Angiographically occult arteriovenous malformations

Angiographically occult arteriovenous malformations not associated with clinically recognizable intracranial hemorrhage appear to be rare. We are reporting three cases of histologically proven arteriovenous malformations of the brain that were angiographically occult. These cases presented with seizures or attacks of dizziness, and were detected by computed tomography scan, radionuclide scan, or both. The preoperative diagnosis was granuloma in the first case and meningioma in the other two. After surgical exploration, biopsy revealed an arteriovenous malformation in each case. A review of 47 cases in the literature is tabulated and etiologies of the angiographically occult arteriovenous malformations are discussed. The routine use of computed tomography scan and timely, appropriate surgical intervention with the operating microscope for the removal of these deeply situated lesions is necessary for the diagnosis and therapy.     

Angiographically occult arteriovenous malformations of the brainstem

Two cases of infratentorial arteriovenous malformations that were occult to angiography but detected by computed tomography are discussed. In both cases a preoperative diagnosis of low-grade glioma was considered. Attention is drawn to the relative paucity of such lesions below the tentorium.     

Angiographically occult vascular malformations in childhood

Five infants and children with angiographically occult vascular malformations of the brain detected by computed tomography (CT) are presented. Four malformations were located in the cerebral hemisphere, and one was in the brain stem. CT demonstrated high density lesions with little or no enhancement after infusion of the contrast material. The malformations were resected and histologically proven. All patients have done well. The pertinent literature is reviewed. These lesions are uncommon during infancy and childhood and mimic gliomas clinically and radiographically. The need for surgical extirpation of these lesions is stressed.     

Angiographically occult vascular malformations causing intracranial hemorrhage

In 5 patients, angiographically occult vascular malformations led to intracerebral or intracerebellar hemorrhages. Angiographic findings were not suggestive of vascular abnormalities, but signs of a mass were present in 4 patients. Computed tomography (CT) scanning suggested the presence of cryptic vascular lesions accompanied by intraparenchymal hemorrhage in 2 patients. In all patients surgical treatment was successful. Histological examination confirmed these lesions to be venous malformations in the cerebellum in 2 patients and in the left frontal region in 1, and arteriovenous malformations in the cerebellum and right putaminal region in 1 patient each.     

Angiographically occult vascular malformations in the posterior fossa

Three cases of spontaneous intraparenchymal hemorrhage in the posterior fossa were operated upon, and the diagnosis of thrombosed vascular malformation was histologically confirmed in two of them. So-called "angiographically occult" vascular malformations often present characteristic magnetic resonance (MR) images, namely, iso- to high intensity signal core surrounded by a low intensity signal rim or area on both T1 and T2 weighted images. Such findings are thought to indicate that subacute and chronic intraparenchymal hematoma has a relatively short T1 and long T2 relaxation times, resulting in an area of relatively increased signal intensity, and that hemosiderin deposits apparently decrease T2 relaxation time by paramagnetic effect. Most such lesions do not show significant perifocal edema. Occasionally, however, perifocal edema may be seen as in our Case 3, and the differential diagnosis from the tumor, particularly bleeding tumor, may become difficult even with the recent technical standards of high resolution CT and MRI. Reasons responsible for non-visualization of such vascular malformations at angiography are discussed. Small size of the lesion, slow blood flow through it, compression by adjacent clot or gliotic scar, spontaneous or secondary thrombosis with hyalin degeneration, and destruction at its rupture are possible factors.     

Angiographically occult cerebral vascular malformations with abnormal computed tomography

Two cases of histologically proven cerebrovascular malformation were detected by computed tomography (CT) scanning but not by cerebral angiography. One of the patients had a cavernous angioma and the other an arteriovenous malformation. Caution is advised in assuming that angiographically avascular lesions demonstrable by CT scanning are not vascular malformations.     

Angiographically occult epidural arteriovenous fistula of the craniocervical junction

BACKGROUND: Spinal dural and intradural arteriovenous fistulas (AVFs) have been the subject of numerous reports but purely epidural AVFs causing venous congestion within the spinal cord are rare. CASE DESCRIPTION: We describe a patient with an exclusively epidural arteriovenous fistula and congestive myelopathy. There are three interesting features of this case as described below: 1) The presence of a purely epidural AVF of the cranio-cervical junction. According to our knowledge this is the first case of an AVF in this location. 2) The lesion was angiographically occult. This was probably because of the extremely slow flow of the fistula. 3) Despite the negative angiograms, exploratory surgery was conducted because of positive clinical and MR findings. CONCLUSIONS: Epidural AVF/AVM of the foramen magnum should be considered in the differential diagnosis in patients with chronic myelopathy, even if cranial and spinal angiograms are negative. In these cases, we recommend that if clinical and radiological investigations strongly suggest the presence of an arteriovenous fistula, surgical exploration should be performed.     

Angiographically occult arteriovenous malformation in the septal region--case report.

An occult arteriovenous malformation (AVM) in the septal region occurred in a 14-year-old boy, manifesting as headache and vomiting. Computed tomography showed a high-density mass in the septal region, faintly enhanced postcontrast. Mild hydrocephalus was also seen. Angiography revealed no abnormalities other than hydrocephalic signs. The lesion was totally removed by the transventricular approach after corticotomy of the left frontal lobe. The histological diagnosis was AVM. He was discharged without neurological or endocrinological deficits.     

Angiographically occult dural arteriovenous malformation in the anterior cranial fossa--case report.

A 62-year-old male presented with a dural arteriovenous malformation located in anterior cranial fossa manifesting as acute right frontal intracerebral and subdural hematomas. Cerebral angiography showed only mass sign, but surgical exploration disclosed the dural arteriovenous malformation in the anterior cranial fossa. Anterior cranial fossa dural arteriovenous malformation should be considered if computed tomography reveals intracranial bleeding involving the frontal base, even if cerebral angiography does not demonstrate vascular anomalies.     

Angiographically cryptic cerebrovascular malformations

Three cases of angiographically cryptic cerebrovascular malformations are presented and a review of the cases in the English literature is tabulated. The typical patient is a 30- to 40-year-old woman with a history of seizures and headache. There is no antecedent history suggesting hemorrhage. On nonenhanced computerized tomographic scans, these lesions are denser than normal brain. They enhance with contrast administration. The angiogram demonstrates an avascular mass. The history, physical findings, and radiographic studies suggest brain tumor. An accurate diagnosis requires operation and pathological examination of the lesion.     

Angiographically occult spinal dural arteriovenous fistula located using selective computed tomography angiography. Case report

Spinal dural arteriovenous fistula (DAVF) is the most common type of spinal arteriovenous malformation and may cause progressive myelopathy but is usually treatable in the early stages by direct surgery or intravascular embolization. Selective spinal angiography has been the gold standard for diagnosis, but angiographically occult DAVF is not uncommon. A 67-year-old man presented with a 2-year history of progressive paraparesis. Magnetic resonance (MR) imaging demonstrated segmental atrophy of the spinal cord and dilated coronary veins on the dorsal surface of the spinal cord. A DAVF was suspected, but repeated selective angiography failed to demonstrate the fistula. Findings from spoiled gradient echo MR imaging suggested that the draining vein flowed into the dilated venous plexus at the T-9 level. Selective computed tomography (CT) angiography of the right T-9 intercostal artery confirmed the location of the fistula. The authors successfully occluded the draining vein through surgery, and they observed that the fistula was low flow. The patient exhibited improvement in his symptoms, and postoperative MR imaging confirmed closure of the fistula. Selective CT angiography is useful in locating the draining vein of angiographically occult DAVF and therefore minimizing the extent of the surgical procedure.     

Angiographically occult high cervical dural arteriovenous malformation secondary to intracranial hypertension: a case report

We have recently encountered a case of high cervical arteriovenous malformation which caused subarachnoid hemorrhage. A 54-year-old male was admitted to our hospital due to sudden onset of severe headache. Neurological examination revealed right sixth nerve palsy which suggested elevated intracranial pressure. A CT scan showed subarachnoid hemorrhage predominantly in the posterior fossa, massively ventral to the brain stem, with reflux into the fourth ventricle. No abnormal vascular lesions were found in the first cerebral angiography which included four vessels and bilateral thyrocervical trunks. Ten days later, the second cerebral angiography demonstrated an arteriovenous shunt via the right vertebral artery draining into the epidural space of the upper cervical region. A suboccipital craniotomy and laminectomy of the atlas were performed. An abnormally dilated vein along the right C1 nerve ventral root which drained into the tortuous dilated coronary venous plexus on the ventral side of the spinal cord was found. We made a diagnosis of dural arteriovenous malformation fed by the C1/C2 radicular artery via the right vertebral artery and draining into the radiculomedullary vein and the epidural venous plexus. The interruption of both intra- and extradural draining veins was carried out. The postoperative course was uneventful.     

Comparison of the clinical presentation of symptomatic arteriovenous malformations (angiographically visualized) and occult vascular malformations.

The authors compared the clinical presentations of angiographically apparent arteriovenous malformations (AVMs) and angiographically occult vascular malformations (AOVMs) of the brain in 188 consecutive patients treated when computed tomography and magnetic resonance were available. There were 133 patients (70.7%) with AVMs and 55 patients (29.2%) with AOVMs. AOVMs tended to occur more frequently in male patients and in the posterior fossa and to present earlier clinically than AVMs, but differences were not significant. One distinctive feature was the greater size of AVMs, as compared with AOVMs. Presentation by hemorrhage occurred in 64.3% of the patients with AVMs and in 61.8% of those with AOVMs. Malformations of both types located in the posterior fossa presented with hemorrhage more frequently (84.2% of AVMs and 78.5% of AOVMs) than similar lesions lying above the tentorium (60.8% of AVMs and 56% of AOVMs). Bleeding was more severe in patients with AVMs than in those with AOVMs, as indicated by the higher mortality associated with hemorrhage (7.5 vs. 3.6% of the cases) and the more frequent and marked decrease in the level of consciousness observed at admission (34 vs. 16.2% of drowsy or comatose patients). Brain hematomas caused by AVMs were on average bigger than those caused by AOVMs (58.8 and 20% of large hematomas, respectively), and intraventricular and subarachnoid hemorrhages were also more common and profuse in patients with AVMs. However, AOVMs bled subsequently more times than AVMs (61.7 vs. 15.6%), before they were diagnosed and treated, leading to a higher nonoperative morbidity (16.3 vs. 13.6%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Intracranial arteriovenous malformations

Intracranial arteriovenous malformations (AVM) are rare lesions that are often discovered fortuitously. They should be identified on CT scan and MRI before resorting to angiography; the latter is used to prepare the treatment. This article describes the various types of subpial or dural AVM and the specific characteristics that enable their differentiation with non-invasive imaging. The factors that determine the severity of these lesions, whether discovered before or after a haemorrhage, are described, as well as prognostic indicators.