gms | German Medical Science

Objective: Communication of the ventricular system and the passage of cerebrospinal fluid (CSF) into the basal cisterns is crucial during weaning of external ventricular drainage (EVD). For this purpose computed tomography of the ventricular system with intraventricular application of contrast agent is necessary. Because intrahospital transfer of critical ill patients is associated with a higher mortality, bedside techniques are necessary to demonstrate the craniospinal transfer of the CSF. In this study, transnuchal contrast enhanced ultrasound (CEUS) was used to demonstrate the passage of CSF through the formamina Luschkae und Magendi.

Method: Ultrasound (US) was performed in ten patients with EVD. US was emitted using a Siemens Acuson X 300 with a 2.5 MHz phased array transducer through a transnuchal approach. Penetration depth was 10 cm with a dynamic range of 45 dB. A commercially ultrasound contrast agent (UCA) was used after relatives/guardians written informed consent for the off-label use. To obtain the harmonics of the USCA the US system was set to tissue harmonic imaging with a mechanical index of 0.1. A sample of 3 ml CSF was obtained under sterile conditions followed by 1 ml of the USCA. US images were stored in DICOM format.

Results: In five cases the transnuchal examination demonstrated CSF transmission from the 4^th ventricle through foramen of Magendi and Luschkae into the subarachnoid space. The mean duration for CEUS-ventriculography was 3:15 minutes (SD ± 56 sec). The preparation of the US examination included the setting of the US system, preparation of the UCA, NaCl 0.9% and withdrawal of the CSF. This procedure took about 3 minutes. Injections of the UCA was well tolerated without affecting intraventricular– or blood pressure, ECG or oxygen saturation within 30 minutes of observation after CEUS ventriculography. We found no abnormalities of CSF-glucose, -protein or cell count in the routine follow-up examinations.

Conclusions: CEUS of the posterior fossa is an effective bedside procedure in critically ill patients during EVD weaning. CEUS allows real-time measurement of CSF transfer to the subarachnoidal space through the cisternal foramina Magendi and Luschkae.