Pontine hemorrhage at a microbleed site in a patient with central pontine myelinolysis

Abstract

Central pontine myelinolysis (CPM) is an uncommon disorder, characterized by non-inflammatory demyelination, which may be caused by an abrupt change of serum osmolarity, especially of sodium concentration [1]. Although rapid correction of chronic hyponatremia leads to the disruption of the blood–brain-barrier (BBB) [2], CPM associated with intracerebral hemorrhage (ICH) has rarely been reported [3, 4]. Cerebral microbleed (CMB) is a 2–5-mm sized small hypointense lesion that is generally detected by gradient echo (GRE) magnetic resonance imaging (MRI), which is thought to be associated with advanced microangiopathy, focal breakdown of the BBB and risk of bleeding [5]. In view of the possible effects of CPM and CMB on the BBB, we can postulate that the affected region is in a hemorrhagic-prone state. We describe a patient who suffered CPM and subsequent ICH at the site of pontine microbleeds. An 89-year-old female attended the emergency room (ER) with stuporous mentality. In the past, she had suffered from hypertension and chronic kidney disease with antihypertensives and diuretics without dialysis. Seven days before visiting the ER, her general condition had worsened after fall down and oral intake was poor. It had not been possible to wake her for the last 5 h before she appeared in the ER. Neurological examination revealed stupor mentality with decreased corneal, vestibulo-ocular and gag reflexes. Her withdrawal response to painful stimuli on all extremities was reduced especially on her left side. Laboratory findings revealed mild anemia (hemoglobin 9.3 g/dL) and elevated renal function values (blood urea nitrogen 42 mg/dL, creatinine 3.2 mg/dL) and normal range electrolyte values. Total protein (4.9 g/dL) and albumin (2.6 g/dL) levels were low, suggesting malnutrition. Brain fluid attenuated inversion recovery (FLAIR) MRI revealed diffuse high signal areas in the basis pontis (Fig. 1a). In addition, multiple microbleed signals were detected in the whole brain area as well as the lower pons within FLAIR high signal area on GRE imaging (Fig. 1b). Her diagnosis was CPM without any hyponatremia correction and we initiated general and nutritional care. Three days after admission, she became alert and motor power was partially recovered. However, on the 8th day, her mental functioning deteriorated abruptly to stupor. Neurological examination showed pin-pointed pupils with impaired light reflex. Brainstem reflexes were also completely absent. Brain MRI revealed pontine hemorrhage in two different foci that coincided with microbleed sites on the previous MRI (Fig. 1c, d). The patient died from respiratory and renal failure 3 weeks after admission. CPM is an osmotic demyelination syndrome (ODS) which is a well-known disease caused by rapid correction of hyponatremia, alcoholism, liver transplantation and malnutrition [1]. Although the exact mechanism of ODS is not clear, it has been suggested that any rapid change in serum osmolality with resulting changes in brain cell volume may lead to stereotyped injury to myelin sheaths [2]. Therefore, ICH, which is due to rupture of intracerebral arteries, is an unusual complication and has been rarely reported [3, 4]. However, these previous reports differ from Y. S. Kim and J. Lee equally contributed to this work.