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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.

Sturge-Weber syndrome (SWS) is a neurocutaneous syndrome characterized by a facial nevus flammeus associated with seizures, developmental delay, and, often, with hemiparesis and hemianopia. On MRI, the most characteristic finding has been reported to be leptomeningeal enhancement, believed to represent leakage of contrast medium through the anomalous pial vessels that characterize the disease. We present a case of SWS with no evidence of leptomeningeal enhancement. This case illustrates that leptomeningeal enhancement need not be present in SWS, and the absence of this characteristic finding does not preclude the diagnosis.

Our goal was to find MRI signs of use for identifying a spinal arachnoid diverticulum. Three cases of spinal arachnoid diverticula, one extradural and two intradural, were examined on a 1.5 T imager. There was obvious mass effect on the adjacent structures in one case and increased signal intensity in the diverticulum on proton density- and T2-weighted images in two cases. Signal changes due to turbulent movement of the spinal fluid inside the diverticula were seen in all cases on sagittal fast spin-echo (FSE) proton density- and T2-weighted images; it was difficult to tell whether these signal changes imply a communication or are simply FSE artefacts. On contrast-enhanced studies, all cases showed partial enhancement inside the diverticula. There thus are four signs of diverticula: mass effect, the increased signal, signal void sign and partial enhancement; the last of these, the most reliable, has never been reported before.

Extradural arachnoid cysts are uncommon expanding lesions in the spinal canal which may communicate with the subarachnoid space. Usually in the lower thoracic spine, they may cause symptoms by compressing the spinal cord or nerve roots. We report cases of thoracic and lumbar arachnoid cysts studied by cystography, myelography, CT and MRI. These techniques showed extradural cystic lesions containing cerebrospinal fluid, with variable communication with the subarachnoid space, causing anterior displacement and flattening of the spinal cord.

We report CT, MRI and angiographic findings of an arachnoid granulation in the straight sinus in a young man. Its density and signal intensity were isodense and isointense with cerebrospinal fluid on CT and MRI, respectively. The lesion appeared as a filling defect on MR venography and conventional angiography.

We describe a young woman with a glioblastoma multiforme in whom angiography showed multiple intracranial stenoses. The resected tumour was found to be invading cerebral vessels.

We studied the anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbe 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 Labbe and the transverse sinus; the vein of Labbe 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 Labbe. This study confirms the close, constant anatomic relationship between arachnoid granulations in the transverse sinus and the termination of the vein of Labbe. 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.

Leptomeningeal contrast enhancement (LMCE) is one of the MRI features of moyamoya. Its clinical significance, however, is not elucidated. Our purpose was to characterise LMCE on MRI and to evaluate its role in the assessment of circulation through a surgically established bypass in moyamoya. We studied 16 patients with idiopathic moyamoya (seven males, nine females, includingt four children, aged 7 to 54 years, mean 24 years) who underwent T1-weighted MRI before and after intravenous contrast medium. The presence of LMCE, its intensity and anatomical distribution, catheter angiographic findings, and relation of LMCE to the bypass surgery were assessed. More LMCE was seen in the cerebrum in most patients with moyamoya than in normal controls. LMCE in the brain stem and cerebellum was minimal, similar to that seen in the controls. LMCE was less prominent following surgery than before operation or in patients who did not undergo surgery. In three patients examined both before and after operation LMCE became less prominent following bypass surgery. As LMCE becomes less prominent after "effective" bypass surgery, this may be used for evaluation of effectiveness of surgery in moyamoya.

Involvement of the brain and meninges is rare in Wegener's granulomatosis (WG); it has been reported in 1.2-8 % of patients. Meningeal involvement in WG has been reported in imaging as being confined to the dura mater, and is thought to represent granulomatous infiltration. We present a case of WG with abnormal pial enhancement and involvement of the perivascular spaces on MRI, pathologically proven to represent granulomatous infiltration due to the primary disease rather than to infection.

The CT appearances of the pacchionian body, confirmed at autopsy, are reported. The pacchionian body appears as a low density mass in the dural venous sinus, of almost the same density as the subarachnoid space.

A case of subarachnoid-pleural fistula detected by radionuclide myelography is reported. Review of the literature shows that radionuclide myelography is proving to be more sensitive than contrast myelography in confirming the diagnosis.

The clinical and roentgenographic findings in ten patients with infratentorial retrocerebellar cysts are presented. An approach to the neuroradiological evaluation of retrocerebellar cysts and their differential diagnosis are discussed.

Two patients with an arachnoid cyst of the middle fossa showed paradoxical changes of the adjoining bony structures of the skull. There was a diminution of the middle fossa and hyperplasia of the sphenoid sinus (pneumosinus dilatans) as well as a marked bulging of the squamous part of the temporal bone. In one case in which scinticisternography was performed, communication between the cyst and the subarachnoidal space was proven as well as an extremely slow cerebrospinal fluid circulation in the cyst. The pathogenesis of the cyst is discussed, based upon the structural changes of the skull, the angiographic findings and the locally disturbed cerebrospinal fluid circulation. The primary disturbance seems to be a temporal lobe agenesis.

The perfusion of Berlin blue and trypan blue into the spinal subarachnoid spaces of dogs and sheep, during fixation, colored and distended the arachnoid proliferations, thus making them visible macroscopically. The findings were verified histologically. Dogs have small, simple villi while sheep have larger, more complex granulations. The distribution of the spinal arachnoid proliferations in these animals is recorded.

During the first two years with the 160 X 160 matrix EMI scanner at Rigshospitalet, Copenhagen 108 consecutive patients referred with the suspicion of intra- or juxtasellar tumor were subjected to 166 computed tomography (CT) examinations. The X-ray attenuation and contrast enhancement patterns of the various lesions were analyzed. In general, it was difficult to correlate these parameters with the histopathological features. Arachnoid cysts, however, had typical low preinjection attenuation and no contrast enhancement. Chromophobe and eosinophilic pituitary adenomas rarely contained calcium and only in minute amounts, hardly visible on the polaroid pictures. Craniopharyngiomas and low grade suprasellar gliomas frequently contained large calcifications. Grade I gliomas, when located in the optic nerves or hypothalamus, showed significantly higher contrast enhancement than elsewhere in the brain. Three purely intrasellar adenomas were demonstrated with CT only. The diagnostic accuracy of CT was compared to that of carotid angiography, PEG and plain skull films in the lesions verified by initial operation (n = 32). CT gave the highest accuracy of the four methods, but the accuracy of CT differed statistically only from that of carotid angiography.

A case of myelopathy with both intradural and extradural spinal arachnoid cysts is reported treated by cysto-peritoneal shunt, the spinal end of which was inserted percutaneously under fluoroscopic control. The site of drainage was determined by findings at computed myelography. The case illustrates the value of the latter in demonstrating the pathological bio-mechanics producting myelopathy in this condition.

The clinical and radiological findings in six extradural and nine intradural arachnoid cysts are discussed in relation to previous reports. Only two cysts failed to opacify during positive contrast myelography; in both cases Myodil was used and in one of them contrast medium had entered the cyst on delayed films taken at 24 h. Pain was always improved and generally cured by operation, only two patients having some residual backache. There was permanent improvement of neurological function in only eight cases. The factors associated with poor permanent recovery after surgical treatment were: 1) very marked thinning of the spinal cord by the cyst, and 2) relatively longer duration of paresis--only one case had paresis for under 2 years (mean 4.8 years) compared with only two cases for over 1 year (mean 2 years) in those with good recovery.

Intravenously administered iodinated contrast media have been demonstrated, since early experience with computed tomography of the brain, to improve clinical value of the procedure for detecting intracranial lesions. There is no universal agreement about the amount and the method of administration of the contrast medium. Many authors maintain that the use of large doses gives better results for the diagnosis of tumors and metastases. The purpose of this paper is to evaluate the tolerance of iopamidol administered by rapid intravenous infusion in a large number of patients undergoing contrast enhanced computed tomography to detect brain metastases. The authors examined 969 consecutive adult patients suffering from lung cancer, brain metastases have been detected in 17% of cases. Adverse reactions to contrast media occurred in 3 patients. Non ionic contrast media are recommended in this diagnostic procedure.

The morphological difference between cerebral calcification and ossification is discussed. A case of encephalopathy with leptomeningeal ossification, probably of infectious origin, is described.

An unusual form of rhinorrhoea, presenting itself by repeated bouts of meningitis but without clinical leak of cerebrospinal fluid from the nose, is described. An arachnoidial cyst communicating with the nose is the cause of the infections. Three patients having this kind of rhinorrhoea are described. Rihsa cisternography established the diagnosis. The pathogenesis and the value of isotope cisternography are discussed.

A detailed analysis of the angiographic findings with a congenital retrocerebellar arachnoid cyst in an infant is reported. The angiographic features are a huge retrocerebellar extra-axial avascular mass compressing and displacing the fourth ventricle anteriorly, dysgenesis of the cerebellum, a tight posterior fossa and transtentorial upward herniation of the monticulus and brainstem.

A patient with agenesis of the temporal lobe and an arachnoid cyst was studied by radionuclide cisternography. The value of cisternography in establishing communication between the cyst and the subarachnoid space is emphasized.

A 7-year old male child with an abnormal ophthalmic artery arising from the A1 segment of the anterior cerebral artery is described. The patient suffered growth inhibition which was thought to be caused by a craniobasal cystic lesion affecting the hypothalamus. Preoperative angiograms revealed no vascular abnormalities. The right ophthalmic artery, however, could not be identified. During resection of a large arachnoid cyst the ophthalmic artery was found to arise from the A1 segment of the anterior cerebral artery. To the best of our knowledge, this exact anomaly has not previously been reported. The clinical, neuroradiological and intraoperative findings are presented.

125I labelled Amipaque (metrizamide) was introduced by cisternal puncture into six rabbits and perfused at various pressures. The torcular was exposed, frozen rapidly, and excised intact. Sections of arachnoid proliferations were made from the frozen specimen and either freeze dried or sandwiched directly for autoradiography. Some specimens were freeze dried en bloc prior to sectioning and sandwiching. All sections were exposed for 2-3 weeks at -80 degrees C prior to development of the autoradiographs. On microscopic examinations of the autoradiographs most of the activity was in the tubules or between cells suggesting intercellular passage. Some label was also present within the brain. The significance of this is discussed.

We have reported the case of an infant with bilateral temporal arachnoid cysts. In addition to the characteristic angiographic findings at both sides, a very distinct accumulation of radiopharmacon (99mTc-pertechnetate) in one cyst was demonstrated by routine intravenous scintigraphy. Previous complicating haemorrhage in the cyst appears to have caused both local high protein content and thickening of the arachnoidal wealls with increased vascularisation, thus leading to a positive brainscan. A repeated scintigraphic examination after removal of the lesion showed no abnormalities.

Intracranial arachnoid cysts do not usually present diagnostic problems when studied by CT, since they appear as low density images similar to those produced by CSF, do not change on intravenous contrast perfusion, and are located extraparenchymatously. Sometimes, however, their diagnosis can become difficult or doubtful mainly in cases of deep, basal or paramedian cysts [12, 18, 22, 24]. on the other hand, the functional or dynamic aspects of these structures remain unkown when the study is limited to simple CT. Computed cysternography with metrizamide (CCM) and time control will not only show the relationship between these structures and the arachnoid space but also their dynamic aspect, which may determine the surgical treatment.

A very rare cause of perception deafness wass found in a child with an intrameatal arachnoid cyst. This case is the second reported in the literature.

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.

High resolution CT of the parasellar region was carried out in 50 patients studied for suspected pituitary microadenoma, but who showed normal pituitary gland or microadenoma on CT. This control group of patients all showed an ellipsoid low-density area in the posterior parasellar region. Knowledge of the gross anatomy and correlation with metrizamide cisternography suggest that the low density region represents Meckel's cave, rather than just the trigeminal ganglion alone. Though there is considerable variation in the size of Meckel's cave in different patients as well as the two sides of the same patient, the rather constant ellipsoid configuration of the cave in normal subjects will aid in diagnosing small pathological lesions, thereby obviating more invasive cisternography via the transovale or lumbar route. Patients with “idiopathic” tic douloureux do not show a Meckel's cave significantly different from the control group.

The contribution of computed tomography (CT) in the assessment of macrocrania has been axamined with reference to a consecutive series of 93 cases. In the great majority a definitive diagnosis could be made without resorting to more noxious procedures. Hydrocephalus was present in 46% of this group. The incidence of macrocrania with childhood hydrocephalus and its relationship to the aetiology and other CT features was examined with reference to 109 consecutive cases with hydrocephalus shown on CT. Macrocrania was present in only 11% of cases with an underlying tumour, but in 71% with other obstructing lesions.

1. The angiographic anatomy of the horizontal segment of the anterior cerebral artery is presented as a tridimensional concept. Two anatomical types are described.—2. The angiographic appearances of segment A. 1 of the anterior cerebral artery in suprasellar masses may fall into one of three categories:—a) Unequivocal, upward displacement of the horizontal segment of the anterior cerebral artery. This is seen with anteriorly situated suprasellar tumours and with an anterior cerebral artery of the anatomical type 1 (36% of the cases).—b) No upward displacement of the horizontal segment of the anterior cerebral artery. This is seen in posteriorly situated tumours and in the presence of an anterior cerebral artery of the anatomical type 2 (39% of the cases).—c) No apparent upward displacement of the horizontal segment of the anterior cerebral artery in the A.P. view. The displacement is concealed by the concurrent elevation of the point of carotid bifurcation (25% of the cases). The correct interpretation is obtained by measuring the distance of the anterior communicating point above the nasion-tuber-culum line (In 99% of the normal the maximum height is 15 mm).—3. We wish to emphasise the great importance of visualising the horizontal segment of the anterior cerebral and the anterior communicating point both in the lateral and A.P. planes arteriograms.

This is a case report of a unique osteolytic lesion of the skull. Following a workup for convulsive seizures, a circumscribed osteolytic lesion of the left occipital bone was found by X-ray. Surgical exploration revealed an arachnoid cyst eroding the skull. A history of head injury to the left occiput two years previously was obtained. There was no fracture.

The basic microvascular anatomy of the human dura is described. The named dural arteries give rise to two outer anastomotic sets of vessels. From the outer arteries, penetrating vessels descend to supply a rich capillary network located near the arachnoid. Arteriovenous shunts are present in the midportion of the dura, which may function to bypass the capillary network.

A case of post-traumatic arachnoid spinal cyst with haemorrhagic contents is presented. CT findings were indistinguishable from those of epidural or subdural haematomas. The use of CT myelography permits a more accurate diagnosis by localizing the lesion into one of the three spaces. In our case, bleeding into a preexisting arachnoid cyst was thought to occur, but we cannot exclude a newly formed cyst of traumatic origin.

The CAT scan is insufficient to make the differential diagnosis between an arachnoid cyst and an epidermoid cyst in the cistern of Galen. Gas encephalography is necessary. This procedure reveals arachnoid cysts of the commmunicating type, but is insufficient in distinguishing between an epidermoid cyst and a non-communicating arachnoid cyst. In this situation, histograms of the absorption values in each section of the lesion may be helpful for the diagnosis.