The thickness and texture of temporal bone in brain CT predict acoustic window failure of transcranial Doppler.

BACKGROUND AND
PURPOSE: Although transcranial Doppler (TCD) is useful for evaluation and treatment of ischemic stroke, temporal acoustic window failure (TAWF) limits its application. We performed this study to reveal whether initial brain CT of acute stroke patients predicted TAWF.
METHODS: We performed TCD in 92 acute ischemic stroke patients (57 males, aged 38-84 years) with brain CT scans. We measured the thickness (BTW) and evaluated the texture of the temporal bone in acoustic windows shown in the CT scan with the use of picture archiving and communication system. The bone mineral density (BMD) of the vertebral bodies, femurs, and whole body was also measured.
RESULTS: Doppler signals were adequately obtained in 121 (65.8%) of the 184 middle cerebral arteries (MCA) from both cerebral hemispheres. BTW and inhomogeneity of temporal bone, besides age, sex, and hypercholesterolemia, was strongly correlated with TAWF. BMD was not directly correlated with TAWF, but inhomogeneous temporal bone was correlated with lower BMD scores. If the brain CT scan showed thick (BTW >or= 2.7 mm) and inhomogeneous temporal bone, the possibility of TAWF was 93.5%, while if brain CT scan showed thin (BTW < 2.7 mm) and homogenous temporal bone, it was only 5.4%.
CONCLUSIONS: The texture as well as the thickness of the temporal bone was the most important determinant of TAWF. When acute stroke patients had thin and homogeneous temporal bones in initial brain CT scan, TAWF was very rare, and loss of MCA signals on TCD specifcally indicated the absence of blood flow in MCA.