Further evidence for the topography and connectivity of the corpus callosum: an FMRI study of patients with partial callosal resection.

BACKGROUND AND PURPOSE: This functional MRI study was designed to describe activated fiber topography and trajectories in the corpus callosum (CC) of six patients carrying different degree of partial callosal resection. METHODS: Patients receiving gustatory, tactile, and visual stimulation according to a block-design protocol were scanned in a 1.5 Tesla magnet. Diffusion tensor imaging (DTI) data were also acquired to visualize spared interhemispheric fibers. RESULTS: Taste stimuli evoked bilateral activation of the primary gustatory area in all patients and foci in the anterior CC, when spared. Tactile stimuli to the hand evoked bilateral foci in the primary somatosensory area in patients with an intact posterior callosal body and only contralateral in the other patients. Callosal foci occurred in the CC body, if spared. In patients with an intact splenium central visual stimulation induced bilateral activation of the primary visual area as well as foci in the splenium itself. CONCLUSION: Present data show that interhemispheric fibers linking sensory areas crossed through the CC at the sites where the different sensory stimuli evoked activation foci, and that topography of callosal foci evoked by sensory stimulation in spared CC portions is consistent with that previously observed in subjects with intact CC.

Diffusion tensor tracking of callosal fibers several years after callosotomy.

Diffusion tensor imaging (DTI) can provide more detailed in vivo information on the structural preservation of transected white matter tracts than conventional imaging methods. Here we show for the first time tracks of severed callosal fibers up to 17 years from resection. Five patients subjected to complete or partial callosotomy several years before the study were examined with DTI and compared to a normal control. Transected fibers were traced in all patients and were more clearly visible in the anterior and posterior parts than in the middle of the commissure. These findings suggest that microstructural changes persist for many years in the severed fibers, as also reflected by fractional anisotropy and apparent diffusion coefficient values, enabling a reconstruction of the longitudinal organization of severed central tracts that could not be achieved with previous techniques.

Phenylketonuria: white-matter changes assessed by 3.0-T magnetic resonance (MR) imaging, MR spectroscopy and MR diffusion.

PURPOSE: This study evaluated the sensitivity of a 3.0-Tesla (T) magnetic resonance imaging (MRI) in measuring cerebral phenylalanine using proton magnetic resonance spectroscopy and in assessing MR-documented white-matter changes by means of diffusion studies (diffusion-weighted imaging, apparent diffusion coefficient map; diffusion tensor imaging) in patients with phenylketonuria. MATERIALS AND METHODS: Thirty-two patients with the classical clinical and biochemical deficits of phenylketonuria underwent biochemical (blood phenylalanine), genotypic (phenylalanine hydroxylase gene) and radiological investigation by means of MRI, proton magnetic resonance spectroscopy and diffusion magnetic resonance imaging with a 3.0-T scanner. RESULTS: Periventricular and subcortical white-matter changes were detected on all MR scans. In 29/32 patients, proton magnetic resonance spectroscopy easily documented abnormal signal elevation at 7.36 ppm, corresponding to phenylalanine, despite its low concentration. Phenylalanine signal amplitude relative to the creatine/phosphocreatine signal increased linearly with blood phenylalanine values (r 0.7067; p<0.001). Diffusion MRI demonstrated hyperintensity in the areas exhibiting MRI changes as well as decreased apparent diffusion coefficient values, but fractional anisotropy indices were normal. CONCLUSIONS: The high signal, together with better spectral, spatial, contrast and temporal resolution, makes the 3.0-T MR the most suitable technique in the study of the phenylketonuria. In particular, the multimodal approach with MRI, proton magnetic resonance spectroscopy and diffusion magnetic resonance imaging can provide more information than previous studies performed with low-field systems.

Role of advanced MR imaging modalities in diagnosing cerebral gliomas.

The objective of this study was to evaluate the potential role of newly developed, advanced magnetic resonance (MR) imaging techniques (spectroscopy, diffusion and perfusion imaging) in diagnosing brain gliomas, with special reference to histological typing and grading, treatment planning and posttreatment follow-up. Conventional MR imaging enables the detection and localisation of neoplastic lesions, as well as providing, in typical cases, some indication about their nature. However, it has limited sensitivity and specificity in evaluating histological type and grade, delineating margins and differentiating oedema, tumour and treatment side-effects. These limitations can be overcome by supplementing the morphological data obtained with conventional MR imaging with the metabolic, structural and perfusional information provided by new MR techniques that are increasingly becoming an integral part of routine MR studies. Incorporation of such new MR techniques can lead to more comprehensive and precise diagnoses that can better assist surgeons in determining prognosis and planning treatment strategies. In addition, the recent development of new, more effective, treatments for cerebral glioma strongly relies on morphofunctional MR imaging with its ability to provide a biological interpretation of these characteristically heterogeneous tumours.

Ultrasonography of salivary glands in primary Sjögren's syndrome: a comparison with contrast sialography and scintigraphy.

OBJECTIVE: To compare ultrasonography (US) of salivary glands with contrast sialography and scintigraphy, in order to evaluate the diagnostic value of this method in primary SS (pSS). METHODS: The diagnostic value of parotid gland US was studied in 77 patients with pSS (male/female ratio 3/74; mean age 54 yrs) and in 79 with sicca symptoms but without SS. The two groups were matched for sex and age. Imaging findings of US were graded using an ultrasonographic score ranging from 0 to 16, which was obtained by the sum of the scores for each parotid and submandibular gland. The sialographic and scintigraphic patterns were classified in four different stages. The area under receiver operating characteristic curve (AUC-ROC) was employed to evaluate the screening method's performance. RESULTS: Of the 77 patients with pSS, 66 had abnormal US findings. Mean US score in pSS patients was 9.0 (range from 3 to 16). Subjects without confirmed pSS had the mean US score 3.9 (range from 0 to 9) (P < 0.0001). Results of sialography showed that 59 pSS patients had abnormal findings at Stage 1 (n = 4), Stage 2 (n = 8), Stage 3 (n = 33) or Stage 4 (n = 14), and 58 patients had abnormal scintigraphic findings at Stage 1 (n = 11), Stage 2 (n = 18), Stage 3 (n = 25) or Stage 4 (n = 4). Through ROC curves US arose as the best performer (AUC = 0.863 +/- 0.030), followed by sialography (AUC = 0.804 +/- 0.035) and by salivary gland scintigraphy (AUC = 0.783 +/- 0.037). The difference between AUC-ROC curve of salivary gland US and scintigraphy was significant (P = 0.034). Setting the cut-off score >6 US resulted in the best ratio of sensitivity (75.3%) to specificity (83.5%), with a likelihood ratio of 4.58. If a threshold >8.0 was applied the test gained specificity, at the cost of a serious loss of sensitivity (sensitivity 54.5%, specificity 97.5%, likelihood ratio 21.5). CONCLUSIONS: Salivary gland US is a useful method in visualizing glandular structural changes in patients suspected of having pSS and it may represent a good option as a first-line imaging tool in the diagnostics of the disease.

3.0-T functional brain imaging: a 5-year experience.

The aim of this paper is to illustrate the technical, methodological and diagnostic features of functional imaging (comprising spectroscopy, diffusion, perfusion and cortical activation techniques) and its principal neuroradiological applications on the basis of the experience gained by the authors in the 5 years since the installation of a high-field magnetic resonance (MR) magnet. These MR techniques are particularly effective at 3.0 Tesla (T) owing to their high signal, resolution and sensitivity, reduced scanning times and overall improved diagnostic ability. In particular, the high-field strength enhances spectroscopic analysis due to a greater signal-to-noise ratio (SNR) and improved spectral, space and time resolution, resulting in the ability to obtain high-resolution spectroscopic studies not only of the more common metabolites, but also--and especially--of those which, due to their smaller concentrations, are difficult to detect using 1.5-T systems. All of these advantages can be obtained with reduced acquisition times. In diffusion studies, the high-field strength results in greater SNR, because 3.0-T magnets enable increased spatial resolution, which enhances accuracy. They also allow exploration in greater detail of more complex phenomena (such as diffusion tensor and tractography), which are not clearly depicted on 1.5-T systems. The most common perfusion study (with intravenous injection of a contrast agent) benefits from the greater SNR and higher magnetic susceptibility by achieving dramatically improved signal changes, and thus greater reliability, using smaller doses of contrast agent. Functional MR imaging (fMRI) is without doubt the modality in which high-field strength has had the greatest impact. Images acquired with the blood-oxygen-level-dependent (BOLD) technique benefit from the greater SNR afforded by 3.0-T magnets and from their stronger magnetic susceptibility effects, providing higher signal and spatial resolution. This enhances reliability of the localisation of brain functions, making it possible to map additional areas, even in the millimetre and submillimetre scale. The data presented and results obtained to date show that 3.0-T morphofunctional imaging can become the standard for high-resolution investigation of brain disease.

3.0-T morphological and angiographic brain imaging: a 5-years experience.

Ever since the introduction of magnetic resonance (MR), imaging with 1.5 Tesla (T) has been considered the gold standard for the study of all areas of the body. Until not long ago, higher-field MR equipment was exclusively employed for research, not for clinical use. More recently, the introduction of 3.0-T MR machines for new and more sophisticated clinical applications has resulted in important benefits, especially in neuroradiology. Indeed, their high gradient power and field intensity (3.0 T) allow adjunctive and more advanced diagnostic methodologies to be performed with excellent resolution in a fraction of the acquisition time required with earlier machines. The purpose of this paper is to illustrate the distinctive semeiological characteristics of 3.0-T morphological and angiographic brain imaging compared with lower-field systems and highlight the respective advantages and drawbacks based on the experience gained in the first 5 years from the installation of a 3.0-T magnet.

Contribution of the corpus callosum to bilateral representation of the trunk midline in the human brain: an fMRI study of callosotomized patients.

Human brain studies have shown that the cutaneous receptors of trunk regions close to the midline are represented in the first somatosensory cortex (SI) of both hemispheres. The present study aims to establish whether in humans, as in non-human primates, the bilateral representation of the trunk midline in area SI depends on the corpus callosum. Data were obtained from eight callosotomized patients: three with complete callosal resection, one with a partial posterior resection including the splenium and the callosal trunk, and four with partial anterior resections sparing the splenium and in one case also the posterior part of the callosal trunk. The investigation was carried out with functional magnetic resonance imaging. Unilateral tactile stimulation was applied by rubbing ventral trunk regions close to the midline (about 20 x 10 cm in width) with a soft cotton pad (frequency 1 Hz). Cortical activation foci elicited by unilateral stimulation of cutaneous regions adjacent to the midline were detected in the contralateral post-central gyrus (PCG), in a region corresponding to the trunk ventral midline representation zone of area SI, as described in a previous study of intact subjects. In most patients, activation foci were also found in the ipsilateral PCG, again as in subjects with an intact corpus callosum. The data confirm that the skin regions adjacent to the trunk midline are represented bilaterally in SI, and indicate that ipsilateral activation is at least partially independent of the corpus callosum.

Effects of ionic and non-ionic paramagnetic contrast media on brain bio-electric activity.

The potential neurotoxic effects of gadolinium (Gd)-based compounds for enhanced MRI are not completely understood. We investigated electroencephalography changes induced by ionic and non-ionic Gd-based compounds administered intravenously in patients affected by lesions of the central nervous system (CNS) characterized by breakdown of the blood-brain barrier. This double-blind, randomized, study of two parallel groups involved 40 patients scheduled for an MRI examination with contrast medium for known CNS lesions. Twenty patients were randomly allocated to receive non-ionic Gd-DTPA-BMA/gadodiamide and 20 patients were randomly allocated to receive ionic Gd-DTPA/gadopentetate. For both groups the intravenous dose was 0.1 mmol/kg body weight. Three electroencephalography recordings were performed: immediately before, during, and 15 min after contrast medium injection. Mean and peak frequencies of the beta band and absolute power of the delta and/or theta bands of the electroencephalograms (EEGs) were noted. Each EEG was also evaluated to detect any alterations. The values of the 8-12 Hz band showed a significant increase during and after injection versus baseline in the gadopentetate group (P<0.05) and a significant decrease during injection in the gadodiamide group (P<0.05). The values of the 12-16 Hz band showed a significant increase versus baseline during and after injection in the gadopentetate group (P<0.05). The electrophysiological method based on computerised spectral analysis is a sensitive tool for evaluating effects of contrast media on brain bio-electric activity. EEG changes are detectable, even in the absence of any clinical evidence. It would appear that there might be clinical advantages in the use of non-ionic compounds.

The importance of suspecting superficial siderosis of the central nervous system in clinical practice.

Once the central nervous system surface is greatly encrusted with haemosiderin, even removing the source of bleeding will have little effect on the progression of clinical deterioration. Superficial siderosis of the central nervous system is rare and insidious, but magnetic resonance imaging has turned a previously late, mainly autoptical diagnosis into an easy, specific, in vivo, and possibly early one. Avoiding long diagnostic delay will be very important in those cases susceptible of causal treatment.

Is haemosiderin visible indefinitely on gradient-echo MRI following traumatic intracerebral haemorrhage?

Gradient-echo (GE) MRI has been demonstrated to be the most sensitive current technique for detection of intracerebral haemosiderin, especially in the chronic stage of haemorrhage. Our purpose was to see whether GE MRI shows old haemorrhage indefinitely. We reviewed serial GE images of 105 adults with imaging features consistent with post-traumatic intracerebral haemorrhage, who had serial MRI at 1, 4-6, 12, and 24 months after trauma. Of 1235 scattered low-signal foci consistent with isolated intracerebral haemosiderin deposits on images at 4-6 months, 248 (20.1%) were not seen at 24-month assessment. Reviewing individual patients, we saw that in 71.8% of those with scattered haemosiderin deposits and 46.4% of those with haemosiderin surrounded by gliosis, the low-signal foci appeared less conspicuous with time. Even given certain limitations to the interpretation of these findings, it would appear that, even with the use of GE MRI, time affects the visibility of haemorrhagic intracerebral lesions. We therefore conclude that a time of 4-6 months to 1 year or slightly more should be recommended for most precise detection of haemosiderin deposits on MRI of head-injured patients, should this be thought desirable. Normal GE images may not exclude old haemorrhage.

Magnetic Resonance applications in dental implantology: technical notes and preliminary results.

PURPOSE: To evaluate the possible use of Magnetic Resonance Imaging (MRI) in the field of dental implantology, for identifying the mandibular nerve, as proposed by several authors. MATERIALS AND METHODS: MRI was used for the study of the mandible in ten subjects (five healthy volunteers and five subjects awaiting dental implants). Imaging was performed on a 1.0-T MR scanner with a brain coil. T2 TSE, T1 spin-echo and T2 gradient-echo sequences were performed, both parallel and perpendicular to the horizontal portion of the mandible, with a thickness of 3 mm. RESULTS: In all the subjects MRI clearly identified the intraosseous course of the inferior alveolar neurovascular bundle within the mandibular canal. CONCLUSIONS: MRI appears useful for the depiction of the mandibular canal before dental implantation. Further studies are required to compare the accuracy of MRI and CT based on a statistically significant sample.

Spinal epidural en-plaque meningioma with an unusual pattern of calcification in a 14-year-old girl: case report and review of the literature.

A 14-year-old girl who presented with a severe sensory-motor-sphincter syndrome was found to be harboring an epidural tumor situated posteriorly in the spinal canal from C5 through C7 levels. The mass had computerized tomography and magnetic resonance imaging features suggesting an unusual stratified architecture, with a conspicuous highly calcific component firmly adherent to the dura and a non-calcific mass surrounding it posteriorly and laterally. Although meningiomas have a low incidence in the first two decades of life, and in the spine they rarely have entirely extradural location at any age, a meningioma was suspected. Intraoperative biopsy confirmed the tumor to be benign, and careful total resection including the whole large dural implant was carried out; the wide dural defect was grafted with fascia lata. A meningothelial meningioma with a largely calcified psammomatous component was diagnosed. The girl made a complete recovery, and is tumor-free 9 years postoperatively. Outcome from surgery for spinal meningiomas can be good, despite the severity of the preoperative condition; however, enplaque and highly calcific tumors still bear a poorer prognosis. Complete resection is mandatory in children, in whom they are extremely rare. Modern imaging techniques help in making a correct initial diagnosis and optimizing surgery in order to provide good results, even in more-challenging cases.

Mechanical noxious stimuli cause bilateral activation of parietal operculum in callosotomized subjects.

The patterns of cortical activation evoked by tactile and mechanical painful stimulation in six normal subjects and three patients with complete resection of the corpus callosum are described and compared, with emphasis on the parietal operculum. Stimulus-related cortical activation was investigated by functional magnetic resonance imaging. In both groups, painful stimulation activated the first somatosensory, insular and cingulate cortices in the contralateral hemisphere, and the parietal opercular cortex in both hemispheres. Comparison between the two patterns of cortical activation demonstrated that ipsilateral activation by unilateral painful stimulation is at least partially independent of the corpus callosum and suggests a different organization of the pain and touch systems.

Acute posttraumatic paraplegia caused by epidural hematoma at the vertex.

Vertex epidural hematomas (VEDHs) are well known but uncommon. Their clinical presentation may be misleading and missed by routine CT axial scanning; thus, diagnosis may be delayed, with possibly fatal consequences. We report a case of acute posttraumatic paraplegia caused by a VEDH, which was evident at CT and for which the patient underwent successful surgery.

Spontaneous intracranial hypotension: the value of brain measurements in diagnosis by MRI.

Caudal brain displacement is inconstantly reported as an MRI feature of spontaneous intracranial hypotension (SIH). We reviewed the clinical data and MRI of eight patients diagnosed as having SIH and investigated the possibility of more precise assessment. On midsagittal images we measured four anatomical landmarks: the position of the cerebellar tonsils, fourth ventricle, and infundibular recess, plus the angle between the bicommissural line and a line tangential to the floor of the fourth ventricle; midsagittal images from 89 normal controls were also measured. On statistical analysis, all measurements differed in the two groups, and the difference was significant for the cerebellar tonsils, fourth ventricle, and infundibular recess. Some overlap between patients and controls was found for each measurement; however, all the patients had two (two patients) or more (six) values outside the range in normal controls range or not above their 1st quartile. Measurement of the position of the third ventricle seemed particularly sensitive. We suggest that examination of midsagittal images can help in diagnosing clinically suspected SIH.

An unusual spinal presentation of Whipple disease.

SUMMARY: When Whipple disease (WD) is confined to the CNS, diagnosis may be difficult. We report a case of WD with spinal presentation in an otherwise healthy woman who had a 5-year history of relapsing-remitting cervico-thoracic myelopathy. We suggest that the diagnosis of WD should be considered in the presence of an enlarged and enhancing spinal cord even in the absence of any systemic involvement.