Pilonidal sinus of the prepuce

Two possible explanations for the appearances of oedema need to be considered. The first is that the low u numbers reflect an increased fluid content of brain tissue-that is, true oedema-perhaps related to regional cerebral ischaemia due to vasospasm or to arteriovenous shunting with bypassing of the microcirculation.1 Alternatively, a reduction in , numbers and increased blackening on the Polaroid film might be due to a decreased content of blood per matrix cell if regional cerebral blood flow were decreased at the time of scanning. Further observations with both CAT and cerebral blood flow techniques in the prodromal and headache phases of migraine are required to throw further light on the significance of this finding. The significance of the mild cerebral atrophy found in some patients is uncertain. In view of the lack of data from normal volunteers,2 the possibility that the mild widening of the subarachnoid space and ventricular system in these patients may in fact represent one end of the spectrum of normality rather than being truly indicative of early cerebral atrophy cannot be excluded. Nevertheless, in view of the fact that a greater degree of atrophy was found in two cases, it is tempting to consider the possibility that some degree of cerebral atrophy may result from the effects of recurrent episodes of regional cerebral ischaemia in migraine.