Central Pontine Myelinolysis

A 68-year-old man was referred to Tokyo Department Hiroo Hospital because of non-projectile vomiting and watery diarrhea which continued for three days. On admission, his initial blood tests were normal except for severe hyponatremia with a sodium level of 99 mmol/L (normal, 135–145 mmol/L). Normal saline was administered intravenously, and the sodium level began to normalize at 99 mmol/L on day 2, 105 mmol/L on day 3, 120 mmol/L on day 5, and 129 mmol/L on day 7. One week later, he started complaining of difficulty in swallowing and speaking accompanied by unsteadiness of gait and eventual inability to walk. Initial magnetic resonance imaging (MRI) and computed tomography (CT) of the brain on day 7 showed no abnormality. However, his condition continued to deteriorate, and a repeat MRI on day 14 revealed a well-defined lesion in the pons of low T1 signal intensity (Figure 1 A) as well as a trident-shaped lesion of high T2 signal pontine intensity (Figure 1 B). A diagnosis of central myelinolysis (CPM) was made. CPM is an acute demyelinating condition of the brain stem and recognized complication of the treatment of patients with chronic hyponatremia (>48 h). The risk of CPM is believed to be associated with a rapid (>8 mmol/L/day) correction or overcorrection of the serum sodium concentration. However, there is no accepted safe rate of correction [1]. Other risk factors identified include alcoholism, malnutrition, liver disease, and interestingly, liver transplantation. Symptoms of CPM include tetraplegia, pseudobulbar palsy, and acute changes in mental status leading to coma or death without intervention. Conventional imaging findings (MRI and CT) typically lag behind clinical manifestations, thus limiting the utility of imaging in early diagnosis, and imaging is advocated later to confirm CPM diagnosis [2]. There are no effective therapeutic methods for CPM treatment and recovery varies ranging from none to substantial improvement [3].

1. Adrogué HJ, Madias NE. N Engl J Med. 2000;342:1581-9. 2. Laureno R, Illo wsky Karp B. Myelinolysis after correction of hyponatremia. Ann Intern Med. 1997;126:57–62 3. Menger H, Jörg J. Outcome of central pontine and extrapontine myelinolysis (n = 44). J Neurol. 1999;246:700-5.