ORIGINAL CONTRIBUTION
Diagnostic Value of N-methyl-D-aspartate Receptor
Antibodies in Women With New-Onset Epilepsy
Pitt Niehusmann, MD; Josep Dalmau, MD, PhD; Christian Rudlowski, MD; Angela Vincent, FRCPath;
Christian E. Elger, FRCP; Jeffrey E. Rossi, BA; Christian G. Bien, MD
Background: In women younger than 45 years, a new
form of encephalitis associated with ovarian teratoma and
presenting with seizures and psychiatric symptoms has
been described. Most patients have antibodies to NR1/
NR2 heteromers of the N-methyl-D-aspartate receptor
(NMDAR).
Objective: To assess the frequency and significance of
antibodies to NMDAR in otherwise unexplained newonset epilepsies in young women.
Design: Prospective cohort study.
Setting: University department of epileptology.
Patients: From January 1, 2005, to June 30, 2007, we
identified 19 female patients aged 15 to 45 years with
unexplained new-onset epilepsy. In addition, we studied
61 cerebrospinal fluid–serum sample pairs from patients
with other cryptogenic epilepsies and 11 cerebrospinal
fluid–serum sample pairs from surgically treated
patients with epilepsy with no evident encephalitic
abnormalities.
A
Main Outcome Measures: Antibodies to NMDAR and
characteristics of affected patients.
Results: Five of the 19 patients had antibodies against
NMDAR. These patients had diffuse cerebral dysfunction
and seizure origins. Psychiatric symptoms and pleocytosis were significantly associated with this group of patients. The disease course was episodic, in part relapsingremitting, with full recoveries either spontaneously or after
corticosteroid or intravenous immunoglobulin treatments. Only 1 patient had a neoplasm (multiple neuroendocrine tumors that included the ovaries) identified to
date. In the control series, one 22-year-old man with a cryptogenic, severely encephalopathic seizure disorder was
NMDAR antibody positive, and he also recovered fully.
Conclusions: Anti-NMDAR encephalitis accounts for a
relevant proportion of otherwise unexplained newonset epilepsies. Patients harboring NMDAR antibodies
usually have prominent psychiatric symptoms and pleocytosis, and they may develop hypoventilation. AntiNMDAR encephalitis is not always paraneoplastic.
Arch Neurol. 2009;66(4):458-464
NEW TYPE OF ENCEPHALITIS
in female patients younger
than 45 years has recently
been described.1 The associated syndrome is characterized by an acute organic psychiatric disorder, seizures, dyskinesias, autonomic
instability, abnormal cardiac conduction, a
decreased level of consciousness, and centralhypoventilation,suggestingdiffusebrain
dysfunctioninmostpatients.1,2 Manypatients
Author Affiliations:
Departments of Epileptology
(Drs Niehusmann, Elger, and
Bien) and Gynecology
(Dr Rudlowski), University of
Bonn, Bonn, Germany;
Department of Neurology,
University of Pennsylvania,
Philadelphia (Dr Dalmau and
Mr Rossi); and Weatherall
Institute of Molecular Medicine,
University of Oxford, John
Radcliffe Hospital, Oxford,
England (Dr Vincent).
tumor removal and subsequent immunotherapy.1 This distinguishes this encephalitis from paraneoplastic encephalitides with
“well-characterized” onconeural antibodies5
directed to intracellular antigens.6
In a series of 100 patients, 76 had seizures.7 We, therefore, wondered whether
anti-NMDAR antibodies might contribute to the classification and management
of otherwise unexplained new-onset epilepsies in young women.
METHODS
CME available online at
www.jamaarchivescme.com
and questions on page 430
have an ovarian teratoma, but the disorder
may occur without tumor association.3,4 The
target epitopes are contained in NR1/NR2
heteromers of the N-methyl-D-aspartate receptor (NMDAR).1 Despite severe and potentially lethal symptoms, most patients
experience remarkable improvement after
(REPRINTED) ARCH NEUROL / VOL 66 (NO. 4), APR 2009
458
PATIENTS
We reviewed information from all 847 female
inpatients aged 15 to 45 years studied in the
Department of Epileptology, University of
Bonn, between January 1, 2005, and June 30,
2007. We selected those with unexplained newonset epilepsy (ie, those who had recurrent seizures starting in the past 5 years with neither
an obvious provoking factor nor an apparent
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remote origin, such as a brain malformation or tumor, trauma,
central nervous system infection, or idiopathic generalized epilepsy).
Studies included medical history, physical examination, interictal electroencephalography (EEG), cerebral magnetic resonance imaging (MRI), tumor search, routine blood and cerebrospinal fluid (CSF) tests (cell count, protein content,
oligoclonal bands, albumin CSF to serum ratio, and IgG CSF
to serum ratio for the determination of blood-brain barrier disturbance and intrathecal IgG synthesis according to Reiber8),
and studies for the most common neurotropic agents: varicellazoster virus in 19 patients (as assessed by polymerase chain reaction [PCR] and antibodies), herpes simplex virus in 18 (as
assessed by PCR and antibodies), human herpesvirus 6 in 14
(as assessed by PCR and antibodies), cytomegalovirus in 10 (as
assessed by PCR and antibodies), measles virus in 12 (as assessed by PCR and antibodies), enterovirus in 2 (as assessed
by PCR and antibodies), spring summer meningoencephalitis
in 11 (as assessed by antibodies), Treponema pallidum in 10 (as
assessed by Treponema pallidum particle agglutination assay),
and Borrelia burgdorferi in 12 (as assessed by antibodies).
IMMUNOHISTOCHEMICAL ANALYSIS FOR THE
DETECTION OF NEURONAL ANTIBODIES
Indirect immunohistochemical analysis was used to screen for
autoantibodies in serum and CSF by one of us (C.G.B.). Samples
were stored at −20°C until testing. Testing was performed on sections of brains obtained from 28-day-old male Wistar rats (Charles
River WIGA Deutschland, Sulzbach, Germany). Rats were anesthetized and perfused transcardially with 4% paraformaldehyde.
The brains were removed and kept for 4 hours in 2% paraformaldehyde, then in 20% sucrose overnight at 4°C and subsequently for approximately 3 days in 30% sucrose. They were slowly
frozen over isopentane and liquid ammonia and were stored at
−80°C. Seven-micrometer-thick sections were cut and mounted
on glass slides. For use, they were defrosted and washed in 0.1M
phosphate-buffered saline (PBS). As a blocking step, sections were
incubated for 30 minutes at room temperature in 10% fetal calf
serum in wash buffer (Dako, Hamburg, Germany). Patient serum was applied for 3 hours at 37°C at a 1:500 dilution in the
same blocking solution; CSF was used undiluted. After thorough washing in PBS, the sections were incubated for 30 minutes at room temperature with biotinylated anti–human IgG (sheep
antibody, Amersham Pharmacia Biotech, Uppsala, Sweden) at a
dilution of 1:200 in 10% fetal calf serum in wash buffer. After thorough washing in PBS, avidin peroxidase (Sigma-Aldrich Corp,
St Louis, Missouri) at a 1:100 dilution was applied for 30 minutes at room temperature. After another thorough washing step
in PBS, labeling was visualized with 3,3-diaminobenzidinetetrahydrochloride (Sigma-Aldrich Corp). Sections were counterstained with hemalum. Using this assay, antibodies to hippocampal neuropil,9 voltage-gated potassium channel (VGKC)
antibodies at high titers,10 onconeural antibodies,11 and glutamic
acid decarboxylase (GAD) antibodies12,13 can be visualized.
OTHER ANTIBODY TESTS
To confirm positive findings, serum samples were tested by means
of radioimmunoprecipitation assay for antibodies to VGKC (A.V.)
(values of 100-400 pmol/L were regarded as low positive, and
values ⬎400 pmol/L as high positive10,14,15), antibodies to anti–
thyroid peroxidase (TPO) (run by the Department of Nuclear
Medicine, University of Bonn; reference range, ⬍40 U/mL), and
antibodies to GAD (commercially performed by Labor Limbach, Heidelberg, Germany; reference range, ⬍0.6 U/mL; “neurologic range,” ⬎70 U/mL). All serum and CSF samples (not only
those positive on the immunohistochemical screening test described previously herein) from the women with new-onset epilepsies were also tested for antibodies to NMDAR using immunocytochemical analysis on cultures of neurons (to demonstrate
cell surface epitopes) and cells specifically transfected with NR1/
NR2 heteromers, as reported previously.1
CONTROL SERIES
Sixty-one patients (24 females) older than 15 years (mean [SD]
age, 55 [16] years) with unexplained new-onset epilepsy (“cryptogenic epilepsies”16) (mean [SD] disease duration, 1.6 [1.3] years)
presenting in the same period (all of them ⬎45 years old at onset) underwent CSF and serum studies for routine investigation.
They formed control group 1.
Eleven patients with epilepsy (4 females) treated surgically
for pharmacoresistant epilepsy with noninflammatory histopathologic findings (hippocampal sclerosis, 4 patients; tumor,
5 patients; dysplasia, 1 patient; and nonspecific, 1 patient; patients’ mean [SD] age, 46 [9] years) underwent CSF and serum studies. They formed control group 2.
Serum samples from the control patients were tested by means
of immunohistochemical analysis (as described previously herein)
for antibodies against the neuropil of hippocampus and, if positive, were further studied using specific tests (NMDAR and GAD
antibodies); VGKC antibodies were determined in all of them
by means of radioimmunoprecipitation assay.
STATISTICS
For nominal data, Fisher 2-sided exact tests, and for metric data,
2-sided Mann-Whitney tests, were applied (SPSS 14.0; SPSS Inc,
Chicago, Illinois).
RESULTS
Nineteen female inpatients aged 15 to 45 years studied during the 30-month period had otherwise unexplained newonset epilepsy. The remaining 828 female inpatients during this period had chronic epilepsy with a history longer
than 5 years (as is commonly found at tertiary care centers), had a distinct lesional epilepsy cause, or were outside the indicated age range. The mean (SD) age of the 19
study patients at assessment was 26 (9) years (range, 16-44
years). At the time of assessment, the mean (SD) disease
duration was 1.5 (1.2) years (range, 0.1-4.8 years).
ANTIBODIES
New-Onset Epilepsy Without Obvious Origin
Antibodies reacting with the neuropil of hippocampus were
identified in 5 of 19 patients’ undiluted CSF; the serum
samples (at a 1:500 dilution) of these patients were negative by means of immunohistochemical analysis. Specific
tests with NR1/NR2 heteromers of the NMDAR confirmed the presence of these antibodies in all the patients’
serum and CSF samples. In all cases using equivalent
amounts of serum and CSF IgG, the reactivity was substantially higher in CSF, compatible with intrathecal synthesis of anti-NMDAR antibodies (data not shown).
Figure 1 shows the antibody reactivity compared with
other antibodies that also immunolabel the neuropil of hippocampus. The NMDAR antibodies predominantly bind
to the hippocampus, as previously reported.1
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A
B
C
D
Figure 1. Indirect immunohistochemical analyses using undiluted cerebrospinal fluid on perfused, sagittally sectioned rat brain. A, Antibodies to
N-methyl-D-aspartate receptor (patient 4). B, Negative control. C, Glutamic acid decarboxylase antibodies: diffuse labeling pattern plus perisomatic staining of the
Purkinje cells extending into adjacent layers (cerebellar inset, bar= 50 µm). D, Voltage-gated potassium channel antibodies (diffuse staining). The insets (upper
right-hand corners) show the hippocampi. Bar= 2 mm and is valid for parts A through D.
Ofthe14patientsnegativeforNMDARantibodies,3were
positiveforGADantibodiesbymeansofimmunohistochemicalanalysisandradioimmunoprecipitationassay(titers,100200 U/mL), all with clinical and neuroradiologic features
reminiscent of limbic encephalitis.13 One patient had MRInegative extratemporal epilepsy with cognitive impairment
and was strongly positive for TPO antibodies (2826 U/L)
and at the same time was low positive for VGKC antibodies (143 pmol/L) and very low positive for GAD antibodies (3.2 U/mL on radioimmunoprecipitation assay and negative on immunohistochemical analysis). She responded to
corticosteroidssuggestingasteroid-responsiveencephalopathy associated with autoimmune thyroiditis (SREAT).17 Another 2 patients also had MRI-negative epilepsies with psychiatric symptoms and elevated anti-TPO antibody titers
but were not treated with corticosteroids. Therefore, a diagnosis of SREAT cannot be made. All serum samples were
negative for onconeural antibodies. There was no case of
viral or paraneoplastic encephalitis.
ables, and a tumor search (thoracoabdominal computed
tomography [CT]) were unremarkable, but TPO antibody levels were abnormal at 939 U/L. The patient recovered completely while taking high-dose oral corticosteroids. The serum sample positive for antibodies to
hippocampal neuropil but negative for NMDAR antibodies came from a 69-year-old man with remote posterior cerebral artery infarction; it remained unclear whether his recent-onset epilepsy was related to this postischemic lesion.
Other antibodies detected in the cryptogenic epilepsy cohort were reacting with VGKC (6 patients, 5 of whom fulfilled the clinical criteria for limbic encephalitis).10 The 3
samples with titers greater than 1000 pmol/L reacted on
immunohistochemical testing with rat brain neuropil in a
diffuse manner, not restricted to the hippocampus; the 3
samples with titers less than 1000 pmol/L were negative
by immunohistochemical analysis. In the epilepsy surgery control series, one 29-year-old man with a 7-year history of TLE and a histopathologic diagnosis of hippocampal sclerosis had GAD antibodies (110 U/mL).
Control Cohorts
Final Diagnoses and Results of Tumor Searches
In the cryptogenic epilepsy control series, antibodies to hippocampal neuropil were found by means of immunohistochemical analysis in 2 patients (CSF in 1 and serum in
1, but only the CSF antibodies were reacting with NMDAR.
The sample came from a 22-year-old man with a few weeks
of temporal lobe epilepsy (TLE), confusion, delusions, and,
finally, stupor. Brain MRI findings, standard CSF vari-
In the 6 patients who were positive for NMDAR antibodies (including the male patient from the control series),
no alternative diagnosis to “anti-NMDAR encephalitis”
could be established. In patient 4, multiple neuroendocrine tumors were already known and treated at manifestation of the neurologic syndrome and subsequent dem-
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Patient 1
Patient 2
Patient 3
Patient 4
Bilateral ovariectomy for multiple neuroendocrine tumors
Brain biopsy
Patient 5
Corticosteroid
therapy
Seizures only
Anti-NMDAR
antibodies in CSF
Monthly IVIG
Seizures + neuropsychiatric symptoms
2 mo
Aphasia only
Figure 2. Clinical courses of the 5 patients positive for N-methyl-D-aspartate receptor (NMDAR) antibodies. CSF indicates cerebrospinal fluid; IVIG, intravenous
immunoglobulin.
onstration of NMDAR antibodies. Fifteen months later,
bilateral ovariectomy was performed for ovarian manifestation of the same tumor type. The ovarian tumors contained nerve cells positive for NMDAR (demonstrated immunohistochemically18 by a monoclonal mouse antibody
to microtubule-associated protein 2 [Sigma-Aldrich Corp]
and a polyclonal rat antibody to NMDAR-2B [Zymed, San
Francisco, California] [data not shown]). In the other 4
patients, extensive searches for tumors were performed.
All these patients underwent at least 1 transvaginal ultrasound study, performed by an experienced gynecologist
(C.R.), and pelvic MRI. Whole-body CT–positron emission tomography was performed in patients 2 and 4. In
patients 3 and 5, ovarian cysts were detected by means of
ultrasound and MRI. Follow-up ultrasound studies were
performed at different time points during the individual’s
menstruation cycles. Cysts had regressed and were, therefore, classified as functional. Whole-body positron emission tomography and pelvic MRI showed a suspect area
in the left gluteal muscles of patient 2; the structure was
removed surgically, and the histopathologic diagnosis was
hibernoma (a rare benign tumor that arises from remnants of fetal brown adipose tissue that may be found in
muscle and subcutaneous tissue).19
Patient 5 and the NMDAR antibody–positive male patient from the cryptogenic control series underwent open
brain biopsies while taking corticosteroids. In the absence of MRI lesions, biopsy sites were selected based on
maximal EEG abnormalities outside eloquent areas (frontal lobe in 1 patient and temporal neocortex in 1 patient).
Histopathologic findings were unremarkable apart from
moderate, nonspecific microglial activation and some perivascular T and B lymphocytes without signs of vasculitis.
The 14 NMDAR antibody–negative patients received
the following diagnoses: TLE with hippocampal sclerosis
(2 patients [1 subsequent to febrile seizures and 1 subsequent to recent status epilepticus of unknown origin]), histopathologically confirmed nonparaneoplastic limbic encephalitis (1 patient [see the “Case Vignette” in the study
by Bien et al20]), unclassified chronic encephalitides (3 patients [in 2 the diagnosis was based on clinical and MRI
courses plus abnormalities on standard CSF tests, and in
1 there was bioptic evidence of encephalitis]), SREAT (1
patient), and TLE with slight unilateral amygdalar signal
and volume increase of uncertain significance (4 patients
[1 with additional insular signal increase and dyskinesias]); 3 patients remained without etiological diagnosis.
All the patients underwent a tumor search (minimal ex-
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tent: chest radiograph; abdominal ultrasound; and gynecologic examination, including transvaginal ultrasound;
7 had thoracic and abdominal CT with contrast enhancement and 3 had whole-body positron emission tomography with CT co-registration). No tumors were found.
CLINICAL FEATURES
AND PARACLINICAL FINDINGS
Disease Duration
The 5 NMDAR antibody–positive patients had a shorter
mean (SD) disease duration at assessment than the other
14 young women with recent-onset epilepsies (5 [4]
months vs 22 [15] months, P = .02).
The Epilepsies
Semiologic features and interictal EEG findings suggested
extratemporal epilepsies in all NMDAR antibody–positive
patients, whereas, in the other patients, TLE was diagnosed
in 10 patients and extratemporal epilepsy in 4 (P=.01).
The Neuropsychiatric Syndrome
Four of the 5 NMDAR antibody–positive patients had
prominent psychiatric signs and symptoms. Such features were present in only 2 of the antibody-negative patients (P=.02). Other neurologic signs were speech dysfunction and a decreased level of consciousness. Features
that suggest involvement of subcortical central nervous system structures were present in 2 antibody-positive patients (nystagmus, dyskinesias, dystonia, and hypoventilation) and in 2 antibody-negative patients (dyskinesias).
The courses of the 5 antibody-positive patients (mean follow-up, 26 months; range, 15-36 months) are depicted in
Figure 2. Two patients had a relapsing-remitting course
with full recovery between disease episodes. The other 3
patients had only 1 disease episode. Altogether, the 5 patients had 10 disease episodes. Four patients had recovered completely at the most recent follow-up. The remaining patient with left temporal EEG abnormalities improved
slowly but had a residual speech problem at the most recent follow-up, which was potentially aggravated by topiramate therapy.21 For a summary, see Table 1.
Laboratory Findings
These are summarized in Table 2. Patients positive for
NMDAR antibodies more frequently had an elevated CSF
cell count than did antibody-negative patients (5 of 5 vs
2 of 14, P = .02).
Response to Treatment
All NMDAR antibody–positive patients were started on
antiepileptic medication in the first 2 months of epilepsy onset. Despite that, patients 2 and 5 had seizure
relapses. Patients 2, 3, and 5 received corticosteroids or
monthly intravenous immunoglobulins. None relapsed
while undergoing immunotherapies. On the other hand,
patients 1 and 4 were relapse free without ever receiving immunotreatment.
COMMENT
As many as 5 of 19 young women with otherwise unexplained new-onset epilepsies, identified during a 30month period in a single institution had anti-NMDAR encephalitis. In 4 of these 5 patients, no tumor was found
despite thorough investigations (note, however, that follow-up may have been too short to rule out a tumor in
all patients). The same holds true for the additional
NMDAR antibody-positive male patient from the cryptogenic epilepsy control series.
All the patients share many similarities with those found
in the largest available series.7 Our patients had a diffuse
central nervous system syndrome rather than one with a
clear accentuation of temporal lobe dysfunction (compare with limbic encephalitis); none of our patients had
temporomedial MRI abnormalities, and there was CSF pleocytosis. The high frequency of acute psychiatric features
was striking in these patients, and it distinguished them
from antibody-negative patients. Our patients had a favorable outcome, but this did not necessarily depend on
tumor removal or immunotherapy, which also confirms
previous study findings.1,3 Neuropathological findings in
brain biopsy specimens were without distinctive parenchymal inflammatory changes, as in the previous study.1
The present study, however, extends previous observations. To our knowledge, this is the first prospective
series of patients with new-onset epilepsy tested for antibody positivity. The single patient with neoplastic disease did not have an ovarian teratoma but she did have
multiple neuroendocrine tumors with NMDAR expression. Functional ovarian cysts in this age group are sometimes not easily differentiated from tumor cysts; therefore, follow-up investigations in doubtful cases could be
preferable to immediate surgical interventions. In the cryptogenic control series, only 39% were women, which may
diminish its power. However, 1 additional NMDAR antibody–positive patient was detected in this control series (and none among the 11 surgically treated patients
with well-defined, focal, noninflammatory epilepsy): a
22-year-old man without evidence of tumor but an otherwise typical syndrome (similar to a previously reported male patient).4 This additional patient also harbored TPO antibodies, and his disorder was initially
classified as SREAT.17 This diagnosis can now be replaced by the more specific diagnosis of anti-NMDAR encephalitis (an example for the expected reclassification
of patients with SREAT into more specific immunologic
syndromes due to identification of a new diagnostic category with likely uniform pathogenesis22). Samples from
7 patients (5 from the core group and 2 from the control
groups) contained antibodies to hippocampal neuropil,
as evident by immunohistochemical analysis, but only 6
were NMDAR antibody positive. This shows that some
antibodies to hippocampal neuropil react with different
(unknown) antigens. On the other hand, in the core study
group of 19 otherwise unexplained new-onset epilepsies in young females, no NMDAR antibody positivity was
missed by immunohistochemical screening using CSF.
Several questions remain unanswered. Whereas classic
paraneoplastic encephalitis results in tissue loss and irre-
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Table 1. Demographic, Clinical, EEG, MRI, and Tumor Search Data for the 6 Anti-NMDAR–Positive Patients
Patient
No.
EEG
Disease
Age, Duration,
y
y
Seizures
Background
Rhythm
1
18
0.3
3 SGTCSs
Alpha
2
22
0.7
R-sided motor
SPS,
SGTCS
Alpha
3
24
0.3
CPS, R-sided
motor SPS
Alpha
4
44
0.1
CPS
Alpha
5
15
0.9
Head version
to the R,
SGTCS
Theta
Male patient 22
from
control
series
0.5
CPS
Theta
Slowing
Bitemp
theta
L hem
thetadelta
Temporal/
Extratemporal
Epilepsy
Epileptiform
Activity
Gen spike-wave Extratemporal
paroxysms
None
Extratemporal
Neurologic
Signs and
Symptoms
Psychiatric
Signs and
Symptoms
None
None
Aphasia
Depression,
hallucinations
MRI
Findings
Normal
Immunotherapy a
None
Nonspecific
Corticosteroid
hyperintense
pulses, 3-5 g of
WM spots
IV-MP/mo
IVIG, 2 g/kg
bw/mo
Corticosteroid
L temp
None
Extratemporal
Aphasia, Babinski Pathologic crying Normal
pulse, 2.5 g of
and laughter,
periodic
sign R side
IV-MP, followed
grimacing
delta
positive,
by 100 mg of oral
hypoventilation
prednisone/day
for 11⁄2 mo;
thereafter, IVIG,
0.4 g/kg bw/mo
R hem
L temp sharp
Extratemporal
Disturbed vision,
Delusions,
Normal
None
delta
waves
(⫹temporal?)
dysesthesia L side agitation,
of body
depression
Status-related 2nd episode:
Paranoia,
Gen theta R par spikes;
Extratemporal
Stupor,
corticosteroid
regressive
hallucinations,
subsequently,
rotatory/
pulses, 10 g of
bilateral
pathologic
R hem status
downbeat
cortical signal IV-MP/mo, slow
nystagmus, facial crying and
oral
increase
laughter
dyskinesias,
corticosteroid
hypoventilation
tapering
3rd episode: 100
mg/d of slow
oral prednisone,
tapering
Oral prednisone,
Gen theta None
Temporal⫹
Aphasia, mild
Lability of mood, Nonspecific
start with 150
hyperintense
extratemporal
hemiparesis
pathologic
mg/d, plus
WM spots
R side
laughter,
azathioprine, 150
agitation at
mg; prednisone
night,
tapered down
confusion
over 11⁄2 y
Abbreviations: Bitemp, bitemporal; bw, body weight; CPS, complex partial seizure; EEG, electroencephalography; gen, generalized; hem, hemispheric; IVIG,
intravenous immunoglobulin; IV-MP, intravenous methylprednisolone; L, left; MP, methylprednisolone; MRI, magnetic resonance imaging; NMDAR, N-methyl-Daspartate receptor; par, parietal; R, right; SGTCS, secondarily generalized tonic-clonic seizure; SPS, simple partial seizure; status, status epilepticus; temp, temporal;
WM, white matter.
a For the temporal details, see Figure 2.
Table 2. Laboratory Results for the 6 Anti-NMDAR–Positive Patients
Autoantibodies
CSF
Patient
No.
1
2
3
4
5
Male patient
from
control
series
Serum
Standard CSF Variables
IHC Antibodies
to CSF
Undiluted
NR1/NR2
Antibodies
(CSF Titer)
IHC Antibodies
to Serum 1:500
Diluted
NR1/NR2
Antibodies
(Serum Titer)
VGKC,
pmol/L
Onconeural,
ravo blot
TPO,
U/mL
WBC
Count,
µL
Protein,
g/dL
OCB
BBB
Disturbance
Intrathecal
IgG
Synthesis
Hippocampal
neuropil
Hippocampal
neuropil
Hippocampal
neuropil
Hippocampal
neuropil
Hippocampal
and diffuse
neuropil
Hippocampal
neuropil
1:40
Negative
1:50
Negative
Negative
ND
6
0.027
ND
None
None
1:80
Negative
1:400
Negative
Negative
0
21
0.027
Negative
None
None
1:40
Negative
1:200
Negative
Negative
13
21
0.051
Positive
None
None
1:160
Negative
1:800
Negative
Negative
15
6
0.029
Positive
None
None
1:50
Negative
Negative
0
40
0.031
Positive
None
Yes
1:400
Negative
Negative
939
1
0.037
ND
None
None
1:20
1:160
Hippocampal
and diffuse
neuropil
Negative
Abbreviations: BBB, blood-brain barrier (according to Reiber8); CSF, cerebrospinal fluid; IHC, indirect immunohistochemical analysis of sections of perfused rat brain;
Intrathecal IgG synthesis, intrathecal IgG synthesis (according to Reiber8); ND, not done; NMDAR, N-methyl-D-aspartate receptor; OCB, unmatched oligoclonal bands in
CSF; protein, protein content (reference range, ⬍0.050 g/dL); ravo blot, immuno-dot-blot for well-characterized onconeural antibodies (see the “Methods” section);
TPO, thyroid peroxidase (reference range, ⬍40 U/mL); VGKC, voltage-gated potassium channel (reference range, ⬍100 pmol/L; low positive, 100-400 pmol/L; high
positive, ⬎400 pmol/L); WBC, white blood cell (reference range, ⱕ5/µL).
SI conversion factors: To convert protein to grams per liter, multiply by 10.0; WBC count to ⫻109/L, multiply by 0.001.
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versible dysfunction due to T-cell cytotoxicity,11 an antibodymediated pathogenesis seems plausible in anti-NMDAR encephalitis.7 An “NMDA hypofunction hypothesis” may
explain the clinical features.3,23 The demonstration of neuronlike tumor cells expressing NMDAR subunits constitutes a potential (but, given the nonparaneoplastic patients, not necessary) antigenic prerequisite for generation
of the antibodies. Myasthenia gravis and Lambert-Eaton myasthenic syndrome have similarities with the described disorder. Both occur in the paraneoplastic and nonparaneoplastic forms, and both are associated with antibodies to
cell membrane antigens, which are involved in signal transduction.24 In these disorders, too, a nondestructive (at least
reversible) disease process seems to predominate. Finally,
patients with myasthenia gravis and Lambert-Eaton myasthenic syndrome benefit from immunotreatment that
modulates or suppresses B-cell function.25 Similarly, VGKC
antibodies in limbic encephalitis have been proposed to exert a functional and, thereby, potentially reversible effect
on limbic neurons.10 It is interesting that, even in the apparently nonparaneoplastic NMDAR antibody–related syndromes described herein, all the patients were younger than
45 years and predominantly female. This contrasts with patients who have VGKC antibodies associated with limbic
encephalitis or Morvan syndrome, whose median age at the
onset of symptoms is approximately 60 years, with a male
to female ratio of approximately 3 to 2 (A.V., unpublished
data, 2008).
Finally, there is an emerging group of patients with
paraneoplastic and nonparaneoplastic autoimmune encephalitides in association with antibodies to the neuropil of hippocampus.9,26 The target antigens are unknown, but by immunohistochemical analysis, some of
these antibodies closely resemble NMDAR or VGKC antibodies.27 Therefore, confirmation using specific tests
(NR1/NR2 heteromers of the NMDAR and VGKC for immunoprecipitation) is required for appropriate diagnosis. Further investigations of the epidemiologic features, the pathogenesis, and the effective treatment of this
disorder are required.
Accepted for Publication: October 15, 2008.
Correspondence: Christian G. Bien, MD, Department of
Epileptology, University of Bonn, Sigmund-Freud-Str. 25,
53105 Bonn, Germany (christian.bien@ukb.uni-bonn
.de).
Author Contributions: All authors had full access to all
of the data in the study and take responsibility for the
integrity of the data and the accuracy of the data analysis. Study concept and design: Elger and Bien. Acquisition
of data: Niehusmann, Dalmau, Rudlowski, Vincent, Rossi,
and Bien. Analysis and interpretation of data: Niehusmann, Dalmau, Elger, Rossi, and Bien. Drafting of the
manuscript: Niehusmann and Bien. Critical revision of the
manuscript for important intellectual content: Dalmau, Vincent, Elger, Rossi, and Bien. Statistical analysis: Bien. Administrative, technical, and material support: Dalmau, Rossi,
and Bien. Study supervision: Dalmau, Rudlowski, Vincent, Elger, Rossi, and Bien.
Financial Disclosure: None reported.
Funding/Support: This study was supported in part by
grants RO1CA107192 and 2RO1CA89054-06A2 from the
National Cancer Institute, National Institutes of Health
(Dr Dalmau).
Additional Contributions: We thank Andreas Weidhase,
MD, Troisdorf, Germany, for providing the ovarian specimens from patient 4; Albert Becker, MD, Department of
Neuropathology, University of Bonn, for providing the brain
biopsy specimens; and Claudia Ullmann (stainings), Linda
Clover, BSc (VGKC antibodies), and Hannelore Storma (figure assembly) for their expert technical assistance. Dr Bien
thanks Francesc Graus, MD, Barcelona, Spain, for introducing him to the concepts and techniques of autoantibody detection.
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