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Isaac's syndrome; neuromyotonia; Isaac's-Merten's syndrome; continuous muscle fiber activity syndrome; quantal squander syndrome
Etiology:
1) acquired form may develop in association with:
a) peripheral neuropathy
b) autoimmune disease
Epidemiology:
1) rare neuromuscular disorder
2) age of onset is between ages 15 and 60, with most patients experiencing symptoms before age 40
Pathology:
1) continuous signaling of motor neurons
2) autoimmune form: antibodies that bind to ion channels on motor nerve fibers
Genetics:
- hereditary & acquired forms
Clinical manifestations:
1) progressive muscle stiffness
2) fasciculations
3) cramping
4) hyperhidrosis
5) delayed muscle relaxation
6) sign/symptoms occur even during sleep or when patients are under general anesthesia
7) hyporeflexia
8) myalgias
9) numbness is relatively uncommon
10) symptoms can be limited to cranial muscles
11) in most patients, stiffness is most prominent in limb & trunk muscles
12) speech & breathing may be affected if pharyngeal or laryngeal muscles are involved
Management:
1) anticonvulsants, phenytoin & carbamazepine, usually provide significant relief from the stiffness, muscle spasms, & pain
2) plasmapheresis may provide short-term relief for patients autoantibodies
3) prognosis
a) no cure
b) long-term prognosis is uncertain
Specific
Morfan's syndrome
General
neuromuscular disease; myoneural disease
References
- NINDS Isaacs' Syndrome Information Page
https://www.ninds.nih.gov/Disorders/All-Disorders/Isaacs-Syndrome-Information-Page