Determination of neuronal antibodies in suspected and definite Creutzfeldt-Jakob disease

IgLON5 autoimmunity in a patient with Creutzfeldt-Jakob disease: case report and review of literature

Objective

We present the case of a patient with clinical and imaging features of sporadic Creutzfeldt-Jakob disease (sCJD) and positive IgLON5 antibodies (Abs) in the serum and CSF.

Case report

A 66-year-old Chinese man presented to the hospital with a stroke-like episode, followed by rapidly progressive cognitive decline, mutism, and parkinsonism. The MRI results showed a cortical ribboning sign in diffusion-weighted MRI, periodic triphasic waves with a slow background in EEG, and positive protein 14-3-3 in CSF. There were matching IgLON5 Abs in the serum and CSF. A literature review showed positive autoimmune encephalitis Abs or autoimmune inflammatory disease between 0.5 and 8.6% among patients with clinical suspicion of CJD, most commonly anti-voltage-gated potassium channel (VGKC) complex and anti-N-methyl-D-aspartate receptor (NMDAR) Abs; however, IgLON5 autoimmunity in CJD has been rarely reported. This is an intriguing association as both conditions have been associated with brain deposits of phosphorylated tau protein.

Conclusion

IgLON5 Abs may be observed in patients with a diagnosis of CJD; it is unknown whether a synergistic effect of IgLON5 Abs with CJD exists, increasing neurodegenerative changes.

Pathological findings in autoimmune encephalitis autopsy specimens from cases of suspected prion disease

OBJECTIVE

The underlying pathology of autoimmune encephalitis is not well characterized due to the limited opportunities to study tissue specimens. Autopsy specimens available at prion surveillance centers from patients with suspected Creutzfeldt-Jakob disease offer a unique opportunity to study the pathology of autoimmune encephalitis. Our objective was to describe pathological findings of autoimmune encephalitis specimens submitted to the U.S. National Prion Disease Pathology Surveillance Center.

METHODS

Pathology reports were obtained from the National Prion Center. Specimens negative for prion disease were screened for inflammatory pathology and those suggestive of autoimmune encephalitis were analyzed. Cases identified on autopsy were compared to institutional cases with fatal seronegative autoimmune encephalitis and available brain biopsy.

RESULTS

Between 1998 and 2022, 7934 specimens were evaluated of which 2998 (38%) were negative for prion protein. Querying the database for alternative diagnoses of encephalitis/encephalopathy yielded 43 cases that were screened by an experienced neuropathologist yielding 14 (0.5%) cases consistent with autoimmune encephalitis. Most specimens showed diffuse inflammation involving the limbic system (86%), basal ganglia (86%), cortex (71%), diencephalon (71%), and in some cases the brainstem (43%) and cerebellum (43%). Lymphocytic inflammatory infiltrate was predominantly perivascular with parenchymal extension in 64%. Microglial activation/nodules were seen in 64% of cases. Neuronal loss was present only in 50%. Pathological findings were identical to biopsy specimens from our institutional cohort.

DISCUSSION

Seronegative AE may have consistent pathology with diffuse or multifocal perivascular inflammation and microglial activation. Half the patients do not have neuronal loss suggesting a potential for neurological recovery. These findings are preliminary and require further confirmation.

Antibodies Associated With Autoimmune Encephalitis in Patients With Presumed Neurodegenerative Dementia

BACKGROUND & OBJECTIVES

Autoimmune encephalitis (AIE) may present with prominent cognitive disturbances without overt inflammatory changes in MRI and CSF. Identification of these neurodegenerative dementia diagnosis mimics is important because patients generally respond to immunotherapy. The objective of this study was to determine the frequency of neuronal antibodies in patients with presumed neurodegenerative dementia and describe the clinical characteristics of the patients with neuronal antibodies.

METHODS

In this retrospective cohort study, 920 patients were included with neurodegenerative dementia diagnosis from established cohorts at 2 large Dutch academic memory clinics. In total, 1,398 samples were tested (both CSF and serum in 478 patients) using immunohistochemistry (IHC), cell-based assays (CBA), and live hippocampal cell cultures (LN). To ascertain specificity and prevent false positive results, samples had to test positive by at least 2 different research techniques. Clinical data were retrieved from patient files.

RESULTS

Neuronal antibodies were detected in 7 patients (0.8%), including anti-IgLON5 (n = 3), anti-LGI1 (n = 2), anti-DPPX, and anti-NMDAR. Clinical symptoms atypical for neurodegenerative diseases were identified in all 7 and included subacute deterioration (n = 3), myoclonus (n = 2), a history of autoimmune disease (n = 2), a fluctuating disease course (n = 1), and epileptic seizures (n = 1). In this cohort, no patients with antibodies fulfilled the criteria for rapidly progressive dementia (RPD), yet a subacute deterioration was reported in 3 patients later in the disease course. Brain MRI of none of the patients demonstrated abnormalities suggestive for AIE. CSF pleocytosis was found in 1 patient, considered as an atypical sign for neurodegenerative diseases. Compared with patients without neuronal antibodies (4 per antibody-positive patient), atypical clinical signs for neurodegenerative diseases were seen more frequently among the patients with antibodies (100% vs 21%, p = 0.0003), especially a subacute deterioration or fluctuating course (57% vs 7%, p = 0.009).

DISCUSSION

A small, but clinically relevant proportion of patients suspected to have neurodegenerative dementias have neuronal antibodies indicative of AIE and might benefit from immunotherapy. In patients with atypical signs for neurodegenerative diseases, clinicians should consider neuronal antibody testing. Physicians should keep in mind the clinical phenotype and confirmation of positive test results to avoid false positive results and administration of potential harmful therapy for the wrong indication.

Case report: Anti-CARPVIII autoantibody-associated mixed dementia

Background

Anti-carbonic anhydrase-related protein VIII (CARPVIII) is reported to be associated with paraneoplastic cerebellar degeneration. Our case extends the spectrum of anti-CARPVIII-associated disease to severe cognitive impairment.

Methods

We present the case of a 75-year-old woman who presented to our Department of Psychiatry and Psychotherapy with a dementia syndrome. The diagnostic approach included magnetic resonance imaging (MRI), cerebrospinal fluid analysis (CSF) analysis involving autoantibody determination, and neuropsychological examination.

Results

Neuropsychological examination revealed severe cognitive impairment meeting the criteria for dementia. MRI showed evidence of moderate cerebral microangiopathy. CSF analysis revealed mild pleocytosis, and serum analysis revealed anti-CARPVIII autoantibodies. Based on the dementia syndrome entailing signs of CNS inflammation such as pleocytosis and the repeated detection of anti-CARPVIII autoantibodies in serum, we diagnosed autoimmune dementia as a component of mixed dementia with additional vascular dementia components.

Conclusion

Our finding adds severe cognitive impairment to the spectrum of anti-CARPVIII-associated disease. However, detecting anti-CARPVIII antibodies may also be an incidental finding in conjunction with typical mixed dementia. Further studies are needed to evaluate the relevance of these clinical findings.

Improving Early Recognition of Creutzfeldt-Jakob Disease Mimics

Background and Objectives

Diagnostic criteria emphasize the use of sensitive and disease-specific tests to distinguish patients with rapidly progressive dementia (RPD) due to Creutzfeldt-Jakob disease (CJD) vs other causes (mimics). These tests are often performed in specialized centers, with results taking days to return. There is a need to leverage clinical features and rapidly reporting tests to distinguish patients with RPD due to CJD from those due to other causes (mimics) early in the symptomatic course.

Methods

In this case-control series, clinical features and the results of diagnostic tests were compared between mimics (n = 11) and patients with definite (pathologically proven, n = 33) or probable CJD (with positive real-time quaking-induced conversion [RT-QuIC], n = 60). Patients were assessed at Mayo Clinic Enterprise or Washington University from January 2014 to February 2021. Mimics were enrolled in prospective studies of RPD; mimics met the diagnostic criteria for probable CJD but did not have CJD.

Results

Mimics were ultimately diagnosed with autoimmune encephalitis (n = 6), neurosarcoidosis, frontotemporal lobar degeneration with motor neuron disease, dural arteriovenous fistula, cerebral amyloid angiopathy with related inflammation, and systemic lupus erythematous with polypharmacy. Age at symptom onset, sex, presenting features, and MRI and EEG findings were similar in CJD cases and mimics. Focal motor abnormalities (49/93, 11/11), CSF leukocytosis (4/92, 5/11), and protein >45 mg/dL (39/92, 10/11) were more common in mimics (p < 0.01). Positive RT-QuIC (77/80, 0/9) and total tau >1149 pg/mL (74/82, 2/10) were more common in CJD cases (all p < 0.01). Protein 14-3-3 was elevated in 64/89 CJD cases and 4/10 mimics (p = 0.067). Neural-specific autoantibodies associated with autoimmune encephalitis were detected within the serum (5/9) and CSF (5/10) of mimics; nonspecific antibodies were detected within the serum of 9/71 CJD cases.

Discussion

Immune-mediated, vascular, granulomatous, and neurodegenerative diseases may mimic CJD at presentation and should be considered in patients with early motor dysfunction and abnormal CSF studies. The detection of atypical features-particularly elevations in CSF leukocytes and protein-should prompt evaluation for mimics and consideration of empiric treatment while waiting for the results of more specific tests.

Case Report: Presence of Anti-MAG in the CSF Can Be Associated With a Neurodegenerative Process With Frontal Involvement

Background

Autoimmune encephalitis (AIE) is an increasingly broad nosological framework that may clinically mimic neurodegenerative diseases (NDDs).

Cases Reported

We describe here the clinical, radiological, electrophysiological, and biological evolution of three patients. Two women aged 73 and 72 years and a 69-year-old man presented with complex cognitive and focal neurological symptoms and each had a predominant frontal dysexecutive involvement and an unexpectedly high titer of anti-MAG antibodies in the serum and cerebrospinal fluid (CSF). The question of an autoimmune cause was raised. After 2 years of follow-up and, for two of them, without improvement despite immunosuppressive treatments, diagnoses of NDD were eventually retained: post-radiation encephalopathy, progressive supranuclear palsy (PSP), and Alzheimer's disease.

Conclusion

The presence of a high titer of anti-MAG antibodies may be found in NDD. It could reflect cerebral tissue damages, particularly in the case of significant frontal involvement. Atypical presentations may lead to a search for a paraneoplastic neurologic syndrome or AIE. However, the indirect immunofluorescence staining positivity on a monkey cerebellum section linked with anti-MAG antibodies should not lead to those diagnoses being retained.

Anti-NMDAR Encephalitis in the Netherlands, Focusing on Late-Onset Patients and Antibody Test Accuracy

Background and Objectives

To describe the clinical features of anti-NMDAR encephalitis, emphasizing on late-onset patients and antibody test characteristics in serum and CSF.

Methods

Nationwide observational Dutch cohort study, in patients diagnosed with anti-NMDAR encephalitis between 2007 and 2019.

Results

One hundred twenty-six patients with anti-NMDAR encephalitis were included with a median age of 24 years (range 1–86 years). The mean annual incidence was 1.00/million (95% CI 0.62–1.59). Patients ≥45 years of age at onset (19%) had fewer seizures (46% vs 71%, p = 0.021), fewer symptoms during disease course (3 vs 6 symptoms, p = 0.020), and more often undetectable serum antibodies compared with younger patients (p = 0.031). In the late-onset group, outcome was worse, and all tumors were carcinomas (both p < 0.0001). CSF was more accurate than serum to detect anti-NMDAR encephalitis (sensitivity 99% vs 68%, p < 0.0001). Using cell-based assay (CBA), CSF provided an unconfirmed positive test result in 11/2,600 patients (0.4%); 6/11 had a neuroinflammatory disease (other than anti-NMDAR encephalitis). Patients with anti-NMDAR encephalitis, who tested positive in CSF only, had lower CSF antibody titers (p = 0.003), but appeared to have an equally severe disease course.

Discussion

Anti-NMDAR encephalitis occurs at all ages and is less rare in the elderly patients than initially anticipated. In older patients, the clinical phenotype is less outspoken, has different tumor association, and a less favorable recovery. Detection of antibodies in CSF is the gold standard, and although the CBA has very good validity, it is not perfect. The clinical phenotype should be leading, and confirmation in a research laboratory is recommended, when in doubt.

[Creutzfeldt-Jakob Disease Versus Anti-NMDA Receptor Encephalitis A Case Report]

Clinically differentiating between autoimmune and neurodegenerative disorders can often pose a diagnostic challenge. The differential diagnosis of rapidly progressing neurological and cognitive symptoms includes central nervous system tumours, cerebral vasculitis, and inflammatory, autoimmune, or paraneoplastic encephalopathies. Rarer neurodegenerative diseases such as Creutzfeldt-Jakob disease should also be considered. Detection of treatable causes, such as autoimmune disorders, remains important when potentially occurring in conjunction with Creutzfeldt-Jakob disease. The following report describes a rare case in which autoimmune encephalopathy and prion disease were considered as possible comorbidities.

Case Report: Prominent Brainstem Involvement in Two Patients With Anti-CASPR2 Antibody-Associated Autoimmune Encephalitis

Anti-contactin-associated protein-like 2 (CASPR2) antibody-associated autoimmune encephalitis is commonly characterized by limbic encephalitis with clinical symptoms of mental and behavior disorders, cognitive impairment, deterioration of memory, and epilepsy. The classical lesions reported are located at the medial temporal lobe or hippocampus, whereas prominent brainstem lesions have not been addressed to date. Herein, we reported two patients mimicking progressive brainstem infarction with severe neurological manifestations. On brain magnetic resonance imaging (MRI), prominent brainstem lesions were noted, although multifocal lesions were also shown in the juxtacortical and subcortical white matters, basal ganglia, hippocampus, and cerebellar hemisphere. Unexpectedly and interestingly, both cases had detectable CASPR2 antibodies in sera, and an exclusive IgG1 subclass was documented in the further analysis. They were treated effectively with aggressive immunosuppressive therapies including corticosteroids, intravenous immunoglobulin G, and rituximab, with the first case achieving a rapid remission and the other undergoing a slow but gradual improvement. To the best of our knowledge, this is the first report on prominent brainstem involvement with definite MRI lesions in anti-CASPR2 antibody-associated autoimmune encephalitis, which helps to expand the clinical spectrum of this rare autoimmune disease and update the lesion patterns in the CNS.

Autoimmune Encephalitis versus Creutzfeldt-Jakob disease in a patient with typical Facio-brachial dystonic seizures: A case report with Diagnostic challenges

Background

Diagnosis of rapidly progressive dementia (RPD) is very challenging. There are many conditions that fall into category of RPD ranging from autoimmune causes to neurodegenerative causes. Autoimmune encephalitis should be readily diagnosed and treated because of its response to immunomodulators. However there is no treatment available for conditions like Creutzfeldt-Jakob disease (CJD).

Case presentation

Here we present a case of anti-leucine-rich glioma inactivated 1 (LGI1) encephalitis who presented with only typical facio-brachial dystonic seizures at presentation. On follow up, patient had a rapid cognitive decline with development of myoclonic jerks, akinetic mute state and ultimately death. Neuroimaging showed presence of hyperintensities in two cortical regions namely parietal and occipital on fluid-attenuated inversion recovery (FLAIR) sequence. Electroencephalogram showed diffuse slowing with occasional periodic sharp wave complexes. Thus a diagnosis of probable CJD was made.

Conclusion

Autoimmune encephalitis mimicking CJD or vice versa is not a very commonly encountered phenomenon. This case discusses the clinical overlap of these two conditions and its diagnostic dilemmas. This case presented with typical LGI1 encephalitis and in spite of therapy with immunomodulators had a rapid decline and ultimately turned out to be CJD. This has been rarely described in literature.

Autoimmune Encephalitis Resembling Dementia Syndromes

Objective

As autoimmune encephalitis (AIE) can resemble neurodegenerative dementia syndromes, and patients do not always present as encephalitis, this study evaluates how frequently AIE mimics dementia and provides red flags for AIE in middle-aged and older patients.

Methods

In this nationwide observational cohort study, patients with anti–leucine-rich glioma-inactivated 1 (LGI1), anti–NMDA receptor (NMDAR), anti–gamma-aminobutyric acid B receptor (GABA_BR), or anti–contactin-associated protein-like 2 (CASPR2) encephalitis were included. They had to meet 3 additional criteria: age ≥45 years, fulfillment of dementia criteria, and no prominent seizures early in the disease course (≤4 weeks).

Results

Two-hundred ninety patients had AIE, of whom 175 were 45 years or older. Sixty-seven patients (38%) fulfilled criteria for dementia without prominent seizures early in the disease course. Of them, 42 had anti-LGI1 (48%), 13 anti-NMDAR (52%), 8 anti-GABA_BR (22%), and 4 anti-CASPR2 (15%) encephalitis. Rapidly progressive cognitive deterioration was seen in 48 patients (76%), whereas a neurodegenerative dementia syndrome was suspected in half (n = 33). In 17 patients (27%; 16/17 anti-LGI1), subtle seizures had been overlooked. Sixteen patients (25%) had neither inflammatory changes on brain MRI nor CSF pleocytosis. At least 1 CSF biomarker, often requested when dementia was suspected, was abnormal in 27 of 44 tested patients (61%), whereas 8 had positive 14-3-3 results (19%). Most patients (84%) improved after immunotherapy.

Conclusions

Red flags for AIE in patients with suspected dementia are: (1) rapidly progressive cognitive decline, (2) subtle seizures, and (3) abnormalities in ancillary testing atypical for neurodegeneration. Physicians should be aware that inflammatory changes are not always present in AIE, and that biomarkers often requested when dementia was suspected (including 14-3-3) can show abnormal results. Diagnosis is essential as most patients profit from immunotherapy.

Antibodies to neuronal surface antigens in patients with a clinical diagnosis of neurodegenerative disorder

OBJECTIVES

Autoimmune encephalitis due to antibodies against neuronal surface antigens (NSA-Ab) frequently presents with cognitive impairment, often as the first and prevalent manifestation, but few studies have systematically assessed the frequency of NSA-Ab in consecutive patients with established neurodegenerative disorders.

METHODS

We studied sera of 93 patients (41F, 52 M), aged 69.2 ± 9.4 years, with neurodegenerative conditions, and of 50 population controls aged over 60 years. Specific NSA-Abs were investigated by antigen-specific cell-based assays (CBAs). After testing, we evaluated the association between the NSA-Abs and clinical, CSF and radiological features.

RESULTS

The patients included 13/93 (13.8%) who had specific antibodies to neuronal surface antigens: 6 GlyR, 3 GABA_AR (1 also positive for AMPAR), 2 LGI1, 1 CASPR2 and 1 GABA_BR. One of the 50 controls (2%) was positive for NMDAR antibody and the others were negative on all tests (P = 0.020). No difference was observed in antibody frequency between patients presenting with parkinsonism and those presenting with dementia (P = 0.55); however, NSA-Ab were more frequent in those with unclassified forms of dementia (5/13, 38.5%) than in those with unclassified parkinsonism (2/9, 22.2%) or with classified forms of dementia (4/43, 9.3%) or parkinsonism (2/28, 7.1%) (P = 0.03). A logistic regression analysis demonstrated that an unclassified diagnosis (P = 0.02) and an irregular progression (P = 0.024) were predictors of seropositive status.

CONCLUSIONS

NSA-Abs are relatively frequent in patients with neurodegenerative disorders, particularly in those with an irregular disease progression of atypical clinical features, inconsistent with a recognized diagnosis. The significance of these antibodies and their possible primary or secondary roles need to be investigated in prospective studies.

Current Nosology of Neural Autoantibody-Associated Dementia

Background

The detection of neural autoantibodies in patients with cognitive decline is an increasingly frequent phenomenon in memory clinics, and demanding as it does a specific diagnostic approach and therapeutic management, it deserves greater attention. It is this review’s aim to present the latest nosology of neural autoantibody-associated dementia.

Methods

A specific literature research via PubMed was conducted to describe the nosology of neural autoantibody-associated dementia.

Results

An autoimmune dementia comprises with an early onset, atypical clinical presentation and rapid progression in conjunction with neural antibodies, signs of inflammation in the cerebrospinal fluid, and a non-neurodegenerative pattern in neuroimaging. An autoimmune dementia is probably present if the patient responds to immunotherapy. Atypical dementia involving neural autoantibodies with mostly N-methyl-D-aspartate receptor antibodies might not fulfill all the autoimmune-dementia criteria, thus it may constitute an independent disease entity. Finally, a neurodegenerative dementia such as the frontotemporal type also coincides with neural autoantibodies such as the subunit ionotropic glutamate receptors 3 of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antibodies, dementia with Lewy bodies with myelin oligodendrocytic protein, myelin basic protein antibodies, or Creutzfeldt-Jakob disease with Zic4 or voltage gated potassium channel antibodies. These dementia entities may well overlap in their clinical features and biomarkers, i.e., their neural autoantibodies or neuroimaging patterns.

Conclusion

There are three main forms of neural autoantibody-associated dementia we can distinguish that might also share certain features in their clinical and laboratory presentation. More research is urgently necessary to improve the diagnosis and therapy of these patients, as the progression of their dementia might thus be improved or even reversed.

Anti-N-methyl-D-Aspartate Receptor Encephalitis Mimicking Sporadic Creutzfeldt-Jakob Disease

Objectives: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis and sporadic Creutzfeldt–Jakob disease (sCJD) share similar clinical features. Here, we present two unusual cases of anti-NMDAR encephalitis who were misdiagnosed as sCJD at first.

Methods: We described two patients' clinical manifestations, as well as the string of symptomatological evolution, treatments, and follow-up results.

Results: Our patients presented with rapidly progressive dementia, memory problems, psychiatric symptoms, and movement disorders, and we considered all these symptoms as a presenting feature of sCJD at first, but the cerebrospinal fluid examination showed positive results for both the 14-3-3 protein and antibodies against NMDAR. Immunomodulatory treatment led to a resolution of these deficits, and both of them remained in remission after treatment.

Conclusion: Anti-NMDAR encephalitis can present with rapidly progressive cognitive decline, and sometimes laboratory investigations can be misleading. The examination for the presence of NMDAR antibodies is necessary, even with the presence of 14-3-3 protein. Early immunomodulatory therapy should be considered, especially for patients with high titers of NMDAR antibodies.

Systematic review of the clinical spectrum of CASPR2 antibody syndrome

BACKGROUND

Contactin-associated protein-like 2 (CASPR2) autoantibody disease has a variable clinical phenotype. We present a case report and performed a systematic review of the literature to summarize: (1) the clinical phenotype of patients with CASPR2 antibodies, (2) the findings in neurological investigations, and (3) the associated neuroimaging findings.

METHODS

A chart review was performed for the case report. A systematic review of the medical literature was performed from first available to June 13, 2018. Abstracts were screened, and full-text peer-reviewed publications for novel patients with CASPR2 positivity in serum or cerebrospinal fluid (CSF) were included. Selected publications were reviewed, and relevant information was collated. Data were analyzed to determine overall frequency for demographic information, clinical presentations, and investigation findings.

RESULTS

Our patient was a previously healthy 61-year-old male with both serum and CSF CASPR2 antibodies who presented with limbic encephalitis and refractory epilepsy. He was successfully treated with immunosuppression. For our systematic review, we identified 667 patients from 106 studies. Sixty-nine percent were male. Median age was 54 years (IQR 39-65.5). Median disease duration was 12 months (IQR 5.6-20). Reported overall clinical syndromes were: autoimmune encephalitis [69/134 (51.5%)], limbic encephalitis [106/274 (38.7%)], peripheral nerve hyperexcitability [72/191 (37.7%)], Morvan syndrome [57/251 (22.7%)], and cerebellar syndrome [24/163 (14.7%)]. Patients had positive serum [642/642 (100%)] and CSF [87/173 (50.3%)] CASPR2 antibodies. MRI was reported as abnormal in 159/299 patients (53.1%), and the most common abnormalities were encephalitis or T2 hyperintensities in the medial temporal lobes, or hippocampal atrophy, mesial temporal sclerosis, or hippocampal sclerosis. FDG-PET was abnormal in 30/35 patients (85.7%), and the most common abnormality was temporomesial hypometabolism. The most commonly associated condition was myasthenia gravis (38 cases). Thymoma occurred in 76/348 patients (21.8%). Non-thymoma malignancies were uncommon [42/397 (10.6%)].

CONCLUSIONS

Most patients have autoimmune or limbic encephalitis and corresponding abnormalities on neuroimaging. Other presentations include peripheral nerve hyperexcitability or Morvan syndromes, cerebellar syndromes, behavioral and cognitive changes, and more rarely movement disorders. The most commonly associated malignancy was thymoma and suggests a role for thymoma screening in CASPR2-related diseases.

Treatable causes of adult-onset rapid cognitive impairment

OBJECTIVES

Acute and subacute cognitive decline, defined collectively as rapid cognitive impairment (RCI), is attributed to diverse disorders and brings great challenges for differential diagnosis. In this study we investigated the RCI patients to determine the underlying causes and the cognitive outcome of the treatable RCI.

PATIENTS AND METHODS

We reviewed medical records of consecutively hospitalized patients (n = 346) with significant and new cognitive dysfunction between January 2014 and December 2015. Based on the duration of their cognitive dysfunction, patients were divided into two groups with the RCI (< 12 months) and the chronic cognitive impairment (CCI, ≥ 12 months), respectively. Etiologies of the RCI and the CCI were analyzed; the cognitive outcomes of the RCI patients with the treatable disorders were assessed in the follow-up visits.

RESULTS

Potentially treatable or reversible causes were identified in 134 (72%) of 187 RCI patients and in 34 (21%) of 159 CCI patients. The causes in the 134 (72%) RCI patients were immune/inflammation (50, 37%), infection (30, 22%), vascular diseases (29, 22%), neoplasm (16, 12%), metabolic/toxic disorders (7, 5%), and others (2, 1%). The treatable disorders found in both the RCI and the CCI patients were vascular diseases, autoimmune encephalitis, viral encephalitis, inflammatory demyelinating diseases, Hashimoto encephalopathy, neurosyphilis, hydrocephalus, and Vitamin B12 deficiency. Total 114 RCI patients with the treatable disorders were followed up for 6∼39 (median 21) months. Poor cognitive outcomes were found in 24 (21%) of the 114 followed-up patients, comprising patients with infection (1, 3%), immune/inflammation (12, 25%), vascular diseases (8, 28%), and metabolic/toxic disorders (3, 43%).

CONCLUSIONS

Treatable or reversible causes are common underlying RCI. Poor outcomes with severe cognitive deficits are considerably present in the treatable RCI patients and result in permanent dementia.

The autoantibody-mediated encephalitides: from clinical observations to molecular pathogenesis

The autoimmune encephalitis (AE) syndromes have been characterised by the detection of autoantibodies in serum and/or cerebrospinal fluid which target the extracellular domains of specific neuroglial antigens. The clinical syndromes have phenotypes which are often highly characteristic of their associated antigen-specific autoantibody. For example, the constellation of psychiatric features and the multi-faceted movement disorder observed in patients with NMDAR antibodies are highly distinctive, as are the faciobrachial dystonic seizures observed in close association with LGI1 antibodies. These typically tight correlations may be conferred by the presence of autoantibodies which can directly access and modulate their antigens in vivo. AE remains an under-recognised clinical syndrome but one where early and accurate detection is critical as prompt initiation of immunotherapy is closely associated with improved outcomes. In this review of a rapidly emerging field, we outline molecular observations with translational value. We focus on contemporary methodologies of autoantibody detection, the evolution and distinctive nature of the clinical phenotypes, generalisable therapeutic paradigms, and finally discuss the likely mechanisms of autoimmunity in these patients which may inform future precision therapies.

[Recent progress in autoimmune encephalitis and its related disorders]

After the discovery of a series of autoantibodies against neuronal cell surface antigens (NSAs) of the CNS in the past 10 years, the concept of encephalitis has changed dramatically. Accordingly, a practical, syndrome-based diagnostic approach to autoimmune encephalitis was proposed in 2016. These autoantibodies have also been identified in a subset of overlapping encephalitis and demyelinating syndrome, epilepsy, first episode psychosis, movement disorders, post-herpes simplex encephalitis, progressive dementia, postpartum psychosis, stiff-person spectrum disorders, or non-REM/REM sleep behavior disorder. Although not all neuronal antibody tests are available in Japan, we have entered a new era that we have to make a correct diagnosis and start appropriate immunotherapy based on initial neurological assessment and conventional tests, without being constrained by conventional fixed ideas or normal-appearing brain MRIs while waiting for neuronal antibody test results. Although many issues need to be resolved in Japan in terms of diagnosis and treatment in autoimmune encephalitis, this review focusses on recent progress in autoimmune encephalitis and its related disorders closely related to clinical practice, including Hashimoto encephalopathy and new-onset refractory status epilepticus (NORSE).

Heidenhain variant sporadic Creutzfeldt-Jakob disease diagnosed as an autoimmune encephalitis due to a false-positive GAD autoantibody

A 64-year-old man presented with a subacute history progressive visual field defects, illusions and misperceptions. An initial MRI brain revealed a right occipital signal abnormality on diffusion-weighted imaging (DWI) with serum glutamic acid decarboxylase (GAD) autoantibodies markedly elevated. A diagnosis of autoimmune encephalitis was made, with the patient being treated with intravenous immunoglobulin. One month after discharge, the patient represented with worsening frank and well-formed visual hallucinations, ataxia and progressive cognitive impairment. Progress MRI displayed characteristic T2 ribboning on diffusion weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences, along with periodic sharp wave complexes on electroencephalogram (EEG) and a raised CSF protein 14-3-3. Repeat serum, as well as cerebrospinal fluid (CSF), GAD antibodies were again markedly elevated as measured by ELISA (RSR, Cardiff, UK), although archival CSF from the original presentation as well as CSF from the second presentation had undetectable GAD autoantibodies as measured via radioimmunoassay (DIAsource, Ottignies-Louvain-la-Neuve, Belgium). Creutzfeldt-Jakob disease was confirmed at autopsy.

N-Methyl-d-aspartate Receptor Antibody Encephalitis: A Concise Review of the Disorder, Diagnosis, and Management

Anti-NMDA ( N-methyl-d-aspartate) receptor (anti-NMDAR) encephalitis is one of the most common paraneoplastic encephalitides. It occurs in both sexes, across all age ranges, and may occur in the presence or absence of an associated tumor. Its pathogenesis and clinical presentation relate to the presence of IgG1 or IgG3 antibodies targeting the NR1 subunit of the NMDA receptor, leading to a disinhibition of neuronal excitatory pathways. Initial clinical manifestations may be nonspecific, resembling a viral-like illness; however, with disease progression, symptoms can become quite severe, including prominent psychiatric features, cognitive problems, motor dysfunction, and autonomic instability. Anti-NMDAR encephalitis may even result in death in severe untreated cases. Diagnosis can be challenging, given that initial laboratory and radiographic results are typically nonspecific. The majority of patients respond to first or second-line treatments, although therapeutic options remain limited, usually consisting of tumor removal (if there is confirmation of an underlying malignancy) in conjunction with prompt initiation of immunosuppressive medications along with intravenous immunoglobulins and/or plasma exchange. Although the clinical presentation of anti-NMDAR encephalitis overlaps with several other more common neurological and psychiatric disorders, early diagnosis and treatment is essential for a positive prognosis. Here, we concisely review the pathogenesis, diagnosis, and clinical management of this disease.

The impact of self-replicating proteins on inflammation, autoimmunity and neurodegeneration-An untraveled path

The central nervous system (CNS) in neurodegenerative diseases is a battlefield in which microglia fight a highly atypical battle. During the inflammatory process microglia themselves become dysfunctional and even with all the available immune arsenal including cytokine or/and antibody production, the battle is eventually lost. A closer look into the picture will reveal the fact that this is mainly due to the atypical characteristics of the infectious agent. The supramolecular assemblies of misfolded proteins carry unique features not encountered in any of the common pathogens. Through misfolding, proteins undergo conformational changes which make them become immunogenic, neurotoxic and highly infective. The immunogenicity appears to be triggered by the exposure of previously hidden hydrophobic portions in proteins which act as damage-associated molecular patters (DAMPs) for the immune system. The neurotoxicity and infectivity are promoted by the small oligomeric forms of misfolded proteins/peptides. Oligomers adopt conformations such as tubular-like, beta-barrel-like, etc., that penetrate cell membranes through their hydrophobic surfaces, thus destabilizing ionic homeostasis. At the same time, oligomers act as a seed for protein misfolding through a prion/prion-like mechanism. Here, we propose the hypothesis that oligomers have catalytic surfaces and exercise their capacity to infect native proteins through specific characteristics such as hydrophobic, electrostatic and π-π stacking interactions as well as the specific surface area (SSA), surface curvature and surface chemistry of their nanoscale supramolecular assemblies. All these are the key elements for prion/prion-like mechanism of self-replication and disease spreading within the CNS. Thus, understanding the mechanism of prion's templating activity may help us in the prevention and development of novel therapeutic strategies for neurodegenerative diseases.

Early-Onset Creutzfeldt-Jakob Disease Mimicking Immune-Mediated Encephalitis

Objectives

The objective of this study is to explore the clinical, radiological, and pathological manifestations of a rare subtype of prion disease and their implication for differential diagnosis in case of an early onset neuropsychiatric deterioration.

Methods

We discuss a patients’ clinical history, as well as the string of investigations and symptomatological evolution that finally led to a pathological diagnosis.

Results

Our patient had the extremely rare VV1 type sporadic Creutzfeldt-Jakob disease (sCJD). We explain the differential diagnosis of progressive encephalomyelitis with rigidity and myoclonus and its implications for treatment.

Conclusion

sCJD, especially the VV1 subtype, can present at an early age with an insidious psychiatric onset. Classical findings of prion disease—14-3-3 protein, PSWC on electroencephalography, and magnetic resonance imaging patterns—are not always present. The presence of neural autoantibodies does not always implicate pathogenicity in the presence of other neurological/neurodegenerative conditions.

Autoimmune encephalitis with anti-leucine-rich glioma-inactivated 1 or anti-contactin-associated protein-like 2 antibodies (formerly called voltage-gated potassium channel-complex antibodies)

PURPOSE OF REVIEW

Twenty years since the discovery of voltage-gated potassium channel (VGKC)-related autoimmunity; it is currently known that the antibodies are not directed at the VGKC itself but to two closely associated proteins, anti-leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (Caspr2). Antibodies to LGI1 and Caspr2 give well-described clinical phenotypes. Anti-LGI1 encephalitis patients mostly have limbic symptoms, and anti-Caspr2 patients have variable syndromes with both central and peripheral symptoms. A large group of patients with heterogeneous symptoms are VGKC positive but do not have antibodies against LGI1 or Caspr2. The clinical relevance of VGKC positivity in these 'double-negative' patients is questionable. This review focusses on these three essentially different subgroups.

RECENT FINDINGS

The clinical phenotypes of anti-LGI1 encephalitis and anti-Caspr2 encephalitis have been described in more detail including data on treatment and long-term follow-up. A specific human leukocyte antigen (HLA) association was found in nontumor anti-LGI1 encephalitis, but not clearly in those with tumors. There has been increasing interest in the VGKC patients without LGI1/Caspr2 antibodies questioning its relevance in clinical practice.

SUMMARY

Anti-LGI1 encephalitis and anti-Caspr2 encephalitis are separate clinical entities. Early recognition and treatment is necessary and rewarding. The term VGKC-complex antibodies, lumping patients with anti-LGI1, anti-Caspr2 antibodies or lacking both, should be considered obsolete.

Antibody-associated CNS syndromes without signs of inflammation in the elderly

OBJECTIVE

To report the CNS syndromes of patients ≥60 years of age with antibodies against neuronal surface antigens but no evidence of brain MRI and CSF inflammatory changes.

METHODS

This was a retrospective clinical analysis of patients with antibodies against neuronal surface antigens who fulfilled 3 criteria: age ≥60 years, no inflammatory abnormalities in brain MRI, and no CSF pleocytosis. Antibodies were determined with reported techniques.

RESULTS

Among 155 patients ≥60 years of age with neurologic syndromes related to antibodies against neuronal surface antigens, 35 (22.6%) fulfilled the indicated criteria. The median age of these 35 patients was 68 years (range 60-88 years). Clinical manifestations included faciobrachial dystonic seizures (FBDS) in 11 of 35 (31.4%) patients, all with LGI1 antibodies; a combination of gait instability, brainstem dysfunction, and sleep disorder associated with IgLON5 antibodies in 10 (28.6%); acute confusion, memory loss, and behavioral changes suggesting autoimmune encephalitis (AE) in 9 (25.7%; 2 patients with AMPAR, 2 with NMDAR, 2 with GABAbR, 2 with LGI1, and 1 with CASPR2 antibodies); and rapidly progressive cognitive deterioration in 5 (14.3%; 3 patients with IgLON5 antibodies, 1 with chorea; 1 with DPPX antibody-associated cerebellar ataxia and arm rigidity; and 1 with CASPR2 antibodies).

CONCLUSIONS

In patients ≥60 years of age, the correct identification of characteristic CNS syndromes (FBDS, anti-IgLON5 syndrome, AE) should prompt antibody testing even without evidence of inflammation in MRI and CSF studies. Up to 15% of the patients developed rapidly progressive cognitive deterioration, which further complicated the differential diagnosis with a neurodegenerative disorder.

Clinical manifestations of the anti-IgLON5 disease

OBJECTIVE

To report the presentation, main syndromes, human leukocyte antigen (HLA) association, and immunoglobulin G (IgG) subclass in the anti-IgLON5 disease: a disorder with parasomnias, sleep apnea, and IgLON5 antibodies.

METHODS

This was a retrospective clinical analysis of 22 patients. The IgG subclass was determined using reported techniques.

RESULTS

Patients' median age was 64 years (range 46-83). Symptoms that led to initial consultation included sleep problems (8 patients; 36%), gait abnormalities (8; 36%), bulbar dysfunction (3; 14%), chorea (2; 9%), and cognitive decline (1; 5%). By the time of diagnosis of the disorder, 4 syndromes were identified: (1) a sleep disorder with parasomnia and sleep breathing difficulty in 8 (36%) patients; (2) a bulbar syndrome including dysphagia, sialorrhea, stridor, or acute respiratory insufficiency in 6 (27%); (3) a syndrome resembling progressive supranuclear palsy (PSP-like) in 5 (23%); and (4) cognitive decline with or without chorea in 3 (14%). All patients eventually developed parasomnia, sleep apnea, insomnia, or excessive daytime sleepiness. HLA-DRB1*10:01 and HLA-DQB1*05:01 were positive in 13/15 (87%) patients; the DRB1*10:01 allele was 36 times more prevalent than in the general population. Among 16 patients with paired serum and CSF samples, 14 had IgLON5 antibodies in both, and 2 only in serum (both had a PSP-like syndrome). Twenty of 21 patients had IgG1 and IgG4 antibodies; the latter predominated in 16.

CONCLUSIONS

Patients with IgLON5 antibodies develop a characteristic sleep disorder preceded or accompanied by bulbar symptoms, gait abnormalities, oculomotor problems, and, less frequently, cognitive decline. IgG4 subclass antibodies predominate over IgG1; we confirm a strong association with the HLA-DRB1*10:01 allele.

Emerging psychiatric syndromes associated with antivoltage-gated potassium channel complex antibodies

Antibodies against the voltage-gated potassium channel (VGKC) were first recognised as having a potential pathogenic role in disorders of the central nervous system in 2001, with VGKC antibodies described in patients with limbic encephalitis, and the subsequent seminal paper describing the clinical phenotype and immunotherapy treatment responsiveness in 13 patients with VGKC antibodies and limbic encephalitis in 2004. These initial case descriptions were of a progressive neuropsychiatric syndrome with abnormalities of mood, sleep and cognition recognised alongside the neurological symptoms of seizures and autonomic instability. The clinical syndromes associated with VGKC complex (VGKCC) antibodies have broadened considerably over the last 15 years, with multiple cases of more restricted 'formes fruste' presentations associated with VGKCC antibodies being described. However, the relevance of antibodies in these cases has remained controversial. The understanding of the pathogenic nature of VGKC antibodies has further advanced since 2010 with the discovery that VGKC antibodies are not usually antibodies against the VGKC subunits themselves, but instead to proteins that are complexed with the potassium channel, in particular leucine-rich, glioma-inactivated protein 1 (LGI1) and contactin-associated protein 2 (Caspr2). Antibodies against these proteins have been associated with particular, although overlapping, clinical phenotypes, each also including neuropsychiatric features. Our aim is to critically review the association between VGKCC, LGI1 and Caspr2 antibodies with isolated psychiatric presentations-with a focus on cognitive impairment, mood disorders and psychosis. We recommend that screening for VGKCC, LGI1 and Caspr2 antibodies be considered for those with neuropsychiatric presentations.

The importance of recognizing faciobrachial dystonic seizures in rapidly progressive dementias

BACKGROUND

Creutzfeldt-Jakob Disease (CJD) is the prototypical cause of rapidly progressive dementia (RPD). Nonetheless, efforts to exclude reversible causes of RPD that mimic prion disease are imperative. The recent expanding characterization of neurological syndromes associated with antibodies directed against neuronal cell surface or sympathic antigens, namely autoimmune encephalitis is shifting paradigms in neurology. Such antigens are well known proteins and receptors involved in synaptic transmission. Their dysfunction results in neuropsychiatric symptoms, psychosis, seizures, movement disorders and RPD. Faciobrachial dystonic seizure (FBDS) is a novel characterized type of seizure, specific for anti-LGI1 encephalitis.

OBJECTIVE

In order to improve clinical recognition we report the cases of two Brazilian patients who presented with characteristic FDBS (illustrated by videos) and anti-LGI1 encephalitis.

METHODS

We have included all patients with FBDS and confirmed anti-LGI1 encephalitis and video records of FDBS in two tertiary Brazilian centers: Department of Neurology of Hospital das Clínicas, Sao Paulo University, Sao Paulo, Brazil and Hospital Geral de Fortaleza, Fortaleza, Brazil between January 1, 2011 and December 31, 2015.

RESULTS

Both patients presented with clinical features of limbic encephalitis associated with FBDS, hyponatremia and normal CSF. None of them presented with tumor and both showed a good response after immunotherapy.

CONCLUSION

FBDSs may be confounded with myoclonus and occurs simultaneously with rapid cognitive decline. Unawareness of FDBS may induce to misdiagnosing a treatable cause of RPD as CJD.

Anti-LGI1-associated cognitive impairment: Presentation and long-term outcome

OBJECTIVE

We investigated a series of patients with LGI1 antibody (Ab)-related cognitive deterioration to determine the clinical presentation, long-term outcome, and LGI1 Ab evolution.

METHODS

We retrospectively analyzed the clinical information of 76 patients with LGI1 Ab-related cognitive deterioration. Presenting syndromes were classified as limbic encephalitis (LE), non-LE, or encephalopathy (normal MRI and no CSF pleocytosis). Frequency of relapses and clinical outcome were assessed in 48 patients with prolonged follow-up (median 39 months, range 18-200).

RESULTS

Sixty-three patients (83%) developed LE, 3 (4%) non-LE, and 10 (13%) encephalopathy. All patients received steroids, IV immunoglobulins (Ig), or both. At 2 years, 17 (35%; 95% CI 21%-49%) fully recovered, 17 (35%) became functionally independent but not at baseline or were unable to return to work, 11 (23%) required assistance because of moderate or severe cognitive deficits, and 3 (6%) died. Predictors of bad outcome included no response to initial immunotherapy (odds ratio 23.0, 95% CI 2.4-215.6, p = 0.006) and clinical relapses (odds ratio 10.2, 95% CI 1.0-100.1, p = 0.047) that occurred in 13 patients (27%). In all patients, the LGI1 Abs were IgG4 and usually detectable in both serum and CSF (only CSF, 8%). Abs remained positive in serum of 4 of 16 patients with long-term follow-up; 3 of these 4 patients fully recovered and none showed class switch to IgG1.

CONCLUSIONS

Up to 13% of patients with LGI1 Abs develop cognitive impairment without criteria of encephalitis. After immunotherapy, only 35% of patients return to their baseline cognitive function. Serum LGI1 Abs may remain detectable after full clinical recovery.

Autoimmune encephalitis mimicking sporadic Creutzfeldt-Jakob disease: A retrospective study

Autoimmune encephalitis associated with anti-voltage-gated potassium channel antibodies are most likely to be misdiagnosed as sporadic Creutzfeldt-Jakob disease (sCJD). Our goal was to delineate patients who were initially suspected to have CJD but were later found to have AE. We performed a retrospective clinical review of cases of individuals and made a comparison between groups of patients diagnosed with sCJD and AE. Patients who had rapidly progressing dementia and focal neurological impairment, such as aphasia, gait disturbance, visual disturbance, and depression, at onset were diagnosed with sCJD, whereas epilepsy, hyponatremia and dysautonomia were strong hints for AE. Fluoroscope-positron emission tomography (PET) of patients with AE revealed variable metabolism and normative and long-term immunosuppression were less likely to relapse.

Anti-NMDAR encephalitis and other glutamate and GABA receptor antibody encephalopathies

Over the last few year, antibodies to various central nervous system receptors, particularly the glutamate and γ-aminobutyric acid (GABA) receptors, have been found to be associated with autoimmune neurologic disorders. The receptors include the N-methyl-d-aspartate receptor (NMDAR), the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), the metabotropic glutamate receptors (mGluRs), and GABA type A and B receptors (respectively GABAAR and GABABR). Compared to the previously described paraneoplastic antibodies directed at intracellular targets, the patients with receptor antibodies are often younger, they less frequently have malignancies, and they respond better to immunotherapy. Many of the patients have limbic encephalitis with amnesia, disorientation, seizures, and psychological or psychiatric symptoms, but those with NMDAR antibodies usually develop a more widespread form of encephalitis, often leading to a decrease in consciousness and requirement for long-term intensive care treatment. The autoantibodies bind directly to the synaptic or extrasynaptic receptors on the membrane surface, and have direct effects on signal transduction in central synapses. These conditions are very important to recognize as the symptoms and complications can be fatal when not treated in time, whereas with immunotherapy many patients recover considerably.

Recognizing Autoimmune-Mediated Encephalitis in the Differential Diagnosis of Limbic Disorders

Limbic encephalitis is far more common than previously thought. It is not always associated with cancer, and it is potentially treatable. Autoantibodies against various neuronal cell antigens may arise independently or in association with cancer and cause autoimmune damage to the limbic system. Neuroimaging plays a key role in the management of patients with suspected limbic encephalitis by supporting diagnosis and excluding differential possibilities. This article describes the main types of autoimmune limbic encephalitis and its mimic disorders, and emphasizes their major imaging features.

Pathologically confirmed autoimmune encephalitis in suspected Creutzfeldt-Jakob disease

Objective:

To determine the clinical features and presence in CSF of antineuronal antibodies in patients with pathologically proven autoimmune encephalitis derived from a cohort of patients with suspected Creutzfeldt-Jakob disease (CJD).

Methods:

The Dutch Surveillance Centre for Prion Diseases performed 384 autopsies on patients with suspected CJD over a 14-year period (1998–2011). Clinical information was collected from treating physicians. Antineuronal antibodies were tested in CSF obtained postmortem by immunohistochemistry on fresh frozen rat brain sections, by Luminex assay for the presence of well-characterized onconeural antibodies, and by cell-based assays for antibodies against NMDAR, GABA_BR1/2, GABA_AR GLUR1/2, LGI1, Caspr2, and DPPX.

Results:

In 203 patients, a diagnosis of definite CJD was made, while in 181 a variety of other conditions were diagnosed, mainly neurodegenerative. In 22 of these 181, the neuropathologist diagnosed autoimmune encephalitis. One patient was excluded because of lack of clinical information. Inflammatory infiltrates were predominantly perivascular and consisted mainly of T cells. The predominant locations were basal ganglia and thalamus (90%) and temporal lobes and hippocampus (81%). In 6 patients (29%), antineuronal antibodies were detected in postmortem CSF, directed against Hu, NMDAR, GABABR1/2, Caspr2, and an unidentified synaptic antigen in 2. The most frequent symptoms were dementia (90%), gait disturbance (86%), cerebellar signs (67%), and neuropsychiatric symptoms (67%). Immunopathologic and clinical findings did not differ between autoantibody-negative patients and patients with antineuronal antibodies.

Conclusions:

It is important to consider immune-mediated disorders in the differential diagnosis of rapidly progressive neurologic deficits.

Neuronal antibodies in patients with suspected or confirmed sporadic Creutzfeldt-Jakob disease

OBJECTIVES

There have been reports of patients with antibodies to neuronal antigens misdiagnosed as sporadic Creutzfeldt-Jakob disease (sCJD). Conversely, low levels of antibodies to neuronal proteins have been reported in patients with sCJD. However, the frequency of misdiagnoses, or of antibodies in patients with subsequently confirmed sCJD, is not clear.

METHODS

We reviewed 256 consecutive cases of sCJD seen in the National Prion Clinic, of whom 150 had sera previously referred for selected antibody tests. Eighty-two available samples were retested for antibodies to N-methyl-d-aspartate receptor (NMDAR), the glycine receptor (GlyR), voltage-gated potassium channel (VGKC)-complex and the associated proteins, leucine-rich glioma inactivated 1 (LGI1) and contactin-associated protein 2 (CASPR2).

RESULTS

Four of the initial 150 sera referred were positive; two had antibodies to NMDAR, and two to the VGKC-complex, one of which was also positive for GlyR antibodies. Of the 82 sCJD sera retested, one had VGKC-complex antibodies confirming the previous result, two had CASPR2 and GlyR antibodies and one had CASPR2 and NMDAR antibodies; all antibodies were at low levels. Over the same period three patients with autoimmune encephalitis and high VGKC-complex antibodies were initially referred as sCJD.

CONCLUSIONS

This study indicates that <5% patients with sCJD develop serum antibodies to these neuronal antigens and, when positive, only at low titres. By contrast, three patients referred with possible prion disease had a clinical picture in keeping with autoimmune encephalitis and very high VGKC-complex/LGI1 antibodies. Low titres of neuronal antibodies occur only rarely in suspected patients with sCJD and when present should be interpreted with caution.

[Clinical spectrum and treatment strategy in anti-NMDA receptor encephalitis: current status and issues]

Anti-NMDA receptor encephalitis is a disorder caused by IgG antibodies to the extracellular conformal epitope of the NR1 subunits. This disorder predominantly affects young female with ovarian teratoma;however, any person of any age, unrelated to gender or the presence of tumor, can be affected. This disorder usually follows multistage beginning with prodromal symptoms, followed by psychiatric symptoms, unresponsive state accompanied by intractable dyskinesias, seizure and central hypoventilation. Diversity of clinical spectrum has recently been emphasized based on antibody detection in various disorders, including schizophrenia, epilepsy, CJD, neuromyelitis optica, and HSV encephalitis, but these data must be cautiously interpreted; low serum titers may be false positive or clinically not relevant. This disorder has been regarded as treatment-responsive; however, only a half of the patients respond to the first-line immunotherapy (corticosteroids, immunoglobulins or plasma exchange) or tumor removal, and 19 percent remain highly disabled at 24 months with an estimated morality rate of 7%. In refractory cases early initiation of the second-line immunotherapy (rituximab and/or cyclophosphamide) recommended; however, it is difficult to follow the recommendation due to many issues, among those, off-label use is the major reason that prevents initiation of the second-line immunotherapy in Japan.

Creutzfeldt-Jakob disease mimicking autoimmune encephalitis with CASPR2 antibodies

Background

Differential diagnosis of severe progressive dementia includes a wide spectrum of inflammatory and neurodegenerative diseases. Particularly challenging is the differentiation of potentially treatable autoimmune encephalitis and Creutzfeldt-Jakob disease. Such a coincidence may indeed complicate the correct diagnosis and influence subsequent treatment.

Case presentation

A 75-year-old woman was admitted due to rapid progressive cognitive impairment. Her husband observed a temporal disorientation and confusion. The initial neurological examination and an extensive neuropsychological evaluation showed significant impairments in almost all tested cognitive domains. All other neurological functions including motor, sensory and coordinative function were intact. Initial diagnostics included EEG, MRI and lumbar puncture with unspecific results. Complementary blood testing revealed a positive result for antineural antibodies to Contactin-associated protein 2 (CASPR2) and the patient received treatment for CASPR2 autoimmune encephalitis. Further symptoms and results, including 14-3-3 proteins, led to suspected Creutzfeldt-Jakob disease. The postmortem examination supported the diagnosis of a definitive Creutzfeldt-Jakob disease.

Conclusion

One could argue that global screening for antineural antibodies may lead to a false diagnosis triggering intense and potentially dangerous procedures. We believe, however, that potentially treatable causes of dementia should aggressively sought out and subsequently treated in an attempt to curtail the course of disease and ultimately reduce the rate of mortality.

Autoimmune encephalopathies

Over the past 10 years, the continual discovery of novel forms of encephalitis associated with antibodies to cell-surface or synaptic proteins has changed the paradigms for diagnosing and treating disorders that were previously unknown or mischaracterized. We review here the process of discovery, the symptoms, and the target antigens of 11 autoimmune encephalitic disorders, grouped by syndromes and approached from a clinical perspective. Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, several subtypes of limbic encephalitis, stiff-person spectrum disorders, and other autoimmune encephalitides that result in psychosis, seizures, or abnormal movements are described in detail. We include a novel encephalopathy with prominent sleep dysfunction that provides an intriguing link between chronic neurodegeneration and cell-surface autoimmunity (IgLON5). Some of the caveats of limited serum testing are outlined. In addition, we review the underlying cellular and synaptic mechanisms that for some disorders confirm the antibody pathogenicity. The multidisciplinary impact of autoimmune encephalitis has been expanded recently by the discovery that herpes simplex encephalitis is a robust trigger of synaptic autoimmunity, and that some patients may develop overlapping syndromes, including anti-NMDAR encephalitis and neuromyelitis optica or other demyelinating diseases.

Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease

Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is the rare instance when a positive VGKC complex antibody titre occurs in a definite case of prion disease. We present a pathologically and genetically confirmed case of CJD with elevated serum VGKC complex antibody titres. This case highlights the importance of interpreting the result of a positive VGKC complex antibody with caution and in the context of the overall clinical manifestation.

Gerstmann-Straüssler-Scheinker disease: novel PRNP mutation and VGKC-complex antibodies

OBJECTIVE

To describe a unique case of Gerstmann-Straüssler-Scheinker (GSS) disease caused by a novel prion protein (PRNP) gene mutation and associated with strongly positive voltage-gated potassium channel (VGKC)-complex antibodies (Abs).

METHODS

Clinical data were gathered from retrospective review of the case notes. Postmortem neuropathologic examination was performed, and DNA was extracted from frozen brain tissue for full sequence analysis of the PRNP gene.

RESULTS

The patient was diagnosed in life with VGKC-complex Ab-associated encephalitis based on strongly positive VGKC-complex Ab titers but no detectable LGI1 or CASPR2 Abs. He died despite 1 year of aggressive immunosuppressive treatment. The neuropathologic diagnosis was GSS disease, and a novel mutation, P84S, in the PRNP gene was found.

CONCLUSION

VGKC-complex Abs are described in an increasingly broad range of clinical syndromes, including progressive encephalopathies, and may be amenable to treatment with immunosuppression. However, the failure to respond to aggressive immunotherapy warns against VGKC-complex Abs being pathogenic, and their presence does not preclude the possibility of prion disease.

Antibody titres at diagnosis and during follow-up of anti-NMDA receptor encephalitis: a retrospective study

BACKGROUND

Anti-N-methyl-d-aspartate (NMDA) receptor encephalitis is a severe but treatable autoimmune disorder which diagnosis depends on sensitive and specific antibody testing. We aimed to assess the sensitivity and specificity of serum and CSF antibody testing in patients with anti-NMDA receptor encephalitis, and the relation between titres, relapses, outcome, and epitope repertoire.

METHODS

In this observational study, we used rat brain immunohistochemistry and cell-based assays (CBA) with fixed or live NMDA receptor-expressing cells to determine the sensitivity and specificity of antibody testing in paired serum and CSF samples. Samples were obtained at diagnosis from patients with anti-NMDA receptor encephalitis and from control participants worldwide. We deemed a patient to be antibody positive if their serum, their CSF, or both tested positive with both immunohistochemistry and CBA techniques; we determined titres with serial sample dilution using brain immunohistochemistry. We examined samples from 45 patients (25 with good outcome [modified Rankin Scale, mRS 0-2], ten with poor outcome [mRS 3-6], and ten with relapses) at three or more timepoints. We determined the epitope repertoire in the samples of 23 patients with CBA expressing GluN1-NMDA receptor mutants.

FINDINGS

We analysed samples from 250 patients with anti-NMDA receptor encephalitis and 100 control participants. All 250 patients had NMDA receptor antibodies in CSF but only 214 had antibodies in serum (sensitivity 100.0% [98.5-1000%] vs 85.6% [80.7-89.4%], p<0.0001). Serum immunohistochemistry testing was more often in agreement with CBA with fixed cells (77 [71%] of 108) than with CBA with live cells (63 [58%] of 108, p=0.0056). In multivariable analysis, CSF and serum titres were higher in patients with poor outcome than in those with good outcome (CSF dilution 340 vs 129, difference 211, [95% CI 1-421], p=0.049; serum dilution 7370 vs 1243, difference 6127 [2369-9885], p=0.0025), and in patients with teratoma than in those without teratoma (CSF 395 vs 110, difference 285 [134-437], p=0.0079; serum 5515 vs 1644, difference 3870 [548-7193], p=0.024). Over time there was a decrease of antibody titres in the 35 patients with good or poor outcome and samples followed at three timepoints regardless of outcome (from diagnosis to last follow-up: CSF 614 to 76, difference 538 [288-788]; serum 5460 to 1564, difference 3896 [2428-5362]; both p<0.0001). Relapses were associated with a change in titre more often in CSF than in serum (14 of 19 vs seven of 16, p=0.037). After recovery, 24 of 28 CSF samples and 17 of 23 serum samples from patients remained antibody positive. Patients' antibodies targeted a main epitope region at GluN1 aminoacid 369; the epitope repertoire did not differ between patients with different outcomes, and did not change during relapses.

INTERPRETATION

The sensitivity of NMDA receptor antibody testing is higher in CSF than in serum. Antibody titres in CSF and serum were higher in patients with poor outcome or teratoma than in patients with good outcome or no tumour. The titre change in CSF was more closely related with relapses than was that in serum. These findings emphasise the importance of including CSF in antibody studies, and that antibody titres can complement clinical assessments.

FUNDING

Dutch Cancer Society, National Institutes of Health, McKnight Neuroscience of Brain Disorders award, the Fondo de Investigaciones Sanitarias, ErasmusMC fellowship, and Fundació la Marató de TV3.