Michito Adachi

Clinical and Neuroradiological Features of Intracranial Vertebrobasilar Artery Dissection

BACKGROUND AND PURPOSE We sought to determine the clinical and neuroradiological features of intracranial vertebrobasilar artery dissection. METHODS The clinical features and MR findings of 31 patients (20 men and 11 women) with intracranial vertebrobasilar artery dissections confirmed by vertebral angiography were analyzed retrospectively. The vertebral angiography revealed the double lumen sign in 11 patients (13 arteries) and the pearl and string sign in 20 patients (28 arteries). RESULTS The patients ranged in age from 25 to 82 years (mean, 54.8 years). Clinical symptoms due to ischemic cerebellar and/or brain stem lesions were common, but in 3 cases the dissections were discovered incidentally while an unrelated disorder was investigated. Headache, which has been emphasized as the only specific clinical sign of vertebrobasilar artery dissection, was found in 55% of the patients. Intramural hematoma on T1-weighted images has been emphasized as a specific MR finding. The positive rate of intramural hematoma was 32%. Double lumen on 3-dimensional (3-D) spoiled gradient-recalled acquisition (SPGR) images after the injection of contrast medium was identified in 87% of the patients. The 3-D SPGR imaging method is considered useful for the screening of vertebrobasilar artery dissection. CONCLUSIONS Intracranial vertebrobasilar artery dissection is probably much more frequent than previously considered. Such patients may present no or only minor symptoms. Neuroradiological screening for posterior circulation requires MR examinations, including contrast-enhanced 3-D SPGR. Angiography may be necessary for the definite diagnosis of intracranial vertebrobasilar artery dissection because the sensitivity of the finding of intramural hematoma is not satisfactory.

Dilated Virchow-Robin spaces: MRI pathological study

Abstract We performed a histopathological study of two human brains to look at dilated Virchow-Robin (V-R) spaces in the anterior perforated substance and putamen. We measured the diameter of 74 arteries in 54 dilated V-R spaces. In 28 patients without neurological deficits we ascertained the characteristic location of dilated V-R spaces in the anterior perforated substance and basal ganglia on MRI, measuring the distance from 64 foci of cerebrospinal fluid signal intensity to the centre of the mamillary body on 1 mm thick images. In the histopathological study, the mean diameter of the arteries was 39.0 ± 36.0 μm. Dilatation of the V-R space was observed from the end of the indentation of the pial membrane towards the brain surface along the perforating artery. In the MR images, the mean distance from the dilated V-R space to the mamillary body was 10.0 ± 4.5 mm. The V-R space was confined to a fixed level in the lower part of the basal ganglia, and not found near the brain surface.

Upper midbrain profile sign and cingulate sulcus sign: MRI findings on sagittal images in idiopathic normal-pressure hydrocephalus, Alzheimer's disease, and progressive supranuclear palsy.

PurposeOn magnetic resonance imaging (MRI) sagittal sections, we sometimes encounter abnormal aspects of the superior profile of the midbrain and the cingulate sulcus in patients with dementia. In this preliminary study, we refer to these findings as the “upper midbrain profile sign” and the “cingulate sulcus sign.” We prospectively evaluated the usefulness of these signs for the diagnosis of idiopathic normal-pressure hydrocephalus (iNPH), Alzheimers disease (AD) and progressive supranuclear palsy (PSP).Materials and methodsWe evaluated the upper midbrain profile sign and the cingulate sulcus sign on MRI sagittal images obtained from 21 people with headaches but no neurological deficit (controls), 10 iNPH patients, 11 AD patients, and 5 PSP patients. The upper midbrain profile sign indicated a concave shape to the superior profile of the midbrain on mid-sagittal images, and the cingulate sulcus sign indicated a narrow, tight aspect of the posterior part of the cingulate sulcus on paramedian-sagittal images.ResultsThese signs were never seen in any images from the controls. The upper midbrain profile sign was seen in 7 of 10 patients with iNPH, 5 of 11 with AD, and 3 of 5 with PSP. The cingulate sulcus sign was seen in all 10 patients with iNPH but was never seen in any patient with AD or PSP.ConclusionThe upper midbrain profile sign could support a diagnosis of PSP but cannot discriminate among iNPH, AD, and PSP. In contrast, the cingulate sulcus sign has a very high sensitivity for iNPH and should facilitate the distinction of iNPH from other dementias. In the clinical setting, it is momentous to evaluate these signs easily by one simple MRI sequence.

Diffusion- and T2-weighted MRI of the transverse pontine fibres in spinocerebellar degeneration.

Abstract Because the transverse pontine fibres degenerate in some subtypes of spinocerebellar degeneration (SCD), demonstration of these fibres may be helpful for radiological diagnosis of SCD. Using multishot diffusion-weighted MRI, we attempted to find a way to show the transverse pontine fibres. We assessed the quality of demonstration of these fibres on DWI and of abnormal high signal in the pons and middle cerebellar peduncles on T2-weighted images. We examined evaluated 24 control subjects and 12 patients with SCD: two with sporadic olivopontocerebellar atrophy (OPCA), five with spinocerebellar ataxia type 1 (SCA1), two with SCA3, and three with SCA6. In all control subjects and patients with SCA6, we succeeded in demonstrating the transverse pontine fibres as clear low-signal bundles using DWI. In two patients with SCA3, these fibres were identified less distinctly. In contrast, in two patients with sporadic OPCA and in four of five patients with SCA1, the fibres were not identified. In both patients with sporadic OPCA, abnormal high-signal foci were seen in the base of the pons and middle cerebellar peduncles on T2-weighted images; no such foci were detected in any patient with SCA1, SCA3 or SCA6. DWI seems to be useful for demonstrating transverse pontine fibres. Abnormal high signal in the pons and middle cerebellar peduncles may provide a clue to differentiation of sporadic OPCA from other types of SCD.

Asymptomatic hereditary Alexander's disease caused by a novel mutation in GFAP

We report on a family with dominantly inherited asymptomatic Alexanders disease due to a novel Glial fibrillary acidic protein (GFAP) mutation. The proband, a 16-month-old boy, presented with megalocephaly and brain magnetic resonance imaging (MRI) showing the typical findings of Alexanders disease. Molecular analysis showed that he was a heterozygote of the L331P mutation of GFAP. His mother and sister, without megalocephaly or other neurological abnormalities, were also heterozygotes of the mutation and their brain magnetic resonance imaging showed mild changes in the caudates and deep frontal white matters. These results suggest the existence of a forme fruste of Alexanders disease. The L331P mutation may be associated with the mild phenotype of Alexanders disease. To elucidate the genotype-phenotype correlation in Alexanders disease, molecular diagnosis and MRI examination are required for many patients and their families.

Abducens nerve enhancement demonstrated by multiplanar reconstruction of contrast-enhanced three-dimensional MRI

Abstract We describe contrast enhancement of the cisternal portion of the abducens nerve and discuss its clinical significance. We examined 67 patients with ophthalmoplegia using contrast-enhanced 3-dimensional (3D) MRI with multiplanar reconstruction along the nerves and found 16 patients (ten men, six women), aged 10–73 years (mean 34.4 years), with contrast enhancement of the abducens nerve. Of the 36 patients who had an abducens palsy, 14 (39 %) showed contrast enhancement. In the 16 patients, 23 abducens nerves enhanced; 13 were symptomatic and 10 asymptomatic at the time. The causes were disseminated tumour (1), an inflammatory process (3), trauma (2), ischaemia (2) and autoimmune diseases (8), such as the Miller Fisher syndrome, acute ophthalmoparesis, polyneuropathy and multiple sclerosis. Abducens and/or oculomotor nerve enhancement was the only abnormality on MRI in the patients with traumatic or ischaemic neuropathy or autoimmune diseases. There were 14 patients who recovered fully within 1–6 months after treatment, and resolution of the enhancement correlated well with recovery.

MR and CT findings of craniopharyngioma during and after radiation therapy.

Abstract. Long-term changes in craniopharyngioma treated with radiation therapy (RT) were investigated by computed tomography (CT) and/or magnetic resonance (MR) imaging. Eight patients with craniopharyngioma were treated with incomplete resection or conservative surgical intervention followed by postoperative RT. The periods of tumor shrinkage were often long and varied (range: 6–68 months, mean: 29.1 months). Temporary enlargement of the solid component of a tumor usually occurs during RT and does not represent tumor progression. Cystic enlargement also occurs sometimes comparatively early after RT, and enlarged cysts often shrink with no treatment or with conservative treatment. These changes should be differentiated from tumor recurrence, with careful follow-up. After shrinkage, small solid or cystic nodules enhanced with contrast medium often remain. Long-term follow-up is necessary to differentiate uncontrolled tumors from controlled tumors with imaging modalities.

MRI anatomy of white matter layers around the trigone of the lateral ventricle

Abstract MRI was obtained in eight normal volunteers and seven patients with brain oedema around the trigone. In addition to the conventional sequences, diffusion-weighted and intravoxel-incoherent-motion images using motion-proving anteroposterior and/or lateral direction gradients were obtained to show the white matter pathways better. Coronal proton-density-weighted images showed three thin relatively high-intensity layers in addition to the tapetum and the internal and external sagittal strata. Although they have not been confirmed anatomically, the thin layer between the internal and the external sagittal strata was corroborated by diffusion-weighted and intravoxel-incoherent-motion images, and by characteristics of the spread of oedema into the sagittal stratum. We propose that this layer be named the central sagittal lamina. The other two layers medial and lateral to the sagittal stratum were outside, but in contact with the medial and lateral parts of the sagittal stratum, respectively. We provisionally named them medial and lateral sagittal laminae; they were not evident on any other images. The low-intensity layer on T2-weighting was the internal sagittal stratum. The optic radiation, comprising the external sagittal stratum, appeared as an intermediate to slightly high-intensity layer on T2-weighted images and a low-intensity layer on T1-weighted images as did the corticospinal tract in the posterior internal capsule.

Analysis of Radiation Scatter during Angiographic Procedures: Evaluation of a Phantom Model and a Modified Radiation Protection System

PURPOSE To study the radiation scattering associated with the digital subtraction angiography (DSA) unit in angiographic procedures and to design an effective radiation protection shield based on these data. MATERIALS AND METHODS The number of scattered photons was measured at three points relative to the operators position. Anteroposterior abdominal and lateral cranial fluoroscopy were evaluated. As protective devices, a lead curtain, sliding shields, and a brim-shaped image intensifier (II) hood were designed. RESULTS In abdominal fluoroscopy, radiation was found to scatter to the operators lower limbs from the underside of the catheter table, to the abdomen from the side of the patients body, and to the head and neck from the table surface adjacent to the patient. The use of protective devices reduced exposure from 2.89 to 0.058 mR/min for the operators lower limbs, from 0.987 to 0.069 mR/min for the operators abdomen, and from 0.696 to 0.139 mR/ min for the operators head and neck area. With lateral cranial fluoroscopy, radiation was detected to scatter to the operators lower limbs from the underside of the catheter table, to the abdomen from the patients temporal area, and to the head and neck from the patients face. The use of protective devices reduced exposure from 0.248 to 0.010 mR/min for the operators lower limbs, from 0.129 to 0.010 mR/min for the operators abdomen, and from 0.162 to 0.018 mR/min for the operators head and neck area. CONCLUSIONS The characteristic directions of scattering to the operator were identified. An effective modified radiation protection system was designed based on this information.

Relative Decrease in Signal Intensity of Subcortical White Matter in Spontaneous Intracranial Hypotension on Fluid-Attenuated Inversion Recovery Images

BACKGROUND AND PURPOSE: In reviewing MR images of patients with spontaneous intracranial hypotension (SIH), we found an accentuated decrease in the subcortical white matter on fluid-attenuated inversion recovery (FLAIR) images. Our aim was to determine whether the signal intensity of the subcortical white matter decreases on FLAIR and T2-weighted images in SIH. MATERIALS AND METHODS: We retrospectively examined pretreatment MR images including 7 FLAIR and 10 T2-weighted images obtained from 10 patients with SIH and follow-up images (5 FLAIR and 7 T2-weighted images). Two observers measured the signal intensities in the subcortical white matter on MR images at the level of the centrum semiovale and, to calculate the signal intensity ratios, measured those of the adjacent cortex and corpus callosum. Furthermore, 4 observers performed visual evaluation for accentuated signal intensity decreases for receiver operating characteristic (ROC) analysis. RESULTS: The intensity ratios of the subcortical white matter, both to the adjacent cortex and corpus callosum, were significantly different between the control and pretreatment images in SIH and between pretreatment and follow-up images in SIH on FLAIR images, whereas these showed no significant differences between the control and follow-up images in SIH. On visual inspection, an accentuated decrease in signal intensity in the subcortical white matter was shown on pretreatment FLAIR images, which returned to the control level on follow-up images. However, on the T2-weighted images we could hardly recognize the decrease in the signal intensity. CONCLUSIONS: Awareness of the decreased signal intensity of the subcortical white matter on FLAIR images could help in the diagnosis of SIH.