Thermography in vascular disorders affecting the brain.

Increasing interest in the field of cerebrovascular disease has resulted in a demand for diagnostic procedures free from risk which can be used for screening purposes to decide which cases should be further investigated. Thermography, which combines a high degree of accuracy with complete safety, meets the need. The first reports of the value of this method (Wood, 1965; Wood, Hill, and Heyman, 1965) have received recent confirmation (Mawdsley, Samuel, Sumerling, and Young, 1968) which is extended by the present report. Thermography involves the detection of heat energy by an infra-red sensitive device, with subsequent conversion to electrical energy, amplification, and a suitable means of display. As the heat emitted from the skin is related to blood flow, measurement of the heat emission gives a measure of blood flow. The main application of thermography to cerebrovascular disease is made possible by the fact that, whereas the skin of the face is mainly perfused by branches of the external carotid artery, there is an area in the medial supraorbital region which is nearly always supplied by the terminal branches of the ophthalmic artery, which derives directly from the internal carotid artery immediately distal to the cavernous portion (Fig. 1). It follows therefore that a lesion of the internal carotid artery between its origin in the neck and the origin of the ophthalmic artery is liable to produce a reduced blood flow in the medial supraorbital skin, which will be detectable thermographically as a cool area (Fig. 2). A normal thermogram is shown for comparison (Fig. 3).