Neurological manifestations in Japanese Ama divers.

Repetitive breath-hold (BH) diving can lead to accumulation of nitrogen (N2) in blood and tissues, which may give rise to decompression illness (DCI). An unusual condition is "Taravana", the diving syndrome reported by Cross in the 1960s. That report generated wide discussion as to whether BH diving can cause DCI. Paulev was the first person to suggest the link between DCI and BH diving. He, a submarine medical officer developed symptoms of DCI after a series of BH dives, having proceeded the dives by spending time in a hyperbaric chamber at 20 meters for 8 minutes. Recently four professional Japanese BH divers (Ama) with histories of diving accidents were reported. Magnetic resonance imaging of these divers detected cerebral infarcts localized in the watershed areas of the brain. A survey conducted on their island revealed that many Ama divers had experienced stroke-like events. A clinical feature of DCI in BH diving is that the damage is limited to the brain. Although the mechanisms of brain damage in BH diving are unclear, N2 bubbles passing through the lungs or the heart so as to become arterialized are most likely to be the etiological factor.

Chordoma with postoperative subcutaneous implantation and meningeal dissemination: MRI.

Chordomas are histologically benign tumours which are locally invasive. We present an unusual case of recurrent chordoma with subcutaneous implantation and widespread meningeal dissemination after surgery. Contrast-enhanced MRI was useful for determining the extent of the tumour.

Facial nerve palsy: evaluation by contrast-enhanced MR imaging.

AIM: The purpose of this study was to investigate the value of contrast-enhanced magnetic resonance (MR) imaging in patients with peripheral facial nerve palsy. MATERIALS AND METHODS: MR imaging was performed in 147 patients with facial nerve palsy, using a 1.0 T unit. All of 147 patients were evaluated by contrast-enhanced MR imaging and the pattern of enhancement was compared with that in 300 control subjects evaluated for suspected acoustic neurinoma. RESULTS: The intrameatal and labyrinthine segments of the normal facial nerve did not show enhancement, whereas enhancement of the distal intrameatal segment and the labyrinthine segment was respectively found in 67% and 43% of patients with Bell's palsy. The geniculate ganglion or the tympanic-mastoid segment was enhanced in 21% of normal controls versus 91% of patients with Bell's palsy. Abnormal enhancement of the non-paralyzed facial nerve was found in a patient with bilateral temporal bone fracture. CONCLUSION: Enhancement of the distal intrameatal and labyrinthine segments is specific for facial nerve palsy. Contrast-enhanced MR imaging can reveal inflammatory facial nerve lesions and traumatic nerve injury, including clinically silent damage in trauma.

Arterial fraction of cerebral blood volume in humans measured by positron emission tomography.

In quantitative functional neuroimaging with positron emission tomography (PET) and magnetic resonance imaging (MRI), cerebral blood volume (CBV) and its three components, arterial, capillary, and venous blood volumes are important factors. The arterial fraction for systemic circulation of the whole body has been reported to be 20-30%, but there is no report of this fraction in the brain. In the present study, we estimated the arterial fraction of CBV with PET in the living human brain. C(15)O and dynamic H2(15)O PET studies were performed in each of seven healthy subjects to determine the CBV and arterial blood volume (Va), respectively. A two-compartment model (influx: K1, efflux: k2) that takes Va into account was applied to describe the regional time-activity curve of dynamic H2(15)O PET. K1, k2 and Va were calculated by a non-linear least squares fitting procedure. The Va and CBV values were 0.011 +/- 0.004 ml/ml and 0.031 +/- 0.003 ml/ml (mean +/- SD), respectively, for cerebral cortices. The arterial fraction of CBV was 37%. Considering the limited first-pass extraction fraction of H2(15)O, the true arterial fraction of CBV is estimated to be about 30%. The estimated arterial fraction of CBV was quite similar to that of the systemic circulation, whereas it was greater than that (16%) widely used for the measurement of cerebral metabolic rate of oxygen (CMRO2) using PET. The venous plus capillary fraction of CBV was 63-70% which is a important factor for the measurement of CMRO2 with MRI.

High-intensity facial nerve lesions on T2-weighted images in chronic persistent facial nerve palsy.

Our aim was to estimate the value of MRI in detecting irreversibly paralysed facial nerves. We examined 95 consecutive patients with a facial nerve palsy (14 with a persistent palsy, and 81 with good recovery), using a 1.0 T unit, with T2-weighted and contrast-enhanced T1-weighted images. The geniculate ganglion and tympanic segment had gave high signal on T2-weighted images in the chronic stage of persistent palsy, but not in acute palsy. The enhancement pattern of the facial nerve in the chronic persistent facial nerve palsy is similar to that in the acute palsy with good recovery. These findings suggest that T2-weighted MRI can be used to show severely damaged facial nerves.

Evaluation of novel PET ligands (+)N-[11C]methyl-3-piperidyl benzilate ([11C](+)3-MPB) and its stereoisomer [11C](-)3-MPB for muscarinic cholinergic receptors in the conscious monkey brain: a PET study in comparison with.

The novel muscarinic cholinergic ligands (+)N-[11C]methyl-3-piperidyl benzilate ([11C](+)3-MPB) and its stereoisomer [11C](-)3-MPB were evaluated in comparison with [11C]4-MPB in the brains of conscious monkeys (Macaca mulatta) using high-resolution positron emission tomography (PET). The regional distribution patterns of [11C](+)3-MPB and [11C]4-MPB at 60-91 min postinjection were almost identical: highest in the striatum and occipital cortex; intermediate in the temporal and frontal cortices, cingulate gyrus, hippocampus, and thalamus; lower in the pons; and lowest in the cerebellum. The uptake of [11C](+)3-MPB in all regions was higher and the dynamic range of regional uptake differences of [11C](+)3-MPB was better than those of [11C]4-MPB. The levels of [11C](-)3-MPB were much lower in all regions of the brain than [11C](+)3-MPB and [11C]4-MPB. Administration of scopolamine, a muscarinic cholinergic antagonist, at a dose of 50 microg/kg reduced the radioactivity of [11C](+)3-MPB and [11C]4-MPB in all regions except the cerebellum. Time-activity curves of [11C](+)3-MPB peaked in all regions, while those of [11C]4-MPB showed gradual increases with time in all regions except the thalamus, pons, and cerebellum. Two graphical analyses (Logan plot and Patlak plot) with plasma radioactivity as an input function into the brain were applied to evaluate receptor binding in vivo. [11C](+)3-MPB showed linear regression curves on Logan plot analysis and nonlinear curves on Patlak plot in all regions, suggesting that [11C](+)3-MPB bound reversibly to the muscarinic receptors. The in vivo binding parameters as well as uptake at 60-91 min postinjection of [11C](+)3-MPB were consistent with muscarinic receptor density in the brain as reported in vitro.

Volumetric analysis of the germinal matrix and lateral ventricles performed using MR images of postmortem fetuses.

BACKGROUND AND PURPOSE: The volumetric changes of the ventricular system and germinal matrix are important to understand brain maturation and the mechanism of subependymal hemorrhage. Our purpose was to show the 3D configuration of the brain, germinal matrix, and lateral ventricles and to discuss the volumetric changes of each structure with maturation by using high-resolution MR imaging. METHODS: Three-dimensional MR images of 13 formalin-fixed fetal brains ranging from 7 to 28 weeks' gestational age (GA) were obtained on a 4.7-T unit. Each 3D configuration of the brain surface, germinal matrix, and ventricles was rendered from the cross-sectional imaging data sets and its volume measured. RESULTS: The germinal matrix was detected on MR images at 9 weeks' GA. Its volume exponentially increased by 23 weeks' GA (maximum, 2346 mm3) and then sharply decreased at 28 weeks' GA. The volume of the lateral ventricles increased gradually and reached 2646 mm3 peak volume at 23 weeks' GA. Between 11 and 23 weeks' GA, total brain and germinal matrix volumes were exponentially increasing, but the volume ratio of germinal matrix to brain was stable at about 5%. On the other hand, the volume ratio of lateral ventricles to brain was large between 10 and 13 weeks' GA. This period corresponded to the lateral ventricle showing a "vesicular" aspect with a thin mantle, and the developing mantle thickness of the hemisphere resulted in the decreasing ratio. CONCLUSION: Volumetric information concerning the germinal matrix and lateral ventricles may be useful in the accurate interpretation of clinical echograms and MR images of the fetal brain in utero.

Neurological accidents caused by repetitive breath-hold dives: two case reports.

We report two Japanese male professional breath-hold divers (33 and 39 years of age) who experienced neurological disorders during repetitive dives to over 20 m of seawater. One patient had right homonymous hemianopsia, and the other presented with right hemiparesis with facial involvement and sensory deficit. In addition, they each had a history of neurological problems following such dives. Magnetic resonance images of their brains disclosed multiple T2-weighted hyperintensities corresponding to their neurological symptoms. Their brain lesions suggest a multiple cerebral infarction caused by occlusion of the cerebral arteries. We conclude that the repetitive deep breath-hold dives induced the brain involvement.

[Imaging of perivascular spaces of the brain: MR-clinical correlation].

1. We evaluated the perivascular spaces(PVS) of the intraparenchymal arteries of the brain obtained from MRI, and compared them with the microangiograms of the injected autopsied brains of normal adults. 2. The three dimensional microangiograms revealed 3 types of intraparenchymal arteries: intracortical, subcortical(including arteries of arcuate fibers) and medullary arteries. PVS of those arteries had punctuated or small linear-shaped appearances according to the dimension and level of MR slices. 3. Basic MR findings of normal PVS showed smooth and well-defined round or elliptical configurations up to 3 mm in diameter without a halo in the surrounding tissue, located along the intraparenchymal arteries, and isointense with cerebro-spinal fluid. 4. PVS around the medullary arteries was dilated with age. Definite PVS was found in the lower portion of the basal ganglia in almost all healthy children and relatively young adults, however, it was less frequent in the subcortical white matter of frontal and parietal lobes. In adults over 60 years of age, dilatation of PVS along the medullary arteries was quite common and progressed into the frontal and parietal lobes. 5. Dilatation of PVS around the medullary arteries was prominent and increased with the number of lacunar infarcts. The sclerotic change of medullary arteries was more accelerated in subjects with hypertension.

Regional differences in cerebral vascular response to PaCO2 changes in humans measured by positron emission tomography.

Hypercapnia and hypocapnia produce cerebral vasodilation and vasoconstriction, respectively. However, regional differences in the vascular response to changes in Paco2 in the human brain are not pronounced. In the current study, these regional differences were evaluated. In each of the 11 healthy subjects, cerebral blood flow (CBF) was measured using 15O-water and positron emission tomography at rest and during hypercapnia and hypocapnia. All CBF images were globally normalized for CBF and transformed into the standard brain anatomy. t values between rest and hypercapnia or hypocapnia conditions were calculated on a pixel-by-pixel basis. In the pons, cerebellum, thalamus, and putamen, significant relative hyperperfusion during hypercapnia was observed, indicating a large capacity for vasodilatation. In the pons and putamen, a significant relative hypoperfusion during hypocapnia, that is, a large capacity for vasoconstriction, was also observed, indicating marked vascular responsiveness. In the temporal, temporo-occipital, and occipital cortices, significant relative hypoperfusion during hypercapnia and significant relative hypoperfusion during hypocapnia were observed, indicating that cerebral vascular tone at rest might incline toward vasodilatation. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve by hypercapnia and in the correction of CBF measurements for variations in subjects' resting Paco2.

Assessment of lacunar hemorrhage associated with hypertensive stroke by echo-planar gradient-echo T2*-weighted MRI.

BACKGROUND AND PURPOSE: Echo-planar gradient-echo T2*-weighted MR imaging (GRE-EPI) may detect hypointense lesions representing microhemorrhages with high sensitivity. The aim of this study was to evaluate the effectiveness of GRE-EPI for detecting old lacunar hemorrhages in hypertensive patients with stroke. METHODS: GRE-EPI was performed with a 1.5-T MRI system in 198 hypertensive patients with stroke (130 patients with hemorrhagic stroke and 68 patients with multiple lacunar stroke) and 66 age-matched healthy elderly individuals. RESULTS: Concomitant hypointense foci were found in 84 (66%) patients with hemorrhagic stroke, 46 (68%) patients with multiple lacunar stroke, and 3 (5%) healthy elderly individuals. These hypointense foci were noted in the lentiform nucleus in 61 (47%) patients with hemorrhagic stroke, in the caudate nucleus in 9 (7%) patients, in the thalamus in 54 (42%) patients, in the corticosubcortical region in 57 (44%) patients, in the brain stem in 40 (34%) patients, and in the cerebellum in 32 (25%) patients. CONCLUSIONS: GRE-EPI is effective for the detection of lacunar hemorrhages induced by hypertension.

Development of the cavernous sinus in the fetal period: a morphological study.

The development and morphological structure of the lateral sellar compartment (LSC), an interdural space containing the cavernous sinus (CS), cranial nerves, and internal carotid artery (ICA), was investigated by histological examination of sections of the LSC and cerebral venograms from human fetal specimens. Twenty-eight LSC coronal sections were obtained from 14 fetuses of 13-32 weeks' gestation. Venograms of 11 other fetuses of 13-32 weeks' gestation were studied to observe changes in venous drainage. The CS appeared as a collection of small venous canals with an endothelial layer. These venous canals gradually became much larger through expansion and unification. The CS and basilar venous plexus were demonstrated as a faint cluster of small vessels on venograms obtained after 13 weeks' gestation. The dura mater increased in thickness and collagen fiber networks developed around all the components in the LSC after 23 weeks' gestation. The LSC lateral wall could not be histologically differentiated as separate multiple layers. Branching and joining of the cranial nerve fascicles were completed with the envelopment of collagen fibers after 23 weeks' gestation. The ICA at 13-15 weeks' gestation ran straight within the LSC, becoming tortuous before birth. CS formation occurs through the development of venous canals without smooth muscle layers, followed by web-formation by collagen fibers in the mesenchymal interstices. LSC formation, including the dense dura mater and an internal structure like that seen in the adult, is largely completed before birth.

Effects of scatter correction on regional distribution of cerebral blood flow using I-123-IMP and SPECT.

The transmission dependent convolution subtraction method which is one of the methods for scatter correction of SPECT was applied to the assessment of CBF using SPECT and I-123-IMP. The effects of scatter correction on regional distribution of CBF were evaluated on a pixel by pixel basis by means of an anatomic standardization technique. SPECT scan was performed on six healthy men. Image reconstruction was carried out with and without the scatter correction. All reconstructed images were globally normalized for the radioactivity of each pixel, and transformed into a standard brain anatomy. After anatomic standardization, the average SPECT images were calculated for scatter corrected and uncorrected groups, and these groups were compared on pixel by pixel basis. In the scatter uncorrected group, a significant overestimation of CBF was observed in the deep cerebral white matter, pons, thalamus, putamen, hippocampal region and cingulate gyrus as compared with scatter corrected group. A significant underestimation was observed in all neocortical regions, especially in the occipital and parietal lobes, and the cerebellar cortex. The regional distribution of CBF obtained by scatter corrected SPECT was similar to that obtained by O-15 water PET. The scatter correction is needed for the assessment of CBF using SPECT.

Positron emission tomography in juvenile Alexander disease.

A 13-year-old boy with cervical kyphosis was diagnosed as having juvenile Alexander disease because of the typical MRI findings, abnormally elevated alphaB-crystallin and heat shock protein 27 in the cerebrospinal fluid. Positron emission tomography with 18F-fluorodeoxyglucose demonstrated hypometabolism in the frontal white matter corresponding to the areas with leukodystrophy. However, the overlying gray matter preserved normal glucose metabolism.

Cerebral blood volume in acute brain infarction: A combined study with dynamic susceptibility contrast MRI and 99mTc-HMPAO-SPECT.

BACKGROUND AND PURPOSE: The aim of this study was to correlate the abnormality in cerebral blood volume (CBV) measured by dynamic susceptibility contrast-enhanced MRI with that in cerebral blood flow (CBF) estimated by single-photon emission CT with [99mTc]hexamethylpropylenamine-oxime in patients with acute ischemic stroke. METHODS: Nine patients with unilateral occlusion of either the middle cerebral artery or the internal carotid artery (4 men and 5 women; mean+/-SD age, 74.4+/-11.6 years) were studied within 6 hours after stroke onset. The relative CBV (relCBV) and CBF (relCBF) in the lesions were defined relative to the contralateral mirror regions. RESULTS: In the brain regions with mild (relCBF >/=0.60), moderate (0.401.0) regions was significantly lower than that for hypovolemic (relCBV <1.0) regions in the relCBF range between 0.40 and 0.50 (P<0.02). CONCLUSIONS: In acute ischemic stroke within 6 hours of onset the CBV can be either increased, normal, or decreased, depending on the severity of hypoperfusion. The increased CBV has a protective effect on evolving infarction. Although the CBF is a better predictor of tissue outcome, the CBV measurement may help detect potentially salvageable brain tissue in the penumbra with compromised blood flow.

Cranial MRI of neurologically impaired children suffering from neonatal hypoglycaemia.

BACKGROUND: Metabolic disturbances such as anoxia and hypoglycaemia are important in causing maldevelopment of the neonatal brain. While there have been some pathology studies of the effects of neonatal hypoglycaemia on brain development, reports of MRI findings in such infants have been rare. OBJECTIVES: To describe the MRI findings in neurologically handicapped children who had suffered from neonatal hypoglycaemia and to evaluate the relationship between the neurological impairment and neonatal hypoglycaemia. MATERIALS AND METHODS: We retrospectively evaluated the MRI findings in eight full-term infants with neonatal symptomatic hypoglycaemia who later exhibited neurological handicap. The age at which the MRI scans were obtained ranged from 9 months to 8 years 10 months (mean 4 years 1 month, median 4 years). RESULTS: The most striking findings were prolonged T1 weighting and T2 weighting in the parieto-occipital periventricular deep white matter in six patients, suggesting abnormal or delayed myelination. Dilatation of the lateral ventricles, especially of the trigones, was observed in five patients in whom the distance between the posterior horns of the lateral ventricles and the adjacent sulci was reduced. The volume of white matter relative to grey matter was reduced in two patients. In addition, four patients exhibited cerebral cortical atrophy, mainly in the occipital lobe. CONCLUSIONS: These findings suggest that neonatal hypoglycaemia may cause delayed or abnormal myelination, especially in the parieto-occipital, periventricular, deep white matter, and may cause cerebral cortical atrophy, especially in the occipital lobe.

Micro-angiographical studies of the medullary venous system of the cerebral hemisphere.

In order to identify the zones of convergence of the medullary veins of the cerebral white matter, gelatin-mixed barium sulfate was injected into normal brains at autopsy. A catheter was inserted into the internal jugular veins or the carotid and vertebral arteries. Serial soft tissue roentgenograms of whole brains and brain slices were used to determine the zones of convergence. The deep med-ullary veins had four zones of covergence before draining into the subependymal veins: the first (superficial), second (candelabra), third (palmate) and fourth (subependymal). The zones of various convergence within the white matter were due to the crossing of nerve fiber tracts (e.g. the pes of the corona radiata, the radiation of the corpus callosum, the superior occipitofrontal fasciculus, the tapetum and the sagittal strata). Similar but less conspicuous information about the parenchymal arteries was observed in the arterial injection studies. These results suggest that micro-angiographical studies of the medullary veins of the cerebral white matter provide detailed information on veno-architecture and convergence zones. This information may help in understanding the pathogenesis of medullary venous malformations.

Multiple cerebral infarction in Japanese breath-hold divers: two case reports.

We report on two Japanese breath-hold divers (ama) who developed neurological disturbances following more than 3 hours of consecutive dives to 15-25 meters of seawater. Their magnetic resonance images of the brain showed multiple cerebral infarcts which were consistent with their neurological symptoms. The cerebral lesions seem to have been caused by repetitive breath-hold dives for extended periods of time. Immediate recompression is required when neurological symptoms develop after such dives.

Parapharyngeal meningioma extending from the intracranial space evaluated by FDG PET.

We report a rare case of parapharyngeal meningioma extending from the intracranial space evaluated by PET with [18F]-2-fluorodeoxyglucose (FDG). Although the parapharyngeal meningioma had a high rate of glucose metabolism, it was proved to be pathohistologically benign. The high rate of glucose metabolism of the tumor reflected tumor aggressiveness well because the tumor grew in a relatively short time.

Subcortical hypoperfusion associated with asymptomatic white matter lesions on magnetic resonance imaging.

BACKGROUND AND PURPOSE: We examined whether hemodynamic and metabolic abnormalities in the cerebral white matter, basal ganglia, and thalamus are associated with asymptomatic white matter lesions (WML) depicted on MR images. METHODS: A positron emission tomographic study with H2(15)O, C15O, and 15O2 was performed in eight normal control subjects without any WML (mean +/- 1 SD age, 68.5 +/- 10.2 years) and in 15 asymptomatic subjects with WML (71.3 +/- 8.5 years) to measure regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and oxygen metabolic rate. RESULTS: In the cerebral white matter in the asymptomatic subjects with WML, significantly lower CBF (20.3 +/- 3.9 mL/100 mL per minute; P < .05) and significantly higher OEF (0.43 +/- 0.08; P < .05) were found compared with those for control subjects (23.5 +/- 2.6 mL/100 mL per minute and 0.37 +/- 0.06, respectively). The severity of WML was not related to the magnitude of hypoperfusion. In the basal ganglia, significantly lower CBF (44.9 +/- 6.9 mL/100 mL per minute; P < .01) and significantly higher OEF (0.54 +/- 0.08; P < .01) were found in the WML group than in control subjects (70.1 +/- 12.0 mL/100 mL/min and 0.39 +/- 0.03, respectively). In the thalamus, there was no significant difference in CBF and OEF between the control and WML groups. CONCLUSIONS: Hypoperfusion of the cerebral white matter and basal ganglia in asymptomatic WML subjects may be induced by the arteriosclerosis of long penetrating medullary arteries and lenticulostriate arteries but may not be directly related to the production of WML. The role of hypoperfusion in the production of WML and acceleration of its development remains to be elucidated.