Cerebrovascular reactivity to CO2 inhalation was studied by transcranial Doppler sonography in 30 patients with classic or common migraine and 39 healthy controls without clinical or ultrasonic signs of arteriosclerosis. Systolic and diastolic Doppler frequencies of the middle cerebral artery were plotted against end-tidal CO2 partial pressure; the reactivity index (I x R) was defined as relative frequency change during a PCO2 increase of 5 mmHg. In the normal subjects, I x R was 20.0 +/- 6.3 for systolic velocities, and 26.0 +/- 8.2 for diastolic values. Migraineurs during their headache-free interval had significantly higher I x R values on the affected side (mean: 41.6 systolic, 61.2 diastolic), compared with either controls (P less than 0.01) or the contralateral side (mean: 28.3 systolic, 30.8 diastolic; P less than 0.01). During the headache attack, CO2 reactivity was significantly lower than normal only for systolic velocities (mean: 8.3; P less than 0.05). Increased CO2 reactivity is thought to be one phenomenon of migraine. Transcranial Doppler CO2 testing of cerebrovascular reactivity is a reliable method that may be of interest for the diagnostic evaluation and management of migraine patients.

No abstract

The vascular reactivity to CO₂ inhalation was studied simultaneously in the ipsilateral middle cerebral (MCA) and ophthalmic arteries (OphA) of 10 healthy subjects using 2-vessel transcranial Doppler sonography. Flow velocities were measured simultaneously in both arteries during normo- and hypercapnia. A reactivity index (Ix_R) was defined in terms of the relative velocity change in response to an increase in end-tidal CO₂ pressure of 5 mm Hg. In the MCA Ix_Rwas 21.9 ± 3.6%, whereas in the OphA flow velocity decreased significantly (Ix_R(= –4.8 ± 2.9%). This latter change may reflect dilation of the ophthalmic artery during hypercapnia. Testing of oculovascular CO₂ reactivity is a reliable method that may be of interest for the evaluation and management of patients suffering from ocular ischemic syndromes due to carotid artery obstructions.