[Acute respiratory failure as the sol inaugural sign of Arnold-Chiari malformation. Two cases].

Arnold-Chiari malformation is an occipitocervical malformation where the cerebellar amygdales descend below the occipital foramen. Acute respiratory failure is an exceptional inaugural sign. We report two cases disclosed by alveolar hypoventilation associated with type I Arnold-Chiari malformation. The two patients age 51 and 52 years had an uneventful past history and presented with hypercapnic encephalopathy with acute respiratory failure requiring ventilatory assistance. Respiratory function tests, helicoidal thoracic computed tomographic angiography, electromyogram, cardiac echography, and thyroid and immunological tests were normal. Blood gases and polysomnography were in favor of central hypoventilation without sleep apnea. Magnetic resonance imaging demonstrated type I Arnold-Chiari malformation. The course was complicated by recurrent respiratory failure in both patients. Surgical decompression performed for the first patient provided no improvement. This patient died two months after surgery subsequent to aspiration pneumonia. The second patient was treated with continuous positive pressure noninvasive ventilatory assistance and had a good outcome at 25 months. These two cases illustrate the absence of any neurological sign, acute respiratory failure being the only sign of Arnold-Chiari malformation.