A follow-up study by CT and MRI in 3 cases of Japanese encephalitis

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Bilateral thalamic bleed and cerebral venous sinus thrombosis in Japanese encephalitis

Japanese encephalitis (JE) is a potentially serious form of viral encephalitis with varied clinicoradiological manifestations. We report the case of a 19-year-old girl admitted with headache, vomiting and altered sensorium in the absence of fever, whose cerebrospinal fluid analysis showed lymphocytic pleocytosis with significant protein content and positive serum IgM JE antibodies. MRI with venography revealed bilateral thalamic haemorrhage and cerebral venous sinus thrombosis. Although thalamic hypodensities are a well-described feature, thalamic haemorrhage and cerebral venous thrombosis are distinctly rare in JE. This report highlights the role of imaging in cases of encephalitis in general and JE in particular, in the early detection of uncommon manifestations that may complicate these diseases.

Effect of surgical closing in total knee arthroplasty at flexion or extension: a prospective, randomized study

PURPOSE

The aim of this study was to evaluate the effect of knee position during wound closure (flexed vs. extended) in total knee arthroplasty on knee strength and function, as determined by knee society scores and isokinetic testing of extensor and flexor muscle groups.

METHODS

In a prospective, randomized, double-blind trial, 29 patients were divided in two groups: for Group 1 patients, surgical closing was performed with the knee extended, and for Group 2 patients, the knee flexed at 90°. All the patients were treated with the same anaesthesia method, surgical team, surgical technique, prosthesis type, and rehabilitation process. American Knee Society Score values and knee flexion degrees were recorded. Isokinetic muscle strength measurements of both knees in flexion and extension were taken using 60° and 180°/s angular velocity. The peak torque and total work values, isokinetic muscle strength differences, and total work difference values were calculated for surgically repaired and healthy knees.

RESULTS

No significant difference in the mean American Knee Society Score values and knee flexion degrees was observed between the two groups. However, using isokinetic evaluation, a significant difference was found in the isokinetic muscle strength differences and total work difference of the flexor muscle between the two groups when patients were tested at 180°/s. Less loss of strength was detected in the isokinetic muscle strength differences of the flexor muscle in Group 2 (-4.2%) than in Group 1 (-23.1%).

CONCLUSION

For patients undergoing total knee arthroplasty, post-operative flexor muscle strength is improved if the knee is flexed during wound closure.

LEVEL OF EVIDENCE

II.

May early intervention with high dose intravenous immunoglobulin pose a potentially successful treatment for severe cases of tick-borne encephalitis?

Background

Arthropod-borne viral encephalitis of diverse origins shows similar clinical symptoms, histopathology and magnetic resonance imaging, indicating that the patho mechanisms may be similar. There is no specific therapy to date. However, vaccination remains the best prophylaxis against a selected few. Regardless of these shortcomings, there are an increasing number of case reports that successfully treat arboviral encephalitis with high doses of intravenous immunoglobulins.

Discussion

To our knowledge, high dose intravenous immunoglobulin has not been tested systematically for treating severe cases of tick-borne encephalitis. Antibody-dependent enhancement has been suspected, but not proven, in several juvenile cases of tick-borne encephalitis. Although antibody-dependent enhancement during secondary infection with dengue virus has been documented, no adverse effects were noticed in a controlled study of high dose intravenous immunoglobulin therapy for dengue-associated thrombocytopenia. The inflammation-dampening therapeutic effects of generic high dose intravenous immunoglobulins may override the antibody-dependent enhancement effects that are potentially induced by cross-reactive antibodies or by virus-specific antibodies at sub-neutralizing levels.

Summary

Analogous to the increasing number of case reports on the successful treatment of other arboviral encephalitides with high dose intravenous immunoglobulins, we postulate whether it may be possible to also treat severe cases of tick-borne encephalitis with high dose intravenous immunoglobulins as early in the course of the disease as possible.

An evaluation of the usefulness of neuroimaging for the diagnosis of Japanese encephalitis

Japanese encephalitis virus (JEV) is estimated to cause 30–50,000 cases of encephalitis every year. The disease occurs mainly in rural Asia and is transmitted to humans from birds and pigs by mosquitoes of the genus Culex. JE is diagnosed with antibody testing of the serum and CSF, but this is not available in many hospitals. Neuroimaging abnormalities, particularly thalamic hypodensity on computed tomography (CT) and hyperintensity on T2 weighted magnetic resonance imaging (MRI) have been described in case studies, but their usefulness for diagnosing JE is not known. We have therefore evaluated the usefulness of neuroimaging (CT and MRI) for the diagnosis of JE. The findings of thalamic lesions were compared with the final serological diagnosis in a cohort of 75 patients (children and adults) with suspected CNS infections in Southern Vietnam, a JEV endemic area. Thalamic lesions on CT and/or MRI combined had sensitivity 23% (95% confidence interval 12.9–33.1%), specificity 100%, positive predictive value 100% and negative predictive value 42.1% (95% confidence interval 30.2–53.8%) for a diagnosis of JE in this cohort. Over time, the thalamic lesions resolved in some patients. One patient showed disappearance of lesions on CT followed by reappearance of the lesions some time later, known as the fogging effect. In this setting, the presence of thalamic abnormalities suggested the diagnosis of JE, but their absence did not exclude it.

Acute encephalitis, a poliomyelitis-like syndrome and neurological sequelae in a hamster model for flavivirus infections

Infection of hamsters with the murine flavivirus Modoc results in (meningo)encephalitis, which is, during the acute phase, frequently associated with flaccid paralysis, as also observed in patients with West Nile virus encephalitis. Twenty percent of the hamsters that recover from the acute encephalitis develop life-long neurological sequelae, reminiscent of those observed, for example, in survivors of Japanese encephalitis. Magnetic resonance imaging and histology revealed severe lesions predominantly located in the olfactory-limbic system, both in hamsters with acute encephalitis as in survivors. Prominent pathology was also detected in the spinal cord of hamsters with paralysis. Modoc virus infections in hamsters provide a unique model for the study of encephalitis, a poliomyelitis-like syndrome and neurological sequelae following flavivirus infection.

Pathogenesis of flavivirus encephalitis

Within the flavivirus family, viruses that cause natural infections of the central nervous system (CNS) principally include members of the Japanese encephalitis virus (JEV) serogroup and the tick-borne encephalitis virus (TBEV) serocomplex. The pathogenesis of diseases involves complex interactions of viruses, which differ in neurovirulence potential, and a number of host factors, which govern susceptibility to infection and the capacity to mount effective antiviral immune responses both in the periphery and within the CNS. This chapter summarizes progress in the field of flavivirus neuropathogenesis. Mosquito-borne and tickborne viruses are considered together. Flavivirus neuropathogenesis involves both neuroinvasiveness (capacity to enter the CNS) and neurovirulence (replication within the CNS), both of which can be manipulated experimentally. Neuronal injury as a result of bystander effects may be a factor during flavivirus neuropathogenesis given that microglial activation and elaboration of inflammatory mediators, including IL-1β and TNF-α, occur in the CNS during these infections and may accompany the production of nitric oxide and peroxynitrite, which can cause neurotoxicity.

Radiological and manometric diagnosis of cricopharyngeal dysphagia in a Japanese encephalitis survivor

Japanese encephalitis (JE) is endemic throughout most of the western Pacific region where Taiwan is located. About half the survivors are left with neurological damages. We report a 55-year-old male who survived from JE and was left with sequela of parkinsonism and severe swallowing disorder. Later, it was proved to be cricopharyngeal dysphagia (CPD) using esophagogram and manometry, which disclosed involuntary hypertonic and hyperreflexic cricopharyngeal muscle contraction. CPD, a life-threatening neurological sequel of JE, has never been reported in the JE survivors before and possibly results from disseminated lesions over pyramidal and extrapyramidal systems.

Biphasic illness pattern due to early relapse in Japanese-B virus encephalitis

Japanese-B virus encephalitis (JE) is considered a uniphasic illness with a variable outcome. Biphasic illness patterns have never been reported previously. From an endemic zone in India we observed six patients of JE (from 62 patients treated in 7 years) who had an early relapse resulting in the biphasic clinical course. Five had poor socio-economic status and three had laboratory evidence of nutritional deficiency. Two patients were adults and the other four were children. Fever, rigors, headaches, body aches, altered consciousness, rigidity and tremors predominated the first phase of illness. During the second phase, behavioural changes, dystonia, pen-oral dyskinesia, drooling, mutism and muscle wasting due to anterior horn cell involvement were the important features. Though the serial antibody titres against the JE virus showed a four-fold rise in the initial or late convalescent phases, there was no increase during the second phase of the illness as compared to the first phase. On MRI, fresh lesions appeared during the second phase at the sites known for their involvement in JE, suggesting recrudescence of the virus. One patient survived with major sequelae, two with minor sequelae and the other three had complete recovery. We conclude that some patients with JE may have an early relapse after partial recovery, giving rise to the biphasic illness pattern. A locally prevalent genetic variant of the virus or host factors may be responsible for the altered clinical course of the disease. Biphasic illness does not necessarily mean a bad prognosis.

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.

Brainstem auditory evoked potential in Japanese encephalitis

Japanese encephalitis (JE) is associated with varying degrees of coma and brainstem involvement is frequent which can be evaluated and monitored by brainstem auditory evoked potential (BAEP). The present study has been undertaken to evaluate the BAEP changes and their role in predicting the outcome. Twelve adult patients with JE were subjected to CT scan, MRI and BAEP studies after detailed neurological evaluation. The severity of coma was assessed by Glasgow coma scale and outcome was defined at the end of 3 months into good and poor recovery on the basis of Barthel Index score (BI). The mean age of the patients was 28.3 years (range 14-50), and four of them were females. Most of the patients were comatose. The mean Glasgow coma scale (GCS) score was 7 (range 4-11). There were no brainstem signs or cranial nerve palsy. Cranial CT scan revealed thalamic hypodensity in four, whitematter oedema in three and left putaminal hypodensity in one patient. Cranial MRI was carried out in eight patients which revealed bilateral thalamic lesions in all, basal ganglia and midbrain lesions in three each and pontine and cerebellar lesions in one patient each. Brainstem auditory evoked potentials were recordable bilaterally. The absolute latency of wave I, II, III, IV and V and interpeak latencies (IPL) of I-V, III-V, and I-III were normal. The V/I amplitude ratio were significantly reduced in five patients. The BAEP abnormalities correlated with brainstem lesions on CT or MRI but not with severity of coma or outcome. The reduced amplitude ratio of wave V/I may be due to raised intracranial tension or brainstem involvement in JE.

Neurological complications to vaccination against Japanese encephalitis

Japanese encephalitis (JE) vaccine has been used for childhood immunization programmes in Asia since the 1960s. Also, travellers from other parts of the world have been vaccinated before travelling to Asian countries. Some JE vaccines are produced from infected mouse brains and contain small amounts of myelin basic protein. Neurological side effects in larger vaccine trials in Asia have been reported in 1-2.3 per million vaccinees. Statens Serum Institut is the only distributor of JE vaccine in Denmark, delivering 384 000 doses from 1983-96. In 1996, evaluation of initial symptoms and findings in 10 adult travellers from Denmark, who developed moderate-severe neurological symptoms within a few weeks of JE vaccination, was performed as well as follow-up magnetic resonance imaging (MRI) and clinical neurological examination. Three patients initially had symptoms varying from severe encephalitis-like illness to paraesthesia, double vision or parkinsonian gait disturbance. MRI showed severe atrophy of the corpus callosum with altered signal intensity indicating gliosis in one patient, another patient had several hyperintense spots located periventricularly in the white matter, while a third patient had spots with increased signals in the pons, the right substantia nigra and the occipital region. Acute disseminated encephalomyelitis (ADEM) is a possible explanation for these MRI changes, although multiple sclerosis is an alternative diagnosis in one or two of the patients. Another three patients had long-lasting headache, concentration difficulty or intellectual reduction. One man had afebrile convulsions, another gait instability and depression and one parkinsonism. A woman developed myelitis. If these findings are due to JE vaccination the frequency of neurological reactions to the vaccine is considerably higher than previously reported and in the future any minor neurological complaints occurring shortly after vaccination should lead to neurological examination and acute MRI scan should be considered. Copyright 1998 Lippincott Williams & Wilkins

Japanese encephalitis

Japanese encephalitis (JE) is an acute encephalomyelitis which is a primary viral encephalitis accompanying a viral infection. Clinically, the patient who either resides in an endemic region or who has been exposed to the viral vector (mosquito) may have symptoms including high fever, headache, and impaired consciousness. JE involves many portions of the supratentorial and infratentorial compartments including the brain stem, hippocampus, thalamus, basal ganglia, and white matter. Classically MR imaging demonstrates the lesions of JE as hyperintense on T2-weighted images and hypointense on T1-weighted images. Hemorrhagic transformations have also been described in JE lesions, with corresponding expected T1 and T2 changes. Differential considerations based on the MRI appearance are somewhat broad, including but not limited to primary viral encephalitis, acute encephalopathy, limbic encephalitis, and acute disseminated encephalomyelitis. The therapy for JE is primarily conservative and supportive since there is no specific treatment for JE, and the disease has a high fatality rate. The prognosis depends on the extent of involvement at primary presentation, and on the autoimmune mechanisms of this disease.

Pathological laughing and crying

OBJECTIVE

To review the clinical features, neurobiological correlates and treatment of pathological laughing and crying.

METHOD

Selective literature review.

RESULTS

Attacks of involuntary, irresistible laughing or crying have long been recognised as sequelae of brain damage. There is controversy about the clinical features of these attacks, the stimuli that provoke them and their relation to affective disorder. The pathophysiology of pathological laughing and crying is still unclear. It can occur in the presence of focal as well as diffuse brain disease. Treatment with antidepressant medications has been found to be of benefit in patients with cerebrovascular disease and multiple sclerosis.

CONCLUSIONS

Clinicians should remain vigilant for these symptoms, and offer effective treatments, such as antidepressants, where indicated. Further research is needed to delineate the underlying neurobiological correlates of pathological laughing and crying. The efficacy of both pharmacological and non-pharmacological interventions requires critical evaluation.

The substantia nigra is a major target for neurovirulent influenza A virus

Clinical and immunohistochemical studies were done for 3-39 d on mice after intracerebral inoculation with the neurovirulent A/WSN/33 (H1N1; WSN) strain of influenza A virus, the nonneurovirulent A/Aichi/2/68 (H3N2; Aichi) strain, and two reassortant viruses between them. The virus strains with the WSN gene segment coding for neuraminidase induced meningoencephalitis in mice. The mice inoculated with the R96 strain, which has only the neuraminidase gene from the WSN strain, had mild symptoms and weak positive immunostaining to the anti-WSN antibody in meningeal regions. Both the WSN and R404BP strains, which contain the WSN gene segments coding for neuraminidase and matrix protein, were clearly neurovirulent both clinically and pathologically. On day 3 after inoculation with either of these two strains, WSN antigen was detected in meningeal and ependymal areas, neurons of circumventricular regions, the cerebral and cerebellar cortices, the substantia nigra zona compacta, and the ventral tegmental area. On day 7, meningeal reactions and neuronal staining were still seen, and advanced accumulation of the viral antigen was evident in the substantia nigra zona compacta and hippocampus. Double immunostaining demonstrated that the WSN antigen was only seen in neurons and not in microglia or reactive astrocytes. Immunostaining for the lectin maackia amurensis agglutinin, which recognizes the Neu5Ac alpha 2,3 Gal sequence, which serves as a binding site for influenza A virus on target cell membranes, showed that positive staining was localized in the ventral substantia nigra and hippocampus. These results suggest that neurovirulent influenza A viruses could be one of the causative agents for postencephalitic parkinsonism.

Radiological and neurophysiological changes in Japanese encephalitis

Six patients with Japanese encephalitis, four males and two females whose age ranged between 2 and 47 years, were subjected to neurophysiological and radiological studies. An EEG in five of the patients showed diffuse delta wave activity and one had an alpha coma. Delta activity seems to be due to thalamic involvement, which was seen on CT of two and MRI of all the patients. The thalamic lesions were characteristically bilateral and were haemorragic in five. Changes on MRI included abnormalities of the brainstem in three and the basal ganglia and spinal cord in one patient each. Lower motor neuron signs were present in three patients but abnormal MRI signals in the spinal cord were present in only one out of three patients in whom spinal MRI was carried out. Central motor conduction time in the upper limb was prolonged in three patients (five sides) and in the lower limbs in one (both sides), which was consistent with involvement of the cerebral cortex, thalamus, brainstem, and spinal cord. Changes in MRI and EEG in the acute stage may provide early diagnostic clues in patients with Japanese encephalitis.

Magnetic resonance imaging findings in Japanese encephalitis. White matter lesions

Ten patients with Japanese encephalitis diagnosed by serological criteria underwent magnetic resonance imaging (MRI) in axial and coronal sections. In 6, a second MRI study was done. The MRI findings were compared with the clinical outcome. Four patients died within several months of onset, 2 had sequelae such as hemiparesis and dementia, and the remaining 4 had no sequelae. In 9 of 10 patients, either diffuse or patchy white matter lesions were observed bilaterally, together with abnormalities in areas such as the thalamus, basal ganglia, and brainstem. For 3 patients who died or remained demented, the second MRI revealed extensive, diffuse white matter abnormalities. This study indicates that Japanese encephalitis can produce white matter involvement, although gray matter structures such as the thalamus, basal ganglia, and brainstem are more severely affected. The severity of these MRI lesions correlated with the clinical outcome.