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Neurological Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Lambert–Eaton myasthenic syndrome is caused by circulating antibodies to presynaptic voltage-gated calcium channels, leading to impaired recruitment of synaptic vesicles following depolarization. About half of cases are a paraneoplastic phenomenon, usually associated with small cell carcinoma of the bronchus. The main feature is fatiguable limb weakness. Other features include absent reflexes and autonomic features such as dry mouth or impotence. Absent reflexes may return if the relevant muscle groups are exercised (post-tetanic accentuation). Bulbar and ocular features are rare.
Autonomic Nervous System Disorders
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Disorders associated with involvement of acetylcholine receptors: Botulism.Lambert–Eaton myasthenic syndrome.
Diagnosis and Differential Diagnosis
Published in Marc H. De Baets, Hans J.G.H. Oosterhuis, Myasthenia Gravis, 2019
The Lambert-Eaton myasthenic syndrome usually starts with weakness and fatiguability of the proximal leg muscles, while other limb muscles are less affected, and ptosis, diplopia and bulbar weakness are mild or absent. Autonomic disturbances are usually present. This syndrome is frequently missed in the patients in poor condition due to their lung carcinoma or diagnosed as an undefined myopathy. Electromyography (Section III.D.1) is the key for the diagnosis. This syndrome is further discussed in Chapter 4, Section III.B.3.
Lambert-Eaton myasthenic syndrome (LEMS) in a patient with lung cancer under treatment with pembrolizumab: a case study
Published in Journal of Chemotherapy, 2023
Jun Ho Lee, Sun Kyung Baek, Jae Joon Han, Hong Jun Kim, Yeon-Ah Lee, Dallah Yoo, Chi Hoon Maeng
Immune checkpoint inhibitors (ICIs), including pembrolizumab, have been widely used for various types of cancer [1]. Blockade of the interaction between PD-1 and programmed death-ligand 1 (PD-L1) prevents tumors from evading immune surveillance [2]. An immune system enhanced by using ICIs often leads to adverse effects termed immune-related adverse events (irAE), including dermatologic, gastrointestinal, hepatic, endocrine, and other less common inflammatory events [1,3,4]. Furthermore, as ICIs have expanded, the reports of adverse effects that were not well known previously are also increasing. Autoimmune diseases, such as autoimmune thyroid disease and myasthenia gravis, have often been reported in patients who treated with ICIs [5,6]. Lambert–Eaton myasthenic syndrome (LEMS) is an uncommon neuromuscular disorder characterized by muscle weakness and autonomic dysfunction. It is better known as a tumor-associated paraneoplastic syndrome that develops at the time of the initial cancer diagnosis. Approximately 60% of cases of LEMS are associated with malignancy, with small cell lung cancer (SCLC) being the most common malignancy [7,8]. Few cases have reported the relationship between LEMS and ICI to date [9–11]. As ICIs have been used in clinical practice for less than 10 years, adverse effects caused by ICI, even very rare adverse events, are worth reporting and studying. Herein, we report a rare case of LEMS presenting as a pembrolizumab-associated irAE.
Ataxia and ophthalmoplegia: an atypical case of Miller Fisher syndrome (MFS) with anti-GAD antibody
Published in International Journal of Neuroscience, 2022
Ali R. Shoraka, Xiang Fang, Diaa Hamouda, Bhanu Gogia, Xiangping Li
Corticosteroids have been tried as the first-line therapy for GAD-Ab associated neurologic disorders. Additional case reports suggest that a combination of IVIG and delayed plasmapheresis show efficacy regarding symptomatic improvement [18]. Our patient received a course of IVIg and had complete recovery in 3 months. Some other disorders that can manifest with similar presentations are Lambert Eaton Myasthenic Syndrome (LEMS), atypical GAD antibody positive cerebellar degeneration, and paraneoplastic syndrome. Lambert-Eaton myasthenic syndrome (LEMS) is a disorder of neuromuscular junction transmission with the primary clinical manifestation of muscle weakness. GAD antibody positive cerebellar degeneration could cause dysmetria, ataxia, and nystagmus. However, neither entity could explain patient’s new onset numbness and length dependent polyneuropathy seen in the exam. CT chest/abdomen and pelvis did not reveal any underlying malignancy. Patient is a 24-year-old male with no history of smoking or risky behavior, and malignancy is unlikely in his age group.
Ocular Myasthenia: Clinical Course and the Diagnostic Utility of Assaying Acetylcholine Receptor Antibodies
Published in Neuro-Ophthalmology, 2022
Raed Behbehani, Abdullah Ali, Ashraf Al-Moosa
SFEMG was abnormal in 31 of 34 cases (91.1%), and there was a trend (p = .09) for SFEMG to be abnormal in patients who converted to GMG (Table 2). Although SFEMG is very sensitive and specific for the diagnosis of OMG (88%–92%), the test is time-consuming and inconvenient for patients and requires technical expertise.10,21 It can also be abnormal in disorders such as Lambert-Eaton myasthenic syndrome and mitochondrial myopathies.22,23 Therefore, it is probably more helpful in the assessment of seronegative cases. Out of the 34 patients in this study who had an AchRA assay and SFEMG testing, one patient was seronegative with an abnormal SFEMG, while three patients were seropositive with a normal SFMEG. The single AchRA seronegative patient who had an abnormal SFEMG presented with ptosis and showed a good response to pyridostigmine.