Yukinori Takase

Acquired lesions of the corpus callosum: MR imaging

In this pictorial review, we illustrate acquired diseases or conditions of the corpus callosum that may be found by magnetic resonance (MR) imaging of the brain, including infarction, bleeding, diffuse axonal injury, multiple sclerosis, acute disseminated encephalomyelitis, Marchiafava-Bignami disease, glioblastoma, gliomatosis cerebri, lymphoma, metastasis, germinoma, infections, metabolic diseases, transient splenial lesion, dilated Virchow-Robin spaces, wallerian degeneration after hemispheric damage and focal splenial gliosis. MR imaging is useful for the detection and differential diagnosis of corpus callosal lesions. Due to the anatomical shape and location of the corpus callosum, both coronal and sagittal fluid-attenuated inversion recovery images are most useful for visualizing lesions of this structure.

Anterior cerebral artery variations detected by MR angiography.

IntroductionFrom anatomical and angiographic studies, it is well known that there are several variations of the anterior cerebral artery (ACA). However, ACA variations have rarely been studied by magnetic resonance (MR) angiography. The purpose of this study was to investigate not only the type, location, configuration, and incidence of ACA variations, but also coexisting arterial pathology such as aneurysms detected by cranial MR angiography.MethodsWe retrospectively reviewed cranial MR angiography images of 891 patients at our institution. All images were obtained with one of two 1.5-T scanners using the three-dimensional time-of-flight technique. Maximum intensity projection (MIP) images in the horizontal rotation view were displayed stereoscopically. We reviewed these horizontal MIP images, inferosuperior MIP images, and source images, and identified variations of the ACA.ResultsWe found 50 instances (5.6%) of unilateral A1 segment aplasia, 27 (3.0%) of three A2 segments, 18 (2.0%) of an unpaired A2 segment, and 11 (1.2%) fenestrations of the A1 and/or A2 segment. Seven anterior communicating artery (ACoA) aneurysms and one ACA territory embolic infarction were found among the 50 patients with unilateral A1 segment aplasia. One ACoA aneurysm and one pericallosal infarction were found in the 27 patients with three A2 segments. Two distal ACA aneurysms were detected among the 18 patients with an unpaired A2 segment. No associated aneurysm was seen at the fenestrations.ConclusionAlthough the clinical significance of ACA variations is usually minor, an associated aneurysm is found relatively frequently. Thus, recognizing ACA variations during the interpretation of cranial MR angiograms is important.

Manganese accumulation in the brain: MR imaging

Manganese (Mn) accumulation in the brain is detected as symmetrical high signal intensity in the globus pallidi on T1-weighted MR images without an abnormal signal on T2-weighted images. In this review, we present several cases of Mn accumulation in the brain due to acquired or congenital diseases of the abdomen including hepatic cirrhosis with a portosystemic shunt, congenital biliary atresia, primary biliary cirrhosis, congenital intrahepatic portosystemic shunt without liver dysfunction, Rendu-Osler-Weber syndrome with a diffuse intrahepatic portosystemic shunt, and patent ductus venosus. Other causes of Mn accumulation in the brain are Mn overload from total parenteral nutrition and welding-related Mn intoxication.

Middle cerebral artery variations detected by magnetic resonance angiography

Abstract. Middle cerebral artery (MCA) variations are found incidentally on cranial magnetic resonance angiography (MRA). Our goal was to examine the incidence and types of MCA variations detected by MRA. Between April 1996 and March 1999, cranial MRA was performed in 432 cases at our institution. Most of the patients examined had or were suspected to have cerebrovascular disease. After excluding 7 patients with moyamoya disease, we retrospectively reviewed 425 MRA results. A 1.5-T scanner was used in all studies, and maximum-intensity projection images obtained using the three-dimensional time-of-flight technique were displayed stereoscopically. In the 425 patients MRA revealed 16 anomalous MCAs, including 9 duplicated MCAs, 5 accessory MCAs, and 2 fenestrated MCAs, which is a rate of 3.8 %. Thus, although the clinical significance is not great, we found a relatively high incidence of anomalous MCAs on MRA. We stress that knowledge and recognition of these variations are useful and important during the interpretation of cranial MRA.

Persistent trigeminal artery variants detected by MR angiography.

Abstract. Persistent trigeminal artery (PTA) variants are cerebellar arteries that originate directly from the precavernous portion of the internal carotid artery (ICA). The goal of our study was to determine the incidence and MR angiographic features of PTA variants. Between April 1996 and September 1999, 523 cranial MR angiographies were performed at our institution. Most of the patients examined had or were suspected of having cerebrovascular disease. We retrospectively reviewed these 523 MR angiograms. A 1.5-T scanner was used in all studies, and maximum intensity projection (MIP) images obtained using the three-dimensional time-of-flight (3D TOF) technique were displayed stereoscopically. Four PTA variants were detected on MR angiograms, at a rate of 0.76 %. At least three of the four PTA variants were anterior inferior cerebellar arteries (AICAs), small tortuous arteries arising from the precavernous portions of the ICAs and taking a posterior course. Although the clinical significance is not great, we found a relatively high incidence of PTA variants on MR angiograms. We stress that knowledge and recognition of these anomalous cerebellar arteries are useful and important in the interpretation of cranial MR angiograms.

Cerebral Lipiodol Embolism: A Complication of Transcatheter Arterial Chemoembolization for Hepatocellular Carcinoma

We report a case of cerebral lipiodol embolism following transcatheter chemoembolization (TACE) for hepatocellular carcinoma. A 70-year-old woman with a large unresectable hepatocellular carcinoma underwent TACE. Her level of consciousness deteriorated after the procedure, and magnetic resonance imaging and non-contrast computed tomography revealed a cerebral lipiodol embolism. Despite intensive care, the patient died 2 weeks later. The complication might have been due to systemic-pulmonary shunts caused by previous surgeries and/or direct invasion of the recurrent tumor.

Extreme fenestration of the basilar artery associated with cleft palate, nasopharyngeal mature teratoma, and hypophyseal duplication

Abstract. The authors present the case of a newborn girl with extreme fenestration of the basilar artery. This anomaly was found incidentally during MR imaging study for cleft palate and nasopharyngeal teratoma. Magnetic resonance angiography showed a totally duplicated basilar artery with connections at the proximal and distal ends of the artery, suggesting an extreme fenestration. Duplicated pituitary gland was also found on MR imaging.

Intraorbital wooden and bamboo foreign bodies: CT

Abstract We describe the CT findings of intraorbital wooden and bamboo foreign bodies in the acute, subacute, and chronic stages. We examined four patients using CT a total of seven times. The CT findings were reviewed. There were three dry wooden foreign bodies. CT within a day of the accident demonstrated wooden foreign bodies as low density relative to surrounding orbital fat, while CT 8–29 days after the accident showed them as denser than the extraocular muscles. In the acute stage, dry wooden foreign bodies mimic air bubbles. Wooden foreign bodies in the subacute and chronic stages should be included in the differential diagnosis of intraorbital lesions of soft tissue density or above on CT of traumatised orbits. There was one dry bamboo foreign body. Within a day of the accident it was recognised as linear lesion isodense with fat. Therefore, such foreign bodies may be missed on CT when located in the orbital fat.

Brainstem and cerebellar changes after cerebrovascular accidents: magnetic resonance imaging

We illustrate the various types of secondary degeneration in the brainstem and/or cerebellum detected on magnetic resonance (MR) images obtained after cerebrovascular accidents. The changes include: (a) ipsilateral nigral degeneration after striatal infarction; (b) Wallerian degeneration of the pyramidal tract in the brainstem after supratentorial pyramidal tract or motor cortex injury; (c) Wallerian degeneration of the corticopontine tract in the brainstem after frontal lobe infarction; (d) ipsilateral brainstem atrophy and crossed cerebellar atrophy due to an extensive supratentorial lesion; (e) ipsilateral superior cerebellar peduncle atrophy, contralateral rubral degeneration, contralateral inferior olivary degeneration and ipsilateral cerebellar atrophy after dentate nucleus hemorrhage; (f) ipsilateral inferior olivary degeneration after pontine tegmentum hemorrhage; (g) bilateral wallerian degeneration of the pontocerebellar tracts after ventromedial pontine infarction or basis pontis hemorrhage; and (h) ipsilateral cerebellar atrophy after middle cerebellar peduncle hemorrhage.

Extreme fenestration of the right vertebral artery: magnetic resonance angiographic demonstration

Abstract. The authors describe an extreme fenestration of the right vertebral artery. This anomaly was found incidentally in a female patient undergoing MR imaging and MR angiography evaluation for severe dizziness and headache. Magnetic resonance angiography showed that the right posterior inferior cerebellar artery originated possibly extracranially and anastomosed with the terminal portion of the right vertebral artery, indicating the presence of an extremely large fenestration. This, to our knowledge, is the first report of MR angiographic demonstration of this variation.