Value of diffusion-weighted imaging in central pontine and extrapontine myelinolysis

Central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM) are rare neurological disorders characterized by demyelination in and/or outside the pons. Whether diffusion-weighted imaging (DWI) might facilitate an earlier diagnosis has not yet been studied systematically.

We describe demographics, clinical presentation, and early magnetic resonance imaging (MRI) findings with special emphasis on the relevance for diagnosis of CPM and/or EPM in eight patients.

Of the analysed eight patients (aged 37-70 years; two men, six women), CPM was diagnosed in three, EPM in one, and a combination of CPM and EPM in four patients. Aetiology was rapid correction of sodium in two patients; a combination of hyponatremia, alcoholism and alcohol withdrawal in five patients and unclear in one patient. Seven patients suffered from chronic alcoholism and four from malnutrition. Demyelinating lesions were found in the pons, thalamus, caudate nucleus, putamen and midbrain. While the lesions could be clearly delineated on T2- and T1-weighted images, DWI demonstrated a strong signal in only six patients. Furthermore, DWI demonstrated lesions only to some extent in two patients and was completely negative in two patients on initial MRI. In none of the patients did the demonstration of hyperintense lesions on DWI precede detection on conventional MRI sequences. Apparent diffusion coefficient (ADC) values were heterogenous with a decrease in two cases and an increase in the remainder.

We conclude that early DWI changes are a common finding in CPM/EPM but do not regularly precede tissue changes detectable on conventional MRI sequences. Heterogenous ADC values possibly represent different stages of disease.