on coronal images. MR images obtained in five healthy individuals served as controls. RESULTS: No patient had symptoms of hypopituitarism or other endocrine abnormalities. Asymmetric pituitary enhancement was found in five patients; the side with the dural AVF was less enhancing. This finding disappeared after therapy. Although asymmetric enhancement was not detected in the remaining four patients, statistical analysis showed significantly delayed enhancement of the pituitary gland in the patients compared with enhancement patterns in control subjects. After treatment, this delay improved significantly. The pituitary gland significantly decreased in size after treatment. CONCLUSION: Perfusion of the pituitary gland is impaired in patients with a dural AVF in the cavernous sinus. This finding is probably due to venous congestion of the pituitary gland caused by high pressure in the cavernous sinus; it is usually not related to pituitary dysfunction.     

Large arachnoid granulations involving the dorsal superior sagittal sinus: findings on MR imaging and MR venography

BACKGROUND AND PURPOSE: Large arachnoid granulations (AG) within the dorsal superior sagittal sinus (SSS) have been incompletely characterized and can be confused with pathology. This report reviews the characteristics of these anatomic structures to establish common imaging features that allow differentiation from pathology.MATERIALS AND METHODS: Twelve cases of large AG in the dorsal SSS are presented, identified by MR imaging. Signal intensity characteristics, size, location, venographic appearance, and association with adjacent venous and osseous structures were documented.RESULTS: A defect in the dura of the SSS was seen in all of the cases communicating with the subjacent subarachnoid space. The average size of the AG was 8.1 × 9.4 × 10.0 mm (range, 4–19 mm). Ten produced calvarial remodeling, and 11 were in the direct vicinity of the lambda. On T2-weighted images, all were hyperintense to the brain. On T1-weighted images, 8 were hypointense and 4 were hypointense with mixed areas of isointense signal intensity. All of the AGs were associated with cortical venous structures entering the sinus. On MR venography, AGs appeared as focal protrusions into the sinus, displacing, distorting, and narrowing the sinus lumen. Seven patients had headache without other visible cause on MR imaging, and 4 were initially interpreted as thrombosis or tumor.CONCLUSION: Large AGs can occur in the dorsal SSS. They are well-defined projections of the subarachnoid space into the sinus, can cause luminal narrowing and calvarial remodeling, and have typical signal intensity characteristics, position, and morphology differentiating them from other pathology. Association with patient symptoms is uncertain.

Arachnoid granulations (AGs) are normal structures that can be demonstrated on CT and MR imaging.¹ They typically are identified as CSF attenuation or signal intensity protuberances projecting into the lumen of the dural sinuses.¹ Although most commonly identified on standard imaging studies in the midlateral transverse sinuses (TSs),^2,3 when more detailed high-resolution MR imaging examinations with contrast are used, they can be identified throughout the dural sinuses.⁴ Rarely, large AGs have been described in the dorsal (posterior inferior) superior sagittal sinus (SSS) on imaging^1,5 and on anatomic assessment.⁶ Because of their infrequency and large size, they can be misdiagnosed as a thrombus or tumor in this location.⁵ We have identified 12 cases of large AGs in the dorsal SSS on MR imaging (1.5T and 3T), and describe their appearance on standard MR pulse sequences, time-of-flight MR venography (MRV; TOF-MRV) and contrast-enhanced MRV (CE-MRV). We compared these cases with the few cases reported previously in the literature and established common imaging features that allow differentiation from pathology.     

The controversial entity of brain herniations into arachnoid granulations: A report of three cases with literature review

Brain herniation into arachnoid granulation (BHAG) is a quite recently described controversial entity in terms of both etiology and clinical significance. It comprises a herniation of brain tissue into a presumed preexisting arachnoid granulation in dural venous sinuses, calvarium, meningeal or diploic veins. Most often described as an incidental finding in patients examined for unrelated pathologies, some BHAGs can possibly be related to headache, epilepsy or conditions with increased intracranial pressure such as idiopathic intracranial hypertension (IIH) or pseudotumor cerebri (PTC). The number of reported cases is low and there are only three more recently published observational studies on this subject with results lacking statistical significance due to relatively few BHAGs analyzed. Therefore, BHAGs still need an increased focus from both the radiologists and clinicians and more published studies and cases are necessary to help in understanding their factual meaning, clinical and treatment implications. In this article we describe three new cases of BHAGs to the literature, with patients presenting with different symptoms.     

Adhesive arachnoiditis causing cauda equina syndrome in ankylosing spondylitis: CT and MRI demonstration of dural calcification and a dorsal dural diverticulum

We present the radiological features of a 42-year-old man with long-standing inactive ankylosing spondylitis (AS), demonstrating that arachnoiditis is a cause of a cauda equina syndrome (CES) in this disease. CT showed a dorsal arachnoid diverticulum causing scalloped erosion of the laminae, and punctate and curvilinear dural calcification. MRI revealed adhesion and convergence of the cauda equina dorsally into the arachnoid pouch, causing the dural sac to appear empty canal. To the best of our knowledge, dural calcification on CT is a new finding in AS, which may be related to the CES. Our findings support the hypothesis that chronic adhesive arachnoiditis with subsequent loss of meningeal elasticity may be the main cause of CES in AS. Received: 24 August 1998 Accepted: 2 December 1998     

Multiple dural arteriovenous fistulas of the cranium and spine

Dural arteriovenous fistulas are acquired lesions that usually involve the dura around the cavernous sinus. The transverse, sigmoid, and superior sagittal sinuses may be affected occasionally. With the exception of bilateral cavernous sinus dural arteriovenous fistulas, the simultaneous occurrence of dural arteriovenous fistulas at two locations is rare. Among 105 patients evaluated for dural arteriovenous fistulas, we identified seven patients with fistulas at two sites. The age of the patients ranged from 27 to 74 years. Presentation was related to hemorrhage in three patients, loss of vision in four, and a bruit and headaches in one. Patients were treated with combined surgical and endovascular techniques. All treated lesions were completely closed with no mortality or permanent morbidity. The presence of multiple fistulas must be considered in patients being evaluated for dural arteriovenous fistulas. Patients with multiple fistulas usually present with life-threatening hemorrhages or acute neurologic decline; the risk factor for hemorrhages, including those related to venous outflow obstruction, is high in patients with multiple dural arteriovenous fistulas.     

Human spinal arachnoid villi and granulations

Summary Human spinal arachnoid villi and granulations were studied after distension by a subarachnoid perfusion of Berlin blue and trypan blue. These proliferations were distributed on almost every nerve root in the thoracic and lumbar region. Human spinal arachnoid villi and granulations were divided into those located entirely internal to the dura, those that extended into the dura, and those that penetrated the dura completely. Venous sinuses were closely related to most arachnoid proliferations.This investigation was supported by the National Institutes of Health Research Grant No. 2-RO1-NS09198-04.