Spontaneous reduction of tonsillar herniation in acromegaly: A case report

The herniation of the cerebellar tonsils through the foramen magnum into th e cervical subarachnoid space is defined as Chiari I malformation [5] and g enerally considered a congenital condition. Patients with Chiari I malforma tion usually present in adolescence or early adulthood, but the finding of tonsillar "ectopia" is sometimes documented incidentally on routine magneti c resonance (MR) imaging in asymptomatic patients. Recently, the progressiv e ascent of tonsils with age has been stressed [10] and spontaneous resolut ion of Chiari I malformation has been described in periods of rapid,corpore al growth [4]. Some acquired pathological processes can cause displacement of the cerebell ar tonsils into the occipital foramen, such as intracranial masses, brain s welling, benign intracranial hypotension, and lumboperitoneal puncture or s hunting [12,13]. The association with acromegaly has been reported [9]. We report a case of gradual reduction of tonsillar herniation in a 52-year-old man, who underwe nt serial MR examinations because of a pituitary macroadenoma causing acrom egaly that was resected via a transnasosphenoidal approach.