Fatal Morvan Syndrome Associated With Myasthenia Gravis

Clinicopathological Features in Morvan's Syndrome: An Autopsy Case Study

Morvan's syndrome is a rare, complex autoimmune syndrome comprising peripheral nerve hyperexcitability, dysautonomia, insomnia, and encephalopathy. In this case report, we highlight the clinical and pathological findings of an elderly gentleman who presented to us with clinical features of Morvan's syndrome associated with anti-contactin-associated protein 2 (CASPR-2) antibodies. Histopathology [Figure 3] revealed cortical atrophy with gliosis and mild microglial proliferation. Microglial activation and gliosis were observed in the hippocampus, hypothalamus, and thalamus. Brainstem showed multifocal inflammation. Mild inflammation was observed in the leptomeninges. Morvan's syndrome is an autoimmune disease with antibodies targeted against CASPR within the voltage-gated potassium channel (VGKC) complex. Early diagnosis and treatment play a key role in the management of patients. Most patients show a good response when treated with plasmapheresis and steroids. This patient presented to us late into the illness and succumbed.

Paraneoplastic Neurological Syndromes of the Central Nervous System: Pathophysiology, Diagnosis, and Treatment

Paraneoplastic neurological syndromes (PNS) include any symptomatic and non-metastatic neurological manifestations associated with a neoplasm. PNS associated with antibodies against intracellular antigens, known as "high-risk" antibodies, show frequent association with underlying cancer. PNS associated with antibodies against neural surface antigens, known as "intermediate- or low-risk" antibodies, are less frequently associated with cancer. In this narrative review, we will focus on PNS of the central nervous system (CNS). Clinicians should have a high index of suspicion with acute/subacute encephalopathies to achieve a prompt diagnosis and treatment. PNS of the CNS exhibit a range of overlapping "high-risk" clinical syndromes, including but not limited to latent and overt rapidly progressive cerebellar syndrome, opsoclonus-myoclonus-ataxia syndrome, paraneoplastic (and limbic) encephalitis/encephalomyelitis, and stiff-person spectrum disorders. Some of these phenotypes may also arise from recent anti-cancer treatments, namely immune-checkpoint inhibitors and CAR T-cell therapies, as a consequence of boosting of the immune system against cancer cells. Here, we highlight the clinical features of PNS of the CNS, their associated tumors and antibodies, and the diagnostic and therapeutic strategies. The potential and the advance of this review consists on a broad description on how the field of PNS of the CNS is constantly expanding with newly discovered antibodies and syndromes. Standardized diagnostic criteria and disease biomarkers are fundamental to quickly recognize PNS to allow prompt treatment initiation, thus improving the long-term outcome of these conditions.

Autoimmune neuromyotonia

PURPOSE OF REVIEW

Autoimmune neuromyotonia encompasses a group of rare immune-mediated neurological disorders frequently associated with anti-contactin-associated protein-like 2 (CASPR2) antibodies and featuring clinical and electrical signs of peripheral nerve hyperexcitability (PNH). We aim to summarize the current knowledge on immune-mediated neuromyotonia, focusing on clinical presentations, pathophysiology, and management.

RECENT FINDINGS

Neuromyotonia is a major feature of several autoimmune neurological syndromes characterized by PNH with or without central neurological system involvement. Experimental and clinical evidence suggest that anti-CASPR2 antibodies are directly pathogenic in autoimmune neuromyotonia patients.

SUMMARY

Neuromyotonia, a form of PNH, is a major feature in several syndromes associated with anti-CASPR2 antibodies, including cramp-fasciculation syndrome, Isaacs syndrome, Morvan syndrome, and autoimmune limbic encephalitis. Diagnosis relies on the identification of motor, sensory, and autonomic signs of PNH along with other neurological symptoms, anti-CASPR2 antibody-positivity, and of characteristic electroneuromyographic abnormalities. Paraneoplastic associations with thymoma are possible, especially in Morvan syndrome. Patients usually respond to immune-active treatments, including steroids, intravenous immunoglobulins, plasma exchanges, and rituximab.

Bilateral Panuveitis Associated with Morvan Syndrome: A Case Report and Review of the Literature

PURPOSE

Morvan syndrome (MoS) is a neurologic disorder belonging to a spectrum of autoimmune encephalitis, Contactin-associated protein-like 2 (Caspr2) antibody syndrome. We report a case of bilateral panuveitis associated with MoS.

METHODS

Case report and review of the literature.

RESULTS

A 57-year-old male with Morvan syndrome presented with painless vision loss and floaters. Initial visual acuities were 20/50 and 20/60. Hallmarks of this uveitis included persistently active vitritis, and nonhemorrhagic retinitis with nonperfusion and neovascularization. Uveitis consistently flared with attempted immunosuppressive tapers. Vision deteriorated to count fingers (2 ft) OU over 2.5 years despite corticosteroids, mycophenolate mofetil, intravenous immunoglobulin, adalimumab, and rituximab. Explanations for reduced final visual acuity included macular atrophy, disruption of retinal architecture, epiretinal membrane, vitritis, and cataract.

CONCLUSIONS

This case constitutes the first report of uveitis associated with MoS and Caspr2 antibody syndrome, raising the question of autoimmunity targeting the retinal inner and/or outer plexiform layers.

OUP accepted manuscript

A 50-year-old male with history of HIV, syphilis, paraneoplastic Morvan syndrome secondary to thymoma resected in 2013 presented recently with tachycardia, tremors, diarrhea, hyperhidrosis and bilateral lower extremity pain leading to the discovery of thymoma recurrence. He initially developed Morvan Syndrome after thymectomy in 2013 and gradually improved with negative anti-contactin-associated protein-like 2 antibody testing in 2017 and symptom resolution in 2018. Upon return of dysautonomia symptoms, subsequent imaging revealed widespread disease recurrence diffusely in the right lung parenchyma and pleura for which he underwent right extrapleural pneumonectomy. He was managed with low-dose prednisone perioperatively, but when his symptoms worsened, he was started on rituximab and methylprednisolone. Nearly 3 months from surgery, he died from urinary sepsis. This represents a unique case of recurrent paraneoplastic Morvan syndrome leading to the diagnosis of metastatic thymoma as well as the challenges of symptom control during the surgical management of the underlying disease.

CASPR2-Related Morvan Syndrome: Autonomic, Polysomnographic, and Neuropsychological Observations

Objective

Morvan syndrome is characterized by central, autonomic, and peripheral hyperexcitability due to contactin-associated protein 2 (CASPR2) antibody. Our objective was to study the clinical spectrum, electrophysiologic, autonomic, polysomnographic, and neuropsychological profile in patients with CASPR2-related Morvan syndrome.

Methods

Serum and CSF samples that were CASPR2 antibody positive from 2016 to 2019 were assessed. Among them, patients with Morvan syndrome diagnosed based on clinical and electrophysiologic basis were included.

Results

Fourteen (M:F = 10:4) patients with Morvan syndrome were included with age at onset of 37.1 ± 17.5 years. The clinical features were muscle twitching (12), insomnia (12), pain (11), paresthesias (9), hyperhidrosis (7), hypersalivation (6), double incontinence (3), spastic speech (2), dysphagia (2), behavioral disturbances (2), seizures (1), and cold intolerance (1). Neurologic examination revealed myokymia (12), hyperactive tendon reflexes (10), and tremor (6). EMG revealed neuromyotonia (12) and increased spontaneous activity (7). Autonomic function tests conducted in 8 patients revealed definite autonomic dysfunction (4), orthostatic hypotension (2), early dysfunction (1), and postural orthostatic tachycardia syndrome (1). Polysomnography findings in 6 patients revealed insomnia (3), absence of deep sleep (1), high-frequency beta activity (1), REM behavior disorder (1), and 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 neurologic resolution in follow-up with persistent neuropathic pain in 5 patients.

Conclusions

This study has contributed to the growing knowledge on CASPR2-related Morvan syndrome. It is important for an increased awareness and early recognition as it is potentially treatable by immunotherapy.

Afterdischarges in Myasthenia Gravis

Introduction: This study aimed to analyze the clinical features of myasthenia gravis (MG) in combination with the afterdischarges and compare the characteristics of afterdischarges in MG with different serum antibodies. Methods: Ninety-two patients with MG were analyzed retrospectively. The afterdischarges were investigated using motor nerve conduction examination, F-wave examination, and repetitive nerve stimulation (RNS). Results: Afterdischarges were observed after the M wave in 14 of 92 patients. Three of these 14 patients tested positive for the muscle-specific tyrosine kinase antibody (MuSK-Ab), and 11 patients tested positive for the acetylcholine receptor antibody (AchR-Ab). The characteristics of the afterdischarges on RNS differed distinctly between the two antibody groups. The afterdischarges occurred on the first stimulation, but decreased on the second and subsequent stimulations in patients with MuSK-MG, while the afterdischarges continued to occur on each stimulation in patients with AchR-MG. Discussion: The characteristics of the afterdischarges on RNS enabled easy identification of their synaptic or neurogenic nature.

Clinical Profile and Treatment Response in Patients with CASPR2 Antibody-Associated Neurological Disease

Background:

The clinical spectrum of contactin-associated protein-like 2 (CASPR2) antibody-associated disease is wide and includes Morvan syndrome. Studies describing treatment and long-term outcome are limited.

Aims:

We report the clinical profile and emphasize response to treatment and long-term outcome in eight patients with CASPR2-antibody-associated disease.

Methods:

Clinical, radiological, electrophysiological, treatment, follow-up, and outcome data were collected by retrospective chart review.

Results:

Clinical manifestations included Morvan syndrome (n = 7) and limbic encephalitis (n = 1). None of the patients were positive for LGI1 antibody. Associated features included myasthenia (n = 1), thymoma (n = 1), and dermatological manifestations (n = 4). Patients were treated with intravenous methylprednisolone and plasma exchange during the acute symptomatic phase followed by pulsed intravenous methyl prednisolone to maintain remission. Mean-modified Rankin score at admission (pre-treatment), discharge, and last follow-up were 3.75, 2.5, and 0.42, respectively. One patient with underlying thymoma and myasthenic crisis died. The other seven patients were followed up for a mean duration of 19.71 months. All of them improved completely. Relapse occurred in one patient after 13 months but responded favorably to steroids.

Conclusion:

CASPR2 antibody-associated disease has favorable response to immunotherapy with complete improvement and good outcome. Underlying malignancy may be a marker for poor prognosis.

Muscle-Specific Tyrosine Kinase Antibody Positive Myasthenia Gravis With Peripheral Nerve Hyperexcitability: Case Report and Literature Review

OBJECTIVES

Administration of acetylcholinesterase inhibitors can bring about peripheral nerve hyperexcitability symptom in muscle-specific tyrosine kinase antibody positive myasthenia gravis, but the changes in electromyography before and after drug withdrawal have not been described in detail.

METHODS

Electromyography was performed on a case of muscle-specific tyrosine kinase antibody positive myasthenia gravis with peripheral nerve hyperexcitability correlated with the administration of pyridostigmine bromide before and after drug withdrawal, respectively.

RESULTS

Afterdischarges close after M waves appeared on the tibial nerve, common peroneal nerve, median nerve, and ulnar nerve, and these presented unique characteristics in repetitive nerve stimulation. Ten days after pyridostigmine bromide withdrawal, the second electromyography examination was carried out and showed that the afterdischarges on all nerves disappeared dramatically and the amplitude of tibial nerve F waves was elevated than before.

CONCLUSIONS

Afterdischarges can be an important indicator of muscle-specific tyrosine kinase antibody positive myasthenia gravis with peripheral nerve hyperexcitability correlated with acetylcholinesterase inhibitors.

Systematic review of the clinical spectrum of CASPR2 antibody syndrome

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical characteristics of autoimmune disorders in the central nervous system associated with myasthenia gravis

Myasthenia gravis (MG) is occasionally associated with autoimmune diseases in the central nervous system (CNS), such as neuromyelitis optica spectrum disorder (NMOSD), multiple sclerosis (MS), Morvan syndrome, and anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Here, we report five original cases associated with autoimmune disorders in the CNS among 42 patients with MG in a single tertiary hospital in Japan (11.9%). In four of these five cases, the second disease developed when the preceding disease was unstable. Accurate diagnosis of the newly developing disease may be difficult in such cases, because some neurological symptoms can be seen in both disorders. This implies the great importance of recognizing the possible co-occurrence of MG and disorders in the CNS. In addition, a comprehensive review of the literature revealed distinct clinical characteristics depending on the associated disease in the CNS, including thymic pathology and temporal relationship between MG and associated CNS disorders. Notably, NMOSD usually develops after the onset of MG and thymectomy, in clear contrast to MS. Thymoma is highly prevalent among patients with Morvan syndrome, in contract to cases with NMOSD and MS. The analysis of clinical characteristics, representing the first such investigation to the best of our knowledge, suggests different pathogeneses of these autoimmune diseases in the CNS, and provides significant implications for clinical practice.

Current Treatment Options for Peripheral Nerve Hyperexcitability Syndromes

PURPOSE OF REVIEW

Peripheral nerve hyperexcitability (PNH) syndromes are divided into primary and secondary groups based on the presence or absence of demonstrable peripheral nerve disease. In this review, we systematically evaluate the evidence for current therapies and supportive managements based on autoimmune, paraneoplastic, and genetic components in pathophysiology reported in the literature.

RECENT FINDINGS

Current therapy options are based on symptomatic management as well as focusing the underlying immune/genetic/paraneoplastic pathology by immunosuppressants, chemotherapy, and surgery. Further research is desired to provide treatment options geared specifically towards addressing PNH. Supportive care can also be an area for future research.