[Borderline cerebellar tonsillar ectopia in a child with headache. Case report].

Frequent headache is a symptom that leads to significant distress and functional impairment, both in childhood and in adulthood. Some medical conditions are associated with a higher frequency of headaches. Borderline cerebellar tonsillar ectopia which may be defined as the downward extension of cerebellar tonsils of <5 mm below the foramen magnum is among these conditions. Although questions persist about the clinical significance of this rare entity on headache, there are studies reporting severe headache syndrome in 16% of these patients. We report a 9-year old male patient, who presented to our clinic with a frontal headache of 5 years' duration, and was found to have borderline cerebellar tonsillar ectopia on magnetic resonance imaging. To the best of our knowledge, there has not been a reported case of this coexistence at this early stage of life. We would like to contribute to the literature, owing to the very rare and atypical presentation of this entity in the early childhood period.