EXTRAPONTINE MYELINOLYSIS OF THE BASAL GANGLIA WITHOUT CENTRAL PONTINE MYELINOLYSIS

Since the first descriptions of central pontine myelinolysis (CPM) wer e put forth it has become evident that myelinolysis may not be exclusi vely restricted to the pens, In many cases myelinolysis may share othe r brain regions, while in still others the pens may not be affected at all, as in the present case of pure basal ganglia myelinolysis. Regar dless 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 hemiated d iscs, 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 3 7 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 inten sity foci in the basal ganglia 3 weeks before death, Histologically th ere were bilateral, circumscribed, spheroidal areas of demyelination i nvolving the striatal fibers which course through the putamina. The pe ns was spared. This case illustrates that extrapontine, basal ganglia myelinolysis may occur in the absence of CPM or alternate areas of mye linolysis. We discuss other cases of EPM, with and without CPM, to def ine the brain regions involved. MRI is uncovering many new cases of EP M and CPM. This permits one to follow the evolution of the myelinolyti c lesions and to correlate their progression or regression with treatm ent modalities and the neurological findings.