Arginine test is not reliable for diagnosing cerebellar multiple system atrophy.

We evaluated the arginine growth hormone (GH) stimulation test for the diagnosis of cerebellar-type multiple system atrophy (MSAc) in patients with ataxia. Fourteen subjects with MSAc, 11 with idiopathic late-onset cerebellar ataxia (ILOCA), 10 with familial ataxia, and 10 healthy controls were tested. After pituitary GH deficiency was excluded, subjects underwent arginine testing. Peak serum GH response was analyzed. No significant differences in peak GH response were found between subject populations. Thirty-three percent of MSAc subjects mounted responses >10 microg/l GH. Thirty-six percent of ILOCA subjects and 40 percent of healthy controls mounted responses <4 microg/l GH. Arginine thus appears to be unreliable for the diagnosis of MSAc.