Morvan’s syndrome: case report

Introduction: Morvan’s syndrome is a rare neurological condition characterized by the combination of central and peripheral symptoms such as neuromyotonia by fasciculation, dysautonomy and encephalopathy associated with laboratory evidence of the VGKC antibodies LGI1 and CASPR2. Case report: A 77-year-old man was admitted to the emergency room with a 3-month history of mental confusion, alteration in memory and language, visual and auditory hallucinations, and seizures. He had a sudden decrease level of consciousness and generalized myoclonus, being admitted to the intensive care unit. Due to non-improvement of the neurological condition, the possibility of encephalitis rose, herpes simplex virus (HSV) polymerase chain reaction (PCR) and 14.3.3 protein in cerebrospinal fluid (CSF) were performed, which resulted negative later. Analysis of CSF showed a high level of protein and cells. Magnetic resonance imaging (MRI) of the brain showed hypersignal activity in the bilateral internal capsule, temporal and frontal region. An extensive propaedeutic was performed for rapidly progressive dementia, including an autoimmune panel, with anti-glioma rich in inactivated leucine 1 (LGI-1) positive by indirect immunofluorescence. Discussion: the diagnosis of Morvan’s Syndrome is clinical. Some cases are reported with spontaneous remission and others that require extensive treatment, with immunotherapy, including plasmapheresis and immunosuppression. VGKC antibodies have been reported in association with three main clinical syndromes: neuromyotonia, Morvan’s syndrome and limbic encephalitis.

CASPR-2 related morvan’s syndrome: Autonomic, polysomnographic & neuropsychological observations

Background& Objectives:Morvan’s syndrome is characterized by central, autonomic, and peripheral hyperexcitability due to CASPR-2-antibody. Our objective was to study the clinical spectrum, electrophysiological, autonomic, polysomnographic and neuropsychological profile in patients of CASPR-2 related Morvan’s syndrome.Materials & Methods:Serum and CSF samples that were CASPR2-antibody positive from 2016-2019 were assessed. Among them, patients of Morvan’s syndrome diagnosed based on clinical and electrophysiological basis were included.Results:14(M: F-10:4) patients of Morvan’s syndrome were included with age at onset of 37.1±17.5 years. The clinical features were muscle twitching (12), insomnia (12), pain (11), paraesthesias (9), hyperhidrosis (7), hypersalivation (6), double incontinence (3), spastic speech (2), dysphagia (2), behavioral disturbances (2), seizures (1) cold intolerance (1). Neurological examination revealed myokymia (12), hyperactive tendon reflexes (10), tremor (6). Electromyogram revealed neuromyotonia (12) and increased spontaneous activity (7). Autonomic function tests conducted in eight patients revealed definite autonomic dysfunction (4), orthostatic hypotension (2), early dysfunction (1) and postural orthostatic tachycardia syndrome (1). Polysomnography findings done in six patients revealed insomnia (3), absence of deep sleep (1), high frequency beta activity (1), REM (rapid eye movement) behaviour disorder(1), periodic leg movements(1). Neuropsychological evaluation showed subtle involvement of the left frontal and temporal lobe. Malignancy workup was negative. All patients were treated with steroids. There was complete neurological resolution in follow-up with persistent neuropathic pain in five patients.Conclusions:This study has contributed to the growing knowledge on CASPR2-related Morvan’s syndrome. It is important for an increased awareness and early recognition as it’s potentially treatable by immunotherapy.

Stop testing for autoantibodies to the VGKC-complex: only request LGI1 and CASPR2

Autoantibodies to leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein like-2 (CASPR2) are associated with clinically distinctive syndromes that are highly immunotherapy responsive, such as limbic encephalitis, faciobrachial dystonic seizures, Morvan’s syndrome and neuromyotonia. These autoantibodies target surface-exposed domains of LGI1 or CASPR2, and appear to be directly pathogenic. In contrast, voltage-gated potassium channel (VGKC) antibodies that lack LGI1 or CASPR2 reactivities (‘double-negative’) are common in healthy controls and have no consistent associations with distinct syndromes. These antibodies target intracellular epitopes and lack pathogenic potential. Moreover, the clinically important LGI1 and CASPR2 antibodies comprise only ~15% of VGKC-positive results, meaning that most VGKC-antibody positive results mislead rather than help. Further, initial VGKC testing misses some cases that have LGI1 and CASPR2 antibodies. These collective observations confirm that laboratories should stop testing for VGKC antibodies and instead, test only for LGI1 and CASPR2 antibodies. This change in practice will lead to significant patient benefit.

Autoimmune encephalitis and Morvan’s syndrome

Since its first recognition in 2001, hundreds of patients have been identified with autoimmune limbic encephalitis (LE) associated with antibodies that immunoprecipitate voltage-gated potassium channel (VGKC)-complex proteins. Preliminary epidemiology suggests that it is more common in men (2:1) and that the median age at onset is 65 years. The phenotype has been recognized mainly in patients over the age of 18 years at onset. The classic presentation is with subacute onset of short-term memory loss, seizures, disorientation, with psychological disturbance or hallucinations. Additional features that may occur are sleep disturbance, autonomic dysfunction, and neuromyotonia, but these would be more typical of Morvan’s syndrome.

Disrupted AMPA Receptor Function upon Genetic- or Antibody-Mediated Loss of Autism-Associated CASPR2

Neuropsychiatric disorders share susceptibility genes, suggesting a common origin. One such gene is CNTNAP2 encoding contactin-associated protein 2 (CASPR2), which harbours mutations associated to autism, schizophrenia, and intellectual disability. Antibodies targeting CASPR2 have also been recently described in patients with several neurological disorders, such as neuromyotonia, Morvan’s syndrome, and limbic encephalitis. Despite the clear implication of CNTNAP2 and CASPR2 in neuropsychiatric disorders, the pathogenic mechanisms associated with alterations in CASPR2 function are unknown. Here, we show that Caspr2 is expressed in excitatory synapses in the cortex, and that silencing its expression in vitro or in vivo decreases the synaptic expression of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors and the amplitude of AMPA receptor-mediated currents. Furthermore, Caspr2 loss of function blocks synaptic scaling in vitro and experience-dependent homoeostatic synaptic plasticity in the visual cortex. Patient CASPR2 antibodies decrease the dendritic levels of Caspr2 and synaptic AMPA receptor trafficking, and perturb excitatory transmission in the visual cortex. These results suggest that mutations in CNTNAP2 may contribute to alterations in AMPA receptor function and homoeostatic plasticity, and indicate that antibodies from anti-CASPR2 encephalitis patients affect cortical excitatory transmission.

Morvan’s syndrome treated successfully with rituximab and lacosamide

We describe a woman with both central and peripheral nervous system symptoms consistent with Morvan’s syndrome who was successfully treated with immunosuppression including rituximab and the new antiepileptic drug lacosamide against peripheral nerve hyperexcitability. Despite being over 8 months in hospital and 4 months in an intensive care unit she recovered fully. It is also the first case where cerebrospinal fluid neurofilament-light (NfL) levels were followed during the disease course. The clinical course resembled that of anti-NMDA receptor encephalitis, where patients often recover surprisingly well despite severe symptoms and an extensive time in intensive care. A possible explanation is the comparatively low levels of NfL, indicating disease processes that are not characterised by extensive neuroaxonal degeneration.

THUR 153 Antibodies against the voltage-gated potassium channel complex

Voltage-gated potassium channel (VGKC) complex antibodies have been associated with a spectrum of presentations including peripheral nerve hyperexcitability (PNH), Morvan’s syndrome, autoimmune encephalopathy, epilepsy and recently psychosis.We retrospectively reviewed the medical records of 70 patients from the Greater Manchester Neuroscience Centre, who had tested positive for VGKC-complex antibodies between 2012 and 2015 to identify the clinical relevance of positive results.The majority were diagnosed with autoimmune encephalopathy(19) followed by epilepsy(14), psychosis(10) and PNH(6). The remaining fifteen had other neurological presentations and six had no primary neurological disorder. 39/70 patients who had antibody titres>400 pM, were diagnosed with autoimmune encephalopathy(19), epilepsy(9), psychosis(4), PNH(3) and other disorders(4). 24/39 patients, who received treatment with one or a combination of corticosteroids, intravenous immunoglobulins, cyclophosphamide, plasma exchange, azathioprine or rituximab, had a diagnosis of autoimmune encephalopathy(18), epilepsy(2), psychosis(2) and malignancy(2). 16/24 were treatment responsive. 3/31 patients with lower titres were also treated, but only one with the classic phenotype (PNH) responded to treatment.The classic phenotype often had a titre >400 pM. PNH may have a titre ≤400 pM. The patients without classic presentations typically had titres≤400 pM. Consistent with previous studies, clinical phenotyping and antibody titre helped to determine the relevance of VGKC-complex antibodies.

Confusion, Muscle Cramps, and Weight Loss

Morvan’s syndrome is a rare autoimmune antibody syndrome causing central, peripheral, and autonomic manifestations. It has been most consistently associated with Caspr2 antibodies, although LGI1 antibodies have also been found in some patients. The Caspr2 protein is located throughout the central and peripheral nervous system. This may account for the diversity of presentations that have been reported in patients with Caspr2 antibodies. The seven core symptoms of Caspr2 antibodies include cognitive dysfunction/seizures, cerebellar symptoms, peripheral nerve hyperexcitability, autonomic dysfunction, insomnia, neuropathic pain, and weight loss. Treatment of Morvan’s syndrome and other Caspr-associated antibody syndromes is largely empirical. Typically, patients are given steroids, intravenous immunoglobulin, and if necessary, other immunosuppressive agents. Prognosis for remission is very good, but relapses may occur.