MR imaging features of Nipah encephalitis

OBJECTIVE: The newly discovered Nipah virus causes an acute febrile encephalitic illness in humans that is associated with a high mortality. The purpose of this study is to describe the MR imaging findings of Nipah encephalitis. MATERIALS AND METHODS: MR imaging of the brain was performed in 31 patients with Nipah encephalitis divided into three groups. The first group (14 patients) underwent MR imaging during the acute phase of the illness and the second group (10 patients) during the later phase of the acute illness. The third group consisted of six patients who underwent MR imaging because they experienced neurologic relapse and one patient who had late-onset encephalitis. Spin-echo T1- and T2-weighted sequences and T2-weighted fluid attenuated inversion recovery (FLAIR) sequences were performed. Contrast-enhanced MR imaging was performed in four patients. RESULTS: The FLAIR sequences revealed abnormalities in all patients studied. MR imaging findings in both the acute and later phases of encephalitis were similar; the main feature of both phases was the presence of discrete high-signal-intensity lesions, measuring 2-7 mm, disseminated throughout the brain, mainly in the subcortical and deep white matter of the cerebral hemispheres. Neither mass effect nor cerebral edema was seen. There was no correlation with the focal neurologic signs, depth of coma, and outcome of the patients. The lesions were attributed to widespread microinfarctions from underlying vasculitis of cerebral small vessels. Features found on MR imaging in relapsed and late-onset encephalitis differed from the features in acute encephalitis in that confluent cortical involvement was the prominent finding in the former, as opposed to discrete focal lesions in the subcortical and deep white matter in the latter. CONCLUSION: MR imaging is a sensitive and specific diagnostic tool for evaluating Nipah encephalitis.     

MR Imaging of BK virus encephalitis

BK virus infection is most often associated with urologic disease in patients who have undergone renal or bone marrow transplantation. We report a rare case of biopsy-confirmed BK virus encephalitis in an immunocompromised patient with hemorrhagic cystitis, in whom dramatic imaging findings were present despite relatively mild clinical symptoms. MR imaging demonstrated widespread increased signal intensity on T2- and fluid-attenuated inversion recovery-weighted images, with restricted diffusion, in the cerebellum, cerebral white matter, and deep gray matter structures. The simultaneous presence of urologic abnormalities and neurologic deficits in certain immunocompromised patients should prompt consideration of BK virus encephalitis.     

Rapid spongiform degeneration of the cerebrum and cerebellum in Creutzfeldt-Jakob encephalitis: serial MR findings.

We report the cerebral MR imaging findings in a patient with pathologically proved Creutzfeldt-Jakob disease in whom predominant gray and white matter degeneration was seen within 1 year of symptom onset. The initial MR signal abnormalities in the basal ganglia were subtle. A follow-up MR examination revealed diffuse cerebral and cerebellar atrophy and demyelination.     

Lupus-related myelitis: serial MR findings.

PURPOSETo correlate the MR findings in transverse myelitis secondary to systemic lupus erythematosus with clinical findings during disease exacerbation and remission.METHODSFour patients (ages 33 to 47 years) with episodes of transverse myelitis secondary to systemic lupus erythematosus were identified. Three patients had recurrent transverse myelitis episodes (one patient with two recurrences), for a total of eight episodes. MR examinations (six after contrast administration) were performed during each transverse myelitis episode, as well as during four periods of remission (in three patients) after therapy with steroids and/or immunosuppressive agents. MR examinations were reviewed for the presence of spinal cord enlargement, intramedullary signal abnormality, and contrast enhancement.RESULTSProlongation of T1 or T2 signal (or both) was seen in eight episodes (100%). Spinal cord enlargement was seen in six (75%) of eight transverse myelitis episodes, although it was mild during two episodes. Contrast enhancement was seen in three of six transverse myelitis episodes (dense, inhomogeneous enhancement during two episodes in one patient, and a small focus of enhancement in one patient). During periods of remission, spinal cord diameter returned to normal, and no contrast enhancement was seen, although abnormal signal was present in three examinations performed within 2 months of a transverse myelitis episode.CONCLUSIONSpinal cord widening and signal abnormalities are common MR findings during episodes of transverse myelitis related to systemic lupus erythematosus, and contrast enhancement is less frequently seen. Improvement or resolution of these findings correlates with clinical improvement.     

Multiple sclerosis: serial study of gadolinium-enhanced MR imaging

Thirteen patients with definite multiple sclerosis (MS), studied 16-24 months previously with magnetic resonance (MR) imaging with and without enhancement by intravenously administered gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine, were reexamined with a similar protocol. Assessment of enhancement and clinical activity in both studies revealed that enhancement was observed in 13 of 14 cases in which clinical activity had changed within 4 weeks of the study and thus appeared more sensitive than clinical examination in determining active disease. The 3-minute postinjection, short repetition time image (TR) was the most efficient for depicting enhancement. Enhancing lesions (active plaques) arose from previously hyper- or isointense regions on long TR images. Previously active lesions reverted to areas of iso- or hyperintensity on long TR images. Serial comparison of long TR images in this population reveals a decrease in high-intensity lesions on long TR images in some cases and an increase in others. The findings of high-intensity regions on long TR images and previously enhancing lesions both becoming isointense suggests that transient inflammatory changes with concomitant edema without demyelination and/or with significant remyelination may occur in some MS lesions. MS lesions are dynamic; both active and inactive lesions may show dramatic change on longitudinal MR imaging studies.     

Diffusion-weighted MR imaging of encephalitis.

OBJECTIVE: Our purpose was to evaluate how well diffusion-weighted MR imaging shows viral or bacterial encephalitis in comparison with conventional MR imaging that includes T1- and T2-weighted spin-echo and fluid-attenuated inversion-recovery sequences. CONCLUSION: In nine of the 13 patients examined, diffusion-weighted imaging was superior to other diagnostic imaging sequences (fluid-attenuated inversion-recovery sequences in eight patients and a T2-weighted spin-echo sequence in one patient). Diffusion-weighted imaging can serve as a method of detecting early encephalitic changes.     

单纯疱疹病毒性脑炎的CT及MRI表现

目的：探讨单纯疱疹病毒性脑炎的影像学表现。方法：回顾性分析9例经PCR（polymerasechainreaction）证实的单纯疱疹病毒性脑炎患者的影像及临床资料,9例患者均行颅脑MRI及增强检查,3例行头部CT扫描。结果：2例病灶位于单侧颞叶、岛叶和扣带回;2例位于双侧颞叶,岛叶、基底节、额叶内侧回及海马钩回;5例位于双侧额叶、颞叶、岛叶,一侧为重,病灶多累及皮层及皮层下白质;其中2例出现不同程度的占位效应。CT扫描病灶呈低密度;MRl扫描病灶呈长T,长T2信号,TIRM序列上病灶呈高信号,DWI显示病灶区扩散受限,增强扫描5例出现脑膜样强化,4例无强化。结论：单纯疱疹病毒性脑炎影像学表现具有一定特征性,常侵犯颞叶、额叶、基底节及岛叶,尤其一侧颞叶、岛叶和眶额区为重．MRI对病灶的显示优于CT．     

Rocky Mountain spotted fever encephalitis: MR findings.

We describe a case of Rocky Mountain spotted fever encephalitis and present the associated findings of an MR examination of the brain, which showed increased signal intensity in the distribution of perivascular spaces. Resolution of the MR abnormalities coincided with clinical improvement.     

Herpes simplex encephalitis: diffusion MR imaging findings.

We studied five patients with herpes simplex encephalitis type 1 with diffusion-weighted MR imaging, as this sequence provides information regarding tissue integrity. Diffusion-weighted imaging was obtained using the echo-planar sequence. True diffusion images (i.e. b=1000s/mm(2) images), and the ADC (apparent diffusion coefficient) values were studied. In addition, diffusion imaging of 12 normal cases, 46 patients with acute ischemia (cytotoxic edema), and 12 patients with vasogenic edema were studied for comparison. In patients with herpes encephalitis, two distinct types of diffusion imaging findings (on b=1000s/mm(2) images, and ADC maps) were noted: lesions similar to cytotoxic edema, and lesions similar to vasogenic edema. The patients with the former type of lesions had fulminating disease, and were in severe clinical condition. Those with the latter represented early cases, and they were in fairly good clinical condition with a good outcome by prompt therapy. Diffusion imaging appears to be a promising sequence to monitor the changes in the brain tissue in herpes encephalitis, and in other infections as well with respect to restriction of movement (cytotoxic edema) or relatively high-motion (vasogenic edema) of water molecules, providing data on the severity of the disease.     

Progressive brain failure after diffuse hypoxic ischemic brain injury: a serial MR and proton MR spectroscopic study.

The findings at sequential MR imaging and proton MR spectroscopy of a patient with profound hypoxic-ischemic brain injury are reported. The pattern of structural and biochemical changes observed closely reflected the known evolution of postasphyxic brain degeneration. Particularly noteworthy were the sharp decrease of cortical N-acetylaspartate in the acute phase, suggesting the severity of the neuronal insult, and the subsequent progressive increase of choline, paralleling the delayed degeneration of white matter.     

Multiple reversible MR signal changes caused by Epstein-Barr virus encephalitis

This report presents the imaging findings of an unusual case of Epstein-Barr virus (EBV) encephalitis. A young man presented with a short-lasting history of febrile infection, neuropsychologic deficits, ataxia, and seizures. MR imaging revealed fully reversible signal intensities (T2, diffusion-weighted imaging with a decreased apparent diffusion coefficient) in the splenium of the corpus callosum and both posterior hemispheres. EBV infection must be added to the list of differential diagnoses of (reversible) splenial lesions.     

Hydatid disease: MR imaging study

Fifteen patients with hydatidosis, 13 with hepatic echinococcosis and two with isolated lesions of the spleen and the shoulder, were examined with magnetic resonance (MR) imaging. Of the 13 patients with hepatic hydatidosis, four had secondary peritoneal lesions, and one also had involvement of the dorsal spine. The presence of a hypointense rim and a multiloculated or multicystic appearance are distinctive features. When evaluating the viability of hydatid cysts the authors found that MR imaging findings were not particularly valuable, as the MR imaging signs (daughter cysts and detachment of the membranes) are rare and are also evident at computed tomography and ultrasound examinations. T2 measurements were not useful due to the wide range of values obtained. Despite these limitations, MR imaging is still an important technique in the study of echinococcosis to depict the presence of a rim as a characteristic sign and to obtain a complete anatomic evaluation.     

Macroprolactinomas: serial MR imaging in long-term bromocriptine therapy.

PURPOSE: To study the changes in macroprolactinomas during long-term bromocriptine therapy by means of serial MR imaging, and to correlate the findings to the serum prolactin (S-PRL) levels. PATIENTS AND METHODS: Thirteen patients with macroprolactinomas were studied before and during bromocriptine therapy; six to 11 MR examinations were performed with a duration of follow-up of 22 to 74 months. Tumor size, extension, relationship to adjacent structures, and signal intensity patterns were evaluated. Signal intensity ratios and T2 values were calculated in areas of apparently solid tumor tissue. RESULTS: Bromocriptine effectively reduced the size of all tumors; the size reduction was already significant at 1 week, but often continued for several years. Reenlargement during therapy was seen in three cases. The development of chiasmal herniation parallel to increasing cisternal invagination into the sella was a common finding, but was not correlated to visual symptoms. Signal intensity patterns corresponding to hemorrhage, cysts or necrosis were frequently observed, and transitions from one pattern to another were common. Hemorrhage occurred mainly in tumors corresponding to high initial serum prolactin levels. After 1 year of therapy, there was a significant increase in T2 values, indicating an increased water content in residual solid tumor tissue. CONCLUSIONS: MR is valuable for follow-up in bromocriptine therapy of macroprolactinomas, and provides new information on the tumor size changes, the inner structure of the tumors, and the optic chiasm.     

Early infantile form of Krabbe disease with optic hypertrophy: serial MR examinations and autopsy correlation.

The development of white matter lesions in a case of autopsy-proved early infantile form of Krabbe disease was monitored by serial MR examinations. Hypertrophy of the optic nerves was present late in the course of the patient''s disease and is a remarkable feature in this case.     

Marchiafava-Bignami disease: longitudinal MR imaging and MR spectroscopy study

A case of Marchiafava-Bignami disease was serially evaluated with MR imaging and MR spectroscopy at 1, 2, 4, and 11 months after the onset of symptoms. The first MR imaging study showed extensive abnormal signal intensity of the corpus callosum without macroscopic changes; a diagnosis of Marchiafava-Bignami disease was made, and vitamin therapy was initiated. Follow-up studies showed progressive reduction of signal intensity abnormalities and residual callosal atrophy. MR spectroscopy revealed progressive reduction of the N-acetylaspartate:creatine ratio, with partial recovery in the last study, and a normalization of the choline:creatine ratio, which was initially slightly increased. Lactate was detectable during the subacute phase and was replaced by lipids after 4 months. This study confirmed the role of MR imaging in diagnosing Marchiafava-Bignami disease and particularly the value of MR spectroscopy in focusing the pathogenesis of the disease, monitoring its evolution and changes related to therapy.     

肠道病毒71型感染手足口病合并脑炎的MRI表现及特征

目的探讨肠道病毒71型感染手足口病合并脑炎的MR表现及特征,为临床诊断及及时治疗提供帮助。方法回顾性分析2009年4月～2011年7月临床诊断为手足口病合并脑炎并行颅脑MR扫描的64例患儿的图像资料,所有病例均经病原学检查证实为肠道病毒71型感染。结果脑干病变共计32例,其中桥脑6例(主要位于桥脑背侧),延髓8例(6例表现为延髓背侧对称性小片状信号,2例为偏中心病灶),桥脑-延髓交界区8例,中脑10例(多位于双侧大脑脚,呈片状);小脑齿状核4例(双侧);丘脑4例(均为单侧丘脑,斑点状或小片状);右侧内囊后肢1例(呈条形);基底节区9例(多为斑点状信号);放射冠区、半卵圆中心及双侧额、顶叶皮质下区者共38例(病变多为多发斑点状信号);其中病灶位于单个部位者35例(35/64,54.69%),位于多个部位者29例(29/64,45.31%)。结论手足口病合并脑炎发病部位广泛,不只局限于脑干,基底节、内囊后肢、丘脑、小脑齿状核及双侧大脑白质区均可累及。总结其易发病部位,依次为脑干、脑白质、基底节、丘脑、小脑齿状核,MR颅脑扫描能真实、准确显示手足口病合并脑炎脑部受损情况,可为临床诊断及时治疗提供可靠的影像学依据。     

Fresh blood imaging of the peripheral vasculature: an emerging unenhanced MR technique

OBJECTIVE: There is an increasing demand for MR angiography (MRA) techniques that do not require the administration of exogenous contrast material. Fresh blood imaging utilizes an ECG-gated fast spin-echo sequence to acquire images in both the systolic and diastolic phases of the cardiac cycle. Fast systolic arterial flow is differentiated from slower diastolic flow and a subtraction technique is used to produce angiographic images. We describe the technical aspects of performing lower extremity MRA and illustrate some sample cases. CONCLUSION: Fresh blood imaging is an emerging unenhanced MRA technique that has recently become commercially available. Early clinical trials appear promising and it is anticipated that fresh blood imaging will become invaluable, particularly in patients with impaired renal function. Technical refinements are still required to perfect this novel MR application, particularly for the assessment of distal calf and pedal vessels and for the evaluation of patients with arrhythmias and those with impaired cardiac function.     

Coexistent neurocysticercosis and Japanese B encephalitis: MR imaging correlation.

BACKGROUND AND PURPOSE: An increased incidence of intestinal helminthic infections has been observed in patients with viral encephalitis in endemic areas. Both Japanese B encephalitis (JE) and neurocysticercosis (NCC) share some common socio-demographic and ecologic factors, and pigs act as the intermediate carrier for both. Our purpose was to show the coexistence of JE and NCC in brain on MR images and highlight the possible role of NCC as an amplifier of JE. METHODS: MR images from 10 cases of coexistent JE and NCC were studied retrospectively. T1-weighted axial and sagittal, proton T2-weighted axial and coronal, and T2-weighted fluid-attenuated inversion recovery axial and coronal sections of the brain were evaluated. NCC was diagnosed on the basis of neuroimaging. Diagnostic serologic testing for JE was conducted using paired blood and CSF samples. RESULTS: The JE changes were bilateral and asymmetrical and were more severe on the side harboring the solitary cyst or the side bearing the greater number of cysts or lodging the degenerating cyst. In each of nine of 10 cases, at least one degenerating cyst was found on the side of predominant JE pathologic abnormality. CONCLUSION: The study suggests that the co-occurrence of JE and NCC is not just a chance coincidence. NCC apparently predisposes a person to JE infection and is a positive modulator of the encephalitic process. The study shows a spectrum of MR imaging findings of coexistent JE and NCC.