RESUMEN
The patient, a 78-year-old female with history of headache and progressive gait disturbance for almost one year, was admitted to our department because of dysphagia and dysphonia since three months before. Neurological examination revealed nystagmus, cerebellar ataxia, deafness, and vesical incontinence. No cerebral injuries were detected by computed tomography (CT) scan, although Paget's. Disease of Bone (PDB) was suggested, confirmed by biochemical and scintigraphic studies. The plain skull X-ray showed platybasia. As all the disarrangements were not explained by PDB complications alone, nuclear magnetic resonance imaging (MRI) was performed which demonstrated an Arnold-Chiari malformation (ACM) type I, with mild tonsillar herniation and anterior compression of the brainstem due to basilar impression, without syringomyelia. The association of PDB and ACM is a peculiarity seldom reported. The surgical approach was rejected, but the severity of symptoms and osteitis deformans biochemical activity needed a treatment; it was orientated to modify bone turnover using etidronate, a bisphosphonate, which induced clinical improvement and a decrease in serum alkaline phosphatase as well as in other bone resorption markers, without side effects. The good status and biochemical remission have been maintained a year later.