[Functional evaluation of temporo-sylvian anastomoses by ultrasonic transcutaneous flow measurement]

The intra-extracranial bypass using the superficial temporal artery remains a matter of controversy about its usefulness and indications. The improvement in ultrasonic technics allows henceforward to measure the blood flow inside this anastomosis with a good precision. In that purpose, we use a duplex Doppler system and a vascular echotomograph. This system brings us the necessary informations to calculate the blood flow: the Doppler frequency shift, the internal diameter of the vessel, and the incidence of the Doppler beam. The spectral analysis of the Doppler signals not only gives us informations concerning the local circulation but also the distal circulatory resistance. An intra-extracranial operation and this examination have been performed in thirty seven patients. The blood flow inside this anastomosis ranges between ten and 360 ml/minute. Patients presenting a blood flow superior to 40 ml/minute seem to improve more frequently. Otherwise there is also an excellent correlation between the blood flow inside the anastomosed temporal artery and its diameter. The evaluation of the cerebral circulatory index of resistance is a good criteria to predict the becoming of the anastomosis and the expected clinical improvement. The functional study of the temporo to middle cerebral artery anastomosis using the duplex echography-Doppler provides essential data to test their efficacy. The expected progress in ultrasonic technics will allow to know, the value of the cerebral circulatory resistances before the operation and so to predict the possible gain for the patient.