Kazuhiko Sadamoto

Initial experience in evaluating the prevalence of unruptured intracranial aneurysms detected on 3-tesla MRI.

Background: Given the very poor outcome of ruptured intracranial aneurysms, detection and treatment of unruptured intracranial aneurysms by a less invasive examination have become important. For this purpose, 3-tesla (3T) magnetic resonance imaging (MRI) is the most suitable candidate, owing to its high signal/noise ratio and frequency resolution. However, few reports have investigated the prevalence of intracranial aneurysms with high-tesla MRI. Here, we evaluated the prevalence of intracranial aneurysms and the effectiveness of a 3T MRI system in their detection. Methods: During a 1-year period, a total of 3,414 consecutive patients undergoing MR angiography with 3T MRI for the first time were enrolled. Diagnosis of intracranial aneurysm was made by two neuroradiologically trained medical doctors under complete blinding to patient information. When intracranial aneurysm was suspected, volume-rendering images were created for more accurate diagnosis. Results: Surprisingly, 317 unruptured intracranial aneurysms were identified in 286 of 3,414 cases (8.4%); 151 unruptured aneurysms (47.6%) occurred in the internal carotid artery, 85 (26.8%) in the middle cerebral artery, 54 (17.0%) in the anterior cerebral artery, and 27 (8.5%) in the posterior circulation. Of these, 152/317 (47.9%) were <3 mm, 104 (32.8%) ranged from 3 to 5 mm, 5 (11.0%) from 5 to 7 mm, and 26 (8.2%) were >7 mm. No significant difference in size was seen among the four locations.Conclusions: For the first time, this study assessed the detection rate of intracranial aneurysms using 3T MRI. Results showed a higher detection rate than previously documented. The reason for this higher rate is likely the improved ability of this modality to detect unruptured aneurysms in the internal carotid artery and those <3 mm.

Minimum dose contrast bolus in computed angiotomography of the brain

We have carried out basic investigations of an intravenous minimum dose bolus (MinDB) injection method for cerebral computed angiotomography by comparing blood iodine concentrations with high resolution computed tomography (CT) images of cerebral blood vessels. With the GECT/T 8800 scanner, a MinDB injection of 1 ml/kg of 60% Conray at a rate of 2 ml/s made it possible to increase the blood iodine concentration in the carotid artery to more than 15 mg/ml for about 20 s. Computed tomography performed during this period enabled us to obtain clear images of the circle of Willis, including other main cerebral arteries, deep veins, and cortical and lenticulostriate arteries. Cerebral computed angiotomography using this method should be useful for noninvasive screening or detection of cerebrovascular lesions themselves, such as cerebral aneurysms, cerebrovascular obstructions, arteriovenous malformations, and moyamoya disease, and should also be useful for determining the anatomical relationship between the cerebral blood vessels and other parenchymal or space occupying lesions.

Computed angiotomography of unruptured cerebral aneurysms.

Twenty-seven unruptured cerebral aneurysms in 25 patients were detected by computed angiotomography. A comparison of the computed angiotomographic features in common aneurysm sites with plain CT and conventional arteriography was carried out. An isodense, round cisternal defect and a calcification or high-density mass in the basal cisterns on plain CT are important findings suggestive of unruptured aneurysms larger than 7 mm in diameter. The identification of the aneurysm, as well as of the afferent and efferent arteries on computed angiotomography is essential for the direct diagnosis of smaller unruptured aneurysms related to the circle of Willis. This is possible in a number of cases when the aneurysms are relatively large. It appears that the aneurysm size must be larger than 3 mm in diameter to permit its recognition on the basis of angiotomography and the avoidance of false-positive findings.

Screening and treatment of unruptured cerebral aneurysms

Thirty outpatients with unruptured cerebral aneurysms screened by computed angiotomography have been analysed and followed up in our clinic since 1979. Seventeen were men and the age range was 41 to 74 years old (mean 57.7 years). Patients had no or only mild neurological symptoms, such as headache, sensorimotor or speech impairment and others, which were scarcely related to the unruptured aneurysms themselves. It is important to realize that these first aneurysms which remain unruptured, have a primary significance to the individual in the protective aspect of an initial subarachnoid haemorrhage. Operation was successfully performed in fifteen patients. Transient aggravation of previous diseases, e.g. cerebral infarction, occurred in three after operation. Follow-up studies of fifteen patients without operation revealed no change in eight and some worsening or death due to other or previous diseases in six. One died of aneurysmal rupture in the 5th month after its detection. Because of the low operative risk, we advocate the operative treatment of unruptured aneurysms, following careful selection of the indicated patients.

Normal anatomy of cerebral vessels by computed angiotomography in the coronal, Towne, and semisagittal planes.

This report presents a detailed analysis of the normal cerebrovascular anatomy on the modified coronal, Towne (half-axial), and semisagittal computed tomographic (CT) images. Direct multiplane CT scans were obtained from fresh cadavers injected with gelatinous iodine solution. The modified coronal plane is optimal for delineation of the internal carotid bifurcations and the anterior and the middle cerebral arteries, and for identification of the lenticulostriate arteries and the angiographic sylvian point. The Towne plane is optimal for delineation of the vertebrobasilar arterial system. Thorough knowledge of the normal appearance of cerebral blood vessels in biplane or multiplane computed angiotomography is a prerequisite for understanding the spatial relationships of the abnormal cerebrovascular anatomy.

Normal anatomy of cerebral vessels by computed angiotomography in the axial transverse plane

A detailed analysis of normal cerebrovascular anatomy on axial transverse computed tomographic (CT) images is presented. Fresh cadavers were injected with gelatinous iodine solution for clear visualization of cerebral blood vessels. A detailed knowledge of the normal cerebrovascular anatomy on the axial transverse CT image in relation to other intracranial structures is a prerequisite for the interpretation of cerebral computed angiotomograms.

Uncommon Type of Meningiomas with Conspicuous Plasmo-lymphocytic Infiltration: An Immunohistochemical and Histochemical Study

Two cases of meningioma revealing conspicuous plasmo lymphocytic tissue and hyalinized fibrous tissue components are reported. Histopathological examination of the plasmo lymphocytic infiltration was performed. Both lesions showed polyclonality of plasma cells as revealed by positive reactions for 1gG and paraimmunoglobulin χ‐ and λ light chains, and amyloid infiltration into the fibrous stroma and blood vessel walls. The histochemical and immunohistochemical characteristics of the lesion in relation to its etiology are briefly discussed. Acta Pathol. Jpn. 32: 190∼194, 1989.

Mismatch between TOF MR Angiography and CT Angiography of the Middle Cerebral Artery may be a Critical Sign in Cerebrovascular Dynamics

Purpose Although time-of-flight (TOF)-magnetic resonance angiography (MRA) can clearly depict intracranial arteries, the arterial flow of middle cerebral artery (MCA) is occasionally not detected. We evaluated this phenomenon with reference to cerebrovascular dynamics. Materials and Methods Seventeen patients with suspected occlusion of MCA or internal carotid artery on TOF-MRA were enrolled. All patients underwent CT angiography (CTA) and quantitative cerebral blood flow (CBF) examination for measurement of resting CBF and cerebrovascular reactivity (CVR). Depending on appearance, patients were categorized into three groups. Group A (n=6) had MCA delineation on both MRA and CTA, while groups B (n=6) and C (n=5) had no signal on MRA, but Group B had a MCA delineation on CTA. Results No significant difference between resting CBF and CBF after the administration of acetazolamide was seen among 3 groups. In contrast, mean CVR in group B was -19.7±18.1%, which was significantly lower than group A [36.4±21.7% (p<0.05)], but not than group C (21.4±35.2%). Furthermore, all patients in group B displayed a so-called steal phenomenon. Conclusion This study is the first to show that visualization of MCA on TOF-MRA closely correlates with CVR, and that a vascular pattern showing no MCA signal intensity on MRA but with MCA delineation on CTA indicates a critical cerebrovascular condition.

Usefulness of multiangle MRI in aortic arch dissection.

A multiangle scan technique was used in combination with usual spin echo and cine MR techniques to study a patient with aortic arch dissection. The intimal flap was seen with each technique and the jet into the entry site was observed with cine MR technique. Exact short axis images of aortic arch were obtained only with multiangle scan. Retrograde dissection and involvement of left subclavian artery were detected clearly on the short axis images.

Malignant Fibrous Histiocytoma of the Temporal Bone with Multiple Metastases

Malignant fibrous histiocytoma (MFH) is well known as a soft tissue tumor of the extremities. MFH of the skull is relatively rare, especially with multiple metastases. A 59-year-old female was admitted with complaint of a painless tumor in the left temporal region in March, 1983. Skull plain film showed an osteolytic and osteosclerotic lesion, with a “moth-eaten” appearance, of the temporal bone. Computed tomography (CT) scans revealed a high density mass lesion invading intraand extracranially. Selective external carotid angiography revealed abnormal tumor vessels like a corkscrew and a marked tumor stain. The tumor was extirpated. The histological diagnosis was MFH. The patient received chemotherapy with mitomycin C intraoperatively, and was discharged without any neurological deficits. She was readmitted with complaint of general fatigue 7 months later. Plain chest X-ray films showed a tumor in the mediastinum and depressed fracture of the third thoracic vertebra. CT scans revealed the invasion of the mediastinal tumor to the spinal canal and the hydrothorax. She died in July, 1984. The autopsy showed multiple metastases of MFH to the mediastinum, the third thoracic vertebra, and the right lung, and an associated meningioma in the left cerebellopontine angle. There was no local recurrence.