SPECT and MR imaging in herpes simplex encephalitis

Two cases of necrotizing herpes simplex encephalitis (HSE) were investigated with 99mTc-hexamethylpropyleneamineoxime (HMPAO) SPECT and MR. The clinical course was compared with the neuroimaging results. In the acute stage, the increased HMPAO uptake matched the MR hyperintense signal in the limbic temporal lobe and in the basal ganglia. Protracted inflammation was accompanied by persistently high HMPAO uptake. The sequelae of HSE were characterized by decreased HMPAO uptake and postnecrotic widening of the temporal horns. The "limbic" pattern recognized in both SPECT and MR reflects the basic pathophysiology and neuropathology of HSE. Both methods may be useful in the diagnosis and follow-up of HSE.     

Viral encephalitis in children: detection with technetium-99m HMPAO brain single-photon emission CT and its value in prediction of outcome.

PURPOSETo assess the role of regional cerebral blood flow measured by technetium-99m hexamethyl propyleneamine oxime (HMPAO) brain single-photon emission CT (SPECT) in viral encephalitis of children.METHODSEighteen children diagnosed as having viral encephalitis (12 Epstein-Barr virus, 4 herpes simplex virus, and 2 Japanese B virus) underwent Tc-99m HMPAO brain SPECT and brain MR and/or CT.RESULTSDuring the acute episode, 4 (22%) of the 18 patients had localized abnormality on brain MR and/or CT. Tc-99m HMPAO brain SPECT in the acute phase showed that 17 (94%) of the 18 patients had increased regional cerebral blood flow and 1 (6%) of the 18 children had a normal brain SPECT. Follow-up brain SPECT was performed at least 15 days after the acute episode. In 17 patients with abnormal first brain SPECT, 12 (71%) had normal second brain SPECT and 5 (29%) had decreased regional cerebral blood flow. The group of patients with normal regional cerebral blood flow on the follow-up brain SPECT had a better outcome than the group of patients with decreased regional cerebral blood flow.CONCLUSIONS(a) The Tc-99m HMPAO brain SPECT was abnormal more often than CT or MR in children with acute viral encephalitis and provided better location. (b) In acute episodes of encephalitis, most patients showed locally increased regional cerebral blood flow. (c) After acute episodes, the regional cerebral blood flow returned to normal in most cases. (d) A normal Tc-99m HMPAO brain SPECT in the subacute phase usually indicates a good clinical outcome (no neurologic defect) 1 year after the acute illness in children with viral encephalitis.     

Sequential MR imaging and SPECT studies in herpes simplex encephalitis with crossed cerebellar hyperperfusion

We report a case of herpes simplex encephalitis in which sequential MR imaging and SPECT studies showed interesting findings. SPECT in the acute stage showed wide increased uptake in the left cerebral hemisphere, as well as increased uptake in the contralateral right cerebellar hemisphere. Tl-weighted images in the subacute stage showed hyperintense signals along the cerebral cortices, but T2*-weighted gradient-echo images did not show any signal decrease caused by the magnetic susceptibility effect of hemoglobin degradation. Sequential SPECT studies in addition to MR imaging facilitate precise understanding of the pathophysiology of herpes simplex encephalitis.     

Temporal lobe involvement in Japanese encephalitis: problems in differential diagnosis

BACKGROUND AND PURPOSE: On MR imaging and CT, Japanese encephalitis (JE) shows lesions in the thalami, substantia nigra, basal ganglia, cerebral cortex, cerebellum, brain stem, and white matter, whereas temporal lobe involvement is characteristically seen in Herpes simplex encephalitis (HSE). Temporal lobe involvement in JE may cause problems in differentiating it from HSE. We undertook this study to show the temporal lobe involvement pattern in JE and highlight differentiating features from temporal lobe involvement in HSE. METHODS: Sixty-two patients with JE underwent CT or MR imaging or both. MR imaging was done in 53 and CT in 53. The diagnosis of JE was confirmed by cerebrospinal fluid (CSF) IgM enzyme-linked immunosorbent assay. RESULTS: Eleven (17.7%) patients showed temporal lobe involvement with abnormal MR imaging in all. All the patients showed hippocampal involvement. Two patients showed extension of lesions into the amygdala and uncus with insular involvement in 1. The rest of the temporal lobe was spared. All patients had thalamic and substantia nigra involvement with basal ganglia involvement in 7. Six of 9 CT scans were abnormal and the temporal lesions were seen in 2. CONCLUSIONS: The temporal lobe involvement pattern is fairly characteristic and mostly involves the hippocampus, usually sparing the rest of the temporal lobe. This and the concurrent involvement of the thalami, substantia nigra (SN), and basal ganglia allow differentiation from HSE. However, if the temporal lobe involvement is more severe, laboratory tests may be the only way to differentiate it from HSE, and it may be prudent to start antiviral therapy in the interim period.     

Reverse crossed cerebellar diaschisis in partial complex seizures related to herpes simplex encephalitis.

Tc-99m HMPAO brain SPECT was performed in a patient who had partial complex seizures for 1 year after successful acyclovir treatment of biopsy-proven herpes simplex encephalitis 2 years earlier. In spite of antiepileptic medications, her seizures were intractable and occurred daily. Tc-99m HMPAO was administered intravenously while she was having subclinical seizures, and brain SPECT demonstrated an area of hyperperfusion in the right temporal lobe medially and in the contralateral cerebellum. This reverse of the crossed cerebellar diaschisis phenomenon in epileptic disorders has not previously been documented.     

Similarities and differences of MR findings between Japanese encephalitis and Wilson's disease

Although Japanese Encephalitis (JE) and Wilson's disease (WD) are different entities, MR findings in both these conditions are quite similar. The purpose of this retrospective study was to find out the similarities and differences between JE and WD on MR imaging. The study group comprised 25 proven cases of JE and 10 cases of WD. Spin echo (SE) TI- and T2-weighted imaging was performed on a 1.5-T MR system. Fourteen of these 35 cases (10 JE, 4 WD) were also examined using T1-weighted magnetization transfer (MT) SE sequence before and after contrast administration. Although both JE and WD showed similar topographical distribution of lesions, predominant involvement of the basal ganglia and thalami, there were some differences. Brain stem lesion was more frequent for WD than for JE, and posteromedial part of the thalami was spared in WD. The lesion characteristics were also different between both; in WD mixed intensity in the basal ganglia and hyperintense linear rim at the peripheral putamen was observed frequently, whereas hyperintense basal ganglia on T2-weighted images, subacute hemorrhage in the thalami and meningeal enhancement were seen only in the patients with JE. These characteristic lesion criteria may help in differentiation of JE from WD on MR imaging.     

Unusual Acute Encephalitis Involving the Thalamus: Imaging Features

Objective

To describe the brain CT and MR imaging findings of unusual acute encephalitis involving the thalamus.

Materials and Methods

We retrospectively reviewed the medical records and CT and/or MR imaging findings of six patients with acute encephalitis involving the thalamus. CT (n=6) and MR imaging (n=6) were performed during the acute and/or convalescent stage of the illness.

Results

Brain CT showed brain swelling (n=2), low attenuation of both thalami (n=1) or normal findings (n=3). Initial MR imaging indicated that in all patients the thalamus was involved either bilaterally (n=5) or unilaterally (n=1). Lesions were also present in the midbrain (n=5), medial temporal lobe (n=4), pons (n=3), both hippocampi (n=3) the insular cortex (n=2), medulla (n=2), lateral temporal lobe cortex (n=1), both cingulate gyri (n=1), both basal ganglia (n=1), and the left hemispheric cortex (n=1).

Conclusion

These CT or MR imaging findings of acute encephalitis of unknown etiology were similar to a combination of those of Japanese encephalitis and herpes simplex encephalitis. In order to document the specific causative agents which lead to the appearance of these imaging features, further investigation is required.     

Computed tomographic findings in acute viral encephalitis in adults with emphasis on herpes simplex encephalitis

Nine patients with acute viral encephalitis were diagnosed by CT. Seven had herpes simplex and two had nonherpetic acute viral encephalitis. All patients with herpes simplex encephalitis initially were febrile. They developed confusion and seizures. Five had focal neurological deficit and two had papilledema. The CT scan showed an abnormality on the initial CT in 6 of 7 cases. In one case initial CT study was normal; however follow-up scan (performed 5 days later) showed a definite abnormality. CT showed the characteristic pattern of herpes simplex encephalitis in all cases. This is a temporal lobe hypodense lesion (unilateral, 5 cases; bilateral, 2 cases) with a small interspersed hyperdense region. The hyperdense component represents hemorrhage. Mass elrect was seen in all cases. Two patients showed enhancement which was diffuse or patchy in one case and cisternnl-gyral in the other; however enhancement was absent in 5 cases. One patient showed progression of the size of the hypodense lesion despite antiviral treatment. Follow-up CT showed hypodense lesion(s) in the, temporal lobe region with enlargement of the temporal horns and contiguous basal cisterns in 4 cases. In 2 other cases of acute viral encephalitis the patients initially developed fever, confusion and seizures. CT showed basal ganglia calcification or hypodense lesions.     

N-isopropyl I-123 p-iodoamphetamine single photon emission computed tomography of herpes simplex encephalitis

Two patients with herpes simplex encephalitis were studied with N-Isopropyl I-123 p-Iodoamphetamine (IMP) single photon emission computed tomography (IMP-SPECT) and X-ray computed tomography (CT). In both cases the affected temporal lobes showed an increased IMP uptake. In case 1, the initial increased IMP uptake decreased as symptoms and CT findings improved. In case 2, the increased IMP uptake was shown at the time of symptoms progressed, while CT had no abnormal findings. IMP uptake is sensitive for its demonstration of inflammatory processes of herpes simplex encephalitis.     

Neuroradiologic findings in children with mitochondrial disorders.

PURPOSEWe report the neuroradiologic findings in 25 children with various mitochondrial diseases.METHODSTwenty-two children with a mitochondrial disorder had MR imaging of the brain and three children had CT studies. In all cases, the diagnosis was based on examination of muscle morphology, analysis of oxygen consumption and respiratory chain enzyme activity in isolated muscle mitochondria, and analysis of rearrangements of the mitochondrial DNA.RESULTSFifteen patients were found to have the classical syndromes of mitochondrial diseases. Four children had Kearns-Sayre syndrome, but only one had the typical neuroradiologic findings of basal ganglia and brain stem lesions, T2 hyperintensity of the cerebral white matter, and cerebellar atrophy; the others had nonspecific or normal findings. Eight patients had Leigh syndrome, and all showed changes in the putamina. Involvement of the caudate nuclei, globus pallidi, thalami, and brain stem was common, and diffuse supratentorial white matter T2 hyperintensity was seen in two of these patients. Three patients had mitochondrial encephalopathy with lactic acidosis and strokelike episodes (MELAS), with infarctlike lesions that did not correspond to the vascular territories. Ten children with complex I or IV deficiencies and abnormal muscle morphology had nonspecific imaging findings, such as atrophy and abnormal or delayed myelination. One patient with combined complex I and IV deficiency had extensive white matter changes. None of the patients with clinical encephalopathy had normal findings.CONCLUSIONMR imaging is helpful in the diagnosis of the classical mitochondrial diseases; however, nonspecific findings are common.     

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.     

MRI of herpes simplex encephalitis

Summary The magnetic resonance imaging (MRI) findings in eight patients with herpes simplex meningoencephalitis were reviewed: 14 examinations were analysed. The most striking finding was high signal intensity in the temporal lobe(s) with the typical configuration known from CT. Meningeal enhancement after Gd-DTPA administration was clearly seen in four patients. Haemorrhagic changes are much better seen on MRI than on CT. When adequate motion control can be achieved, MRI becomes the examination of choice in the diagnosis and follow-up of herpes simplex encephalitis. Localized¹H MR spectroscopy also proved promising in the study of neuronal loss.     

Crossed cerebellar diaschisis in herpes simplex encephalitis

Diaschisis is extremely rare in patients with viral encephalitis. We report the phenomenon of crossed cerebellar diaschisis (CCD) in a 73-year-old man with acute herpes simplex type-1 (HSV-1) encephalitis. The diagnosis of HSV-1 encephalitis was confirmed by detecting HSV-1 deoxyribonucleic acid in the cerebrospinal fluid (CSF). Magnetic resonance images (MRI) showed enhancing lesions at bilateral temporal lobes, insular cortices, and right frontoparietal lobes. Increase signal intensity on T2-weighted images was seen in the mesecephalon. Technetium-99m ethyl cysteinate dimer (99mTc-ECD) single photon emission computed tomography (SPECT) of the brain showed a large area of hypoperfusion in the right frontotemporoparietal lobes. The side-to-side cerebellar count revealed 19% reduction of the radioisotope tracer uptake in the left cerebellum. The phenomenon of CCD was proposed to be due to both anterograde disconnection of the corticopontocerebellar tracts and retrograde deafferentation of dentatothalamocortical projections.     

Use of thallium-201 brain SPECT to differentiate cerebral lymphoma from toxoplasma encephalitis in AIDS patients.

PURPOSETo determine whether thallium-201 brain single-photon emission CT could be used to make the distinction between central nervous system lymphoma and toxoplasma encephalitis, which may not be possible by routine MR and CT.METHODSA total of 37 patients with acquired immunodeficiency syndrome who had intracranial mass lesions found during a 9-month prospective study by either MR or CT underwent further evaluation with Tl-201 brain single-photon emission CT.RESULTSTwelve patients had increased intense focal Tl-201 uptake. All of these patients had either biopsy- or autopsy-proven lymphoma. Twenty-five of the patients studied had no Tl-201 brain uptake in the lesion(s); 24 of these patients had toxoplasma encephalitis on clinical follow-up. One patient with no Tl-201 uptake was found by cerebrospinal fluid analysis to have mycobacterium tuberculosis abscess.CONCLUSIONPatients with acquired immunodeficiency syndrome who have intracranial mass lesions on MR or CT may benefit from Tl-201 brain single-photon emission CT because it can help distinguish between lymphoma and infectious lesions such as toxoplasma encephalitis.     

MR relative cerebral blood flow mapping of Alzheimer disease: correlation with Tc-99m HMPAO SPECT

RATIONALE AND OBJECTIVES: To evaluate the value of magnetic resonance (MR) perfusion imaging for diagnosis of Alzheimer disease (AD), the authors compared relative cerebral blood flow (CBF) maps obtained with MR perfusion imaging and technetium-99m hexamethyl-propyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) in patients with AD. MATERIALS AND METHODS: Eight patients with AD were studied with MR perfusion imaging and HMPAO SPECT. The relative CBF maps from the two techniques were spatially coregistered, and relative CBF values in 13 cerebral gray matter regions (total, 26 regions of interest) were compared with regression analysis. To evaluate the degree of deviation of each brain region from the regression line, a P value for the residual was calculated for each region. RESULTS: A significant overall correlation was seen between the relative CBF values produced by the two techniques (r = .68, P < .0001). Smaller P values for the residuals were obtained in the anterior cingulate cortex (P = .05) and posterior cingulate cortex (P < .001), indicating larger deviations in these regions. When data from these two regions were eliminated, the correlation coefficient rose to 0.80 (P < .0001). CONCLUSION: Despite fairly large discrepancies in the anterior and posterior cingulate cortices, the relative CBF map obtained with MR imaging is generally in close agreement with the HMPAO SPECT map, suggesting that MR perfusion imaging can provide clinically useful information regarding CBF abnormalities in patients with AD.     

Dynamic susceptibility contrast MR imaging of regional cerebral blood volume in Alzheimer disease: a promising alternative to nuclear medicine.

BACKGROUND AND PURPOSEThe goal of our study was to evaluate the sensitivity and specificity for Alzheimer disease of semiquantitative dynamic susceptibility contrast (DSC) MR imaging as compared with results of qualitative single-photon emission computed tomography (SPECT) in the same patients and with previously published semiquantitative SPECT results.METHODSFifty subjects were studied: 19 patients with probable Alzheimer disease with moderate cognitive impairment, eight mildly impaired patients with possible or probable Alzheimer disease, 18 group-matched elderly healthy comparison subjects, and five elderly comparison patients with psychiatric diagnoses. Relative values of temporoparietal regional cerebral blood volume (rCBV) were measured as a percentage of cerebellar rCBV, and group classification was assessed with logistic regression. The DSC MR imaging results were compared with SPECT scans in these same subjects and with previously published semiquantitative SPECT data.RESULTSTemporoparietal rCBV ratios were reduced 20% bilaterally in the patients with Alzheimer disease. Using left and right temporoparietal rCBV as index measures, sensitivity was 95% in moderately affected patients with Alzheimer disease and 88% in patients with mild cases. Specificity was 96% in healthy comparison subjects and in psychiatric comparison subjects. Sensitivity with DSC MR imaging was considerably better than with visual clinical readings of SPECT scans (74% in moderate and 50% in mild Alzheimer disease cases), and was similar to previous published SPECT temporoparietal measurements (90%). Specificity with SPECT was 100% visually and 87% based on previous temporoparietal measurements.CONCLUSIONSDSC MR imaging of rCBV is promising as a safe, potentially lower-cost alternative to nuclear medicine imaging for the evaluation of patients with dementia.     

Role of fast data acquisition method with Tc-99m HMPAO brain SPECT in patients with acute stroke

The first data acquisition method for Tc-99m hexamethylpropyleneamineoxime (Tc-99m HMPAO) brain SPECT was used in two patients with acute stroke 5 and 8 hours after the event. In one patient Tc-99m HMPAO fast SPECT showed perfusion defects before the same was manifested on CT. In the other patient, Tc-99m HMPAO fast SPECT showed larger defects than the edema seen on CT. The Tc-99m HMPAO fast SPECT might be feasible for the evaluation of acute stroke patients. Since the time required for fast SPECT is much shorter than usual SPECT, it appears to be more suitable for some patients with acute stroke who are brought to the hospital in a very critical condition.     

Coinfection of Japanese encephalitis with neurocysticercosis: an imaging study

BACKGROUND AND PURPOSE: Coinfection of neurocysticercosis (NCC) and Japanese encephalitis (JE) has been advocated as more than a chance occurrence resulting in poor outcome. We undertook this study to determine whether the association of the 2 infections is more than a chance occurrence, to define the imaging characteristics of coinfections, and to explore the synergistic effect of NCC in JE.MATERIALS AND METHODS: Sixty-two patients with JE were studied by MR imaging and CT. CT was done in 53 and MR imaging in 53 patients. The diagnosis of JE was established by CSF JE virus immunoglobulin M capture (MAC) enzyme-linked immunosorbent assay (ELISA). NCC was diagnosed from imaging. A control group of 385 patients was evaluated by imaging for prevalence of NCC in the general population.RESULTS: A significantly high association of NCC with JE (19.3%) was observed in comparison with prevalence of NCC in control subjects (1.04%; P = .0003). JE lesions in coinfection were significantly asymmetric with lateralization to the side of the brain having the maximum NCC or a cyst with edema. The JE lesions in coinfections were more florid, with a significantly higher proportion of abnormal CT scans and more abnormal MR imaging. Coinfections were significantly more common in children. Significantly lower CSF MAC-ELISA units in patients with coinfection reflected low CSF IgM levels, suggesting altered immune status.CONCLUSION: In our series, there was a strong association between JE and NCC, and, thus, this coinfection was more than a chance occurrence.

Japanese encephalitis (JE) is a mosquito-borne viral encephalitis that is endemic to several tropical and semitropical countries in Asia. A total of 50,000 new cases occur annually across the endemic regions of the world, of which 10,000 people die. JE is endemic in India, with outbreaks reported in several Indian states in the past decades. Pigs act as amplifier of the JE virus (JEV). Epidemics occur in the summer rainy season in India when mosquitoes are abundant. Clinically, the disease manifests as fever, headache, and altered sensorium with or without focal neurologic symptoms.¹ On CT and MR imaging, JE lesions are most commonly seen in the thalami. Other areas involved are the substantia nigra, basal ganglia, cerebral cortex, hippocampus, pons, midbrain, medulla, cerebellum, and white matter.^2–4Neurocysticercosis (NCC) is caused by the larval stage of the pork tapeworm, Taenia solium and results from the ingestion of the eggs of the adult tapeworm by the fecal-oral route. It is endemic to and a public health problem in India. Neuroimaging by CT or MR imaging is useful for establishing the diagnosis.⁵Coinfection of JE and NCC has been reported in China and India.^6–8 Although both diseases have common epidemiologic and sociodemographic factors like pig rearing, poor socioeconomic status, hygienic conditions, malnutrition, and so forth, more than a casual association of the 2 conditions has been suggested. The presence of NCC has been advocated as a prognosticator of poor outcome in JE.^6,7 Few imaging studies have studied this coinfection.^9,10 These have drawn conflicting conclusions. Singh et al⁹ reported the imaging features in coinfection but did not compare with a cohort of JE patients without coinfection. Azad et al¹⁰ found an increased prevalence of NCC in patients with JE but did not find any statistically significant difference from the prevalence of NCC in control subjects. We undertook this study to find out if there is a significant association of JE with NCC, to define the imaging characteristics of coinfection of JE and NCC, to compare them with a cohort of JE subjects without coinfections, and to explore the synergistic effect of NCC in JE.     

Atypical finding of brain Tc-99m-ECD SPECT imaging in herpes simplex encephalitis

Lesions in acute herpes simplex encephalitis (HSE) have been reported to show decreased uptake of Tc-99m ethyl cysteinate dimer (ECD). A patient with acute HSE displaying a lesion in the left temporal lobe was evaluated by means of Tc-99m ECD single-photon emission computed tomography (SPECT). Dynamic SPECT images indicated regionally increased uptake of tracer in the ipsilateral temporal lobe in early phases, followed by slight washout of Tc-99m ECD from the lesion. Static SPECT images revealed increased tracer uptake in the same region. MRI later demonstrated that the HSE lesion involved the whole cortex of the temporal lobe on the affected side. These findings suggest that acute HSE lesions do not always exhibit hypoactivity on static Tc-99m ECD SPECT, and that dynamic Tc-99m ECD SPECT may help physicians diagnose acute HSE.     

小儿流行性乙型脑炎磁共振波谱特征及随访研究

目的：探讨磁共振氢质子波谱（1H-MRS）对小儿流行性乙型脑炎预后评价的价值。方法：对17例常规MRI有信号异常的乙脑患儿行1H-MRS扫描,并选择15例同龄健康志愿者对照。病例组在3个月内进行随访并复查MRI,根据随访结果将患者分治愈组和未治愈组,回顾性分析两组患儿首次1H-MRS特征。结果：病灶在T1WI呈斑片状等或稍低信号、T2WI及FLAIR呈稍高或高信号,其中累及灰质核团13例,均呈对称性分布,边界清晰。17例患儿中1H-MRS均见不同高度Lac峰,7例NAA峰有明显下降,2例Cho峰轻度降低,1例出现Cr峰下降,3例出现MI峰。病例组与对照组之间NAA/（Cr＋Cho）值差异有显著性意义（t=5.98,P〈0.05）。根据随访结果,治愈组11例,未治愈组6例,两组NAA/（Cho＋Cr）差异有显著性意义（t=3.45,P〈0.05）。结论：乙脑患儿病变易累及灰质核团,1H-MRS多见Lac双峰,NAA明显下降往往提示患儿病情较重,预后不良。1H-MRS能反映乙脑严重程度并判断预后,是常规MRI有益补充。