• Chiari malformation
• Headache
• Foramen Magnum decompression

Headache is a common complaint in children and adolescents. Around 60% of children and young people report at least three episodes of headache a year and around 8% suffer from migraine.1 Episodic tension-type headache is reported in up to 20% and chronic daily headache affects 1–2% of adolescents. The diagnosis of primary headaches is almost always made on clinical grounds and on the application of the widely used and accepted clinical criteria of the International Classification of Headache Disorders, which are now in their third edition.2 Neuroimaging may be necessary if the course of the primary headache is atypical, headache is unclassifiable and in some cases to alleviate parental anxiety. Secondary headaches due to intracranial pathology are often suspected on clinical assessment but will almost always require further investigations including brain imaging. It is not uncommon for the clinicians to face a situation where an incidental finding of an abnormality of uncertain significance has been reported on the brain MRI including Chiari malformation type 1 (CM1).

CM1 is an abnormality of the posterior fossa that has a smaller volume than normal and its contents are crowded. Routinely, the diagnosis of CM1 is made when isolated cerebellar tonsillar descent, of at least 5 mm below the foramen magnum, is identified …