"La chorée fibrillaire" was first coined by Morvan in 1890 when describing patients with multiple, irregular contractions of the long muscles, cramping, weakness, pruritus, hyperhidrosis, insomnia and delirium.
[4] This rare disorder is characterized by severe insomnia, amounting to no less than complete lack of sleep (agrypnia) for weeks or months in a row, and associated with autonomic alterations consisting of profuse perspiration with characteristic skin miliaria (also known as sweat rash), tachycardia, increased body temperature, and hypertension.
The subject also developed confusional episodes with spatial and temporal disorientation, visual and auditory hallucinations, complex behavior during sleep and progressive nocturnal insomnia associated with diurnal drowsiness.
When left alone, the subject would slowly lapse into a stuporous state with dreamlike episodes characterized by complex and quasi-purposeful gestures and movements (enacted dreams).
[5] Electroencephalography (EEG) in one case was dominated by "wakefulness" and “subwakefulness” states alternating or intermingled with short (< 1 min) atypical REM sleep phases, characterized by a loss of muscle atonia.
Electromyography (EMG) discloses spontaneous, repetitive motor unit or single fiber discharges firing in irregular rhythmic bursts at high intraburst frequencies.
Laryngeal spasm possibly resulting from neuromyotonia has been described previously, and this highlights that, in patients with unexplained laryngospasm, neuromytonia should be added to the list of differential diagnoses.
The absence of morphological alterations of the brain pathology, the suggestion of diffusion of IgG into the thalamus and striatum, more marked than in the cortex (consistent with effects on the thalamolimbic system) the oligoclonal bands in the CSF and the amelioration after PE all strongly support an antibody-mediated basis for the condition.
[1] There have also been reports of non-paraneoplastic limbic encephalitis associated with raised serum VGKC suggesting that these antibodies may give rise to a spectrum of neurological disease presenting with symptoms arising peripherally, centrally, or both.
[1] Antibodies against voltage-gated potassium channels (VGKC), which are detectable in about 40% of patients with acquired neuromytonia, have been implicated in Morvan's pathophysiology.
It has been suggested that the VGKC antibodies may cross the blood–brain barrier and act centrally, binding predominantly to thalamic and striatal neurons causing encephalopathic and autonomic features.
Amnesia, seizures, and mesial temporal lobe structural abnormalities are features of LE, whereas myokymia, hyperhydrosis, and insomnia favor Morvan's Syndrome.
[9] In one case, the dramatic response to high-dose oral prednisolone together with pulse methylprednisolone with almost complete disappearance of the symptoms within a short period should induce consideration of corticosteroids.
[8] In another case, symptomatic improvement with plasmapheresis, thymectomy, and chronic immunosuppression provide further support for an autoimmune or paraneoplastic basis.
[1] Although thymectomy is believed to be a key element in the proposed treatment, there is a reported case of Morvan's Syndrome presenting itself post-thymectomy.
[8] With only a limited number of reported cases, the complete spectrum of the central nervous system (CNS) symptomatology has not been well established.
Others have required a combination of plasmapheresis and long term immunosuppression, although in one of these cases the patient died shortly after receiving plasma exchange (PE).