Encephalitis caused by human immunodeficiency virus: CT and MR imaging manifestations with clinical and pathologic correlation

To determine the computed tomographic (CT) and magnetic resonance (MR) imaging manifestations of central nervous system (CNS) infection by the human immunodeficiency virus (HIV), the authors analyzed the results of imaging of the CNS in 24 patients with HIV encephalitis confirmed at autopsy. Careful pathologic correlation demonstrated that neither CT nor MR imaging enabled detection of microglial nodules with multinucleated giant cells, the hallmark of HIV encephalitis seen in all 24 affected patients. The most common abnormality observed on images of the CNS was atrophy, demonstrated in 18 patients. Demyelination and vacuolation of white matter tracts accompanying severe HIV infection caused hypoattenuation on CT scans and hyperintensity on T2-weighted MR images. These lesions had no mass effect. MR imaging was more sensitive than CT in the detection of lesions caused by HIV or other superimposed infectious agents. Although it is often difficult to attribute any radiologic appearance to a single etiologic agent in patients with acquired immunodeficiency syndrome, the combination of atrophy and symmetric, periventricular or diffuse white matter disease suggests HIV encephalitis.     

MR imaging of white matter disease in children

Twenty-three pediatric patients with white matter abnormalities on MR images were evaluated retrospectively to assess the contribution of MR compared with CT in diagnosing these conditions. In addition, the MR findings in major categories of white matter diseases were analyzed for sensitivity in detecting the presence of an abnormality. White matter disease categories included demyelinating disease (five cases), dysmyelinating disease (eight cases), developmental white matter abnormalities (four cases), and white matter abnormalities of unknown origin (idiopathic) (six cases), as seen on long TR images. We found that MR is not more sensitive than CT in detecting disease in the demyelinating or dysmyelinating categories, although it is more sensitive than CT in detecting the degree of disease present. In cases of developmental delay, MR is distinctly more useful than CT in demonstrating abnormalities of myelination. And in the idiopathic group, MR detected the presence of focal white matter abnormalities on long TR images in children with neurologic complaints and normal CT. MR may serve to redefine and broaden the spectrum of reported imaging abnormalities in pediatric patients.     

Preliminary experience of magnetic resonance imaging in neurosarcoidosis

Summary Twelve MR scans performed on seven patients with neurosarcoidosis are presented. The most common abnormalities were ventricular enlargement (four patients) and diffuse periventricular white matter changes (three patients). Infarcts were seen in three patients and mass lesion in one. The lesions were seen in both T1 and T2 weighted images. The results are compared with CT findings. MRI seems to be more sensitive than CT in detecting white matter changes and infarcts. Ventricular enlargement and granulomas were equally well seen with both modalities.     

Magnetization transfer study of HIV encephalitis and progressive multifocal leukoencephalopathy. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine.

PURPOSETo ascertain whether the use of magnetization transfer (MT) in MR imaging can characterize tissue destruction in human immunodeficiency virus (HIV)-positive patients with presumed progressive multifocal leukoencephalopathy (PML) or HIV encephalitis.METHODSBrain MR studies that included MT were obtained in three groups: 11 healthy control subjects, 10 HIV-positive patients with clinical and radiologic findings of PML, and 13 HIV-positive patients with HIV encephalitis. MT ratios (MTRs) were calculated in PML and HIV encephalitis lesions and in normal-appearing white matter in the patients and control subjects.RESULTSPML lesions revealed a dramatic decrease in MTR (22% +/- 2.3). HIV encephalitis lesions had statistically significantly higher MTR values (40% +/- 3.8) than PML lesions. The MTR of normal-appearing white matter was significantly higher in the control subjects (47% +/- 2.3) than in the PML group (46% +/- 3.3) or the HIV encephalitis group (44% +/- 2.6).CONCLUSIONMTR determinations suggest the possibility of distinguishing PML from HIV encephalitis and of indicating whether HIV encephalitis is involved in white matter that appears normal on conventional MR images.     

MR and CT of tuberous sclerosis: linear abnormalities in the cerebral white matter

A review of MR and CT images in five patients, 8 months to 22 years old, diagnosed as having tuberous sclerosis, revealed linear abnormalities in the cerebral white matter. A linear abnormality connecting a subependymal nodule to a subcortical lesion was shown in two patients as an area of hypointensity on T1-weighted MR images and as an area of hyperintensity on T2-weighted images. These appeared as faintly high-density areas on CT images. Seventeen linear abnormalities extending from the ventricle to the cortex with a subependymal nodule or subcortical lesion on each end were visible in all five patients as areas of hyperintensity on the T2-weighted images. On the T1-weighted images, only nine hypointense lines were noted. CT scans did not show these latter lines. Linear abnormalities in cerebral white matter are suggestive of lesions of demyelination, dysmyelination, hypomyelination, or lines of migration disorder. MR imaging, especially T2-weighted, is particularly sensitive in detecting these abnormalities.     

Comparison of CT, MR, and PET in Alzheimer's dementia and normal aging

We compared the findings of computed tomography (CT), magnetic resonance (MR), and positron emission tomography (PET) scans of glucose metabolism in 30 patients with clinically diagnosed Alzheimer's Disease (DAT) to those noted in 25 age-matched normal controls. Mean ratings of cortical and ventricular atrophy on CT and of metabolic abnormality on PET were significantly different (p less than 0.001 and p less than 0.0001, respectively) between two subject groups, however, there was a considerable overlap in reading of cortical atrophy. CT hypodensities were present in 17% of DAT patients and 12% of controls. MR revealed numerous additional periventricular and deep white matter signal changes. Neither hypodensities nor hyperintensities were correlated with PET abnormalities. Although, not infrequently, hypometabolic areas on PET scans corresponded to atrophic regions on anatomic images, they also occurred without such changes. Interestingly, cortical high signal intensity seen on MRI was frequently observed to be associated with areas of hypometabolism. Our results suggest that PET may be the most sensitive modality for detecting cortical involvement in DAT.     

Gd-DTPA enhanced MR imaging in intracranial tuberculosis

Summary Twenty-six patients with intracranial tuberculosis (Tb) (10 with acute meningitis, 5 with chronic meningitis, 5 with meningitic sequelae and 6 with localized tuberculoma(s) were examined with MR before and after Gd-DTPA enhancement (0.1 mmol/kg), using 2.0T superconducting unit, and the images were retrospectively analyzed and compared with CT scans. Without Gd-DTPA enhancement, the MR images were generally insensitive to detection of active meningeal inflammation and granulomas. The signal intensity of granulomas was usually isointense to gray matter on both T1- and T2-weighted images, whether they were associated with diffuse meningitis or presented as localized tuberculoma(s). A few granulomas showed focal hypointensity on T2-weighted images. Calcifications seen on CT of the meningitic sequelae group usually appeared markedly hypointense on all spin-echo sequences. On Gd-DTPA enhanced T1-weighted images, abnormal meningeal enhancement indicating active inflammation was conspicuous, and the granulomas often appeared as conglomerated ring-enhancing nodules, which seems to be characteristic of granulomas. Thin rim enhancement around the suprasellar calcifications were observed in two out of 5 patients with meningitic sequelae. Compared with CT, MR detected a few more ischemic infarcts, hemorrhagic infarcts, meningeal enhancement and granulomas in the acute meningitis group, but missed small calcifications in the basal cisterns well shown on CT in the sequelae group. Otherwise, MR generally matched CT scans. MR imaging appears to be superior to CT in evaluation of active intracranial Tb only if Gd-DTPA is used, while CT is better than MR in evaluating meningitic sequelae with calcification.     

病毒性脑炎的CT、MRI诊断(附48例报告)

加深对病毒性脑炎ＣＴ、ＭＲＩ表现的认识,以提高临床对该病变诊断的准确性。材料与方法。回顾分析４８例病毒性脑炎（男２６例,女２２例,平均年龄３６岁）的临床及影像学资料,其中单纯疱疹病毒（ＨＳＶ）脑炎８例。经手术病理证实者１例。检查方法：ＣＴ检查２３例,ＭＲＩ检查１４例,同时经ＣＴ和ＭＲＩ检查者１１例。作ＣＴ和ＭＲＩ增强检查者共１２例。结果脑内有多发或单发病灶者４７例,主要位于皮层,皮层下脑侧脑室周围     

Subacute sclerosing panencephalitis: evaluation with CT and MR.

PURPOSETo evaluate the progression of CT and MR changes of the brain in subacute sclerosing panencephalitis (SSPE) as a basis for assessing the effects of different types of therapy.METHODSFifty-two patients with SSPE were examined, 44 with MR imaging and 42 with CT of the brain on one or more occasions. A total of 92 MR and 67 CT studies were performed.RESULTSCorrelation between the clinical status and the MR findings in admission was poor. Of 20 patients with clinically advanced disease, only 8 had marked MR abnormalities; 6 had normal or almost normal findings on MR examinations. Two of 4 patients with clinically mild disease had advanced MR changes. The progression of the MR findings appeared to follow a constant pattern. The earliest pathologic finding was focal, high-T2-intensity white matter changes; later atrophic changes followed. The atrophy lagged behind the white matter changes and was thus mild when white matter changes were moderate or severe. In the most advanced stage, when the patient was in a neurovegetative state, an almost total loss of white matter had usually taken place. At this stage, the corpus callosum was also thin. Basal ganglia changes, usually involving the putamina, were seen in one third of patients and cortical gray matter changes were seen in one fourth of patients examined with MR imaging. In 2 of 20 patients, MR changes regressed in parallel with clinical improvement following therapy, but in 5 patients clinical improvement was accompanied by progression of MR changes.CONCLUSIONThe progress of MR abnormalities seen in patients with SSPE seems to follow a constant pattern, but the severity of MR changes does not always correlate well with the clinical findings. Caution must therefore be used when evaluating the effects of therapy.     

Imaging findings of neonatal herpes simplex virus type 2 encephalitis

Introduction The CT, MR, and diffusion-weighted initial and follow-up imaging findings in neonatal herpes simplex virus type 2 (HSV-2) encephalitis were assessed. Methods The clinical, laboratory and imaging findings in 12 patients (eight girls and four boys) with proven neonatal HSV-2 encephalitis with follow-up were retrospectively reviewed. Patterns of brain involvement and distribution of lesions were studied and the contribution of diffusion-weighted imaging to the imaging diagnosis of this disease was explored. A total of 24 CT and 22 MRI studies were performed with a mean follow-up time of 38 months. Results Neonatal HSV-2 encephalitis can be multifocal or limited to only the temporal lobes, brainstem, or cerebellum. The deep gray matter structures were involved in 57% of patients, and hemorrhage was seen in more than half of the patients. CT images were normal or showed mild abnormalities in the early stages of the disease. Conventional MR images may be normal in the early stages of the disease. Lesions were initially seen only by diffusion-weighted imaging in 20% of the patients and this modality showed a substantially more extensive disease distribution in an additional 50% of patients. In 40% of patients, watershed distribution ischemic changes were observed in addition to areas of presumed direct herpetic necrosis. Conclusion Neonatal HSV-2 encephalitis has a variable imaging appearance. Diffusion-weighted MRI is an important adjunct in the imaging evaluation of this disease. Watershed distribution ischemia in areas remote from the primary herpetic lesions may be seen.     

MR of Leigh's disease (subacute necrotizing encephalomyelopathy)

MR images of three patients with Leigh's disease (subacute necrotizing encephalomyelopathy) were compared with CT findings. In all patients typical lesions in the basal ganglia were identified with both MR and CT. In two patients MR permitted identification of additional lesions not detected with CT. In one patient progression of MR abnormalities over a 4-month period correlated well with clinical deterioration in neurologic status. T2-weighted images with a repetition time (TR) greater than 1950 msec and an echo time (TE) greater than or equal to 60 msec or inversion-recovery images with a 50-msec TE, 1213-msec inversion time, and 3000-msec TR were advantageous in identifying multiple necrotic lesions in the brainstem, deep gray matter, periventricular white matter, and cerebral cortex. In this series MR was more sensitive in detecting and localizing multifocal necrotic lesions of Leigh's disease than CT was, and thus may be a useful diagnostic tool for patients with the appropriate clinical and laboratory abnormalities.     

Encephalopathy in AIDS patients: evaluation with MR imaging

The presence and extent of encephalopathy were evaluated in 47 patients with AIDS or AIDS-related complex (ARC) by the use of MR imaging. Twenty-nine (62%) of the patients showed some form of white matter disease, exhibited as high signal intensity on T2-weighted images. Focal white matter lesions were seen in 23 (49%) of the patients, while a diffuse white matter process was observed in six patients (13%). Of the 29 patients who had white matter disease on MR scans, 17 (36%) had a suggestion of white matter involvement on an initial CT study. Meanwhile, 12 (26%) of the patients had a normal CT scan on the initial examination. MR findings showed predominant disease in the subinsular and peritrigonal white matter areas. Marked cerebral atrophy was observed in 17 (36%) of 47 patients, cerebellar atrophy in 18 (38%), and brainstem atrophy in seven patients (15%). Pathologic findings showed that toxoplasmosis was present in eight patients (17%), and primary CNS lymphoma was present in three patients (6%). Cryptococcal meningitis was noted in two (4%) of the patients at autopsy, and Mycobacterium tuberculosis was seen in one (2%) of the patients at autopsy. MR imaging has been shown to be a valuable technique for the detection of encephalopathy in AIDS patients.     

Subcortical low intensity on MR images of meningitis, viral encephalitis, and leptomeningeal metastasis

BACKGROUND AND PURPOSE: Subcortical low-intensity lesion on T2-weighted images is an uncommon manifestation of ischemia, multiple sclerosis, and Sturge-Weber disease. This study was performed to determine whether subcortical low signal intensity is an MR feature of meningitis, viral encephalitis, or leptomeningeal metastasis and to investigate a cause of subcortical low intensity. METHODS: We retrospectively reviewed MR images of 117 patients with meningitis, encephalitis (viral or unknown), or leptomeningeal metastasis for the presence of subcortical low intensity, meningeal enhancement, signal intensity change of cortex, and change in subcortical low intensity on follow-up images. Diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) maps were obtained in 55 patients. Subcortical low-intensity lesions were also quantitatively analyzed on T2-weighted, fluid-attenuated inversion recovery (FLAIR), and DW images. RESULTS: Subcortical low intensity was found in nine (23.7%) of 38 patients with encephalitis (viral, 31; unknown origin, 7), five (24%) of 21 with leptomeningeal metastasis, and five (9%) of 58 with meningitis. Leptomeningeal enhancement was observed in 100% and cortical hyperintensity in 14 (74%) of 19 patients with subcortical low intensity. Leptomeningeal enhancement was seen in 46 (47%) and cortical hyperintensity in 33 (34%) of 98 patients without subcortical low intensity. Subcortical low intensity disappeared or decreased in extent on follow-up MR images in all seven patients who underwent follow-up. ADC of subcortical low-intensity lesions was lower than that of the contralateral area and decreased by 9.3 +/- 11.4%. CONCLUSION: Subcortical low intensity was uncommonly found in meningitis, viral encephalitis, and leptomeningeal metastasis. It is a nonspecific MR sign of various meningeal and cortical diseases. Although the cause of subcortical low intensity remains uncertain, free radical formation may play a role as a causative factor.     

MR imaging of acute coccidioidal meningitis

BACKGROUND AND PURPOSE: Our purpose was to describe the MR imaging findings in patients with acute coccidioidal meningitis. METHODS: Fourteen patients (11 men, three women; 22-78 years old; mean age, 47 years) with coccidioidal meningitis underwent neuroimaging within 2 months of diagnosis. Thirteen patients had MR imaging and one had an initial CT study with a follow-up MR examination 5 months later. Initial and follow-up MR images were evaluated for the presence of ventricular dilatation, signal abnormalities, enhancement characteristics, sites of involvement, and evidence of white matter or cortical infarction. The patterns of enhancement were characterized as focal or diffuse. Pathologic specimens were reviewed in two patients. RESULTS: Ten of the 14 images obtained at the time of initial diagnosis showed evidence of meningitis. All of the initially abnormal studies showed enhancement in the basal cisterns, sylvian fissures, or pericallosal region. Subsequent studies, which were available for three of the four patients with normal findings initially, all eventually became abnormal, with focal enhancement seen on the initial abnormal examination. Other abnormalities seen at presentation included ventricular dilatation (six patients) and deep infarcts (four patients). Pathologic specimens in two patients showed focal collections of the organism corresponding to the areas of intense enhancement on MR images. CONCLUSION: Early in its disease course, coccidioidal meningitis may show areas of focal enhancement in the basal cisterns, which may progress to diffuse disease. Pathologically, the areas of enhancement represent focal collections of the organism. Deep infarcts and communicating hydrocephalus are associated findings.     

CT and MR evaluation of intracranial involvement in pediatric HIV infection: a clinical-imaging correlation.

PURPOSE: To review the cranial CT and MR examinations of 29 children with perinatally transmitted HIV infection and correlate the imaging findings with clinical and pathologic data. METHODS: 28 children were examined with CT, four with MR. RESULTS: CT abnormalities were seen in 25 children studied (89%), including cerebral atrophy (25 children), basal ganglia calcification (10 children), periventricular frontal white matter calcification (four children), cerebellar calcification (one child), white matter low attenuation areas (two children), intracranial hemorrhage (three children) and cerebral infarction (one child). Intracranial calcifications were only seen in association with cerebral atrophy and were never seen prior to 1 year of age. Calcifications in the periventricular white matter or cerebellum were always associated with basal ganglia calcifications. MR abnormalities were seen in all four children studied; cerebral atrophy (four children), areas of high signal intensity in white matter (four children), loss of normal posterior pituitary high signal intensity (one child). Cerebral atrophy appeared to be a nonspecific finding that was seen in some children in the absence of neurologic signs and symptoms. All children with intracranial calcifications had developmental delay. Intracranial hemorrhage was seen in children with severe thrombocytopenia. Focal intracranial infections were unusual and neoplastic lesions were not found. CONCLUSIONS: Cerebral atrophy, basal ganglia calcifications, and focal white matter lesions were the most common abnormalities seen neuroradiologically in our series of HIV-infected children; cerebral atrophy was a nonspecific finding.     

MR of neuronal migration anomalies

Migration anomalies are congenital malformations caused by insults to migrating neuroblasts during the third to fifth gestational months. Included in this group are agyria, pachygyria, polymicrogyria, unilateral megalencephaly, schizencephaly, and gray matter heterotopias. Patients who have these conditions present clinically with developmental delay and seizures, and abnormal motor skills are noted in the more severely affected infants. To determine the utility of MR as a method for imaging in these patients, we used MR to evaluate 13 patients who had the full spectrum of migration anomalies. MR was more sensitive than CT in detecting these anomalies because of its better contrast between gray and white matter. We found that MR was particularly more sensitive in detecting schizencephaly, where recognizing the presence of gray matter lining the cleft is critical to distinguishing that disease from porencephaly, and in detecting polymicrogyria, where critical details of cortical architecture are obscured on CT by the overlying bone. Multiplanar capabilities were also found to be essential, since narrow clefts may not be detected when the imaging plane is parallel to the cleft. MR should be the primary imaging method for infants who have seizures or developmental delay.     

CT and MR of the brain in glutaric acidemia type I: a review of 59 published cases and a report of 5 new patients.

PURPOSETo identify a pattern of findings on CT or MR of the brain in glutaric acidemia type I typical enough to permit a correct diagnosis.METHODSClinical history and findings and brain CT and MR results in 59 previously reported patients (MR in 12) and in 5 new patients (all examined with MR and 3 also with CT) were reviewed.RESULTSIn half the patients macrocephaly was present, and in half the onset was acute, often following infection and mimicking encephalitis. Although brain atrophy or hypoplasia was found in 61% and white matter changes in 51% of the patients, open opercula (usually very widely open) and often also wide cerebrospinal fluid spaces anterior to the temporal lobes were seen in 93%. Basal ganglia lesions, presenting as volume loss and high T2 signal in the caudate head and often also the lentiform nucleus bilaterally, were found in 44% and extracerebral fluid collections in 7 of 64 patients.CONCLUSIONThe finding of very widely open opercula suggests glutaric acidemia type I, and if combined with basal ganglia lesions is almost pathognomonic, especially in a child with macrocephaly.     

急性甲醇中毒性脑病的CT及MR表现

目的:分析甲醇中毒患者的颅脑CT及MR表现,以提高影像诊断水平。方法:搜集40例甲醇中毒患者的颅脑及眼部的CT和MR资料,回顾性分析其CT及MR表现。结果:40例中额顶叶白质、外囊壳核CT呈低密度及MR呈长或短T1 长T2 改变的18例,占45%。其中双侧外囊壳核CT呈低密度、MR呈长或短T1 长T2 改变共16例,占40%,右侧壳核出血1例。额、顶叶皮层下白质密度减低共6例,迟发(入院后1周)表现1例。双侧颞叶海马CT呈低密度、MR呈长T1 长T2 改变,共8例。红核、黑质边缘模糊共4例。视神经呈长T1 长T2 改变共8 例。结论:双侧外囊壳核出血性坏死、白质水肿为急性甲醇中毒性脑病的CT及MR主要表现,少数有外囊壳核出血表现。视神经筛板板层内段早期表现为水肿、晚期表现为视神经萎缩。MR检查病灶更加明确,更有特征性。     

Brain CT and MR findings in hyperphenylalaninemia due to dihydropteridine reductase deficiency (variant of phenylketonuria)

Two siblings with malignant hyperphenylalaninemia were examined by magnetic resonance (MR) imaging and CT of the brain. Both techniques demonstrated diffuse cerebral atrophy and cystic loss of parenchyma with surrounding white matter changes. T2-weighted MR images demonstrated the white matter changes better than CT. However, MR images gave no definite indication of the presence of calcification, and CT demonstrated the characteristic calcifications in the basal ganglia and subcortical region bilaterally. Both MR and CT are complementary in the evaluation of this disease.     

Usefulness and limitations of neuroradiologic tests (CT, US, MRI) in periventricular leukomalacia

Sixteen young patients, with clinical and radiological signs of periventricular leukomalacia (PVL), were investigated with MR imaging. Twelve of them were investigated with US in the perinatal period. The extant 4 patients, older than the others, had a clinical history of PVL. US scans were capable of yielding precise information about the anatomical features of PVL in both the acute and the middle phases. The lesions appeared as hyperechoic areas which subsequently turned to anechoic cavities. MR imaging and CT scans did not present any particular advantage over US scans in the acute phase, but they did detect periventricular damage when the patient was 6-7 months old. MR imaging was superior to CT in detecting the delayed myelination of white matter. Inversion-recovery sequences gave more anatomical details to distinguish normal from abnormal white matter. Spin-echo proton-density images detected periventricular gliosis, which appeared as persistent hyperintense areas. CT might be useful in the acute phase, after US detection of hyperechoic intraparenchymal areas, for it allowed purely ischemic lesions to be distinguished from hemorrhagic ones.