Digital tapping of the superficial temporal artery: significance in carotid duplex sonography

To determine whether tapping on the superficial temporal artery correctly identifies the ECA during carotid sonography, prospective evaluation of the reflection of the temporal tap on the spectral waveform was recorded and graded as 3+, 2+, 1+, or 0 in each ECA, ICA, and CCA, with 3+ being the most brisk response in each carotid system (ipsilateral CCA, ICA, and ECA). The pattern of response was evaluated in patients with and without hemodynamically significant (> than 50% diameter) stenoses in CCA, ICA, and ECA. The most frequent pattern of response to tapping on the superficial temporal artery was 3+ in the ECA, 2+ in the CCA, and 1+ or 0 in the ICA. This pattern was found in 41% (82/200) of systems overall. Whether or not stenoses were present in any branch of the extracranial carotid system, the strongest response (3+) was found in the ECA (58/200 [87%] with stenosis; 119/200 [89%] without stenosis, and lesser responses in the other arteries: 2+ in the CCA 31/200 [46%] with stenosis; 63/200 [47%] without stenosis, and 1+ or 0 in the ICA 58/200 [87%] with stenosis and 103/200 [77%] without stenosis). This pattern was unaltered by the degree of stenosis in the ECA or in the ICA. In 92.5% of the systems interrogated, the response was greater in the ECA than in the ICA. Tapping on the superficial temporal artery may be used as a reliable method of identifying the ipsilateral ECA even in instances of significant atherosclerotic disease in the ECA, CCA, or ICA.