Multiple System Atrophy and theSyndrome of Inappropriate Secretion of Antidiuretic Hormone

摘要

Multiple system atrophy {MSA) is known to affect the hypothalamus. Lesions in the hypothalamus and the adjacent area potentially lead to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in this disorder. Since SIADH has not been a feature in idiopathic Parkinson's disease so far, it might help distinguishing MSA from idiopathic Parkinson's disease. We recently had such a patient.A 58-year-old woman had a six year-history of right leg tremor and gait disturbance. She was considered to have idiopathic Parkinson's disease at a local neurology clinic, and was started on antiparkinsonian drugs. Her leg tremor and gait disturbance once ameliorated moderately. However, they gradually worsened again. She developed urinary frequency, urinary incontinence and constipation. Histories of postural syncope or laryngeal stridor were not known. The dose of the drugs was increased to levodopa/carbidopa 500 mg/day, selegiline 2.5 rng/day, pramipexole 1.5 mg/day, eabergolme 3 mg/day, trihexyphenidyl 4 mg/day, and amandadjne 150 rng/day. When she was first admitted to our hospital because of acute fever due to pyelonephritis, she was wheelchair-bound. She was alert but slight agitated. Laboratory examination revealed hypo-osmolar (257 mOsm/kg.H2O- 276 < normal < 292) hyponatremia (117 mEq/l; 136 < normal < 147) and a raised serum arginin-vasopressin (AVP) level (11.7 pg/ml; 0.3 < normal < 3.5; data came later); whereas she had raised level in urinary osmolality (405 mOsm/kg-BaG). Serum Cortisol and -other laboratory test results were normal. Her hyponatremia was carefully reversed by an intravenous saline infusion, and she was discharged from hospital. However, two weeks later, she developed hyponatremia .and was admitted to our hospital again. Laboratory examination confirmed hypo-osmolar (237 mGsm/kg.H2O) hyponatremia (116 mEq/L), a raised serum AVP level (8.75 pg/mL), and a raised level in urinary osmolar-ity (up to 722 mOsm/kg.HaO), Serum Cortisol, thyroid function, and other laboratory test results were normal. These findings confirmed the presence of SIADH,5 However, abdominal CT and ultrasound sonography revealed no evidences of malignancy that might cause SIADH. She was taught to perform water restriction, which gradually ameliorated her hyponatremia.