Central pontine myelinolysis associated with pancreatic diabetes

Abstract

A 60-year-old man presented with subacute progression of difficulty in speaking and walking. The patient had been suffering from chronic pancreatitis due to alcoholism, and glucose level in the serum had been remarkably variable for a few months. Blood pressure was normal under treatment with angiotensin II receptor blocker. Clinical examination showed ocular dysmetria, scanning speech, dysphagia, clumsy hands, and wide-based gait, suggesting cerebellar ataxia. He was alert, and his cognitive function and psychological status were normal. Tendon reflexes were intact in all limbs, and there was no sensory disturbance, muscle weakness, involuntary movement, or autonomic dysfunction. Two weeks after the first symptom emerged, the patient was unable to walk by himself because of the ataxic symptoms. Laboratory tests revealed hyperglycemia (685 mg/dl), which was the highest value for the patient, and HbA1c was 16.9%. Blood urea nitrogen was 36.7 mg/dl and creatinine level was 1.61 mg/dl in the serum, which had been the same level for years, reflecting chronic kidney dysfunction. There were no abnormalities detected in the levels of electrolytes including sodium, and no episodes of correction of hyponatremia. Brain magnetic resonance images (MRI) were normal on admission, but after 3 weeks, symmetrical hyperintensity in the central portion of the pons and middle cerebellar peduncles was evident on T2-weighted and fluid-attenuated inversion recovery images (Fig. 1a, b). The periphery of the pons was not affected, and thus, these MRI findings were considered to be typical of central pontine myelinolysis (CPM). The lesions were not enhanced by an administration of gadolinium, suggesting that tumor and inflammation were unlikely. There was no obvious change in the apparent diffusion coefficient, indicating that infarction and reversible posterior leukoencephalopathy were also unlikely. Abdominal computed tomography demonstrated pancreatic lithiasis (Fig. 1c). There was no malignancy in the chest, abdomen, or pelvis. We diagnosed the patient with CPM caused by a rapid progression of hyperglycemia. After initiating treatment with insulin, his hyperglycemia rapidly improved. The ataxic symptoms gradually recovered with the aid of rehabilitation; ocular dysmetria and dysphagia almost disappeared in 2 months, and the patient was able to walk without help in 3 months. Additionally, his hand clumsiness and speech disturbance improved in 4 months. MRI findings remained the same with minimal improvement at 1 year after the onset. There was no apparent change in the levels of electrolytes in the serum throughout the disease course. CPM is recognized as a complication resulting from a rapid change in serum osmolarity, and a rapid correction of sodium in hyponatremic patients is widely accepted as the most common cause of CPM [1, 2]. A marked shift in the level of serum glucose can rarely be another causative factor, probably because the glucose level also influences the serum osmolarity [3, 4]. However, it is uncertain why CPM is observed in only a limited number of diabetic patients. Our patient developed CPM when his serum glucose levels fluctuated severely over the course of chronic H. Kuwahara (&) Department of Neurology and Neurological Science, Graduate School, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan e-mail: h-kuwahara.nuro@tmd.ac.jp