Autoimmune Global Amnesia as Manifestation of AMPAR Encephalitis and Neuropathologic Findings.

OBJECTIVE: To report an unusual clinical phenotype of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and describe associated neuropathologic findings. METHODS: We retrospectively investigated 3 AMPAR encephalitis patients with autoimmune global hippocampal amnesia using comprehensive cognitive and neuropsychologic assessment, antibody testing by in-house tissue-based and cell-based assays, and neuropathologic analysis of brain autopsy tissue including histology and immunohistochemistry. RESULTS: Three patients presented with acute-to-subacute global amnesia without affection of cognitive performance, attention, concentration, or verbal function. None of the patients had epileptic seizures, change of behavior, personality changes, or psychiatric symptoms. The MRI was normal in 1 patient and showed increased fluid-attenuated inversion recovery/T2 signal in the hippocampus in the other 2 patients. Two patients showed complete remission after immunotherapy. The one patient who did not improve had an underlying adenocarcinoma of the lung and died 3.5 months after disease onset because of tumor progression. Neuropathologic analysis of the brain autopsy revealed unilateral hippocampal sclerosis accompanied by mild inflammatory infiltrates, predominantly composed of T lymphocytes, and decrease of AMPAR immunoreactivity. CONCLUSION: AMPAR antibodies usually associate with limbic encephalitis but may also present with immune responsive, acute-to-subacute, isolated hippocampal dysfunction without overt inflammatory CSF or MRI changes.

Studies into the mechanism of measles-associated immune suppression during a measles outbreak in the Netherlands.

Measles causes a transient immune suppression, leading to increased susceptibility to opportunistic infections. In experimentally infected non-human primates (NHPs) measles virus (MV) infects and depletes pre-existing memory lymphocytes, causing immune amnesia. A measles outbreak in the Dutch Orthodox Protestant community provided a unique opportunity to study the pathogenesis of measles immune suppression in unvaccinated children. In peripheral blood mononuclear cells (PBMC) of prodromal measles patients, we detected MV-infected memory CD4+ and CD8+ T cells and naive and memory B cells at similar levels as those observed in NHPs. In paired PBMC collected before and after measles we found reduced frequencies of circulating memory B cells and increased frequencies of regulatory T cells and transitional B cells after measles. These data support our immune amnesia hypothesis and offer an explanation for the previously observed long-term effects of measles on host resistance. This study emphasises the importance of maintaining high measles vaccination coverage.

Association between naturally occurring anti-amyloid ß autoantibodies and medial temporal lobe atrophy in Alzheimer's disease.

BACKGROUND: Naturally occurring autoantibodies against amyloid ß (Aß) peptide exist in the serum and cerebrospinal fluid (CSF) of healthy individuals. Recently, it was reported that administration of intravenous immunoglobulin at the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD) reduces brain atrophy. OBJECTIVE: To examine the association between naturally occurring anti-Aß autoantibodies and brain atrophy in patients with cognitive impairment. METHODS: Serum and CSF levels of anti-Aß autoantibodies and CSF biomarkers were evaluated in 68 patients with cognitive impairment, comprising 44 patients with AD, 19 patients with amnestic MCI and five patients with non-Alzheimer's dementia. The degree of brain atrophy was assessed using the voxel-based specific regional analysis system for AD, which targets the volume of interest (VOI) in medial temporal structures, including the whole hippocampus, entorhinal cortex and amygdala. RESULTS: CSF levels of anti-Aß autoantibodies were inversely correlated with the extent and severity of VOI atrophy, and the ratio of VOI/grey matter atrophy in patients with AD, but not in MCI or non-AD patients. Serum levels of anti-Aß autoantibodies were not associated with these parameters in any of the patient groups. CONCLUSIONS: These results indicate that CSF levels of naturally occurring anti-Aß autoantibodies are inversely associated with the degree of the VOI atrophy in patients with AD. Although the mechanism is unclear, CSF levels of naturally occurring anti-Aß autoantibodies may be implicated in the progression of atrophy of the whole hippocampus, entorhinal cortex and amygdala, in AD.

High avidity HSV-1 antibodies correlate with absence of amnestic Mild Cognitive Impairment conversion to Alzheimer's disease.

Amnestic Mild Cognitive Impairment (aMCI) is an alteration in cognitive abilities that can progress to Alzheimer's disease (AD), a condition in which herpes simplex type 1 (HSV-1) infection might play a pathogenetic role. Prognostic indexes capable of predicting aMCI conversion to AD are only partially understood. The objective of the present work is to verify whether HSV-1 immune responses is involved in conversion of aMCI to AD and correlate with grey matter brain morphometry. Two homogeneous groups of individuals who did or did not convert to AD over a 24-months period were selected after retrospective analysis of a cohort of patients with a diagnosis of aMCI. The selection of subjects was based on: a) clinical follow-up; b) neurocognitive evaluation at baseline and after 24months; c) availability of serum and DNA samples at baseline. 36 aMCI individuals, 21 of whom did (aMCI-converters) and 15 of whom did not (aMCI-non-converters) convert to AD, were included in the study. HSV-1 antibody (Ab) titers, avidity index and APOE genotyping were performed in all the enrolled individuals at baseline. Brain magnetic resonance imaging (MRI) by 1.5T scanner results at baseline were available as well in most (29/36) of these individuals. HSV-1-specific Ab titers were increased at baseline in aMCI-non-converters, and the avidity of these Ab was significantly higher in aMCI-non-converter compared to aMCI-converter (p=0.0018). Receiver operating characteristics analysis showed that HSV-1 avidity had a predictive value in distinguishing between aMCI-non-converters and aMCI-converters (p<0.0001). Notably, a positive correlation was detected as well between HSV-1 antibody titers and MRI-evaluated cortical volumes in the left hippocampus and amigdala (pcorr<0.05). In conclusion, stronger HSV-1-specific humoral responses associate with protection against AD conversion and better-preserved cortical volumes. These results reinforce the hypothesis for a role for HSV-1 in the pathogenesis of AD.

[Paraneoplastic Neurological Syndrome with Dementia].

Paraneoplastic neurological syndrome with limbic encephalopathy tends to progress rapidly, presenting with physical symptoms such as ataxia or sensory disturbance. However, some affected patients demonstrate amnesia, inactivity, or abnormal behavior, which lead to the diagnosis of dementia. It is important to perform an extensive differential diagnosis with autoantibody-examination and tumor survey, so as not to overlook potentially treatable dementia.

Episodic bradycardia as neurocardiac prodrome to voltage-gated potassium channel complex/leucine-rich, glioma inactivated 1 antibody encephalitis.

IMPORTANCE: Voltage-gated potassium channel complex antibody (VGKCc-Ab) encephalitis is an immunotherapy-responsive syndrome usually associated with causative antibodies that target the leucine-rich, glioma inactivated 1 (LGI1) protein. Although it is expressed throughout the brain, LGI1 is not known to be expressed in cardiac tissue. We describe a novel neurocardiac prodrome of VGKCc-Ab/LGI1-encephalitis. OBSERVATIONS: Among 14 patients with VGKCc/LGI1-Ab encephalitis evaluated in the University of California, San Francisco Autoimmune Encephalitis Clinic and Rapid Dementia Research Program, 3 patients (2 men and 1 woman; aged 53, 55, and 64 years) exhibited episodic bradycardia that preceded the onset of encephalopathy by approximately 2 months and was severe enough to lead to pacemaker implantation. Serum LGI1-Ab results were positive when tested at the time of the subsequent encephalopathy. All 3 patients developed hyponatremia; none had faciobrachial dystonic seizures or malignancy. Brain magnetic resonance imaging was abnormal in 2 cases. None of the patients experienced further symptomatic bradyarrythmias after 1.7 to 7 years of follow-up. CONCLUSIONS AND RELEVANCE: Episodic bradycardia is a distinctive neurocardiac prodrome of VGKCc/LGI1-Ab encephalitis. The neuroanatomical localization most likely relates to insular and temporal lobe involvement, cortical regions that modulate cardiac autonomic function. Further study is needed to determine if recognition of this neurocardiac prodrome and earlier institution of immunosuppression can prevent the development of encephalopathy.

Acute amnesia and seizures in a young female.

Limbic encephalitis is a condition characterised by an acute or sub-acute onset of memory disorder, associated with seizures and psychiatric manifestations. Investigations such as brain MRI usually reveal a high intensity signal in the medial temporal lobe and cerebrospinal fluid analysis shows mild pleocytosis and oligoclonal bands. It may occur in association with cancer, infection, or as an isolated clinical condition, often accompanying autoimmune disorders. Immune-mediated limbic encephalitis is now subclassified according to the presence and type of autoantibodies, which has significant consequences regarding the effectiveness of treatment and prognosis. Glutamic acid decarboxylase (GAD) is an enzyme that catalyses glutamic acid into gamma aminobutyric acid. Anti-GAD antibodies are associated with different neurological and non-neurological disorders, but only a few cases of limbic encephalitis associated with anti-GAD antibodies have been reported in the literature, most of them non-paraneoplastic. Here, we report the case of a young female patient with a medical history of psoriasis who developed an acute onset and chronic evolution of anterograde amnesia, associated with drug-resistant epilepsy. Brain MRI showed hyperintensity in the medial temporal lobes and the biochemical studies revealed intrathecal synthesis of anti-GAD antibodies. Screening tests for tumours were negative. Despite antiepileptic drugs, intravenous immunoglobulins and immunosuppressive treatment, the patient did not show clinical improvement and one year later, she continues to present refractory temporal epilepsy and cognitive deficits.

Increase in the IgG avidity index due to herpes simplex virus type 1 reactivation and its relationship with cognitive function in amnestic mild cognitive impairment and Alzheimer's disease.

After infection with herpes simplex virus type 1 (HSV-1), latent infection persists for life in the trigeminal ganglion and reactivation results in an outbreak of cold sores around the mouth. Many previous studies have reported HSV-1 reactivation to be a risk factor for Alzheimer's disease (AD). This study enrolled subjects with AD (n=85), subjects with amnestic mild cognitive impairment (aMCI; a prodromal stage of AD) (n=34), and healthy controls (n=28). The avidity index of anti-HSV-1 IgG antibodies--a known indicator of HSV-1 reactivation--was measured in order to clarify the relationship between HSV-1 reactivation and symptoms of cognitive function in AD. Cognitive function in AD and aMCI were evaluated using scores from the mini-mental state examination (MMSE) and frontal assessment battery (FAB). The results showed that the subjects with aMCI, for which cerebral function is better preserved than subjects with AD, had a higher anti-HSV-1 IgG antibody avidity index than the AD subjects or healthy controls. Furthermore, the anti-HSV-1 IgG antibody avidity index was even higher in the subjects with high MMSE scores on orientation to time and three-step command subscores. We observed a negative correlation between the anti-HSV-1 IgG antibody avidity index and plasma BDNF concentration, which is an indicator of encephalitis. This suggests that HSV-1 reactivation, as observed through an increase in the anti-HSV-1 IgG avidity index, does not progress to encephalitis. These results suggest that HSV-1 reactivation occurs from the stage of aMCI, which is prodromal to AD, and can affect AD symptoms without an intermediary stage of severe encephalitis. The study demonstrates that the anti-HSV-1 IgG antibody avidity index could be a useful biomarker for the early diagnosis of aMCI as well as AD, and suggests that antiviral medication to treat HSV-1 could play a role in preventing the onset of AD.

Plasma neopterin level as a marker of peripheral immune activation in amnestic mild cognitive impairment and Alzheimer's disease.

OBJECTIVE: Alterations of the immune system play important roles in Alzheimer's disease (AD). The primary purpose of this study was to compare the plasma levels of neopterin, a marker of cellular immune activity, in amnestic mild cognitive impairment (aMCI), early (mild to moderate) AD, and cognitively normal controls. In addition, the correlation of plasma neopterin with interferon-gamma (IFN-γ) and interleukin-6 (IL-6) was also examined. METHODS: Plasma samples from patients with mild-to-moderate AD (N = 34), aMCI (N = 27), and cognitively normal controls (N = 30) were obtained from the Johns Hopkins Alzheimer's Disease Research Center. Plasma neopterin, IFN-γ, and IL-6 levels were measured using commercially available ELISAs. Multiple linear regression was performed to study differences in the baseline neopterin levels between normal, aMCI, and AD patients. Pearson correlation coefficients were estimated for neopterin and IFN-γ and IL-6 levels. All analyses were conducted using SAS (SAS Institute, Inc., Cary, NC) and GraphPad Prism version 5.00 for Window (GraphPad Software, San Diego, CA, USA). RESULTS: AD subjects had significantly higher neopterin values compared with aMCI (ß = 0.202, p = 0.004) and normal (ß = 0.263, p = 0.0004) subjects. There was no statistically significant difference between normal and aMCI subjects. Significant associations between neopterin and IFN-γ (r = 0.41, p < 0.0001) and IL-6 (r = 0.35, p = 0.0006) levels were found. CONCLUSIONS: Our study demonstrates that peripheral immune response may be stronger in later stages of AD pathophysiology, when dementia has developed.

[The comparison of neuroprotective action of antibodies to glutamate and drug preparation semax in the focal ischemic damage of the brain prefrontal cortex of rats].

It was stated, that with bilateral photochemically induced thrombosis of the prefrontal cortex peptide semax and the AB-Glu by intranasal injection provoke pronounced neuroprotective and antiamnestic action. Intranasal injection semax (250 mkg/kg/daily during six postoperative days) and AB-Glu (250 mkg/kg in 1 hour after phototrombosis) demonstrate diminishing of cortex damage volume and relieve preservation and reproduction rat passive avoidance reflex, acquired before bilateral photochemically induced thrombosis of prefrontal cortex.

Unusual amnesia in a patient with VGKC-Ab limbic encephalitis: a case study.

We describe the case of a patient with confirmed voltage-gated potassium channel antibody-associated encephalitis (VGKC-Ab). MRI studies revealed bilateral hyper-intensity in the hippocampi, with their volumes preserved. At presentation, the patient's anterograde and retrograde memory skills were found to be impaired and he showed fluctuation in his ability to recall familiar information. Following treatment with immunotherapy, his condition improved considerably and, in a series of follow up assessments, he performed satisfactorily (i.e., within the average range or above) on formal tests of memory, as well as on a range of other cognitive tests, including tests of executive function. By contrast, in the context of contemporaneous unstructured interviews, he showed a strong tendency to confabulate. We argue that the reported case broadens the phenomenology of VGKC-Ab limbic encephalitis and raises important theoretical questions about the aetiology of this patient's most unusual memory disorder.

Anamnestic recall of stroke-related deficits: an animal model.

BACKGROUND AND PURPOSE: Anamnestic recall of stroke-related deficits is a common clinical observation, especially during periods of systemic infection. The pathophysiology of this transient re-emergence of neurological dysfunction is unknown. METHODS: Male Lewis rats underwent 3 hours middle cerebral artery occlusion and were treated with lipopolysaccharide or saline at the time of reperfusion. The delayed-type hypersensitivity (DTH) response to myelin basic protein was examined 28 days after middle cerebral artery occlusion. Changes in behavioral outcomes were assessed after DTH testing and repeat administration of lipopolysaccharide or saline at 34 days. At the time of euthanasia (36 days), the immunologic response of splenocytes to myelin basic protein, neuron-specific enolase, and proteolipid protein was determined by enzyme-linked immunospot assay and the number of lymphocytes in the brain determined by immunocytochemistry. RESULTS: Animals treated with lipopolysaccharide at middle cerebral artery occlusion had a greater DTH response to myelin basic protein than animals treated with saline. Among those animals that had fully recovered on a given behavioral test before DTH testing, those treated with lipopolysaccharide at middle cerebral artery occlusion displayed more neurological deterioration after DTH testing and had more CD8(+) lymphocytes within the ischemic core of the brain. Furthermore, the Th1 immune response to brain antigens in the spleen was more robust among those animals that deteriorated after DTH testing and there were more CD4(+) lymphocytes in the penumbral region of animals with a Th1 response to myelin basic protein. CONCLUSIONS: Our data suggest that an immune response to the brain contributes to the phenomenon of anamnestic recall of stroke-related deficits after an infection. The contribution of the immune response to this phenomenon deserves further investigation.

Plasma levels of monocyte chemotactic protein 3 and beta-nerve growth factor increase with amnestic mild cognitive impairment.

A number of studies have investigated peripheral inflammatory indices, including plasma cytokines and related molecules according to subtypes of dementia, but not in mild cognitive impairment (MCI). In this study, we used multiplex cytokine assay to assess the plasma levels of 22 cytokines in patients with MCI subtyped as amnestic and non-amnestic, according to cognitive features. When comparing the levels of plasma growth factors, chemokines and cytokines, plasma levels of monocyte chemotactic protein 3 (MCP-3), and beta-nerve growth factor (beta-NGF) in these two groups, they were found to be significantly higher in amnestic MCI patients than in non-amnestic MCI patients, after adjusting for age and gender. This suggests that plasma MCP-3 and beta-NGF may be useful in differentiating subtypes of MCI.

Amnesia produced by altered release of neurotransmitters after intraamygdala injections of a protein synthesis inhibitor.

Amnesia produced by protein synthesis inhibitors such as anisomycin provides major support for the prevalent view that the formation of long-lasting memories requires de novo protein synthesis. However, inhibition of protein synthesis might disrupt other neural functions to interfere with memory formation. Intraamygdala injections of anisomycin before inhibitory avoidance training impaired memory in rats tested 48 h later. Release of norepinephrine (NE), dopamine (DA), and serotonin, measured at the site of anisomycin infusions, increased quickly by approximately 1,000-17,000%, far above the levels seen under normal conditions. NE and DA release later decreased far below baseline for several hours before recovering at 48 h. Intraamygdala injections of a beta-adrenergic receptor antagonist or agonist, each timed to blunt effects of increases and decreases in NE release after anisomycin, attenuated anisomycin-induced amnesia. In addition, similar to the effects on memory seen with anisomycin, intraamygdala injections of a high dose of NE before training impaired memory tested at 48 h after training. These findings suggest that altered release of neurotransmitters may mediate amnesia produced by anisomycin and, further, raise important questions about the empirical bases for many molecular theories of memory formation.

Potassium channel antibody-associated encephalopathy: a potentially immunotherapy-responsive form of limbic encephalitis.

Patients presenting with subacute amnesia are frequently seen in acute neurological practice. Amongst the differential diagnoses, herpes simplex encephalitis, Korsakoff's syndrome and limbic encephalitis should be considered. Limbic encephalitis is typically a paraneoplastic syndrome with a poor prognosis; thus, identifying those patients with potentially reversible symptoms is important. Voltage-gated potassium channel antibodies (VGKC-Ab) have recently been reported in three cases of reversible limbic encephalitis. Here we review the clinical, immunological and neuropsychological features of 10 patients (nine male, one female; age range 44-79 years), eight of whom were identified in two centres over a period of 15 months. The patients presented with 1-52 week histories of memory loss, confusion and seizures. Low plasma sodium concentrations, initially resistant to treatment, were present in eight out of 10. Brain MRI at onset showed signal change in the medial temporal lobes in eight out of 10 cases. Paraneoplastic antibodies were negative, but VGKC-Ab ranged from 450 to 5128 pM (neurological and healthy controls <100 pM). CSF oligoclonal bands were found in only one, but bands matched with those in the serum were found in six other patients. VGKC-Abs in the CSF, tested in five individuals, varied between <1 and 10% of serum values. Only one patient had neuromyotonia, which was excluded by electromyography in seven of the others. Formal neuropsychology testing showed severe and global impairment of memory, with sparing of general intellect in all but two patients, and of nominal functions in all but one. Variable regimes of steroids, plasma exchange and intravenous immunoglobulin were associated with variable falls in serum VGKC-Abs, to values between 2 and 88% of the initial values, together with marked improvement of neuropsychological functioning in six patients, slight improvement in three and none in one. The improvement in neuropsychological functioning in seven patients correlated broadly with the fall in antibodies. However, varying degrees of cerebral atrophy and residual cognitive impairment were common. Over the same period, only one paraneoplastic case of limbic encephalitis was identified between the two main centres. Thus, VGKC-Ab-associated encephalopathy is a relatively common form of autoimmune, non-paraneoplastic, potentially treatable encephalitis that can be diagnosed by a serological test. Establishing the frequency of this new syndrome, the full range of clinical presentations and means of early recognition, and optimal immunotherapy, should now be the aim.

Herpes simplex encephalitis with transient global amnesia as an early sign.

Cerebral ischemia has been proposed as the etiology of transient global amnesia. Recently, however, migranous and epileptic etiologies have attracted attention. A 56-year-old man had transient global amnesia and the next day began to display symptoms of meningoencephalitis. Herpes simplex encephalitis was diagnosed based on the titer of herpes simplex virus antibodies. The transient global amnesia appears to have occurred as an early sign of herpes simplex encephalitis and may have been provoked by an epileptic mechanism.