Transcranial Doppler (TCD) ultrasonography is a noninvasive bedside tool that can evaluate cerebral blood flow hemodynamics in major intracranial arteries. TCD-derived pulsatility index (PI) is believed to be influenced by intracranial pressure (ICP).OBJECTIVE
To correlate TCD-PI with cerebrospinal fluid (CSF) pressure (representing ICP), measured by standard lumbar puncture (LP) manometry.METHODS
CSF pressures (CSF-P) were measured in 78 patients by LP manometry. Stable TCD spectra were obtained 5 minutes before LP from either middle cerebral arteries using Spencer's head frame and 2-MHz transducer. PI values were calculated from the TCD spectra by an independent neurosonologist.RESULTS
Factors displaying a significant relationship with CSF-P included age (R= −.426,P< .0005); EDV (R= −.328,P= .002;) and PI (R= .650,P< .0005). On analyzing dichotomized data (CSF-P < 20 vs. ≥ 20 cm H20) TCD-PI was an independent determinant (OR per .1 increase in PI = 2.437; 95% CI, 1.573-3.777;P< .0005). PI ≥ 1.26 could reliably predict CSF-P ≥ 20 cm H20 (sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were 81.1%, 96.3%, 93.8%, 88.1%, and 90.1% respectively).CONCLUSION
TCD-derived PI could be used to identify patients with CSF-P ≥ 20 cm H20 and may play an important role as a monitoring tool.