Brain herniations into arachnoid granulations: about 68 cases in 38 patients and review of the literature

Epilepsy in a Patient With Brain Herniation Into the Arachnoid Granulation

This case report describes epilepsy in a 50-year-old patient with brain herniation into the arachnoid granulation.

Efficacy of Dural Sinus Quantitative Measurements in Idiopathic Intracranial Hypertension : A Practical Diagnostic Feature

BACKGROUND AND PURPOSE

This study aimed to investigate the potential contribution of quantitative measurements of dural venous sinuses to the diagnosis of idiopathic intracranial hypertension (IIH) and the relationship between IIH and dural venous sinus dimensions on 3D post-gadolinium T1-weighted magnetic resonance (MR) images.

MATERIAL AND METHODS

A total of 129 individuals (57 IIH patients and 72 controls) who complained of headache and underwent both magnetic resonance venography (MRV) and precontrast/postcontrast 3D T1-weighted MR imaging between 2018 and 2021 were included in this retrospective study. Dural venous sinus and jugular vein diameters were measured in all cases using post-gadolinium 3D T1 TFE images. The presence of transverse sinus (TS) hypoplasia and occipital sinus variation, the number and size of arachnoid granulations in the TS, and the presence of brain parenchymal herniation were also evaluated. Cut-off values that maximized accurate diagnosis of IIH were established on the receiver operating characteristic curve. The sensitivity and specificity of the diagnosis of IIH based on quantitative measurements of the dural sinus were calculated.

RESULTS

The ratios of the maximum to minimum TS diameters and the minimum TS diameters to minimum sigmoid sinus (SS) diameters were significantly higher in IIH patients than in the control group (p < 0.001). The diagnostic sensitivity and specificity values of TS_max/TS_min and TS_{min sum}/SS_{min sum} parameters for the detection of IIH were 84.2%, 84.7% and 83.3%, 84.2%, respectively.

CONCLUSION

Practical measurements from multiplanar T1 sequences can be useful for both quantitative assessment and overcoming misinterpretation due to anatomical variation.

Brain herniation (encephalocele) into arachnoid granulations: prevalence and association with pulsatile tinnitus and idiopathic intracranial hypertension

PURPOSE

Brain herniation into arachnoid granulations (BHAG) of the dural venous sinuses is a recently described finding of uncertain etiology. The purpose of this study was to investigate the prevalence of BHAG in a cohort of patients with pulsatile tinnitus (PT) and to clarify the physiologic and clinical implications of these lesions.

METHODS

The imaging and charts of consecutive PT patients were retrospectively reviewed. All patients were examined with MRI including pre- and post-contrast T1- and T2-weighted sequences. Images were reviewed separately by three blinded neuroradiologists to identify the presence of BHAG. Their location, signal intensity, size, presence of arachnoid granulation, and associated dural venous sinus stenosis were documented. Clinical records were further reviewed for idiopathic intracranial hypertension, history of prior lumbar puncture, and opening pressure.

RESULTS

Two hundred sixty-two consecutive PT patients over a 4-year period met inclusion criteria. PT patients with BHAG were significantly more likely to have idiopathic intracranial hypertension than PT patients without BHAG (OR 4.2, CI 1.5-12, p = 0.006). Sixteen out of 262 (6%) patients were found to have 18 BHAG. Eleven out of 16 (69%) patients had unilateral temporal or occipital lobe herniations located in the transverse sinus or the transverse-sigmoid junction. Three out of 16 (19%) patients had unilateral cerebellar herniations and 2/16 (13%) patients had bilateral BHAG.

CONCLUSION

In patients with PT, BHAG is a prevalent MRI finding that is strongly associated with the clinical diagnosis of IIH. The pathogenesis of BHAG remains uncertain, but recognition should prompt comprehensive evaluation for IIH.

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.

Tissue damage in herniated brain parenchyma into giant arachnoid granulations: demonstration with high resolution MRI

BACKGROUND

Brain herniation (BH) into arachnoid granulation has been remarkable in recent years.

PURPOSE

To evaluate the damage in herniated parenchyma into the giant arachnoid granulation (GAG) and to investigate the clinical-demographic importance of this damage.

MATERIAL AND METHODS

Patients with BH into GAG were retrospectively included in the study. Each of the patients had at least one high-resolution 3D magnetic resonance imaging (MRI) sequence. The arachnoid granulation dimensions, locations, and origin of herniated parenchyma were evaluated by two experienced radiologists. The demographic and symptomatic features of the patients were recorded from the hospital database.

RESULTS

A total of 27 patients (21 females, 6 males; age range 6-71 years; mean age 41.3 years) were found to contain BH into GAG. It was most commonly seen in the transverse sinus (67%); the origin was most common in the cerebellar parenchyma (56%). Abnormal signal and morphology were detected in herniated parenchyma in 11 (47%) patients, atrophy in six, and atrophy and gliosis in five. The most common complaints were headache (47%), while other frequent symptoms were vertigo (15%) and blurred vision (11%). There was a statistically significant positive correlation between frequency of damage in herniated brain parenchyma and the maximal size of GAG (P<0.05).

CONCLUSION

In patients with BH into GAG, parenchymal damage may be associated with various symptoms, such as headache and vertigo, although they have not been statistically proven. It is important to carefully evaluate hernia tissue, as the risk of tissue damage may increase in larger GAGs.

Transverse sinus stenting for treatment of papilloedema secondary to a large brain herniation into a dural venous sinus with associated tectal plate lesion: Case report and literature review

Brain herniation into a dural venous sinus is a rare entity of unknown clinical significance without a clear relationship to raised intracranial pressure. There are yet to be detailed reports of interventional neuroradiology procedures involving sinus stenting across brain herniations. The authors of this paper present the first case of a stent placed across a large brain herniation into the transverse sinus in a patient with a tectal plate lesion and features of chronically raised intracranial pressure. This case demonstrates objective resolution of papilloedema and venous sinus pressure gradient at six months without complication.

Venous sinus stenting as a treatment approach in patients with idiopathic intracranial hypertension and encephaloceles

BACKGROUND

Stenosis of a dural venous sinus is the most common cause of idiopathic intracranial hypertension (IIH) and can be classified as either intrinsic or extrinsic. Intrinsic stenoses are characterized by a focal filling defect within the sinus secondary to an enlarged arachnoid granulation or fibrous septa while extrinsic stenoses tend to be long and smooth-tapered and are most commonly secondary to external compression from the adjacent brain parenchyma. Brain herniations, or encephaloceles, into arachnoid granulations in dural venous sinuses have rarely been reported in the literature in patients with IIH. We propose that dural venous sinus stenting (VSS) may be a safe and effective treatment approach in patients with an encephalocele and IIH.

METHODS

We retrospectively analyze three cases of patients with encephalocele who underwent VSS for treatment of medically refractory IIH at our institution.

RESULTS

One patient underwent stenting ipsilateral and two patients underwent stenting contralateral to the side of their encephaloceles. No technical related issues or complications occurred during either of the three stenting procedures. Two out of the three patients had complete resolution in their IIH-related symptoms and normalization of cerebrospinal (CSF) pressures shortly after stenting. We await clinical follow-up in the third patient.

CONCLUSIONS

Our results suggest that VSS is a technically feasible and effective approach in treating patients with medically refractory IIH and encephaloceles.

Role of diffusion-weighted imaging in the diagnosis of cerebral venous thrombosis

OBJECTIVE

To evaluate the hyperintense signal (HIS) performance on diffusion-weighted imaging (DWI) in diagnosing cerebral venous thrombosis (CVT).

METHODS

Seventy-eight patients with CVT hospitalized from January 2004 to January 2015 were retrospectively studied alongside 78 controls without intracranial organic diseases. Diagnostic accuracy indices of HIS on DWI or T2-weighted imaging (T2WI) to diagnose CVT at different sites and states were analyzed.

RESULTS

The overall sensitivity of HIS on DWI for the diagnosis of CVT was significantly lower than that of HIS on T2WI (34.6% vs. 79.5%). HIS on T2WI was more sensitive than HIS on DWI in detecting thrombosis, especially in the superior sagittal sinus and transverse sinus. HIS on DWI was inversely related to the time between disease onset and imaging. Compared with HIS on T2WI, combining HIS on DWI and T2WI did not increase the sensitivity for detecting CVT. HIS on DWI was not detected in the control group, but HIS on T2WI was detected in 26.3% of control individuals. The specificity of HIS on DWI for CVT was higher than that of HIS on T2WI (97.4% vs. 76.9%).

CONCLUSION

HIS on DWI has a lower sensitivity, but a higher specificity, than HIS on T2WI for diagnosing CVT.

Prevalence of Asymptomatic Middle Cranial Fossa Floor Pits and Encephaloceles on MR Imaging

BACKGROUND AND PURPOSE

Temporal lobe encephaloceles are increasingly identified and treated as epileptogenic foci. However, there is relatively scant research on the prevalence of asymptomatic encephaloceles. This study set out to describe the frequency of incidental temporal lobe encephaloceles and middle cranial fossa pits.

MATERIALS AND METHODS

A retrospective review was completed of high-resolution (≤0.5-mm section thickness) axial T2WI for internal auditory canal protocol imaging. The presence and laterality of middle cranial fossa pits (small bony defects containing CSF) and encephaloceles (brain parenchyma protrusion through osseous defects with or without bony remodeling) were recorded. Electronic medical records of patients with encephaloceles were searched for a history of seizure.

RESULTS

A total of 203 patients were included in the final cohort; 106 (52.2%) women. Forty-five (22.2%) patients had middle cranial fossa pits: 14 (31.1%) unilateral on the right, 17 (37.8%) unilateral on the left, and 14 (31.1%) bilateral. Ten (5.0%) patients had ≥1 encephalocele, none of whom had a documented history of seizure in the electronic medical record. No significant difference was noted in the frequency of pits or encephaloceles based on sex (P = .332 and P = .383, respectively) or age (P = .497 and P = .914, respectively).

CONCLUSIONS

Incidental middle cranial fossa pits are common findings, and their prevalence is not related to age or sex. Temporal lobe encephaloceles, though rarer, also exist occasionally among asymptomatic patients. Such findings have diagnostic implications for encephaloceles identified during imaging work-up for epilepsy.

Brain herniation into the transverse sinuses' arachnoid granulations in the pediatric population investigated with 3 T MRI

We aimed to evaluate the frequency, radiological-clinical findings of brain herniation into arachnoid granulation (BHAG) in pediatric age group using 3 T magnetic resonance imaging. Patients were under 18 years of age and underwent brain MRI examination which consists of 3D T1, 3D T2 FLAIR and 3D T2 sequences. A total of 2320 patients were enrolled in the study. All cases of AG into transverse sinus were included. The location of the AG, the deep, transverse, vertical and neck diameters and volume of AG were recorded. Clinical findings and imaging findings of patients were also recorded. The patients were categorized as BHAG and AG without brain herniation (AGWBH). The mean diameters (deep, transverse, vertical and neck) of AG, volume of AG, age, sex, clinical findings and imaging findings were evaluated and compared in each group. 135 patients (71 female, 64 male) had AG in a total of 2320 patients (prevalence 5.81%). Fifteen patients (10.7% of all patients, 11 female, 4 male) had BHAG. The mean diameters (deep, transverse, vertical and neck) and volume of AGWBH were 5.23 ± 1.91, 4.07 ± 1.58, 4.99 ± 1.68, 3.64 ± 1.84 mm and 85.05 ± 89.10 mm³, respectively. The mean diameters (deep, transverse, vertical and neck) and volume of BHAG were 7.46 ± 2.6, 6.85 ± 2.34, 8.32 ± 2.35, 5.41 ± 1.79 mm and 331 ± 361.26 mm³, respectively. The mean diameters and volume of BHAG were significantly larger than AGWBH (p < 0.001 for all parameters). There was no significant difference related to clinical and imaging findings between groups (p > 0.05). Brain herniation into arachnoid granulation is seen in pediatric age group as frequently as adults. Its frequency is not related to age. It is not significantly associated with neurological symptoms. As the AG size increases, the risk of BHAG increases.

The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri

BACKGROUND AND PURPOSE

Transverse sinus stenosis can lead to pseudotumor cerebri syndrome by elevating the cerebral venous pressure. The occipital emissary vein is an inconstant emissary vein that connects the torcular herophili with the suboccipital veins of the external vertebral plexus. This retrospective study compares the prevalence and size of the occipital emissary vein in patients with pseudotumor cerebri syndrome with those in healthy control subjects to determine whether the occipital emissary vein could represent a marker of pseudotumor cerebri syndrome.

MATERIALS AND METHODS

The cranial venous system of 46 adult patients with pseudotumor cerebri syndrome (group 1) was studied on CT venography images and compared with a group of 92 consecutive adult patients without pseudotumor cerebri syndrome who underwent venous assessment with gadolinium-enhanced 3D-T1 MPRAGE sequences (group 2). The presence of an occipital emissary vein was assessed, and its proximal (intraosseous) and distal (extracranial) maximum diameters were measured and compared between the 2 groups. Seventeen patients who underwent transverse sinus stent placement had their occipital emissary vein diameters measured before and after stent placement.

RESULTS

Thirty of 46 (65%) patients in group 1 versus 29/92 (31.5%) patients in group 2 had an occipital emissary vein (P < .001). The average proximal and distal occipital emissary vein maximum diameters were significantly larger in group 1 (2.3 versus 1.6 mm, P <.005 and 3.3 versus 2.3 mm, P < .001). The average maximum diameters of the occipital emissary vein for patients who underwent transverse sinus stent placement were larger before stent placement than after stent placement: 2.6 versus 1.8 mm proximally (P < .06) and 3.7 versus 2.6 mm distally (P < .005).

CONCLUSIONS

Occipital emissary veins are more frequent and larger in patients with pseudotumor cerebri syndrome than in healthy subjects, a finding consistent with their role as collateral venous pathway in transverse sinus stenosis. A prominent occipital emissary vein is an imaging sign that should raise the suspicion of pseudotumor cerebri syndrome.

Brain Herniation into Giant Arachnoid Granulation: An Unusual Case

Arachnoid granulations are structures filled with cerebrospinal fluid (CSF) that extend into the venous sinuses through openings in the dura mater and allow the drainage of CSF from subarachnoid space into venous system. Usually they are asymptomatic but can be symptomatic when large enough to cause sinus occlusion. We report a rare case of a brain herniation into a giant arachnoid granulation in an asymptomatic elderly male patient, which was discovered incidentally.