Reliability of cerebral vasoreactivity assessment from the submandibular window

Background and Purpose: Transcranial Doppler (TCD) is a noninvasive and effective technique for the measurement of cerebrovascular function. Measurement of breath holding index (BHI) in the middle cerebral artery is commonly performed to determine cerebrovascular reactivity. Nevertheless, a notable drawback of TCD is the absence of a transtemporal acoustic bone window. The submandibular window offers an alternative way to measure BHI. Here, we studied the diagnostic accuracy of cerebrovascular reactivity (CVR) in the internal carotid artery (ICA) as measured from the submandibular window. Methods: Twenty-five volunteers (13 male, 12 female) with sufficient temporal acoustic bone windows were assessed. BHI was measured by mean blood velocities before and after breath holding. The correlation of BHI measured in ICA (BHIi) and ipsilateral middle cerebral artery (BHIm) was assessed. Results: The mean age of the participants was 39.9 ± 13.7 years. The mean BHIm and BHIi values were 0.93 ± 0.29 and 0.92 ± 0.32, respectively. Spearman’s correlation coefficient between BHIm and BHIi was 0.665 (p = 0.0003). The cutoff point of the BHIi value for CVR impairment determined by BHIm was 0.71 (sensitivity 80.0%, specificity 80.0%). Conclusion: Measuring BHI from the submandibular window may be a useful procedure in the case of temporal bone window insufficiency.