[Doppler ultrasonographic diagnosis of increased intracranial pressure by comparison of flow velocities in the extra- and intracranial secitons of the internal carotid artery].

AIM

By comparison of the flow velocities in the intracranial and extracranial parts of the internal carotid artery the influence of an increased intracranial pressure on cerebral perfusion can be determined. Aim of the study was to establish normal values in healthy infants not displaying clinical signs of increased intracranial pressure.

METHOD

108 healthy infants (35 girls, 73 boys) with a gestational age of 42 +/- 14 weeks and a weight of 2440 +/- 2310 g were investigated. In all infants Doppler sonographic flow measurements were performed within the petrosal part (extracranial) and the cerebral part (intracranial) of the internal carotid artery. From the flow profile the peak systolic (Vs), enddiastolic (Ved) and time average (TAV) flow velocities were estimated. In all infants the I/E-ratio of the intracranial and extracranial flow velocities was calculated.

RESULTS

Flow velocities within the intracranial section of the vessel were lower than in the extracranial part, due to the greater angle of incidence (33 +/- 8 degrees) between the pars cerebralis and the Doppler beam. In the pars petrosa of the internal carotid artery Vs was 59.7 +/- 21.4, Ved 14.6 +/- 9.5 and TAV 17.2 +/- 11.8 cm/sec. Within the pars cerebralis Vs was 48.8 +/- 22.1, Ved 12.3 +/- 8.4 and TAV 12.9 +/- 7.5 cm/sec. I/E-ratio of intracranial and extracranial flow velocities was 0.83 +/- 0.14 for Vs, 0.88 +/- 0.29 for Ved and 0.82 +/- 0.24 for TAV.

CONCLUSION

The relation between intracranial and extracranial flow velocities within the internal carotid artery as described by the I/E-ratio is constant. Alterations of the flow velocities intracranially such as in cases of increased intracranial pressure, may cause changes of the I/E-ratio. Determining the I/E-ratio may be a valuable method for the assessment of increased intracranial pressure.