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Ovid: Fifty Neurologic Cases from Mayo Clinic

Editors: Noseworthy, John H. Title: Fifty Neurologic Cases from Mayo Clinic, 1st Edition Copyright ©2004 Oxford Unversity Press (Copyright 2004 by Mayo Foundation for Medical Education and Research) > Table of Contents > Case 6: Drenching sweats, sleep talking, and weight loss Case 6: Drenching sweats, sleep talking, and weight loss CASE 6 History Over a 1-year period, a 36-year-old man developed paresthesias of the feet, hypertension, drenching sweats, slurred speech, intermittent hallucinations, severe insomnia, and somniloquy (“like telephone conversations at work”). He had a weight loss of 100 lb despite a good appetite. Examination During neurologic examination, he was inattentive and appeared to be experiencing visual hallucinations. Episodes of hyperhydrosis followed by piloerection were observed. His speech was dysarthric. Diffuse myoclonic jerks and continuous involuntary movements characterized as myokymia were seen in major muscle groups. Investigations The results of routine biochemical and hematologic studies and two cerebrospinal fluid (CSF) examinations were normal, aside from an increased protein level (70 mg/dL; normal, 14-45 mg/dL) in the CSF. Antibodies were detected to voltage-gated potassium channels (1,360 pmol/L), GAD65 (0.17 nmol/L; normal, <0.02 nmol/L), and acetylcholine receptor protein binding (0.04 nmol/L; normal, <0.02 nmol/L). Electroencephalography showed diffuse nonspecific slow wave abnormalities. Electromyography (EMG) demonstrated fasciculation potentials, multiplets, and occasional neuromyotonic discharges (Figure). Overnight polysomnography did not demonstrate sleep spindles, K complexes, or neurophysiologic features of sleep. Autonomic testing documented autonomic impairment in addition to autonomic hyperactivity. Computed tomography (CT) of the chest demonstrated a mediastinal mass. P.22

FIGURE. A, Peroneal motor response. Stimulation at ankle produced a normal compound muscle action potential, followed by irregular afterdischarges. B, Needle electromyography from the medial gastrocnemius muscle shows spontaneous short multiplets with high intraburst frequency (50-150 Hz) consistent with neuromyotonia. (From Josephs KA, Vernino S, Silber MH, et al. Arch Neurol (in press). By permission of the American Medical Association.)

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DIAGNOSIS CASE 6 Morvan’s syndrome as a paraneoplastic phenomenon (thymoma)
Commentary by Dr. Keith A. Josephs Morvan’s syndrome, or chorée fibrillaire de Morvan, is characterized by peripheral nerve hyperexcitability, dysautonomia, insomnia, and fluctuating delirium. Typical presenting signs and symptoms include muscle twitching, hyperhydrosis, insomnia, fluctuating cognition, and limb paresthesias. The precise pathophysiologic mechanism of the syndrome is not known, but recent studies support the concept that Morvan’s syndrome is an autoimmune or paraneoplastic disorder. Associations with myasthenia gravis, thymoma, and small cell lung cancer have been demonstrated. CT demonstrated that the patient had a malignant thymoma. Two key features of Morvan’s syndrome are 1) spontaneous muscle fiber activity with fasciculation, multiplets, and myokymic and neuromyotonic discharges seen on EMG and 2) serum antibodies specific for neuronal voltage-gated potassium channels. Other laboratory and imaging findings usually are not notably abnormal, but they may aid with the differential diagnosis. Typically, magnetic resonance imaging (MRI), hexamethylpropyleneamine oxime single photon computer emission tomographic, and fluorodeoxyglucose F 18 positron emission tomographic (PET) findings are normal and can help differentiate Morvan’s syndrome from limbic encephalitis and fatal familial insomnia. In the latter two conditions, MRI and PET scans are usually abnormal. Dysautonomia is a prominent feature of Morvan’s syndrome. Patients may complain of itching, palmoplantar erythema, and excess sweating. Hypertension and tachycardia are also common. These features of dysautonomia most likely result from peripheral autonomic and sudomotor nerve dysfunction. Insomnia in Morvan’s syndrome may be due to interruption of thalamolimbic circuitry. Therapy should involve treatment of any associated malignancy, followed by either plasma exchange or intravenous administration of gamma globulin. Addition of immunomodulating therapies, including corticosteroids, azathioprine, or cyclophosphamide, may be required for long-term immunosuppression. Alleviating the insomnia is important and, in some cases, may require the use of opioids. A definitive diagnosis of Morvan’s syndrome should be reserved for patients who have at least four cardinal features: clinical myokymia, P.24
dysautonomia, insomnia, and fluctuating encephalopathy with vivid hallucinations. Confirmation of Morvan’s syndrome requires evidence of spontaneous EMG discharges (neuromyotonia or myokymia) and antibodies to voltage-gated potassium channels. REFERENCE Josephs KA, Vernino S, Silber MH, et al. Neurophysiologic characterization of Morvan’s syndrome. Arch Neurol (in press).

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