Extrapontine myelinolysis of the basal ganglia without central pontine myelinolysis.

Since the first descriptions of central pontine myelinolysis (CPM) were put forth it has become evident that myelinolysis may not be exclusively restricted to the pons. In many cases myelinolysis may share other brain regions, while in still others the pons may not be affected at all, as in the present case of pure basal ganglia myelinolysis. Regardless of geographic location, too rapid correction of hyponatremia has been invoked as the triggering mechanism which leads to both CPM and extrapontine myelinolysis (EPM). This case of EPM is that of a 61-year-old male who suffered spinal cord compression and quadriplegia due to the breakdown of a double cervical fusion at C4-5/C5-6 for herniated discs. One month later, following vomiting and poor food intake, a low serum Na+ of 101 mmol/l developed and was corrected to 128 mmol/l in 37 h (and from 104 mmol/l to 121 mmol/l in 15 h). Altered mental status ensued and a T2 weighted MRI showed symmetrical, bilateral high intensity foci in the basal ganglia 3 weeks before death. Histologically there were bilateral, circumscribed, spheroidal areas of demyelination involving the striatal fibers which course through the putamina. The pons was spared. This case illustrates that extrapontine, basal ganglia myelinolysis may occur in the absence of CPM or alternate areas of myelinolysis. We discuss other cases of EPM, with and without CPM, to define the brain regions involved. MRI is uncovering many new cases of EPM and CPM. This permits one to follow the evolution of the myelinolytic lesions and to correlate their progression or regression with treatment modalities and the neurological findings.