Can intracranial pressure be measured non-invasively bedside using a two-depth Doppler-technique?
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Measurement of intracranial pressure (ICP) is necessary in many neurological and neurosurgical diseases. To avoid lumbar puncture or intracranial ICP probes, non-invasive ICP techniques are becoming popular. A recently developed technology uses two-depth Doppler to compare arterial pulsations in the intra- and extra-cranial segments of the ophthalmic artery for non-invasive estimation of ICP. The aim of this study was to investigate how well non-invasively-measured ICP and invasively-measured cerebrospinal fluid (CSF) pressure correlate. We performed multiple measurements over a wide ICP span in eighteen elderly patients with communicating hydrocephalus. As a reference, an automatic CSF infusion apparatus was connected to the lumbar space. Ringer’s solution was used to create elevation to pre-defined ICP levels. Bench tests of the infusion apparatus showed a random error (95 % CI) of less than ±0.9 mmHg and a systematic error of less than ±0.5 mmHg. Reliable Doppler signals were obtained in 13 (72 %) patients. An infusion test could not be performed in one patient. Thus, twelve patients and a total of 61 paired data points were studied. The correlation between invasive and non-invasive ICP measurements was good (R = 0.74), and the 95 % limits of agreements were −1.4 ± 8.8 mmHg. The within-patient correlation varied between 0.47 and 1.00. This non-invasive technique is promising, and these results encourage further development and evaluation before the method can be recommended for use in clinical practice.
KeywordsNon-invasive ICP Transcranial-Doppler Intracranial pressure Ophthalmic artery Infusion test
The study is partially sponsored by European Commissions FP7 Project TBI care, NASA (US), and the Swedish National Space Board.
Compliance with ethical standards
Conflict of interest
Dr. Koskinen received an honorarium for lecturing from DePuy Ltd (Codman Inc). Dr. Malm and Dr. Eklund are listed as inventors on a patent regarding the Celda infusion method, for which they received royalties from Likvor AB. Dr. Eklund has received an honorarium for lecturing from DePuy Ltd (Codman Inc). Dr. Ragauskas is an inventor of patented (US, EU and others) non-invasive ICP measurement technology. He consults Vittamed Corporation (Boston US) and its subsidiary, Vittamed UAB (Kaunas, Lithuania) on R&D and D&D of non-invasive ICP measurement technology.
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