Antibodies involved in paraneoplastic SMS:
(1) anti-GAD (glutamic acid decarboxylase)
(2) anti-amphiphysin (a presynaptic vesicle-associated protein)
(3) mixture of both
Tumors associated with paraneoplastic SMS include:
(1) breast cancer
(2) Hodgkin's disease
(3) colon cancer
Clinical findings:
(1) The onset of SMS symptoms may precede, be concurrent with or follow the diagnosis of the cancer.
(2) The patient develops muscle stiffness, most often in the paraspinal and abdominal muscles.
(3) The muscle contractions may result in an exaggerated lumbar lordosis or other abnormal postures.
(4) Muscle contractions may be precipitated by a normal motion, emotional upset or after being startled.
(5) The patient may have loss of reflexes and sphincter dysfunction.
Electromyography (EMG) may show continuous motor activity in an affected muscle.
The patient may respond to:
(1) oral or intravenous diazepam (may be dramatic)
(2) resection of the tumor
(3) corticosteroids
