Brain herniations into the dural venous sinuses or calvarium: MRI of a recently recognized entity

Imaging of Skull Base Tumors

The skull base provides a platform for supporting the brain while serving as a conduit for major neurovascular structures. In addition to malignant lesions originating in the skull base, there are many benign entities and developmental variants that may simulate disease. Therefore, a basic understanding of the relevant embryology is essential. Lesions centered in the skull base can extend to the adjacent intracranial and extracranial compartments; conversely, the skull base can be secondarily involved by primary extracranial and intracranial disease. CT and MRI are the mainstay imaging methods and are complementary in the evaluation of skull base lesions. Advances in cross-sectional imaging have been crucial in the management of patients with skull base pathology, as this represents a complex anatomical area that is hidden from direct clinical exam. Furthermore, the clinician must rely on imaging studies for therapy planning and to monitor treatment response. It is crucial to have a thorough understanding of skull base anatomy and its various pathologies, as well as to recognize the appearance of treatment-related changes. In this review, we aim to describe skull base tumors and tumor-like lesions in an anatomical compartmental approach and present imaging methods that aid in diagnosis, management, and follow-up.

Diagnostic performance of MR black-blood thrombus imaging for cerebral venous thrombosis in real-world clinical practice

OBJECTIVES

MR black-blood thrombus imaging (BTI) has been developed for the detection of cerebral venous thrombosis (CVT). Yet, there is a lack of real-world data to verifying its clinical performance. This study aims to evaluate the performance of BTI in diagnosing and staging CVT in a 5-year period.

METHODS

Patients suspected of CVT were enrolled between 2014 and 2019. Patients with or without BTI scans were classified into group A and group B, respectively. The prevalence of correct diagnosis of CVT and patients with evaluable clot age were compared. The diagnostic performance of BTI including sensitivity, specificity, and specific staging information was further analyzed.

RESULTS

Two hundred and twenty-one of the 308 patients suspected of CVT were eligible in the current study (114 in group A and 97 in group B), with 125 diagnosed by multidisciplinary teams to have CVTs (56 in group A, 69 in group B). The rate of correct diagnosis of CVT was higher in group A than that in group B (94.7% vs 60.8%, p < 0.001, x² = 36.517) after adding BTI images. The percent of patients with evaluable staged segments between the two groups were 96.4% and 33.9%, respectively (x² = 48.191, p < 0.001). BTI showed a sensitivity of 96.4% and 87.9% in the detection of CVT on per-patient and per-segment level, respectively. Up to 98.1% of all thrombosed segments could be staged by BTI and 59.6% of them were matched with clinical staging.

CONCLUSIONS

In the actual clinical practice, BTI improves diagnostic confidence and has an excellent performance in confirming and staging CVT.

KEY POINTS

• Black-blood thrombus imaging has good diagnostic performance in detecting cerebral venous thrombosis compared to traditional imaging methods with strong evidence in the actual clinical setting. • BTI helps clinicians to diagnose CVT with more accuracy and confidence, which can be served as a promising imaging examination. • BTI can also provide additional information of different thrombus ages objectively, the valuable reference for clinical strategy.

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.

Temporal encephalocele into transverse sinus in an adult with partial seizures: MRI evaluation of a rare site of brain herniation

Herniation of brain parenchyma outside its normal enclosure (also known as encephalocele) has long been known to occur at certain classic sites and is classified accordingly. With widespread use of modern neuroimaging, the previously unknown atypical and rare sites of encephalocele have now been identified. Brain herniation into a dural venous sinus is one such recently described entity with case reports extending only upto the earlier part of this decade. With no definite clinical symptomatology, imaging is crucial to diagnose this lesion accurately and differentiate it from the more familiar entity in this region of the brain, the arachnoid granulations. Also known as occult encephalocele, focal brain herniation into dural venous sinus has few specific imaging features and characteristic sites. We report a case of a 21-year-old man with partial seizures in whom MRI of the brain revealed focal herniation of the normal temporal lobe parenchyma into the left transverse sinus and discuss the key imaging features and pathophysiology of this entity.

MR Imaging Features of Middle Cranial Fossa Encephaloceles and Their Associations with Epilepsy

BACKGROUND AND PURPOSE

Middle cranial fossa encephaloceles are an increasingly recognized cause of epilepsy; however, they are also often encountered on neuroimaging in patients with no history of seizure. We characterized the MR imaging features of middle cranial fossa encephaloceles in seizure and nonseizure groups with the hope of uncovering features predictive of epileptogenicity.

MATERIALS AND METHODS

Seventy-seven patients with middle cranial fossa encephaloceles were prospectively identified during routine clinical practice of neuroradiology at a tertiary care hospital during an 18-month period. Thirty-five of 77 (45%) had a history of seizure, 20/77 (26%) had temporal lobe epilepsy, and 42/77 (55%) had no history of seizures. Middle cranial fossa encephalocele features on MR imaging were characterized, including depth, area, number, location, presence of adjacent encephalomalacia, and degree of associated parenchymal morphologic distortion. MR imaging features were compared between the seizure and nonseizure groups.

RESULTS

No significant difference in MR imaging features of middle cranial fossa encephaloceles was seen when comparing the seizure and nonseizure groups. Comparison of just those patients with temporal lobe epilepsy (n = 20) with those with no history of seizure (n = 42) also found no significant difference in MR imaging features.

CONCLUSIONS

Anatomic MR imaging features of middle cranial fossa encephaloceles such as size, number, adjacent encephalomalacia, and the degree of adjacent parenchymal morphologic distortion may not be useful in predicting likelihood of epileptogenicity.

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.

Post-Traumatic Occipital Intradiploic Encephalocele

BACKGROUND

Brain parenchyma herniation through a disrupted inner table into an enlarged diploic cavity with an intact outer table is described as intradiploic encephalocele. Intradiploic encephaloceles share common morphologic characteristics with expanding skull fractures and intradiploic arachnoid cysts. Herein, we describe a case of traumatic occipital intradiploic encephalocele.

CASE DESCRIPTION

Cranial computed tomography of an 11-year-old boy revealed erosion of the inner table of the left side of occipital bone and expansion of the cranial diploë by a soft-tissue density with a gyral pattern. His medical history was positive for head trauma at the age of 3 years to the same region. Magnetic resonance imaging showed herniation of left occipital parenchyma with cystic encephalomalacic changes into the diploë.

CONCLUSIONS

Intradiploic encephaloceles have different features compared with the classic encephalocele and can be considered as a variant of expanding skull fracture and intradiploic arachnoid cyst.

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.

Spontaneous bilateral and concurrent cerebrospinal fluid otorrhoea: case presentation and literature review

BACKGROUND

Cerebrospinal fluid otorrhoea is a rare entity. Only a few cases of spontaneous bilateral cerebrospinal fluid otorrhoea have been reported. In all cases, there was a definite time interval between the two (left and right) presentations.

OBJECTIVES

To raise awareness and report on the very rare entity of bilateral spontaneous cerebrospinal fluid otorrhoea.

CASE REPORT

This paper reports the case of a bilateral, synchronous, spontaneous cerebrospinal fluid otorrhoea in a 44-year-old female. The patient had grommets surgically inserted on two separate occasions for treatment of otitis media with effusion, and received several courses of oral and topical antibiotics. Five years following the patient's initial presentation, a suspicion of concurrent bilateral cerebrospinal fluid otorrhoea was raised. The otorrhoea sample collected proved to be cerebrospinal fluid. Cross-sectional imaging revealed bilateral defects in the tegmen tympani of the skull base. She underwent staged middle fossa craniotomies to repair the defects.

CONCLUSION

Careful observation of the middle-ear fluid characteristics following myringotomy can allow for prompt diagnosis.

Temporal Lobe Parenchyma Herniation into the Transverse Sinus: MRI Findings in a Case

Brain parenchyma herniation into dural venous sinus which is a uncommon entity, can cause dural venous sinus filling and simulate sinus thrombosis and other pathologies. It is isointense to brain parenchyma on all sequences by magnetic resonance imaging, surrounded by a cerebrospinal fluid rim and is seen to be contiguous with brain tissue on images. We report a rare case with spontaneous occult herniation of temporal lobe tissue into the left transverse sinus that may associated with headache.