Aim: We investigated the correlation between intracranial pressure and flow parameters by simultaneous Doppler sonographic flow measurements in the internal carotid arteries and estimation of the intracranial pressure over the anterior fontanelle.
Method: 12 infants (7 boys and 5 girls) with increased intracranial pressure were investigated. The corrected gestational age at investigation was 42 +/- 14 weeks, the weight was 3080 +/- 2540 g. Intracranial pressure was measured by applanation tonometry over the anterior fontanelle. The infants were subdivided into two groups: Group 1 (9 infants) with slightly increased intracranial pressure (16.9 +/- 3.3 cm H2O) and group 2 (3 infants) with moderately increased intracranial pressure (21.6 +/- 3.3 cm H2O). In all infants Doppler sonographic flow measurements within the intra- and extracranial segments of the internal carotid arteries were performed. From the flow profile, the peak systolic flow velocity Vs, the enddiastolic flow velocity Ved as well as the time average flow velocity TAV and the resistance index RI were measured. From the flow velocities, the I/E-ratio was calculated. The measured variables were compared with the values of matched pairs of a healthy control group of similar age and weight.
Results: Group 1 with slightly increased intracranial pressure displayed no significant difference of the RI within intracranial and extracranial sections of the internal carotid artery and the control group. The flow velocities, however, showed a significant increase within the intracranial segment of the internal carotid artery in comparison with the extracranial part of the internal carotid artery as well as the healthy control group. I/E-ratio for Vs increased significantly to 1.29 +/- 0.19, for Ved to 1.24 +/- 0.27 and for TAV to 1.08 +/- 0.27. Group 2 with moderately increased intracranial pressure displayed a significant increase of RI within the intracranial section of the internal carotid artery to 0.89 +/- 0.08 in comparison to the extracranial section with 0.79 +/- 0.07 and to the healthy control group with 0.75 +/- 0.07. All flow velocities decreased significantly within the intracranial section of the internal carotid artery in comparison to the extracranial part of the internal carotid artery and the healthy control group. The I/E-ratio was significantly reduced in group 2 with 0.76 +/- 0.11 for Vs, 0.38 +/- 0.21 for Ved, and 0.58 +/- 0.16 for TAV.
Conclusion: Flow measurements in extra- and intracranial sections of the internal carotid arteries are an accurate method for semiquantitative estimation of increased intracranial pressure. This method is superior to the measurement of the RI. Slightly increased intracranial pressures below 20 cm H2O cause an increase of the I/E-ratio above 1, whereas the RI does not change. Moderately increase of the intracranial pressure above 20 cm H2O lowers the I/E-ratio significantly below normal values of 0.8, whereas the RI increases.