Spontaneous reduction of tonsillar herniation in acromegaly: A case report

The herniation of the cerebellar tonsils through the foramen magnum into the cervical subarachnoid space is defined as Chiari I malformation [5] and generally considered a congenital condition. Patients with Chiari I malformation usually present in adolescence or early adulthood, but the finding of tonsillar ectopia is sometimes documented incidentally on routine magnetic resonance (MR) imaging in asymptomatic patients. Recently, the progressive ascent of tonsils with age has been stressed [10] and spontaneous resolution of Chiari I malformation has been described in periods of rapid,corporeal growth [4]. Some acquired pathological processes can cause displacement of the cerebellar tonsils into the occipital foramen, such as intracranial masses, brain swelling, benign intracranial hypotension, and lumboperitoneal puncture or shunting [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 underwent serial MR examinations because of a pituitary macroadenoma causing acromegaly that was resected via a transnasosphenoidal approach.