Clinical and radiologic correlations of central pontine myelinolysis syndrome

OBJECTIVE: To characterize clinical and radiologic features of patients with central pontine myelinolysis (CPM) and identify variables that predict outcome. PATIENTS AND METHODS: We retrospectively studied patients diagnosed as having CPM identified by a search of Mayo Clinic medical records from January 1, 1999, through December 31, 2010. Diagnosis was made by clinical and radiologic features. Favorable outcome was defined by a modified Rankin Scale score of 2 or lower. Volume of signal abnormality on brain magnetic resonance imaging (MRI) was quantified by a neuroradiologist blinded to outcomes. Wilcoxon rank sum tests were used to assess association between volume of signal abnormality and outcomes at discharge and last follow-up. RESULTS: Of 24 patients, 14 (58%) had only CPM, and 10 (42%) had extrapontine involvement. Hyponatremia was documented in 18 patients (75%), with median sodium nadir of 114 mmol/L. Eighteen patients (75%) had alcoholism, and malnutrition was documented in 12 (50%). Presenting symptoms included encephalopathy (n=18 [75%]), ataxia (n=11 [46%]), dysarthria (n=7 [29%]), eye movement abnormalities (n=6 [25%]), and seizures (n=5 [21%]). Favorable outcome was seen in 15 patients (63%) at last follow-up. Findings on initial brain MRI were normal in 5 patients, but all MRI scans were abnormal with serial imaging. The volume of radiologic signal abnormality was not associated with outcome at discharge or last follow-up (P=.67 and P=.37, respectively). CONCLUSION: Clinical outcome in patients with CPM is not predicted by the volume of radiologic T2 signal abnormality on MRI or the severity of hyponatremia. Serial brain imaging is of value because a substantial proportion of patients have normal findings on initial MRI.