Superior cerebellar artery - a potential pitfall in transcranial posterior cerebral artery insonation

Transcranial color-coded duplexsonography (TCCD) of the posterior cerebral artery (PCA) is commonly performed in an axial midbrain insonation plane. The proximal PCA is easily identified as a vessel, originating from the top of the basilar artery (BA). However, the initial segment of the superior cerebellar artery (SCA) also originates from the top segment of the BA and runs in parallel. Therefore, it is possible to confuse the two vessels. The aim of our study is to anatomically differentiate the proximal PCA and SCA by means of TCCD in the coronal plane using a transtemporal approach and to analyze and compare their flow responses during a visual stimulus paradigm.

60 subjects without a relevant vascular pathology and with a good temporal bone window were examined. The distal BA, the proximal PCA and the SCA were insonated using a coronal insonation plane and identified by their anatomical relationship. The visible length was measured and the blood flow velocities were recorded at rest and during visual stimulation.

The identification and differentiation of both vessels was successful in 101 of 120 hemispheres (84.2 %). The PCA systolic flow velocities at rest and during visual stimulation were 58.4 +/- 11 and 71.8 +/- 13 cm/sec (23.6 % increase), while the SCA velocities were 50.7 +/- 12 and 53.5 +/- 13 cm/sec, respectively (5.8 % increase). The difference was significant (p < 0.001).

Using the coronal transtemporal insonation approach, TCCD makes it possible to identify and distinguish the proximal PCA and SCA. Our study is the first to provide a systematic ultrasound assessment of the SCA and includes data on normal flow velocities and reactivity to a visual stimulus.