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Vol. 73, No. 5 May 2014 pp. 403Y413

ORIGINAL ARTICLE

IgG and Complement Deposition and Neuronal Loss in Cats and Humans With Epilepsy and Voltage-Gated Potassium Channel Complex Antibodies Andrea Klang, DVM, Peter Schmidt, DVM, Sibylle Kneissl, DVM, Zolta´n Bago´, DVM, Angela Vincent, MD, Bethan Lang, PhD, Teresa Moloney, PhD, Christian G. Bien, MD, ´ kos Pa´kozdy, DVM, DECVN Pe´ter Hala´sz, PhD, Jan Bauer, PhD, and A

Abstract Voltage-gated potassium channel complex (VGKC-complex) antibody (Ab) encephalitis is a well-recognized form of limbic encephalitis in humans, usually occurring in the absence of an underlying tumor. The patients have a subacute onset of seizures, magnetic resonance imaging findings suggestive of hippocampal inflammation, and high serum titers of Abs against proteins of the VGKC-complex, particularly leucine-rich, glioma-inactivated 1 (LGI1). Most patients are diagnosed promptly and recover substantially with immunotherapies; consequently, neuropathological data are limited. We have recently shown that feline complex partial cluster seizures with orofacial involvement (FEPSO) in cats can also be associated with Abs against VGKC-complexes/LGI1. Here we examined the brains of cats with FEPSO and compared the neuropathological findings with those in a human with VGKCcomplex-Ab limbic encephalitis. Similar to humans, cats with

VGKC-complex-Ab and FEPSO have hippocampal lesions with only moderate T-cell infiltrates but with marked IgG infiltration and complement C9neo deposition on hippocampal neurons, associated with neuronal loss. These findings provide further evidence that FEPSO is a feline form of VGKC-complex-Ab limbic encephalitis and provide a model for increasing understanding of the human disease. Key Words: Cat, Epilepsy, Feline complex partial cluster seizures with orofacial involvement, hippocampal necrosis, Limbic encephalitis, Voltage-gated potassium channel complex.

INTRODUCTION

From the Institute of Pathology and Forensic Veterinary Medicine, Department for Pathobiology (AK, PS), Clinic for Internal Medicine and Infectious Diseases (AP), Diagnostic Imaging (SK), Department for Companion Animals and Horses, University of Veterinary Medicine Vienna, Vienna, Austria; Department of Neuroimmunology (JB), Center for Brain Research, Medical University of Vienna, Vienna, Austria; Austrian Agency for Health and Food Safety (ZB), Institute for Veterinary Disease Control, Mo¨dling, Austria; Department of Clinical Neurology (AV, BL, TM), Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, England; Hospital Mara (CGB), Epilepsy Center Bethel, Bielefeld, Germany; Institute of Experimental Medicine (PH), Budapest, Hungary. Send correspondence and reprint requests to: Jan Bauer, PhD, Center for Brain Research, Department of Neuroimmunology, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria; E-mail: jan.bauer@ meduniwien.ac.at ´ kos Pa´kozdy share senior authorship. Jan Bauer and A The University of Oxford holds patents and receives royalties and payments for antibody assays. Angela Vincent and Bethan Lang receive a share of royalties for VGKC-complex antibodies. Christian G. Bien performs serum and CSF analysis for external centers and his clinic receives fees to cover the costs. Christian G. Bien received travel expenses from the following companies: Eisai, UCB, Desitin, and Grifols; lecture fees from the following companies: Eisai, UCB, GlaxoSmithKline, Desitin, DiaMed, and Fresenius; fees for participation in advisory boards of the following companies: UCB and Eisai. His laboratory research was supported by DiaMed and Fresenius. The remaining authors report no conflict of interest. This work received financial support from the Vicerectorate for Research and International Relations of the University of Veterinary Medicine Vienna (grant no. Pp13011230).

Antibody (Ab)-associated encephalitides have gained much interest in the last few years (1Y3). The Abs can be directed against neuronal intracellular or surface antigens. The ‘‘classical’’ encephalitides with Abs against intracellular or intranuclear antigens, such as Hu, Ma, or Yo, are associated with tumors, and the Abs are not thought to be pathogenic; by contrast, diseases with Abs against surface antigens such as the voltage-gated potassium channel complex (VGKC-complex) or the N-methyl-D-aspartate receptor (NMDAR), as well as other less frequent targets (4, 5), can be both paraneoplastic and nonparaneoplastic (4). The patients often respond well to treatments that reduce the Ab levels (5Y7), suggesting that the Abs are pathogenic (8, 9). However, despite positive responses to treatment, the outcomes of encephalitis with Abs to the VGKC complex are not always optimal and cognitive deficits may remain (10). In recent years, it has been shown that VGKC-complexAbs are mostly not directed to the potassium channel subunits themselves but to proteins that are tightly complexed with VGKCs, specifically leucine-rich, glioma-inactivated 1 (LGI1), contactin-associated protein-like 2 (CASPR2), and contactin-2 (11Y13); Abs specific for LGI1 are the most common. Patients with VGKC-complex/LGI1 encephalitis present with memory loss, confusion, behavioral changes, and seizures. A novel form of seizure, termed faciobrachial dystonic seizures, may precede the limbic encephalitis (LE) or be noted during the illness (14). The patients respond well to plasma exchange and steroids, suggesting that the Abs to the VGKC-complex/ LGI1 are indeed responsible for the clinical signs (5, 15).

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404

Animal No. Age (y) Sex (f/m) FEPSO 1 10 f 2 7 f 3 7 m 4 ad f 5 2 f 6 2 f 7 3 m 8 1 m 9 14 f 10 2 m 11 6 m 12 11 f 13 1 f 14 7 m 15 12.8 f Average Epileptic controls 16 3 f 17 8 f 18 1 m Average Encephalitic controls 19 0.4 f 20 1 f 21 10 f 22 3 m 23 4.3 f Average Normal feline controls 24 ad f 25 0.6 m Average Human VGKC encephalitis as described VGKC/3 59 m FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO FEPSO

Seizures/HS Seizures/HS Seizures/HS

FIP FIP TOX TOX TOX

CON CON

ESH ESH ESH ESH ESH ESH Siam ESH ESH ESH ESH ESH ESH ESH ESH

ESH Car ESH

Main ESH ESH ELH ESH

Ben BSH in Bien et al (3) NA VGKC encephalitis

Diagnosis

Breed

Unknown

ND ND

ND ND ND ND ND

ND ND ND

Anti-EP + cort Anti-EP + cort Anti-EP + cort No tx Anti-EP Anti-EP Anti-EP Anti-EP Anti-EP Anti-EP No tx No tx Anti-EP No tx Anti-EP + cort

Therapy Summary

5m

0d 0d

4d Unknown 10 d 7d 33 d

7d 3d 23 d

5d 30 d 89 d 2d 8d 10 d 3d 49 d 91 d 2 y 10 m 4m Unknown 6d 3d 90 d

Disease Duration

ND

ND ND

ND ND ND ND ND

ND ND ND

ND HN Normal ND ND ND ND ND ND ND ND ND ND ND HN

MRT

958/ND

ND ND

ND ND ND ND ND

ND ND ND

123/ j 443/ + 791/ + 24/ND ND ND ND ND ND ND ND ND ND ND 686/+

VGKC (pmol/L) /LGI1

13.2

0.0 0.0 0.0 T 0.0

0.4 5.6 4.9 1.3 0.2 2.4 T 1.2

89.4 44.8 3.3 46 T 25

16.7 0.4 0.1 2.4 4.4 5.5 0.9 4.2 1.1 0.5 2.1 0.1 1.2 0.9 2.9 2.9 T 1.1*

CD3 (Cells/ mm2)

4.4

0.0 0.0 0.0 T 0.0

0.0 0.0 0.0 0.0 0.0 0.0 T 0.0

0.0 0.0 0.0 0.0 T 0.0

7.0 3.4 0.0 0.4 2.2 2.3 0.2 0.3 15.6 38.0 0.0 47.2 3.4 2.1 6.9 8.6 T 3.7†

C9neo (Cells/mm2)

1

0 0

0 0 0 0 0

2 3 0

1 1 0 1 1 1 1 1 1 1 0 1 1 1 1

C9neo Pattern

2.0

0.0 0.0 0.0 T 0.0

0.0 0.0 0.0 0.0 0.0 0.0 T 0.0

0.4 10.0 0.0 3.5 T 3.3

8.3 13.8 0.0 3.0 15.7 6.3 16.8 10.6 29.5 22.8 0.3 15.1 2.9 4.2 0.0 10.0 T 2.3‡

TUNEL (Cells/ mm2)

5

0 0

0 0 0 0 0

4 3 3

4 5 0 3 4 4 4 5 5 5 4 4 5 4 4

Neuronal Loss

TABLE. Summary of Results in the Hippocampal Region of Cats With Feline Complex Partial Cluster Seizures With Orofacial Involvement, Seizures and Hippocampal Sclerosis, Encephalitic and Normal Feline Controls, and a Human Case of Voltage-Gated Potassium Channel AntibodyYAssociated Encephalitis

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Age: ad, adult. Sex: f, female; m, male. Breed: Ben, Bengal cat; BSH, British shorthair cat; Car, Carthusian cat; ELH, European longhair cat; ESH, European shorthair cat; Main, Main coon cat; Siam, Siamese cat; NA, not applicable. Diagnosis: Seizures/HS, acute seizures and hippocampal sclerosis; FIP, feline infectious peritonitis; TOX, toxoplasmosis; CON, control. Therapy summary: no tx, no treatment; anti-EP, anti-epileptic treatment; anti-EP + cort, anti-epileptic treatment and corticosteroids. Disease duration: d, days; m, month; y, years. MRT: magnetic resonance tomography; ND, not performed; HN, hippocampal necrosis. VGKC: anti-VGKC titer based on routine immunoprecipitation. LGI1: LGI1 status based on indirect immunofluorescence, þ: positive, j: negative. Pathology: CD3: *, Number of CD3-positive T cells in the hippocampus was significantly lower in FEPSO versus epileptic controls (p = 0.027). No difference was found between FEPSO and encephalitic controls. C9neo (cells/ 2 mm ): †, C9neo-positive hippocampal neurons were significantly higher than in epileptic (p = 0.019) and encephalitic controls (p = 0.003). C9neo pattern: 0, no deposition; 1, deposition as a punctate staining on neurons and processes; 2, parenchymal deposition of C9neo around a large focal inflammatory lesion; 3, C9neo deposition in the walls of blood vessels. TUNEL: TUNEL-positive neurons were quantified in the hippocampus. ‡, No difference in TUNEL-positive neurons was found between FEPSO and epileptic controls but FEPSO animals showed significantly more TUNELpositive neurons than encephalitic controls (p = 0.024). Neuronal loss: Neuronal loss was scored in each region, resulting in a cumulative score of 0 (no cell loss) to 5 (neuronal loss in all 4 hippocampal regions and dentate gyrus). FEPSO, feline complex partial cluster seizures with orofacial involvement; VGKC, voltage-gated potassium channel.

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Whereas LE and the ensuing hippocampal atrophy (i.e. hippocampal sclerosis) in humans has been noted for some time, the association between hippocampal necrosis (HN) and temporal lobe epilepsy in cats has been shown in a relatively low numbers of cases (16Y20). However, a subgroup of cats with temporal lobe epilepsy displayed feline complex partial seizures with orofacial involvement (FEPSO) (21, 22). Our recent investigations revealed that many of these animals, in addition to facial involvement, have VGKC-complex/LGI1 Abs (23). Therefore, FEPSO in cats has much in common with human VGKC-complex-Ab encephalitis including faciobrachial dystonic seizures (14). The neuronal damage in VGKC-associated encephalitis cases seems to be caused, at least partly, by complementmediated mechanisms. In a comparison of 4 VGKC-associated encephalitis patients with other forms of encephalitis, there were low to moderate T-cell infiltrates but gliosis and activated microglia in the hippocampi with neuronal loss. Strikingly, in hippocampal areas with acute neuronal cell death, there was also evidence of immunoglobulin on the surface of neurons and deposition of complement C9neo, indicating functional complement activation (3). The aim of the present study was to investigate immunopathological mechanisms in cats with FEPSO and compare them with human VGKC encephalitis. We found that the cat brain shared many histopathological features with human VGKC-complex-Ab encephalitis including selective complement deposition in neurons and neuronal loss.

MATERIALS AND METHODS Animals Fifteen cats with clinical FEPSO and HN were included in this study. Except for 2 cats that died spontaneously, all animals were killed between 2 days and 34 months of onset of neurological signs because of resistance to therapy or severe clinical course. Therapy of cats consisted of standard antiepileptic treatment with phenobarbital, gabapentin, levetiracetam, or potassium bromide or combination. In addition, 4 cats were treated with prednisolone 1 to 2 mg/kg twice daily (Table). For controls, we used 3 cats with epileptic seizures that did not fit the classification of FEPSO (21) and hippocampal sclerosis. We also selected a group of cats with inflammation of the brain in the absence of seizures (Encephalitic controls): 2 cats suffered from cerebral manifestations of feline infectious peritonitis and 3 cats had Toxoplasma gondiiYassociated encephalitis. In addition, 2 previously healthy cats that died unexpectedly during anesthetic procedures served as normal controls. Further epidemiologic data of these animals are presented in the Table.

Human Anti-VGKC Encephalitis For comparison with the human disease, we used brain tissue from a patient with LE (VGKC/2) with a high titer (958 pmol/L) of VGKC-complex-Ab described in our previous study (3). This case was chosen for 3 reasons. First, this case had the shortest disease duration (5 months). Second, whereas this case is autopsy material containing a complete cross section of the hippocampus, the other 3 cases were biopsies

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consisting of small pieces from the amygdala and uncus. Third (as seen in terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL] staining of all our cases), this case showed the most active neuronal degeneration associated with IgG and complement deposition.

in paraffin, transverse sectioned, and stained by hematoxylin and eosin and Nissl stains. Immunohistochemistry was performed as shown previously (3) at the level of the hippocampus using Abs against cat immunoglobulin (Jackson Immunoresearch, West Grove, PA), C9neo (rabbit-anti-rat; kind gift from S. Piddlesden, University of Cardiff, UK), T lymphocytes (anti-CD3; Labvision, Fremont, CA), a marker for microglia and macrophages (Iba-1; Wako, Osaka, Japan), and astrocytes (antiYglial fibrillary acidic protein; Dakopatts, Hamburg, Germany). Neurons were immunostained with an Ab to microtubule-associated protein 2 (MAP-2; Sigma, St. Louis, MO). To obtain information about cell death pathways in neurons, sections were stained for activated caspase 3 (detects caspase-dependent apoptosis in cells; CM1, Becton Dickinson, San Diego, CA).

Magnetic Resonance Imaging Magnetic resonance imaging (MRI) was performed on 3 cats (Table) with FEPSO using a 1.5-T unit (high-field MRI; Magnetom Espree, Siemens Healthcare, Erlangen, Germany) in sternal recumbency under general anesthesia, with the head in a 15-channel transmit extremity coil. Imaging included transverse T2-weighted 3-dimensional spin echo images (remission time [TR] = 3000Y5370 ms/ echo time [TE] = 111Y388 ms) and T1-weighted 3-dimensional spin echo images (TR = 450Y501 ms/TE = 12Y17 ms), with multiplanar reformatting features, transverse T2*-weighted gradient echo images (TR = 500 ms/TE = 39 ms; flip angle = 10 degrees), and transverse T2-weighted FLAIR (TR = 8500 ms/TE = 82 ms) images. T1-weighted images were re peated after intravenous administration of gadobenate dimeglumine (MultiHance; Bracco ¨ sterreich GmbH, Vienna, Austria) at a dosage of 0.15 mmol/kg O body weight. Slice thickness was 0.8 to 3 mm, and slice separation was 0.1 to 0.8 mm.

Serology Anti-VGKC Abs were assayed in 5 cats with FEPSO by routine immunoprecipitation of VGKC-complexes from rabbit brain extracts as described (5) and were applied for the diagnosis of LE in humans and previously implemented in cats (23). VGKC-complex-Ab positive sera were also tested for binding to LGI1 and CASPR2 using cell-based assays (14). Abs to glutamic acid decarboxylase (GAD) were measured by radioimmunoprecipitation (RSR Ltd, Cardiff, UK). Feline-specific secondary Abs were used as appropriate.

Neuropathology and Immunohistochemistry A general necropsy was performed in all animals. Brains were fixed in 4% neutral-buffered formalin, embedded

TUNEL Qualitative assessment of chronic cell loss was conducted in stained transversal sections at the level of the hippocampus. For the detection of cells with DNA fragmentation, TUNEL staining was performed with the In Situ Cell Death Detection Kit (Roche, Basel, Switzerland) according to Bien et al (3). This was followed by immunohistochemical staining for MAP-2 to identify dying neurons. TUNEL was developed with Fast Blue (Sigma); MAP-2 was developed with 3-amino9-ethylcarbazole (Sigma) as a substrate.

Quantitative and Semiquantitative Scoring Quantification of CD3-positive T cells, C9neo-positive neurons, and TUNEL-positive neurons was performed in hippocampal sections using an ocular morphometric grid covering an area of 1 mm2 at 100 magnification. Numbers of counted cells were divided by the total volume of hippocampal area measured, leading to numbers of cells per squared millimeter (Table). For semiquantitative scoring of chronic neuronal loss in NeuN-stained hippocampal sections, the hippocampus was divided into 5 regions: CA1, CA2, CA3, CA4, and dentate gyrus. Neuronal loss was scored in each region, resulting in a

FIGURE 1. Magnetic resonance imaging (MRI), serology, and neuropathology of cats with feline complex partial cluster seizures with orofacial involvement (FEPSO). Numbers in parentheses indicate the animal number as designated in the Table. (A) T1 with contrast MRI of the brain showing an increase in T1 signal after contrast and an increase in volume of the hippocampi (arrowheads) and surrounding areas. (BYD) Enhanced green fluorescent protein expression of leucine-rich, glioma-inactivated 1 protein (LGI1)transfected cells (B) and staining of antibodies from cat serum (C). Merged images (D) showing binding of cat immunoglobulins to LGI1-expressing cells. (EYL) Double staining for deoxynucleotidyl transferase dUTP nick end labeling (TUNEL, blue) and microtubule-associated protein 2 (MAP-2)Ypositive neurons (red). (E) Hippocampus from a control cat showing dense MAP-2 immunoreactivity. (F) Higher magnification of (E) showing cells in the dentate gyrus (DG) and CA4 region of the hippocampus. (G) Hippocampus from a cat with FEPSO (Case 8) showing variable cell loss in various areas of the hippocampus. MAP2Yimmunoreactive neurons are completely lost in the CA4 region. The rectangles indicated by 1 and 2 are shown at higher power in (H) and (I), respectively. (H) Higher magnification showing cell loss in the CA2 region of the hippocampus. Arrowheads point at TUNEL-positive (blue) nuclei of dying neurons. (I) Higher magnification of the CA3 region showing numerous TUNEL-positive neuronal nuclei and some remaining MAP-2Ypositive neurons and processes. (JYN) TUNEL and MAP-2 double staining of the hippocampus of another cat (Case 2) with FEPSO. (J) Distinct loss of neurons and fibers (arrowheads) in the dentate gyrus. (K) Enlargement of (J) showing numerous TUNEL-positive nuclei and loss of MAP-2Ypositive processes in the dentate gyrus and CA4 region. The rectangle indicates an area enlarged in (L) showing another higher magnification of numerous TUNEL-positive neurons in the dentate gyrus. (M) Hematoxylin and eosin staining showing neurons with eosinophilic cytoplasm and necrosis-like chromatin fragmentation into numerous speckles. (N) Caspase-3 staining in the degenerating hippocampal areas showing a small positive apoptotic cell (arrow) but absence of caspase-3 in neurons (arrowheads). The inset shows an enlargement of the apoptotic cell in which nuclear fragmentation (arrowhead) can be recognized. Scale bars = 1 cm (A); 100 Hm (BYD, F, L); 1 mm (E, G, J); 50 Hm (H, I); 250 Hm (K); 100 Hm (L); 10 Hm (M); 20 Hm (N). Ó 2014 American Association of Neuropathologists, Inc.

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Feline Temporal Lobe Epilepsy Neuropathology

cumulative score of 0 (no neuronal cell loss) to 5 (neuronal loss in all regions).

formed in the 5 FEPSO cats with sera available. In 4 of these cases, VGKC-complex Abs were detected above the control range for humans (9100 pmol/L). Three of the 4 VGKCcomplex Ab-positive cats also were positive for Ab to VGKCcomplex protein LGI1 (Fig. 1BYD; Table). None of the 5 cats had anti-GAD or -CASPR2 Abs. The human VGKC encephalitis case used for comparison was positive for the anti-VGKCcomplex Ab at a titer of 958 pmol/L, and the presence of anti-LGI1 or -CASPR2 Abs was not determined in this case (Table).

Statistics Statistical evaluation was performed with Statgraph Prism 6. For the evaluation of numbers of CD3-positive T cells, C9neo-positive neurons, and TUNEL-positive neurons, a 2-sided Mann-Whitney U test was used. A p value of G0.05 was considered significant.

RESULTS Epileptic Seizures in Cats With FEPSO Seizures in cats were preceded by short episodes of unusual behavior with motionless staring (motor arrest), often in a sitting position. The seizures typically had an acute onset with confusion and characteristic orofacial signs such as facial twitching, excessive salivation, lip smacking, chewing, licking, and swallowing. Other signs observed included mydriasis, secondary generalized seizures, vocalization, and defecation. In addition, most cats showed behavioral changes such as fear or aggression. The 3 epileptic control animals (Table, Cases 16Y18) demonstrated epileptic seizures not fitting FEPSO and other neurological signs such as circling and head tremor.

MRI Only 3 animals had been screened by MRI. Cats with HN and clinical FEPSO-like epileptic seizures commonly show intense enhancement of T2 or T1 with contrast in the hippocampus and surrounding structures, as shown for Case 15 (Fig. 1A). Case 2 had a moderate bilateral increase of volume and T2 signal of the hippocampal region. The T1 signal was slightly decreased but increased after intravenous injection with gadobenate dimeglumine. Case 3 showed no abnormalities and bilaterally symmetric hippocampal volumes and signal.

Serology Assays for Abs to VGKC-complex, the VGKCcomplex proteins LGI1 and CASPR2, and GAD were per-

Brain Pathology Acute Neuronal Cell Death and Loss The human VGKC-complex encephalitis case (previously described in detail [3]) showed clear loss of neurons in all hippocampal subfields (Table). No gross lesions were evident in the brains of the 15 cats with FEPSO at necropsy. Histopathological examination demonstrated that lesions were present and usually distributed bilaterally in the hippocampi. In most cases, neuronal loss was evident in 1 or more of the 4 hippocampal subfields (Fig. 1GYI). In addition, a few cases showed degeneration and cell loss in the dentate granule cell layer (Fig. 1JYL). In single cases, extrahippocampal pathological changes were found in adjacent areas such as the entorhinal cortex, subiculum, parahippocampal gyrus, temporal cortex, basal ganglia, and diencephalon. Hippocampal neuronal degeneration was also present in all epileptic controls (Table). In addition, Case 16 of these controls showed degeneration in the neocortex. Neuronal degeneration was not evident in encephalitic and normal control animals (Table). Acute neuron death was demonstrated by double staining for TUNEL and MAP-2. No TUNEL reactivity in the hippocampus was found in normal or encephalitis controls (Fig. 1E, F); however, 2 of 3 epileptic control cases showed the presence of TUNEL-positive neurons (Table). In the hippocampi of the 15 investigated FEPSO cases, there were on average 10 TUNEL-positive neurons/mm2 hippocampus detected. This number of degenerating cells in FEPSO animals was comparable to the numbers of TUNEL-positive cells in the human VGKC-complex encephalitis patient (Table). The number of

FIGURE 2. Immunopathology of feline voltage-gated potassium channel complex (VGKC-complex) encephalitis in cats with feline complex partial cluster seizures with orofacial involvement (FEPSO) and comparison with human VGKC encephalitis. (A) Staining for CD3 showing perivascular cuffs and parenchymal infiltration of T cells (arrowheads) in the hippocampus of a cat with FEPSO. (B) Perivascular cuff of the brain of a cat with FEPSO immunostained for CD3. There are CD3-positive and CD3-negative lymphocytes. (C) The same cuff as shown in (B) immunostained for CD20 showing that some of the lymphocytes are B cells (arrowhead). (D) Hippocampus of a patient with VGKC encephalitis stained for CD3 showing parenchymal infiltration of T cells. (E) Staining for Iba-1 showing resting microglial cells in control (CON) cat hippocampus. (F) In a cat with FEPSO with neuronal damage Iba-1Ypositive microglia are activated. (G) In a human VGKC encephalitis brain, microglia show activation and upregulation of Iba-1. (HYJ) Staining for glial fibrillary acidic protein (GFAP) showing normal astrocytes in a control cat hippocampus, (H) while in the hippocampus of a cat with FEPSO, there is astrocyte activation and gliosis (I). There is also marked astrogliosis seen in the human VGKC encephalitis brain (J). (K) Immunostaining for cat immunoglobulin revealing the presence of plasma cells (arrowheads) in the perivascular cuffs of the brain of a cat with FEPSO. (L) Immunoglobulin staining of the dentate gyrus of a cat with FEPSO showing leakage of immunoglobulin in the parenchyma and uptake by neurons (arrowheads). (M) In some areas, immunoglobulin deposition is on neuronal membranes (arrowheads). (N) Similar membrane staining for immunoglobulin (black arrowheads) on neurons can also be found in the hippocampus of human VGKC encephalitis brain. In addition, the blue arrowhead points at a parenchymal plasma cell. (OYQ) Staining for C9neo. The hippocampus of a cat with FEPSO showing C9neo staining of almost all neurons of the CA1/CA2 region (O). In a higher magnification of the CA1 region, there is C9neo deposition in a granular pattern in neuronal cell bodies and processes (P, arrowheads). Staining of C9neo in the hippocampal neurons of a human VGKC encephalitis patient (Q, arrowheads) looks identical to the C9neo deposition of neurons in cat FEPSO hippocampus. Scale bars = 100 Hm (A, J); 50 Hm (BYI, N); 25 Hm (KYM, P, Q); 200 Hm (O). Ó 2014 American Association of Neuropathologists, Inc.

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TUNEL-positive cells in FEPSO animals did not differ from that in epileptic controls but was significantly higher than TUNEL-positive cells in the encephalitis group. Among the FEPSO animals, the extents of acute neuronal cell death were highly variable; some animals showed single TUNELpositive neurons spread over the hippocampus, whereas others showed large numbers of TUNEL-positive neurons in distinct parts of the hippocampus (Fig. 1GYL). In all cases, TUNEL reactivity in neurons was associated with loss of MAP-2Yimmunoreactive processes (Fig. 1H). Degenerating neurons showed eosinophilic cytoplasm and chromatin fragmentation into fine speckles (Fig. 1M), as shown in ischemic rat hippocampi (24). Staining for the activated form of caspase-3 revealed the presence of small apoptotic cells, often with apoptotic bodies (Fig. 1N). Caspase-3 was not detected in neurons (Fig. 1N). In summary, although we cannot

exclude the possibility that single neurons undergo apoptosis, the findings suggest that the bulk of degenerating neurons follow necrosis-like cell death rather than caspase-mediated apoptosis (24). Neuron alterations in the FEPSO group were accompanied by moderate to severe astrogliosis as demonstrated by glial fibrillary acidic protein immunostaining (Fig. 2I); in all but 1 case, this was comparable to that in human VGKC encephalitis (3) (Fig. 2J). Astrogliosis was absent in control animals (Fig. 2H), but moderate to severe astrogliosis was also seen in the epileptic and encephalitic control groups.

Inflammation CD3 immunohistochemistry in cats with FEPSO demonstrated that T cells comprised the majority of inflammatory cells. T cells were either localized in meninges only, in

FIGURE 3. Complement C9neo expression in hippocampus of controls (CON), feline complex partial cluster seizures with orofacial involvement (FEPSO), and epileptic controls. Numbers in the panel labels indicate the animal number as shown in the Table. (A) A control animal showing no C9neo expression. (B) C9neo expression in the hippocampus of FEPSO cat. There is strong deposition in hippocampal CA2 and CA3 neurons (inset shows higher magnification). (C) In an epileptic control animal, there is a different (fiber-like) expression pattern around a focal inflammatory lesion. (D) In an epileptic control animal, there is intense C9neo deposition in the walls of blood vessels (bar = 200 Hm). Insets in C and D show higher magnifications. Scale bars = 200 Hm (AYD).

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Feline Temporal Lobe Epilepsy Neuropathology

perivascular cuffs, and/or diffusely infiltrating the parenchyma (Fig. 2A, B). Parenchymal T-cell infiltration in most cases was moderate and on average (2.9 cells/mm2 hippocampus) somewhat lower than the T-cell infiltration in the case of human VGKC encephalitis (13.2 T cells/mm2 hippocampus) (3) (Table and Fig. 2D). Unexpectedly, T-cell numbers in the FEPSO cats were significantly lower than those in epileptic controls (p = 0.027) and did not differ from the encephalitic control cats (Table). No T cells in FEPSO animals were found in apposition to neurons. Except for 1 cat with prominent perivascular infiltrates in the brain (and which displayed papillary adenomas in the lung (Case 1), tumors were not found in any cases. In addition to T cells, perivascular cuffs also contained CD20-positive B cells (Fig. 2C); immunoglobulin staining also showed moderate numbers of plasma cells (Fig. 2K). In all cases, most B cells and plasma cells were confined to the perivascular space; this was also the case in the epileptic and encephalitic controls. FEPSO animals (Fig. 2F), encephalitic and epileptic controls, and the human VGKC encephalitis case (Fig. 2G) all showed strongly activated microglia (i.e. with rounded morphology and shorter and thicker ramifications), as compared to normal feline controls (Fig. 2E).

showed marked inflammation, but C9neo was only present in the walls of blood vessels (Fig. 3D).

Immunoglobulin and Complement Deposition In normal animals, immunoglobulin staining was confined to the lumen of blood vessels (not shown). In FEPSO, epileptic, and encephalitic control animals, staining for immunoglobulin revealed substantial leakage through the blood-brain barrier (BBB). Diffuse immunoglobulin immunoreactivity in the parenchyma was seen on various cell types including neurons (Fig. 2L), astrocytes, and, in some cases, cells with oligodendrocyte or microglial cell morphology. Because of diffuse leakage of immunoglobulins, it was difficult to detect specific staining on the surface of neurons in cats with FEPSO. In some places, however, membranous deposition of immunoglobulins was present (Fig. 2M), which was also seen in the human VGKC-complex-Ab patient (Fig. 2N). We have previously shown that human VGKC encephalitis cases show C9neo deposition in and on the surface of neurons (3). Here, in addition, we counted C9neo-positive cells in the hippocampus of selected VGKC encephalitis case; 4.4 cells/mm2 are positive for C9neo (Table). As in human VGKC encephalitis, C9neo immunostaining revealed a punctate staining both inside and on the surface of neuronal cell bodies and their processes in FEPSO animals (Figs. 2O, P and 3B). This complement deposition was seen in 13 of the 15 FEPSO cases (on average, 8.6 positive neurons/mm2), including the 3 cats with Abs to LGI1 (Table and Fig. 3B). No deposition of C9neo on neurons was found in the 2 remaining cases or in the encephalitic and normal controls (Fig. 3A and Table). In 2 of the 3 epileptic control cases (Cases 16 and 17), the C9neo staining pattern was also positive but located in different compartments and cells: Case 16 displayed strong C9neo immunostaining of the hippocampal parenchyma around a large inflammatory confluent lesion that mainly consisted of lymphocytes and large amounts of activated microglial cells/macrophages (Fig. 3C). Case 17 also

DISCUSSION It has been recognized only recently that feline FEPSO, which often requires euthanasia, is likely to be pathogenically related to the form of human LE that occurs with VGKCcomplex/LGI1 Abs. The presence of these Abs in a proportion of the cats (23) suggests that (like human patients) they may respond clinically to immunotherapies. In the meantime, the existence of postmortem tissue from these animals provides an opportunity to examine the pathology and to compare with the limited material available on the human disease. The results here demonstrate that, in most cases, the immunopathology is dominated by hippocampal neuron loss with relatively mild T cell infiltrates but with substantial IgG and complement deposition. These data suggest that FEPSO is an Ab-mediated disease and add support to the similar findings in the human disease. HN in cats has been described in a number of studies. Supposed etiologies of this type of pathology include secondary epilepsy due to pyriform lobe oligodendroglioma (25), ischemia (26), anesthetic procedures (27), stroke (28), and toxins such as kainic acid (29), whereas causative agents such as feline leukemia virus and feline immunodeficiency virus infections were ruled out (16Y18, 20). In many studies, the etiology of feline HN was not defined (16Y18). Recently, we described a specific type of temporal lobe epilepsy with complex partial cluster seizures with orofacial involvement in cats (FEPSO) (21). The neuron loss and astrogliosis shown here resemble the pathology of feline HN described in the literature to date (16, 17, 20). In addition, we also demonstrate lymphocytic infiltrates in the hippocampus and other regions. These infiltrates contain not only T cells, but also numerous B cells and plasma cells, particularly in the perivascular cuffs. Thus, FEPSO animals have inflammation that is similar to the inflammation in human VGKC encephalitis (3, 30Y32). It can be presumed that some of the idiopathic feline cases of HN reported previously might be associated with VGKC Abs. In humans, LE has traditionally been considered to have a paraneoplastic etiology, but in the last 10 years, it has become clear that patients can have this condition in the absence of tumors, particularly when the LE is accompanied by Abs to the VGKC-complex proteins (5, 13). The most common tumors associated with LE in humans are small cell lung cancer and thymomas (5). Except for Case 1 with pulmonary adenomas, tumors have not been associated with feline HN. Therefore, it is unlikely that paraneoplastic processes are a major cause of the syndrome in cats. The fact that we could study a relatively large number of cases of FEPSO with HN, however, shows that this type of LE may (as in humans [5]) be quite frequent (5); thus, further testing of cats with these seizures could be informative. Unfortunately, in our study, MRI was available from only 3 cats. At the time of MRI, the brain of Case 3 with FEPSO appeared normal, whereas the images of the other cats showed bilateral symmetric hippocampal T2 hyperintensity with contrast intake, indicative of inflammation. In humans,

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MRI findings in VGKC-complex Abs and encephalitis typically demonstrate signal changes in the medial temporal lobes ranging from hippocampal swelling with T2/FLAIR signal increase to hippocampal atrophy. Usually later in the disease, with wider Ab testing, it has become clear that many patients do not show MRI changes at presentation (3, 5). In cats with FEPSO, hippocampal atrophy has not been demonstrated by MRI so far. Probably, this is because the limited anatomic resolution of hippocampal structures in cats makes changes of hippocampal size less evident. Previous testing of sera from animals with FEPSO showed that, in the acute stage of their disease, 36% of these animals had IgG Abs to the VGKC-complex (23). Here, 5 FEPSO animals were available for serological testing, 4 of these were positive for VGKC-complex-Abs and 3 had LGI1 antibodies. The titers of anti-VGKC-complex Abs of these FEPSO cases ranged from 123 to 791 pmol/L, which is only slightly less than the titer in the human case. Therefore, findings in cats are comparable to human patients in whom titers of VGKC-complex Abs may fluctuate. Furthermore, not all Abs against the VGKC-complex also bind to the presently known specific antigens (i.e. LGI1, CASPR2, or Contactin-2) (23). This is also similar to human VGKC encephalitis, where in approximately 80% of the cases the Abs to the VGKCcomplex do not bind to these antigens (13). Thus, it is likely that other antigens are part of the VGKC-complex and need to be identified in both cats and humans. It has been shown that human VGKC encephalitis responds relatively well to immunotherapy such as hemapheresis or corticosteroid treatment (14, 15, 33Y35). Moreover, preliminary evidence suggests that earlier therapy is related to better outcome (14, 34), and that more intense therapy combining immunosuppression with apheresis may be more effective than only monthly pulse methylprednisolone therapies (6, 15). In the present study, some cats were treated with corticosteroids but did not go into remission. Such treatments can, however, reduce VGKC-complex Ab titers (23); moreover, the treated cats in which Abs disappeared went into remission. The reason why some patients respond poorly or are left with clinical deficits (10) might be explained by the massive degeneration found in some brains. Both in human and cat brains, complement deposition on neurons was associated with massive neurodegeneration (3). Our results in cats show that loss of large numbers of degenerated hippocampal neurons can be detected within the first week of disease duration. This degeneration probably leads to functional deficits that cannot be reversed by lowering the Ab titers by immunotherapy. This is clearly different from NMDAR encephalitis in which no clear degeneration is found in most cases (3, 36); the Abs bind to NMDARs but do not seem to engage in complement-mediated destruction of neurons (3, 7, 37Y39). Neuronal loss and acute cell death in the FEPSO cats was accompanied by mild to moderate astrogliosis and activation of microglial cells. Both the chronic loss and the acute cell death detected by TUNEL were highly variable in the hippocampus but similar to that in humans (3). As in human VGKC encephalitis, FEPSO brains showed diffuse staining of immunoglobulin within neural cells, perhaps due to BBB leakage and uptake into neurons. However, in some areas, the

immunoglobulin was detected on the surfaces of neurons, from which the IgG may be internalized as a result of crosslinking of the antigen, as is seen in other diseases such as myasthenia gravis (40) and NMDAR-Ab encephalitis (41). Most importantly, however, we detected C9neo staining, which indicates functional activation of the complement cascade, inside and on the hippocampal neurons of 13 of the 15 FEPSO cases. In particular, Case 1 (which was only of 5 days in duration), had strong C9neo deposition. On the other hand, for unknown reasons, Case 3 with a duration of 89 days and the highest VGKC-complex-Abs (including LGI1) did not show any hippocampal pathology. We hypothesize that Case 1 with low VGKC-complex-Abs and no identified serum Abs to LGI1 or CASPR2 provides a picture of the earliest stages of the acute disease as it develops and that further changes seen later in the other cases differ depending on factors that modify the natural history of the disease. Another possible explanation for the lack of correlation between serology and histopathology may be the different time of examination. Serology was usually carried out at the beginning of the disease and not just before the autopsy. In Case 3, more than 2 months passed between the start of acute LE and accompanying harvesting of serum, and despite corticosteroid treatment, there was development of hippocampal sclerosis and therapy-resistant epilepsy. Overall, the presence of C9neo-positive neurons in the hippocampus of FEPSO animals is a specific feature that is shared with human VGKC-complex encephalitis (3) and clearly separates the FEPSO cases from the epileptic and encephalitic controls animals. The presence of C9neo-positive neurons also separates the VGKC encephalitis cases from other Ab-associated encephalitides such as NMDAR encephalitis (3). An important question in Ab-associated encephalitides that is still unanswered is the question about the initiating event. Both in humans and in cats, VGKC-complex Ab encephalitis can present with fever (21), suggesting a prodromal infection (5, 13). Such a prodromal infection may, via the mechanism of molecular mimicry, generate a pathogenic Ab. However, so far, a specific infectious organism has not been identified in cats or humans, thus arguing against a direct role for molecular mimicry (1). Alternatively, infection with a viral or microbial agent may induce encephalitogenic T cells and trigger a systemic innate immune response that may be sufficient to disrupt BBB integrity (42, 43) and allow the efflux of the serum-predominant Ab into the CSF and brain parenchyma (44). In conclusion, our findings may be helpful for improving diagnostic procedures such as serological testing and optimizing therapy in cats with FEPSO. In particular, immunotherapies may prove to be worthwhile and more effective than standard antiepileptic treatments. The similarities of FEPSO with the human disease extend to the immunopathology, in particular, to the specific presence of complement C9neo deposition on hippocampal neurons. As judged from an epilepsy surgery-based tissue bank (45), encephalitic brain lesions are a rare, specific cause of human epilepsies; similarly, in cats, the lesions described here are not a common finding in feline epilepsy. Further investigations in the nature of these specific well-defined conditions should therefore prove of benefit to the study of intractable seizures and LE in both feline and human patients.

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Feline Temporal Lobe Epilepsy Neuropathology

ACKNOWLEDGMENTS The authors thank Ingrid Friedl, Marianne Leisser, Ulrike Ko¨ck, and Angela Kury for skilled technical assistance and Klaus Bittermann for excellent photographic work.

23. Pakozdy A, Halasz P, Klang A, et al. Suspected limbic encephalitis and seizure in cats associated with voltage-gated potassium channel (VGKC) complex antibody. J Vet Int Med 2013;27:212Y14 24. Muller GJ, Stadelmann C, Bastholm L, et al. Ischemia leads to apoptosisand necrosis-like neuron death in the ischemic rat hippocampus. Brain Pathol 2004;14:415Y24 25. Vanhaesebrouck AE, Posch B, Baker S, et al. Temporal lobe epilepsy in a cat with a pyriform lobe oligodendroglioma and hippocampal necrosis. J Feline Med Surg 2012;14:932Y37 26. Schmidt-Kastner R, Ophoff BG, Hossmann KA. Pattern of neuronal vulnerability in the cat hippocampus after one hour of global cerebral ischemia. Acta Neuropathol 1990;79:444Y55 27. Jurk IR, Thibodeau MS, Whitney K, et al. Acute vision loss after general anesthesia in a cat. Vet Ophthalmol 2001;4:155Y58 28. Altay UM, Skerritt GC, Hilbe M, et al. Feline cerebrovascular disease: Clinical and histopathologic findings in 16 cats. J Am Anim Hosp Assoc 2011;47:89Y97 29. Tanaka T, Kaijima M, Daita G, et al. Electroclinical features of kainic acidYinduced status epilepticus in freely moving cats. Microinjection into the dorsal hippocampus. Electroencephalogr Clin Neurophysiol 1982;54: 288Y300 30. Dunstan EJ, Winer JB. Autoimmune limbic encephalitis causing fits, rapidly progressive confusion and hyponatraemia. Age Ageing 2006;35: 536Y37 31. Park DC, Murman DL, Perry KD, et al. An autopsy case of limbic encephalitis with voltage-gated potassium channel antibodies. Eur J Neurol 2007;14:e5Ye6 32. Khan NL, Jeffree MA, Good C, et al. Histopathology of VGKC antibodyYassociated limbic encephalitis. Neurology 2009;72:1703Y5 33. Szepietowski JC, Nilganuwong S, Wozniacka A, et al. Phase I, randomized, double-blind, placebo-controlled, multiple intravenous, dose-ascending study of sirukumab in cutaneous or systemic lupus erythematosus. Arthritis Rheum 2013;65:2661Y71 34. Reid JM, Foley P, Willison HJ. Voltage-gated potassium channelY associated limbic encephalitis in the West of Scotland: Case reports and literature review. Scott Med J 2009;54:27Y31 35. Irani SR, Stagg CJ, Schott JM, et al. Faciobrachial dystonic seizures: The influence of immunotherapy on seizure control and prevention of cognitive impairment in a broadening phenotype. Brain 2013;136:3151Y62 36. Tuzun E, Zhou L, Baehring JM, et al. Evidence for antibody-mediated pathogenesis in anti-NMDAR encephalitis associated with ovarian teratoma. Acta Neuropathol 2009;118:737Y43 37. Martinez-Hernandez E, Horvath J, Shiloh-Malawsky Y, et al. Analysis of complement and plasma cells in the brain of patients with anti-NMDAR encephalitis. Neurology 2011;77:589Y93 38. Titulaer MJ, McCracken L, Gabilondo I, et al. Treatment and prognostic factors for long-term outcome in patients with anti-NMDA receptor encephalitis: An observational cohort study. Lancet Neurol 2013;12:157Y65 39. Bauer J, Vezzani A, Bien CG. Epileptic encephalitis: The role of the innate and adaptive immune system. Brain Pathol 2012;22:412Y21 40. Drachman DB, Angus CW, Adams RN, et al. Myasthenic antibodies cross-link acetylcholine receptors to accelerate degradation. N Engl J Med 1978;298:1116Y22 41. Dalmau J, Gleichman AJ, Hughes EG, et al. Anti-NMDA-receptor encephalitis: Case series and analysis of the effects of antibodies. Lancet Neurol 2008;7:1091Y98 42. Pohl M, Kawakami N, Kitic M, et al. T cell-activation in neuromyelitis optica lesions plays a role in their formation. Acta Neuropathol Commun 2013;1:85 43. Suidan GL, Pirko I, Johnson AJ. A potential role for CD8+ T-cells as regulators of CNS vascular permeability. Neurol Res 2006;28:250Y55 44. Irani SR, Vincent A. Autoimmune encephalitisVNew awareness, challenging questions. Discov Med 2011;11:449Y58 45. Blumcke I, Spreafico R. Cause matters: A neuropathological challenge to human epilepsies. Brain Pathol 2012;22:347Y49

REFERENCES 1. Vincent A, Bien CG, Irani SR, et al. Autoantibodies associated with diseases of the CNS: New developments and future challenges. Lancet Neurol 2011;10:759Y72 2. Graus F, Dalmau J. CNS autoimmunity: New findings and pending issues. Lancet Neurol 2012;11:17Y19 3. Bien CG, Vincent A, Barnett MH, et al. Immunopathology of autoantibodyassociated encephalitides: Clues for pathogenesis. Brain 2012;135:1622Y38 4. Lancaster E, Dalmau J. Neuronal autoantigensVPathogenesis, associated disorders and antibody testing. Nat Rev Neurol 2012;8:380Y90 5. Vincent A, Buckley C, Schott JM, et al. Potassium channel antibodyassociated encephalopathy: A potentially immunotherapy-responsive form of limbic encephalitis. Brain 2004;127:701Y12 6. Malter MP, Helmstaedter C, Urbach H, et al. Antibodies to glutamic acid decarboxylase define a form of limbic encephalitis. Ann Neurol 2010;67: 470Y78 7. Dalmau J, Lancaster E, Martinez-Hernandez E, et al. Clinical experience and laboratory investigations in patients with anti-NMDAR encephalitis. Lancet Neurol 2011;10:63Y74 8. Graus F, Saiz A, Dalmau J. Antibodies and neuronal autoimmune disorders of the CNS. J Neurol 2010;257:509Y17 9. Vincent A, Irani SR, Lang B. The growing recognition of immunotherapyresponsive seizure disorders with autoantibodies to specific neuronal proteins. Curr Opin Neurol 2010;23:144Y50 10. Frisch C, Malter MP, Elger CE, et al. Neuropsychological course of voltage-gated potassium channel and glutamic acid decarboxylase antibody related limbic encephalitis. Eur J Neurol 2013;20:1297Y304 11. Lancaster E, Huijbers MG, Bar V, et al. Investigations of caspr2, an autoantigen of encephalitis and neuromyotonia. Ann Neurol 2011;69: 303Y11 12. Lai M, Huijbers MG, Lancaster E, et al. Investigation of LGI1 as the antigen in limbic encephalitis previously attributed to potassium channels: A case series. Lancet Neurol 2010;9:776Y85 13. Irani SR, Alexander S, Waters P, et al. Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan’s syndrome and acquired neuromyotonia. Brain 2010;133:2734Y48 14. Irani SR, Michell AW, Lang B, et al. Faciobrachial dystonic seizures precede Lgi1 antibody limbic encephalitis. Ann Neurol 2011;69:892Y900 15. Wong SH, Saunders MD, Larner AJ, et al. An effective immunotherapy regimen for VGKC antibodyYpositive limbic encephalitis. J Neurol Neurosurg Psychiatry 2010;81:1167Y69 16. Fatzer R, Gandini G, Jaggy A, et al. Necrosis of hippocampus and piriform lobe in 38 domestic cats with seizures: A retrospective study on clinical and pathologic findings. J Vet Intern Med 2000;14:100Y4 17. Brini E, Gandini G, Crescio I, et al. Necrosis of hippocampus and piriform lobe: Clinical and neuropathological findings in two Italian cats. J Feline Med Surg 2004;6:377Y81 18. Schmied O, Scharf G, Hilbe M, et al. Magnetic resonance imaging of feline hippocampal necrosis. Vet Radiol Ultrasound 2008;49:343Y49 19. Gelberg HB. Diagnostic exercise: Sudden behavior change in a cat. Vet Pathol 2013;50:1156Y57 20. Yanai H, Palus V, Caine A, Summers B, et al. Feline idiopathic hippocampal necrosis: Findings in a UK case. Vet Times 2013;11:19Y20 21. Pakozdy A, Gruber A, Kneissl S, et al. Complex partial cluster seizures in cats with orofacial involvement. J Feline Med Surg 2011;13:687Y93 22. Marioni-Henry K, Monteiro R, Behr S. Complex partial orofacial seizures in English cats. Vet Rec 2012;170:471

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IgG and complement deposition and neuronal loss in cats and humans with epilepsy and voltage-gated potassium channel complex antibodies.

Voltage-gated potassium channel complex (VGKC-complex) antibody (Ab) encephalitis is a well-recognized form of limbic encephalitis in humans, usually ...
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