Simultaneous Insonation of One MCA through Bilateral Temporal Bone Windows Using M-mode TCD

ABSTRACT

BACKGROUND: Transcranial Doppler ultrasonography (TCD) is limited by insufficient ultrasound penetration through the temporal bone. Recent studies have revealed poor temporal bone windows in 5~30% of patients. In about 38% of the patients with poor temporal bone windows, a temporal window was unilaterally absent. The aim of the present study was to compare the mean flow velocities (MFV) of the middle cerebral arteries (MCA) obtained through the ipsilateral temporal bone window with those obtained through the contralateral one using M-mode TCD. METHODS: Eighteen patients (mean age, 28 y; age range, 21~40 y) who had adequate bilateral temporal bone windows were enrolled and 36 MCAs were investigated. The investigators tried to detect the MCA through the ipsilateral and contralateral temporal windows with two 2-MHz probes simultaneously (ipsilateral insonation and contralateral one, respectively). RESULTS: The MCA MFV measured by ipsilateral insonation was 72.58 +/- 9.78 cm/sec and that demonstrated by contralateral insonation was 70.94 +/- 9.79 cm/sec. Even though the differences between MFVs by either side insonation was 2.25~3.94% (0~13.11%) and had significant difference statistically, those were within side-to-side limit of 30% generally considered as abnormal. The mean bitemporal diameter (BTD) was 130.72 +/- 3.75 cm (126~142 cm). We obtained similar waveforms in the reverse direction to those of ipsilateral insonation at 95.33 +/- 5.19 mm of depths (72.97 +/- 4.23% of BTD) during contralateral insonation. CONCLUSIONS: The demonstration of the MCA through the contralateral insonation provides an opportunity to obtain significant mean flow velocities in patients with absent or insufficient temporal bone window unilaterally.