Headache and Chiari type I malformation: occurrence in female monozygotic twins and first-degree relatives.

The Chiari type I malformation has recently been reported in three generations of a family, including female monozygotic twins. Headache was the main symptom in several family members. Various headache patterns consistent with migraine without aura, cough headache, tension headache and hypoliquorrhoeic headache were present, and different patterns might coexist in the same patient. In the twins and their mother, who all had a headache consistent with migraine without aura, there were atypical features such as occipital pain location, lack of side-shift of the pain, lack of ergotamine effect and precipitation of attacks by Valsalva-like manoeuvres. The headache was significantly relieved by operation in the one twin with major herniation and the most marked headache. We suggest that in these patients the migraine-like headache mimics true migraine but that there is a causal relationship between the different headache types reported and the malformation.