The cortical representation of speech

Abstract In this study, we compare regional cerebral blood flow (rCBF) while French monolingual subjects listen to continuous speech in an unknown language, to lists of French words, or to meaningful and distorted stories in French. Our results show that, in addition to regions devoted to single-word comprehension, processing of meaningful stories activates the left middle temporal gyrus, the left and right temporal poles, and a superior prefrontal area in the left frontal lobe. Among these regions, only the temporal poles remain activated whenever sentences with acceptable syntax and prosody are presented.

Neuroanatomic analysis of diffusion tensor imaging of white matter tracts with dejerine sections and neuroimaging

We present a neuroanatomical comparison with stereotaxic precision correlating modern diffusion tensor imaging (DTI), MRI data and classical neuroanatomical textbooks. The neuroatlas compiled by J. and A. Dejerine deserves emphasis for its role of a bridge between precise classical neuroanatomy techniques with modern neuroimaging methods. We present its utility in identifying major white matter tracts of the brain in concert with DTI in the horizontal-plane axis to elucidate axonal directionality. The axonal directionality of DTI is necessary for understanding white matter connectivity in the brain. Many DTI studies publish findings in selective regions of the brain, and our study is mainly devoted to comparing our images with data from Dejerine for the entire brain.

Construction of a 3D probabilistic atlas of human cortical structures

We describe the construction of a digital brain atlas composed of data from manually delineated MRI data. A total of 56 structures were labeled in MRI of 40 healthy, normal volunteers. This labeling was performed according to a set of protocols developed for this project. Pairs of raters were assigned to each structure and trained on the protocol for that structure. Each rater pair was tested for concordance on 6 of the 40 brains; once they had achieved reliability standards, they divided the task of delineating the remaining 34 brains. The data were then spatially normalized to well-known templates using 3 popular algorithms: AIR5.2.5's nonlinear warp (Woods et al., 1998) paired with the ICBM452 Warp 5 atlas (Rex et al., 2003), FSL's FLIRT (Smith et al., 2004) was paired with its own template, a skull-stripped version of the ICBM152 T1 average; and SPM5's unified segmentation method (Ashburner and Friston, 2005) was paired with its canonical brain, the whole head ICBM152 T1 average. We thus produced 3 variants of our atlas, where each was constructed from 40 representative samples of a data processing stream that one might use for analysis. For each normalization algorithm, the individual structure delineations were then resampled according to the computed transformations. We next computed averages at each voxel location to estimate the probability of that voxel belonging to each of the 56 structures. Each version of the atlas contains, for every voxel, probability densities for each region, thus providing a resource for automated probabilistic labeling of external data types registered into standard spaces; we also computed average intensity images and tissue density maps based on the three methods and target spaces. These atlases will serve as a resource for diverse applications including meta-analysis of functional and structural imaging data and other bioinformatics applications where display of arbitrary labels in probabilistically defined anatomic space will facilitate both knowledge-based development and visualization of findings from multiple disciplines.

White matter fiber tractography and color mapping of the normal human cerebellum with diffusion tensor imaging

Diffusion tensor imaging (DTI) color mapping and fiber tractography was used to study the white matter within the cerebellum along with the afferent and efferent tracts associated with the cerebellum in 24 normal human subjects. The most prominent structures that can be readily identified using these DTI techniques are the middle, inferior and superior cerebellar peduncles. Furthermore DTI shows transverse white matter fiber that cross between the two cerebellar hemispheres at the level of the vermis. At the hemispheric level fibers to the dentate, to the emboliform nuclei are clearly visible on DTI as is the afferent pathway represented by the middle cerebellar peduncle. Selective DTI fiber tractography provides very exquisite images of the cerebellar peduncles and of the fibers projecting to and from the cerebellar cortex. This study demonstrates that DTI is complementary to conventional MRI in that DTI elucidates the orientation of white matter fiber bundles that are associated with the cerebellum. Therefore we anticipate that DTI will become an important adjunct to conventional MRI for clinical and basic studies of cerebellar ataxias and congenital disorders involving the cerebellum and brain stem. This work provides a summary of the normal DTI appearance of the cerebellar white matter which will be useful for interpreting DTI results in clinical populations.

Diffusion tensor MRI shows abnormal brainstem crossing fibers associated with ROBO3 mutations

Horizontal gaze palsy with progressive scoliosis (HGPPS) is caused by mutations in the ROBO3 gene, critical for the crossing of long ascending medial lemniscal and descending corticospinal tracts in the medulla. Diffusion tensor imaging in a patient with HGGPS revealed the absence of major pontine crossing fiber tracts and no decussation of the superior cerebellar peduncles. Mutations in the ROBO3 gene lead to a widespread lack of crossing fibers throughout the brainstem.

The human cerebral cortex on MRI: value of the coronal plane

The evaluation of different cortical areas of the cerebral cortex has been analyzed using MRI of 50 normal subjects without any neurological symptoms. This analysis has been made with different spin echo and gradient echo in T1 or T2 in three different planes: horizontal, sagittal and coronal. The most accurate plane to define important cortical areas such as Broca area, Wernicke area, temporal cortex at the level of the superior temporal sulcus, angular gyrus, supra marginal gyrus, hippocampal and parahippocampal cortices as well as that of the parieto or temporo-occipital areas is the coronal plane. Evidently it must be correlated with the other orthogonal planes. To be compared with the main Atlas of Neuroanatomy these sections must be perpendicular or parallel to the plane passing through the anterior and posterior commissures. MRI of patients with neurological disorders must have, as a routine, a series of MR sections performed in the coronal plane, as well as in horizontal and sagittal ones. The coronal plane is certainly the most precise to evaluate these areas involved in language, memory, visuo spatial or behavioral functions. It must be always compared with the rest of the neuroradiological examination and correlated with the clinical neurological signs.

Analysis of the brain-stem white-matter tracts with diffusion tensor imaging

The authors have reviewed the diffusion tensor imaging (DTI) of the brain stem in 19 subjects, consisting of 15 normal volunteers and four multi-system atrophy patients. The study was performed with 1.5 T MRI scanners. DTI was correlated with an automated program allowing superposition of the structural anatomy. Axial, sagittal, and coronal images demonstrated major white-matter fibers within the brain stem, including cortico-spinal tracts, transverse pontine fibers, and medial lemniscus. Smaller fibers, such as medial longitudinal fascicles and central tegmental tracts are difficult to visualize. To identify the anatomical orientation of the brain stem, white-matter fibers will help us understand the different functional disease processes, and DTI will play an important role for the evaluation of the different white matter fibers in the brain stem.

[Susceptibility weighted imaging. Theory and applications]

Susceptibility Weighted Imaging (SWI) is a new MR imaging technique using the BOLD effect (Blood Oxygen Level Dependent) and the differences of susceptibility between tissues. It is a 3D gradient echo, fully velocity compensated sequence. The echo time is chosen to maximize the signal cancellation in veins and a specific post-processing is applied using the phase images as a complementary source of contrast. It is very useful for the visualization of veins either normal or abnormal. It shows hemorrhage, even of small quantity, better than conventional gradient echo sequences. Its use is still limited by a long acquisition time and some remaining artifacts.

Mutations in a human ROBO gene disrupt hindbrain axon pathway crossing and morphogenesis

The mechanisms controlling axon guidance are of fundamental importance in understanding brain development. Growing corticospinal and somatosensory axons cross the midline in the medulla to reach their targets and thus form the basis of contralateral motor control and sensory input. The motor and sensory projections appeared uncrossed in patients with horizontal gaze palsy with progressive scoliosis (HGPPS). In patients affected with HGPPS, we identified mutations in the ROBO3 gene, which shares homology with roundabout genes important in axon guidance in developing Drosophila, zebrafish, and mouse. Like its murine homolog Rig1/Robo3, but unlike other Robo proteins, ROBO3 is required for hindbrain axon midline crossing.

[Magnetic resonance studies in Alzheimer's dementia. What routine scanning shows]

Magnetic resonance images of the brain acquired in relationship to the commissural plane have been analyzed in twenty cases classified as Probable Alzheimer's disease (Pr. AD). These examinations have been compared to normal aged matched subjects. All examinations have been made in strict correlation with the planes defined by Talairach and Tournoux (1988). The analysis of brain cortical damage was made by evaluating the sulci of the brain mainly on coronal sections correlated with simultaneous image review of the same area on the two other orthogonal planes. In Pr. AD, an asymmetric atrophic pattern was found mainly on the following areas: amygdaloid nucleus, para hippocampal gyrus, hippocampus, areas 22 and 21, temporal pole, insula, dorso frontal cortex, angular gyrus, superior parietal lobule. The primary motor and visual areas were normal in all cases.

A longitudinal study of callosal atrophy and interhemispheric dysfunction in relapsing-remitting multiple sclerosis

OBJECTIVES

To determine if callosal atrophy and interhemispheric dysfunction can be detected in the early stages of relapsing-remitting multiple sclerosis (MS) and to evaluate their progression in relation to the disability and evolution of lesions seen on magnetic resonance imaging during a 5-year period.

METHODS

We compared 30 patients who had clinically definite early-onset replasing-remitting MS and mild disability with control subjects. Regional and segmental callosal size and extent of white matter abnormalities on magnetic resonance imaging, as well as performance on tasks exploring interhemispheric transfer of motor, auditory, and sensory information were assessed. Patients with MS were evaluated at baseline and after 5 years. Physical disability was determined at both times using the Expanded Disability Status Scale score.

RESULTS

Patients with MS were seen with significant callosal atrophy and functional impairment of interhemispheric transfer at baseline that worsened during the 5-year study. A significant correlation was found between the magnitude of disability and the severity of morphological and functional callosal involvement at baseline. This association persisted at year 5. Baseline clinical characteristics such as age and prestudy relapse rate were unrelated to callosal size or interhemispheric performance. However, the number of baseline T2-weighted lesions was correlated with callosal involvement and this relation persisted at year 5.

CONCLUSION

Patients who had relapsing-remitting MS in the early stages of the disease and mild disability had significant callosal involvement that progressed over time. The relationship between disability, T2-weighted lesions load, and degree of morphological and functional callosal impairment confirm the potential value of using callosal dysfunction as a surrogate marker of disease progression in MS.

MRI of the intracranial corticospinal tracts in amyotrophic and primary lateral sclerosis

Our aim was to investigate the corticospinal tracts (CST) in motor neurone disease, using MRI, and to correlate findings with clinical data. We studied 31 patients with amyotrophic (ALS) and eight with primary lateral sclerosis (PLS). The signal from the CST was classified into four grades on T2-weighted images, and compared to T2-weighted images of 37 age-matched control subjects. No abnormalities were seen in the CST on T1-weighted images and were rarely evident on proton-density weighting. Variable high signal in the CST was found on T2-weighted images in 35 patients, and in 29 control subjects. Our grades 0 and 1 were more frequent in control subjects, grades 2 and 3 more frequent in patients. We found no correlation between the high signal and clinical data, including the duration of the illness. We therefore conclude that this technique is neither sensitive nor specific except in grade 3 which is quite specific for ALS. In half the patients we found atrophy of the superior parietal gyrus, which merits further study.

[Divergent asymmetries of the temporo-parietal cortical areas: anatomo-functional correlations and evolutionary and developmental implications]

Human brains present a clear asymmetry of the postero-lateral cortical area, so called "planum temporale" (Geschwind and Levitsky). This asymmetry is on favour of the left brain. A similar asymmetry is observed on the parietal operculum. MRI studies of 37 healthy volunteers have shown a clear difference between individuals. Mixing the index of temporal and parietal asymmetry, the authors consider four types: the most frequent pattern concerns 90% of right handed. For the others, 10% there are left handed as right handed. On conclusion, planum as many asymmetry and opercular asymmetry can be divergent, and both canan to determines handedness.

Contrast-enhanced magnetisation transfer MRI in metastatic lesions of the brain

Our purpose was to compare prospectively the sensitivity of contrast-enhanced magnetisation transfer (MT) MRI and gradient-echo (GE) T1-weighted images in metastatic disease of the brain. We studied 52 patients with brain metastases, using conventional T1-weighted GE and MT spin-echo (SE) images after the same standard dose of gadolinium. Axial 5-mm reconstructions of GE data were compared with 5-mm MT images in the same plane. Metastases were counted independently by two neuroradiologists. In 12 patients (23%) MT imaging showed more metastases than GE images (P = 0.03). We detected 68 more metastases with the former technique.

MRI of intracranial chordomas. Extent of tumour and contrast enhancement: criteria for differential diagnosis

We present six proven cases of chordoma of the clivus studied by CT and MRI, with special attention to the extent of the tumour and to the signal intensity after intravenous gadolinium. MRI is the best technique for assessing the extent of the tumour but CT is important for showing osteolysis. Our aim was to determine differential diagnostic neuroradiological criteria. Reliable signs of chordoma of the skull base are: posterior extension to the pontine cistern; a lobulated, "honeycomb" appearance after gadolinium: the swollen appearance of the bone in the early stages; bone erosion on CT and frequent extension to critical structures such as the circle of Willis, cavernous sinuses and brain stem.

"Follow-up" method for processing of brain function MR images

FMRI with standard 1.5 T scanners requires adapted algorithms because the time course of intensity signal showed a non-linearity of the baseline. The protocol contains sequential images covering periods of rest followed periods of stimulation. The images of each period of rest and stimulation were averaged, offering a series of averaged images. From this series, we conserved only the pixels which presented the alternated variations corresponding to the temporal pattern of the paradigm. A colour scale was used to present the average percentage of variations of each pixel selected. We have performed activation paradigms with a classical motor protocol. This simple "follow-up" method appears effective for the identification of activated areas.

Theoretical situation of brain white matter tracts evaluated by three-dimensional MRI

An accurate knowledge of cerebral anatomy is important in order to evaluate the precise location of a cerebral lesion. Cortical structures are identified by knowledge of the adjacent gyri and sulci; however, white matter tracts are difficult to differentiate from one another due to the lack of clear anatomic landmarks. Therefore, even if MRI shows obvious white matter abnormalities, in some cases it is difficult accurately to localize the lesion. The purpose of this study is to evaluate the location of the main white matter tracts by using three-dimensional MR imaging. MRI study was performed by 1.5 Tesla (Signa: General Electric). Computer assisted analysis with Voxtool software (General Electric) was used to generate both surface brain and tomographic images. The exact anatomic basis of white matter signal abnormalities is important when analyzing patients with disconnective syndromes or neuropsychological deficits such as conduction aphasia, visuospatial deficit etc. This preliminary attempt at constructing a three-dimensional MRI white matter atlas of the brain may be helpful for evaluating the anatomico-clinical correlations in these patients, and also as teaching materials for the clinical (neurologic, neurosurgical), anatomic and radiographic disciplines.

Mutism and auditory agnosia due to bilateral insular damage--role of the insula in human communication

We report a case of transient mutism and persistent auditory agnosia due to two successive ischemic infarcts mainly involving the insular cortex on both hemispheres. During the 'mutic' period, which lasted about 1 month, the patient did not respond to any auditory stimuli and made no effort to communicate. On follow-up examinations, language competences had re-appeared almost intact, but a massive auditory agnosia for non-verbal sounds was observed. From close inspection of lesion site, as determined with brain resonance imaging, and from a study of auditory evoked potentials, it is concluded that bilateral insular damage was crucial to both expressive and receptive components of the syndrome. The role of the insula in verbal and non-verbal communication is discussed in the light of anatomical descriptions of the pattern of connectivity of the insular cortex.

Diverging asymmetries of temporo-parietal cortical areas: a reappraisal of Geschwind/Galaburda theory

The general theory on the biological foundations of cerebral dominance formulated in 1985 by Geschwind and Galaburda entirely relies on a postulated causal relationship between anatomical asymmetry of the planum temporale and functional lateralization of the human brain, but does not take into account asymmetry of another cortical region, the parietal operculum. In 40 normal volunteers whose handedness was specified by the Edinburgh Handedness Inventory, we assessed asymmetries of these two regions on MRI sagittal scans. For both measurements, a significantly larger leftward asymmetry was found in the 24 consistent right-handers compared to the 16 non-right-handers. Moreover, the combination, for each subject, of the two indices of asymmetry, yielded four different subtypes between which handedness distribution significantly differed. We conclude that planum temporale and parietal operculum asymmetries may be divergent and that their convergence is strongly associated with right-handedness. Functional and developmental implications of these findings are discussed by reference to the Geschwind/Galaburda theory.

Functional magnetic resonance imaging at 1.5 T during sensorimotor and cognitive task

Functional activations of the human brain cortex were observed with a standard 1.5-tesla MR imaging system using a long time echo fast low-angle shot sequence. Neural activation increases regional cerebral blood flow resulting in increased capillaries and venous blood oxygenation. Processing requires adapted algorithms because the time course of intensity signal showed fluctuations of the baseline. The use of a 'follow-up' method to generate activation maps is proposed. Brain activation was detected in striate cortex during photic stimulation and in sensorimotor areas while subjects were moving their hands. In mental imagery tasks, we observed a primary and secondary visual cortex activation during memory recall of the flashing light. Motor ideation showed an activation of the rolandic areas.

[Functional cerebral neuro-imaging at 1.5 Tesla. The results of visual, sensorimotor and auditory stimulations]

Functional activation of the cerebral cortex can be observed with a standard 1.5 Tesla MRI magnet. We used a repeated FLASH 2D one-section sequence with a long echo (TE = 60 ms) and a small passing band. Modification of regional cerebral oxygenation due to neurone activation seems to be the main source of contrast. Sensorimotor stimulation was effected by an unusual mobilization of the fingers. Visual stimulation was performed by intermittent lightings at a frequency of 8 Hz. Auditory stimulation relied on listening to speech sounds. Signal increases were localized on the cerebral cortex with precise anatomico-functional correlation. Using a clinical 1.5 Tesla magnet requires an adequate treatment of data. Thus, stimulated cerebral activity can be portrayed by MRI therapy opening a new way for anatomico-functional cerebral studies.

[Spinal dural fistula with peri-medullar venous drainage]

Clinical and neuroradiological findings of 8 patients with a spinal dural arteriovenous fistula are reviewed. Disturbance of micturition or defecation and weakness of the legs were always present and the most frequent initial symptom was a progressive spastic paraparesis. Duration of symptoms before diagnosis was 2 years. Lumbar puncture showed elevation of proteins and myelography demonstrated dilated perimedullar posterior veins. In every case, magnetic resonance imaging of the spinal cord (T2- weighted images) revealed intramedullary high signal intensity of the conus medullaris and selective angiography confirmed the site of the dural fistula. Each patient was treated with endovascular method consisting in liquid adhesive embolization (0.2 cc of N-butyl cyanoacrylate) with hyperselective catheterism of the dorsospinal artery. Embolization procedure was successful in 6 cases with large improvement of leg weakness and partial regression of disturbed micturition and defecation. The pathophysiological mechanisms explaining the clinical signs are discussed.

Location of hand function in the sensorimotor cortex: MR and functional correlation

PURPOSE

To determine the location of hand function in the sensorimotor cortex using MR and positron emission tomography imaging studies.

METHODS

Anatomic and physiological methods were used for this study. Anatomic study was based on the MR analysis of 22 subjects. The length of the sensorimotor cortex was measured in the axial and sagittal planes. Physiologic study was based on the positron emission tomography studies of 4 subjects. Each of the studies was correlated with MR.

RESULTS

We found that the superior genu of the central sulcus corresponds to hand function in the sensorimotor cortex. This level may prove useful for any clinical correlations or for surgery.

CONCLUSIONS

From this study, the hand function area in the sensorimotor cortex is easily understood with its characteristic shape in axial MR scan. The comparison of MR and positron emission tomography data clearly show anatomic correlations. This may be applied to the functional mapping of the pathologic studies in the sensorimotor cortex regions.

A study of GABAergic system in Scrapie-infected hamsters after striatal microinoculation of the agent

Experimental Scrapie in hamster is a simple, reproducible model of prion diseases that occur in humans and animals. Stereotaxic microinoculation (0.5 microliter) of the agent (263 K) into a specific cerebral structure (striatum) in hamster, previously developed in our group, gives the opportunity to further investigate the pathogenesis of these degenerative diseases and to more precisely define the brain areas and the groups of cells more vulnerable to the effects of the agent. In this model, early significant changes of glutamic acid decarboxylase (GAD) activity in striatum suggested a preferential alteration of the GABA system. The present study was focused on the effects of Scrapie agent directly injected into striatum on GABA neurons at the presynaptic level (GABA uptake) and at the postsynaptic level (GABAA receptors). The high-affinity [3H]GABA uptake is not changed in the Scrapie-injected striatum neither in the controlateral site and the kinetics (Km, Vmax) values are not statistically different for control and Scrapie-inoculated animals. The binding of [3H]GABA (Scatchard analysis) to cerebral membranes does not seem to be altered either at the local site of agent inoculation (striatum) neither at distance in the cerebellum: the affinity constant (Kd) to the ligand and the maximal number of receptor sites were of the same magnitude in control and Scrapie animals, but we do not have a statistical analysis. These effects are completely different of those of a neurotoxin. The present data suggest that the effects of prion agent may be very limited and very specific to some cellular mechanisms, without altering the whole cellular machinery, as recently shown in an in vitro model.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional and magnetic resonance imaging correlates of callosal involvement in multiple sclerosis

To investigate functional and anatomical features of callosal involvement in multiple sclerosis (MS), performances of 90 patients with definite MS and 25 matched normal control subjects were compared on three tasks exploring interhemispheric transfer of auditory, sensory, and motor information: a verbal dichotic listening task, a crossed tactile finger localization task, and an alternate finger tapping task. Each patient also underwent a magnetic resonance imaging (MRI) scan (1) to appreciate the extent of white-matter changes by a semiquantitative evaluation of hemispheric brain MRI hyperintensities and (2) to measure the degree of total and regional callosal atrophy using an automatized method of partition of the midsagittal callosal area. Interhemispheric transfer and/or integration was impaired in patients with MS for all modalities explored and proportional to both degree of callosal atrophy and diffusion of white-matter lesions. Moreover, in good agreement with data obtained from partial commissurotomy studies, performance on each functional task was predominantly associated with atrophy of one part of the callosum, namely left-ear dichotic suppression with the posterior callosal region, alternate finger tapping with the anterior region, and cross-localization with midanterior and posterior regions. Finally, a subgroup of patients without MRI white-matter hyperintensities also showed significant impairment of callosal function and relative atrophy of the callosum. These findings suggest the potential clinical value of callosal involvement in MS and the usefulness of MS as a model of interhemispheric disconnection.

PET study of voluntary saccadic eye movements in humans: basal ganglia-thalamocortical system and cingulate cortex involvement

1. The purpose of this work was to explore the cortical and subcortical mechanisms underlying the execution of voluntary saccadic eye movements in humans. 2. Normalized regional cerebral blood flow (NrCBF) was measured using positron emission tomography (PET) and H2(15O) bolus intravenous injections in four right-handed healthy volunteers at rest and while performing self-paced voluntary horizontal saccadic eye movements in total darkness. 3. Magnetic resonance imaging of each subject's brain was matched to PET images, allowing the detection of activation in individually defined anatomic regions of interest. Cortical regions were drawn according to gyri limits; subcortical structures were also defined. 4. Self-paced saccadic eye movements elicited bilateral NrCBF increases in the lenticular nuclei, including putamen and globus pallidus, and in the thalamus. At the cortical level, we found bilateral NrCBF increases in the precentral gyrus, the superior part of the median frontal gyrus that corresponds to the supplementary motor area. There was also a significant NrCBF increase in the cerebellar vermis. 5. Right fusiform and lingual gyri, right insula, and left cingulate gyrus were also activated during the execution of saccades. 6. These results indicate that the classical basal ganglia-thalamocortical motor loop previously described for skeletal movements may also be involved in simple saccadic eye movements in humans.

Putaminal necrosis after methanol intoxication

Images

Cortical region of interest definition on SPECT brain images using X-ray CT registration

We present a method for brain single photon emission computed tomography (SPECT) analysis based on individual registration of anatomical (CT) and functional (133Xe regional cerebral blood flow) images and on the definition of three-dimensional functional regions of interest. Registration of CT and SPECT is performed through adjustment of CT-defined cortex limits to the SPECT image. Regions are defined by sectioning a cortical ribbon on the CT images, copied over the SPECT images and pooled through slices to give 3D cortical regions of interest. The proposed method shows good intra- and interobserver reproducibility (regional intraclass correlation coefficient approximately 0.98), and good accuracy in terms of repositioning (approximately 3.5 mm) as compared to the SPECT image resolution (14 mm). The method should be particularly useful for analysing SPECT studies when variations in brain anatomy (normal or abnormal) must be accounted for.

Effects of handedness and sex on the morphology of the corpus callosum: a study with brain magnetic resonance imaging

In view of conflicting data in the existing literature, we examined 53 normal subjects using a handedness questionnaire and callosal area measurements obtained from midsagittal MRI images. The callosum was found to be significantly larger in nonconsistent right-handers (NCRH), especially in its anterior half and especially for males. A significant hand x sex interaction, favoring consistent right-handed (CRH) females, was also found for the posterior midbody, a region known to house interhemispheric fibers connecting the right and left posterior association cortices. These results (1) confirm Witelson's (1985) first findings on postmortem specimens; (2) validate a dichotomy between CRH and NCRH rather than simply considering the writing hand, as was the case in most other similar studies; and (3) suggest that at least two different sex-related--probably hormonal--factors may be acting during the callosal development, one explaining the larger anterior half in NCRH males and the other the larger posterior midbody in CRH females.

Spontaneous dissection of both extracranial internal carotid arteries

Neurological examination and Doppler sonography of a 50-year-old patient were suggestive of a spontaneous dissection of the left internal carotid artery (left-sided headaches, amaurosis fugax, Horner's syndrome and hemispheric stroke). Four-vessel angiogram performed several days after the onset of the symptoms showed dissection of both extracranial carotid arteries, more pronounced on right side where the dissection was clinically asymptomatic. Angiogram follow-up demonstrated a recanalization of both carotid arteries. A review of 15 other documented reports indicates that bilateral internal carotid dissection is usually associated with fibromuscular dysplasia. A large majority of cases does not clinically differ from unilateral carotid artery dissection.

Magnetic resonance imaging of the brain stem. Anatomico-radiological correlations

Magnetic resonance imaging of 30 normal volonteers' posterior fossae was performed on a CGR Magniscan machine with a magnetic field strength of 0.5 Tesla. We chose the inversion recovery signal with a Tr of 2,000 ms, a TE of 21 ms and an inverse time of 500 ms. This sequence gives a better definition of the grey matter, the white matter and the CSF. To study the brain stem we suggest 8 horizontal and 3 sagittal sections.

MR imaging of epidermoid cysts

After a short review of literature, MRI assessments of four cases of epidermoid cysts (EC) are reported. EC, (characterized in computed tomography by hypo or iso-density areas non-enhanced by contrast), are characterized in MRI by: 1) an important variability of signal intensity between the different cases, and sometimes between the different parts of the same cyst, 2) the absence of edema in surrounding parenchyma, in spite of important mass effect, 3) well defined limits, permitting certainty of the extra-cerebral nature of this tumor, 4) the presence of calcifications easily perceptible in MRI. It is proposed that the variability of signal intensity of EC is caused by different relaxation time values corresponding to different concentrations of keratin, cholesterol and water content.

Intracranial malignant lymphoma. Report of 30 cases and review of the literature

Although primary malignant lymphoma is a rare entity in the gamut of intracranial tumors, it is more frequently seen than the secondary intracranial spread of a primary extracranial lymphoma. In general, the occurrence of lymphomas seems to be provoked by immunosuppression, as with medication (predominantly after transplantation) or with immunodepressive disease such as acquired immunodeficiency syndrome (AIDS). The usual age of onset of this disease is 55 to 65 years; and the male:female patient distribution is roughly 2:1. Characteristically, computerized tomography (CT) scans of lymphomas show a mass which is often large with regular contours, moderate mass effect, and hyper- or isodensity with marked and often homogeneous enhancement. In the series of 30 patients reported, the locations of lesions, in order of decreasing frequency, were the frontocallosal and temporal regions, the basal ganglia, and the cerebellum. Multiple lesions were present in 15% of these cases (20% to 40% in the literature). The following features should raise the suspicion of intracranial lymphoma: mirror lesions of the basal ganglia, bilateral subependymal infiltration, and leptomeningeal involvement contiguous with an intracerebral mass. According to the literature, the angiographic finding typical of lymphoma is an avascular tumor. A blush or vascular encasement of the mass seems to be rare, and the present series was in accordance with other reports in this respect. Differential diagnostic consideration should include meningioma, glioblastoma, metastatic disease, and focal infectious lesions such as toxoplasmosis or multifocal progressive leukoencephalitis, particularly in immunodepressed subjects. Diagnosing lymphoma from CT scans offers the alternative of substituting stereotaxic biopsy and neuropathological diagnosis for the more aggressive open surgical approach, since radiation therapy and possibly chemotherapy usually prove to be the treatment of choice.

Microsurgical management of tuberculum sellae meningiomas. Results in 28 consecutive cases

A series of 28 cases of meningioma of the tuberculum sellae is reviewed. This tumor was most frequent in the fifth decade, with a clear predominance in women. Neurological and endocrine deficits were minimal, whereas ophthalmologic signs were always present. Visual deficits were bilateral in cases with more than a 1-year history. Osteoma of the tuberculum sellae was rare and had no correlation with tumor size. Angiography of the internal carotid artery was found useful in demonstrating vascular displacements and tumor blush. Computed tomography was the most reliable diagnostic tool. All patients underwent a unilateral pterional craniotomy using the operating Outside of patients with total blindness, improvement of visual acuity was the rule, even in cases of long-term duration. Best results were obtained in patients operated upon within 1 year of the onset of visual symptoms.

CT identification of cortical speech areas in the human brain

In four human left cerebral hemispheres the cortical speech areas were identified, having been marked by differential color code before transverse sectioning. The results from the anatomic dissection specimens were compared with thin CT sections in normal individuals, the CT plane being aligned to the orbitomeatal plane as an external reference, and thus closely parallel to the bicommissural plane, as an internal reference. The same cortical structures were identified in the CT sections. A strategic approach to CT examination of the cortical speech areas is formulated, based on the external-internal system of reference.

[Lateral lumbar disk hernia]

Eleven cases are reported of lateral lumbar herniated disc, an anatomical form presenting fairly atypical features and of relatively recent discovery. The patients presented with a highly painful single root lesion usually affecting L4 and L5 roots. Saccoradiculography was negative in almost all cases whereas computed tomography imaging allowed easy diagnosis of a lateral herniated disc, and demonstrated its foraminal or extraforaminal site. An appropriate surgical approach was thus possible, extremely lateral forms requiring an extraisthmian approach.

Neuroradiological study of hemangiopericytomas

The authors report four cases of hemangiopericytoma. The preoperative diagnosis is strongly suggested by the use of selective angiography and post-iodine CT scan which provide images often rather similar to highly vascularized meningiomas.

Proportional localization system for anatomical interpretation of cerebral computed tomograms

The existence of individual variations in size and shape of the human brain constitutes a problem for the anatomical interpretation of brain reconstructed images obtained from scanning devices; it is, for example, responsible for most of the inaccuracies in reading CT scans. One way to account for these variations is to use a proportional localization system. In the 1960s a group of neurosurgeons developed such a system based on two pivotal intracerebral structures, the anterior and the posterior commissures; they published an atlas consisting of horizontal, coronal, and sagittal brain sections interpreted in the proportional system. The atlas also included standard proportional brain schemes based on anatomical and radiological studies on large numbers of individuals. In this article we report a target localization experiment that we carried out to determine if this atlas could be used as a reference for a more accurate interpretation of CT and, eventually, of positron emission tomography (PET) and nuclear magnetic resonance (NMR) scans. Ten radiopaque small targets were inserted through the skull in the cortex of three cadavers; head CT was performed, and the atlas was used for predicting the cortical location of the targets seen on the CT images: The predictions were confirmed. These results strongly support the use of the proportional atlas for the interpretation of CT as well as of PET and NMR scans.

[Primary neuroblastoma. A new form of median line cerebral calcification]

Based on a series of 7 cases the original characteristics of neuroblastomas are described, these tumors being of neuronal origin and exhibiting such constant calcifications and median line sites that they can be evoked in spite of their rareness.

Anatomical basis of the microsurgical approach to the pineal gland

The microanatomic study of the pineal region was made from 18 cadaver brains. The purpose of this paper is to describe the surgical anatomy needed to approach this area, which is deeply located and in the midline, by analysing the different methods of approach.

CT assessment of right-left asymmetries in the human cerebral cortex

Referring to bicommissural coordinates, 10 human brains fixed within their own skull were examined for right-left differences of the posterior Sylvian cortex, a region known to bear the most striking gross anatomical asymmetries. In the first part of the study a millimetric assessment of right-left differences in this region was carried out using life-size lateral photographs of each hemisphere. The second part is more specifically devoted to CT recognition of these cortical areas: Each hemisphere was cut into horizontal, frontal, or sagittal slices in which some cortical landmarks were analyzed to allow accurate CT identification of gyri and sulci showing the most asymmetrical features. This work provides an anatomical framework for correlative studies dealing with cerebral dominance.