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Autoimmune disorders that can be mistaken for viral illness
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
Maxwell Greene, Eric Lancaster
Isaacs syndrome is an acquired autoimmune disorder of peripheral nerve hyper-excitability [22,23]. Patients generally develop diffuse cramps, muscle spasms and fasciculations. Difficulty relaxing the muscles, or “psuedomyotonia,” is also common. When this sort of acquired peripheral nerve hyperexcitability is associated with encephalitis and severe insomnia, the diagnosis of Morvan syndrome is applied. Isaacs syndrome and Morvan syndrome have long been associated with autoantibodies to the voltage-gated potassium channel (VGKC) complex. Morvan syndrome is particularly associated with autoantibodies to the axonal protein Caspr2 (Section 27.3.4). Caspr2 autoantibodies should be particularly suspected in cases or peripheral nerve hyperexcitability where a thymoma is present, although most patients do not have tumors. VGKC and Caspr2 antibodies are discussed in more detail below.
Diseases of Muscle and the Neuromuscular Junction
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Chris Turner, Anthony Schapira
Symptoms may begin at any age but occur most often in late childhood or early adulthood. Muscle stiffness is usually the first symptom and appears in distal limb muscles, slowly spreading over months or years to involve the axial and cranial muscles. Movement becomes slow. Myokymia can be seen in overactive muscles. Muscle relaxation after contraction is slow and percussion myotonia is absent. Increased sweating and muscle weakness with hyporeflexia is seen in some patients. Examination demonstrates mild weakness, which can be proximal, distal or both. Hallucinations, insomnia, seizures and intellectual impairment have been reported in some patients in conjunction with neuromyotonia, a polyneuropathy and sometimes an underlying thymoma (Morvan’s syndrome).
Ocular Neuromyotonia: an update
Published in Expert Review of Ophthalmology, 2021
Subahari Raviskanthan, Peter W Mortensen, Andrew Lee
Peripheral neuromyotonia, also known as Isaac syndrome, is characterized by peripheral nerve hyperexcitability, leading to irregular asynchronous muscle fiber activation, causing myokymia [10]. These cases, however, are not associated with corresponding peripheral nerve disease [10]. Where there is also central nervous system involvement, it is known as Morvan’s syndrome [10]. Muscle twitching and stiffness are the primary clinical manifestations, although autonomic symptoms and sensory symptoms can also be seen [10]. EMG shows characteristic myokymic and rhythmic neuromyotonic discharges up to 300 Hertz frequency [5,10]. The potential pathogenic role of the contactin-associated protein 2 (CASPR2) and leucine-rich glioma-inactivated 1 (LGI1) in peripheral neuromyotonia has been proposed [11,12]There is no proven association between peripheral neuromyotonia and ONM. Nevertheless, first line treatment of both conditions involves membrane stabilizing agents as well as management of the underlying presumed cause if secondary [3,10,13].
Bilateral Panuveitis Associated with Morvan Syndrome: A Case Report and Review of the Literature
Published in Ocular Immunology and Inflammation, 2023
Michael T. Kryshtalskyj, Robert G. Devenyi, Mili Roy
Morvan syndrome (MoS) is a rare neurologic autoimmune disorder marked by encephalopathy, autonomic instability, peripheral nerve hyperexcitability, and severe insomnia. MoS belongs to a newly recognized spectrum of autoimmune encephalitis, Contactin-associated protein-like 2 (Caspr2) antibody associated disease.1 We report a case of bilateral panuveitis in a patient with MoS, constituting the first documented association of intraocular disease with Caspr2 antibody syndrome.