RESUMEN
TOPICALITY: Central pontine and extrapontine myelinolysis is a rare and dangerous form of the demyelinating process of undefined origin, the development of which is associated with a very low sodium level in the blood (hypernatremia). OBJECTIVE: To describe a rare case of extrapontine myelinolysis as a complication occurring in the hemorrhagic period of anterior communicating artery aneurysm rupture as well as to demonstrate that this condition can be diagnosed intravitally. CONCLUSION: Clinical vigilance of extrapontine myelinolysis may promote the timely diagnosis and treatment of this disease, which is a potential cause of death. Pulse-therapy with glucocorticoids provides the opportunity to achieve regression of neurological symptoms and to stabilize the patient's condition.