['Failure to detect the sphenoidal segment of the middle cerebral artery (M1) on transcranial color-coded sonography (TCCS) results from either M1 occlusion or an insufficient temporal bone window (TBW). We sought to identify a simple indicator on B mode images for M1 evaluation.', "Consecutive acute ischemic stroke patients with an intact M1 segment underwent prospective TCCS evaluation. Visibilities of the contralateral temporal bone (CTB), midbrain (MB) and lesser sphenoid wing (LSW) on B mode images were defined as follows: 'invisible', 'poor' if the contour was less than 50% visible, 'fair' if more than 50% visible and 'good' if totally visible. M1 detectability on color Doppler images was defined as follows: 'INVISIBLE', 'POOR' if the M1 was detected as color dots, 'FAIR' if linearly but discontinuously detectable, and 'GOOD' if linearly and continuously detectable. The relationship between each structure's visibility and M1 detectability was assessed.", "Seventy-six patients with 152 TBWs were evaluated. The CTB was 'invisible' in 2%, 'poor' in 22%, 'fair' in 36% and 'good' in 40%. Visibility of the MB was 36, 24, 26 and 14%, respectively. Visibility of the LSW was 16, 22, 29 and 32%, respectively. The M1 was 'INVISIBLE' in 51%, 'POOR' in 7%, 'FAIR' in 7% and 'GOOD' in 35%. Spearman's rank correlation coefficient between each structure's visibility and M1 detectability was 0.68 for the CTB, 0.66 for the MB and 0.80 for the LSW, respectively (p < 0.001 for all)."] Is visibility of the lesser sphenoid wing an important indicator for detecting the middle cerebral artery on transcranial color-coded sonography?