Clinical and radiologic correlations of central pontine myelinolysis syndrome

Abstract

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.

FIGURE 1.

Example of quantification of signal abnormality on sequential axial T2-weighted images in the pons (A and B) and midbrain (C) totaling 3194 μL. Volumes of signal abnormality were obtained by tracing regions of interest around areas of signal abnormality with a semiautomated technique involving seed placement and growing through thresholding.

FIGURE 2.

Example of lack of association between pontine signal and clinical outcome. Axial T2-weighted fluid-attenuated inversion recovery images demonstrate (A) a mild area of pontine hyperintensity (1825 μL total volume of abnormality) in a 67-year-old man with significant ataxia and hyperreflexia who remained moderately disabled (mRS [modified Rankin Scale] score, 3), and (B) severe pontine involvement measuring a total of 6431 μL in a 45-year-old woman with dysarthria and ataxia who achieved a favorable recovery (mRS score, 2).

FIGURE 3.

Lack of association between quantified radiologic volume of signal abnormality (microliter) attributed to osmotic myelinolysis on T2-weighted brain magnetic resonance images and clinical outcome at last follow-up. A score of 2 or lower on the modified Rankin Scale was considered favorable.