Acute Necrotizing Encephalopathy: Diffusion MR Imaging and Localized Proton MR Spectroscopic Findings in Two Infants

In this report, we describe the findings of diffusion MR imaging and proton MR spectroscopy in two infants with acute necrotizing encephalopathy in which there was characteristic symmetrical involvement of the thalami. Diffusion MR images of the lesions showed that the observed apparent diffusion coefficient (ADC) decrease was more prominent in the first patient, who had more severe brain damage and a poorer clinical outcome, than in the second. Proton MR spectroscopy detected an increase in the glutamate/glutamine complex and mobile lipids in the first case but only a small increase of lactate in the second. Diffusion MR imaging and proton MR spectroscopy may provide useful information not only for diagnosis but also for estimating the severity and clinical outcome of acute necrotizing encephalopathy.     

Functional MR Imaging of Working Memory in the Human Brain

Objective

In order to investigate the functional brain anatomy associated with verbal and visual working memory, functional magnetic resonance imaging was performed.

Materials and Methods

In ten normal right handed subjects, functional MR images were obtained using a 1.5-T MR scanner and the EPI BOLD technique. An item recognition task was used for stimulation, and during the activation period of the verbal working memory task, consonant letters were used. During the activation period of the visual working memory task, symbols or diagrams were employed instead of letters. For the post-processing of images, the SPM program was used, with the threshold of significance set at p < .001. We assessed activated brain areas during the two stimulation tasks and compared the activated regions between the two tasks.

Results

The prefrontal cortex and secondary visual cortex were activated bilaterally by both verbal and visual working memory tasks, and the patterns of activated signals were similar in both tasks. The superior parietal cortex was also activated by both tasks, with lateralization to the left in the verbal task, and bilaterally without lateralization in the visual task. The inferior frontal cortex, inferior parietal cortex and temporal gyrus were activated exclusively by the verbal working memory task, predominantly in the left hemisphere.

Conclusion

The prefrontal cortex is activated by two stimulation tasks, and this is related to the function of the central executive. The language areas activated by the verbal working memory task may be a function of the phonological loop. Bilateral prefrontal and superior parietal cortices activated by the visual working memory task may be related to the visual maintenance of objects, representing visual working memory.     

MR Imaging and Histopathologic Findings of A Case of Cerebral Ganglioneurocytoma

We report a case of ganglioneurocytoma manifesting as a complex partial seizure in a young adult male. MR images depicted a well-marginated cystic mass with a heterogeneous solid portion abutting the dura in the parietal lobe. The solid portion showed minimal heterogeneous enhancement, and pressure erosion of the overlying calvarium had occurred. Following gross total resection, the clinical outcome was satisfactory, with no further seizures, and during the five-year follow-up period, the tumor did not recur.     

Functional MR Imaging of Vision in the Deaf

RATIONALE AND OBJECTIVES: Early loss of a sensory modality has been associated with cortical reorganization in both animal models and humans. The purpose of this study was to map visual activation with functional magnetic resonance (MR) imaging and to document possible developmental reorganization in the temporal lobe caused by early deafness. MATERIALS AND METHODS: Six prelingual, profoundly deaf subjects were compared with a similar group of six hearing subjects. Three visual tasks were performed by both groups: attention to movement in the field-of-view periphery, shape matching, and mental rotation. Echo-planar coronal MR imaging was performed at 1.5 T. RESULTS: Regions of interest encompassing the middle and posterior aspects of the superior and middle temporal gyri demonstrated a significantly (P < .05) increased activation in deaf subjects compared with hearing subjects, particularly on the right side (P < .05) and during the tasks involving motion. The most specific effect was noted during the mental-rotation task. CONCLUSION: These results support the hypothesis that portions of the temporal lobe usually involved in auditory processing are more active during certain visual tasks in deaf compared with hearing subjects. Cortical reorganization may be an important factor in the deaf population when considering the physiology of temporal lobe lesions and predicting surgical outcomes. Functional MR imaging may be helpful during preoperative assessment in individuals with deafness.     

Mapping of normal brain maturation in infants on phase-sensitive inversion-recovery MR images

Summary It is illustrated that phase-sensitive inversion-recovery MR images are particularly well suited for the monitoring of brain maturation and myelination in the neonate and young infant. Provided appropriate timings are applied with the inversion-recovery MR pulse sequence, the myelinated areas show up as bright spots in the phase-sensitive images. The chronology of the appearance, and the location of these hyperintense zones correlate well with the chronology of brain maturation, as assessed by other means. In particular, the progressive functional capabilities of the infant correlate well with the progress of myelination, as exhibited by the MR images.     

Diffusion-Weighted MR Imaging of Intracerebral Hemorrhage

Objective

To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images.

Materials and Methods

In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images.

Results

DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage.

Conclusion

DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.     

Perfusion MR Imaging: Clinical Utility for the Differential Diagnosis of Various Brain Tumors

Objective

To determine the utility of perfusion MR imaging in the differential diagnosis of brain tumors.

Materials and Methods

Fifty-seven patients with pathologically proven brain tumors (21 high-grade gliomas, 8 low-grade gliomas, 8 lymphomas, 6 hemangioblastomas, 7 metastases, and 7 various other tumors) were included in this study. Relative cerebral blood volume (rCBV) and time-to-peak (TTP) ratios were quantitatively analyzed and the rCBV grade of each tumor was also visually assessed on an rCBV map.

Results

The highest rCBV ratios were seen in hemangioblastomas, followed by high-grade gliomas, metastases, low-grade gliomas, and lymphomas. There was no significant difference in TTP ratios between each tumor group (p>0.05). At visual assessment, rCBV was high in 17 (81%) of 21 high-grade gliomas and in 4 (50%) of 8 low-grade gliomas. Hemangioblastomas showed the highest rCBV and lymphomas the lowest.

Conclusion

Perfusion MR imaging may be helpful in the differentiation of thevarious solid tumors found in the brain, and in assessing the grade of the various glial tumors occurring there.     

Fetal Pericallosal Lipoma: US and MR Findings

We report a case of fetal pericallosal lipoma occurring at the anterior interhemispheric fissure and associated with agenesis of the corpus callosum. During targeted prenatal ultrasonography at 26 weeks'' gestation, the lesion was seen as a highly echogenic mass. MR imaging performed at 35 weeks'' gestation and during the postnatal period revealed a pericallosal fatty mass and agenesis of the corpus callosum.     

Comparison of T2-weighted spin-echo and fast spin-echo techniques in the evaluation of myelination

To evaluate T2-weighted fast spin-echo (FSE) and conventional spin-echo (CSE) magnetic resonance (MR) techniques in the assessment of brain myelination, 100 consecutive pediatric patients were imaged prospectively with both CSE and FSE sequences. All patients underwent a routine MR examination that included T2-weighted CSE imaging (imaging time, 10 minutes 21 seconds) and T2-weighted FSE imaging (imaging time, 2 minutes 5 seconds). The two techniques were compared for estimating the degree of myelination (using normal anatomic landmarks) by blind review. With T2-weighted CSE images as the “gold standard” for estimation of normal myelination, FSE images were evaluated to determine if they showed the degree of myelination similarly to CSE images. There was a strong correlation (P <.01) between CSE and FSE images in the estimation of myelination over a wide range of patient ages.     

Brain MR Imaging in dietarily treated phenylketonuria

Magnetic resonance imaging is the most efficient imaging modality to evaluate brain gray and white matter of patients with metabolic diseases [1, 2, 3]. The main purpose of out study was to investigate the relation between brain MRI abnormalities and the phenylalanine (phe) and tyrosine (tyr) blood levels in 38 phenylketonuria (PKU) patients. Increased periventricular white matter intensity on T2-weighted brain images was the only pahtologic finding in 24 patients. Brain MRI abnormalities were scored (4) and correlated with the individual mean phe and phe/ tyr levels during 1 year preceding MR examination and with phe tolerance. The appearance of MRI abnormalities on brain T2-weighted images correlates with a threshold mean phe level (averaged over the year preceding the examination).     

Perfusion MR Imaging in Gliomas: Comparison with Histologic Tumor Grade

Objective

To determine the usefulness of perfusion MR imaging in assessing the histologic grade of cerebral gliomas.

Materials and Methods

In order to determine relative cerebral blood volume (rCBV), 22 patients with pathologically proven gliomas (9 glioblastomas, 9 anaplastic gliomas and 4 low-grade gliomas) underwent dynamic contrast-enhanced T2*-weighted and conventional T1- and T2-weighted imaging. rCBV maps were obtained by fitting a gamma-variate function to the contrast material concentration versus time curve. rCBV ratios between tumor and normal white matter (maximum rCBV of tumor / rCBV of contralateral white matter) were calculated and compared between glioblastomas, anaplastic gliomas and low-grade gliomas.

Results

Mean rCBV ratios were 4.90°±1.01 for glioblastomas, 3.97°±0.56 for anaplastic gliomas and 1.75°±1.51 for low-grade gliomas, and were thus significantly different; p < .05 between glioblastomas and anaplastic gliomas, p < .05 between anaplastic gliomas and low-grade gliomas, p < .01 between glioblastomas and low-grade gliomas. The rCBV ratio cutoff value which permitted discrimination between high-grade (glioblastomas and anaplastic gliomas) and low-grade gliomas was 2.60, and the sensitivity and specificity of this value were 100% and 75%, respectively.

Conclusion

Perfusion MR imaging is a useful and reliable technique for estimating the histologic grade of gliomas.     

MR Imaging detection of cerebral metastases with a single injection of high-dose gadoteridol

The utility of a single high-dose (0.3 mmol/kg) injection of gadoteridol, a gadolinium chelate, in the detection of brain metastases on magnetic resonance images was studied. Patients (n = 29) with a high suspicion for brain metastases at clinical examination and by history were imaged on two occasions–separated by more than 24 hours and less than 7 days–with a 0.1 mmol/kg contrast agent dose used for the first study and a 0.3 mmol/kg dose for the second. In patients (n = 15) with confirmed brain metastases by clinical, radiologic, and/or histologic criteria, 40 lesions were detected at the 0.3 mmol/kg dose by a single reader blinded to contrast agent dose, compared with 33 lesions at 0.1 mmol/kg, a 21% increase. Three of 15 patients (20%) demonstrated an increase in the number of lesions detected at the higher dose. Region-of-interest analysis of signal intensity measurements showed that lesion contrast (relative to normal brain) improved from 54% at 0.1 mmol/kg to 92% at 0.3 mmol/kg. A 0.3 mmol/kg dose of gadoteridol, administered in a single injection, permits identification of brain metastases not detected at 0.1 mmol/kg. Such information can influence the choice of therapy.     

Venous sinus thrombosis as a cause of parenchymal and intraventricular hemorrhage in the full-term neonate

A case of parenchymal and intraventricular hemorrhage in a full-term neonate is reported. The underlying cause in our patient is thought to be related to cerebral sinovenous occlusive disease secondary to Protein C deficiency, a rare coagulopathy.     

Diffusion-Weighted MR Imaging in Biopsy-Proven Creutzfeldt-Jakob Disease

Objective

To compare conventional and diffusion-weighted MR imaging in terms of their depiction of the abnormalities occurring in Creutzfeldt-Jakob disease.

Materials and Methods

We retrospectively analyzed the findings of conventional (T2-weighted and fluid-attenuated inversion recovery) and diffusion-weighted MR imaging in four patients with biopsy-proven Creutzfeldt-Jakob disease. The signal intensity of the lesion was classified by visual assessment as markedly high, slightly high, or isointense, relative to normal brain parenchyma.

Results

Both conventional and diffusion-weighted MR images demonstrated bilateral high signal intensity in the basal ganglia in all four patients. Cortical lesions were observed on diffusion-weighted MR images in all four, and on fluid-attenuated inversion recovery MR images in one, but in no patient on T2-weighted images. Conventional MR images showed slightly high signal intensity in all lesions, while diffusion-weighted images showed markedly high signal intensity in most.

Conclusion

Diffusion-weighted MR imaging is more sensitive than its conventional counterpart in the depiction of Creutzfeldt-Jakob disease, and permits better detection of the lesion in both the cerebral cortices and basal ganglia.     

Functional Neuroanatomy in Depressed Patients with Sexual Dysfunction: Blood Oxygenation Level Dependent Functional MR Imaging

Objective

To demonstrate the functional neuroanatomy associated with sexual arousal visually evoked in depressed males who have underlying sexual dysfunction using Blood Oxygenation Level Dependent-based fMRI.

Materials and Methods

Ten healthy volunteers (age range 21-55: mean 32.5 years), and 10 depressed subjects (age range 23-51: mean 34.4 years, mean Beck Depression Inventory score of 39.6±5.9, mean Hamilton Rating Scale Depression (HAMD)-17 score of 33.5±6.0) with sexual arousal dysfunction viewed erotic and neutral video films during functional magnetic resonance imaging (fMRI) with 1.5 T MR scanner (GE Signa Horizon). The fMRI data were obtained from 7 oblique planes using gradient-echo EPI (flip angle/TR/TE=90°/6000 ms/50 ms). The visual stimulation paradigm began with 60 sec of black screen, 150 sec of neutral stimulation with a documentary video film, 30 sec of black screen, 150 sec of sexual stimulation with an erotic video film followed by 30 sec of black screen. The brain activation maps and their quantification were analyzed by SPM99 program.

Results

There was a significant difference of brain activation between two groups during visual sexual stimulation. In depressed subjects, the level of activation during the visually evoked sexual arousal was significantly less than that of healthy volunteers, especially in the cerebrocortical areas of the hypothalamus, thalamus, caudate nucleus, and inferior and superior temporal gyri. On the other hand, the cerebral activation patterns during the neutral condition in both groups showed no significant differences (p < 0.01).

Conclusion

This study is the first demonstration of the functional neuroanatomy of the brain associated with sexual dysfunction in depressed patients using fMRI. In order to validate our physiological neuroscience results, further studies that would include patients with other disorders and sexual dysfunction, and depressed patients without sexual dysfunction and their treatment response are needed.     

MR Imaging Findings of Clonorchiasis

Objective

The purpose of this study was to evaluate the MR spectrum and MR cholangiographic imaging findings of clonorchiasis.

Materials and Methods

We reviewed 26 patients with confirmed clonorchiasis by either stool tests (n=24) or surgery (n=2). MR imaging was performed on a 1.5 T system (GE Medical Systems, Milwaukee, WI) with a torso coil. Axial T1- and T2-weighted, gadolinium-enhanced dynamic images and MR cholangiography were obtained. Image analyses were used to identify abnormalities of the intrahepatic and extrahepatic bile ducts and the presence of hepatobiliary malignancy. All MR examinations were reviewed by the consensus of two abdominal radiologists.

Results

Intrahepatic bile duct abnormalities were seen in 23 (89%) of the 26 patients. The most common finding was mild dilatation of the intrahepatic bile duct which was found in 21 (81%). "Too many intrahepatic ducts" were found in 16(62%), wall enhancement and thickening in 21 (81%) and filling defects and ductal stricture in the intrahepatic bile duct in 6 (24%) and 3 (12%) patients, respectively. Extrahepatic ductal dilation was found in 5 (19%) and 9 (35%) revealed hepatobiliary malignancy.

Conclusion

MR imaging revealed various findings of clonorchiasis, including dilatation, wall enhancement, stricture of the intrahepatic ducts and filling defect within the intrahepatic bile duct.     

Cranial Nerve Clock: Part II: Functional MR Imaging of Brain Activation during a Declarative Memory Task

RATIONALE AND OBJECTIVES: The authors performed this study to assess brain activation during encoding and successful recall with a declarative memory paradigm that has previously been demonstrated to be effective for teaching students about the cranial nerves. MATERIALS AND METHODS: Twenty-four students underwent functional magnetic resonance (MR) imaging during encoding and recall of the name, number, and function of the 12 cranial nerves. The students viewed mnemonic graphic and text slides related to individual nerves, as well as their respective control slides. For the recall paradigm, students were prompted with the numbers 1-12 (test condition) intermixed with the number 14 (control condition). Subjects were tested about their knowledge of cranial nerves outside the MR unit before and after functional MR imaging. RESULTS: Students learned about the cranial nerves while undergoing functional MR imaging (mean post- vs preparadigm score, 8.1 +/- 3.4 [of a possible 12] vs 0.75 +/- 0.94, bilateral prefrontal cortex, left greater than right; P < 2.0 x 10(-12)) and maintained this knowledge at I week. The encoding and recall paradigms elicited distributed networks of brain activation. Encoding revealed statistically significant activation in the bilateral prefrontal cortex, left greater than right [corrected]; bilateral occipital and parietal associative cortices, parahippocampus region, fusiform gyri, and cerebellum. Successful recall activated the left much more than the right prefrontal, parietal associative, and anterior cingulate cortices; bilateral precuneus and cerebellum; and right more than the left posterior cingulate. CONCLUSION: A predictable pattern of brain activation at functional MR imaging accompanies the encoding and successful recall of the cranial nerves with this declarative memory paradigm.     

Localized Proton MR Spectroscopic Detection of Nonketotic Hyperglycinemia in an Infant

Nonketotic hyperglycinemia (NKH) is a rare metabolic brain disease caused by deficient activity of the glycine cleveage system. Localized proton MR spectroscopy (echo-time 166 msec), performed in an infant with the typical clinical and biochemical features of neonatal NKH, showed a markedly increased peak intensity at 3.55 ppm, which was assigned to glycine. Serial proton MR spectrosocpic studies indicated that glycine/choline and glycine/total creatine ratios correlated closely with the patient''s clinical course. Proton MR spectroscopy was useful for the non-invasive detection and monitoring of cerebral glycine levels in this infant with NKH.     

MR Imaging of Lhermitte-Duclos disease: report of two cases

Two cases of Lhermitte-Duclos of the cerebellum are presented. MRI was essential in the radiological diagnosis of both lesions by the demonstration, both on T1- and T2 weighted images of thickened cerebellar folia.