impinging on adjacent pain-sensitive structures The most pain-sensitive intracranial structures are the proximal portions of the large cerebral arteries at the base of the brain, the venous sinuses, and the large cerebral veins Various physiologic mechanisms come into play in causing headache Painful stimuli can be broadly categorized as resulting from vascular effects, muscle contraction, inflammation, and traction/compression ( Table 59.1 ) Examples of each of these types of headache etiology are described in the following discussion of differential diagnosis It should be noted that visual problems are an unlikely cause of significant headaches in children A child with persistent headaches that have previously been attributed to “eye strain” may, therefore, deserve a more careful evaluation Attempting to predict the neuroanatomic location of a pathologic process using only the site of headache described by a child is unreliable In part, this is attributable to the unpredictable displacement of structures caused by a mass lesion In addition, the extremely complex relationships of the various nerves involved in pain sensation of the head and neck lead to unexpected patterns of referred pain Thus, a posterior fossa lesion can cause frontal or orbital pain, and supratentorial lesions may result in pain localized to the occiput or the back of the neck, for example DIFFERENTIAL DIAGNOSIS A comprehensive discussion of the various causes of headache in pediatric patients is beyond the scope of this textbook The conditions described here are those most likely to be seen in acute- and emergency-care settings ( Table 59.2 ) and those with the greatest potential for imminent morbidity or mortality ( Table 59.3 ) Fortunately, the majority of pediatric patients who present to the ED with headache have a benign condition In a study of 432 children and teenagers evaluated in the ED for headache, Conicella et al found that the most common etiologies were upper respiratory infection (19%), migraine (18.5%), posttraumatic headache (5.5%), and tension-type headache (4.6%) Anatomic abnormality (e.g., Chiari malformation), brain tumor, meningitis, idiopathic intracranial hypertension, and ventricular shunt failure were found in a total of 6% of patients Vascular Headaches associated with vascular changes are believed to be caused primarily by vasodilation, although the exact mechanism has yet to be fully elucidated One common example of this type of headache is migraine Migraine headaches are typically chronic and remitting, with a characteristic pattern that is easily