Evaluation of CSF shunt patency by continuous wave Doppler ultrasound technique

In 1975, Flitter et al. proposed a Doppler technique for evaluating CSF shunt patency. Owing to the presence of many false positives, a new method of investigation is proposed in order to achieve more reliable results by using the Doppler technique after air has been injected into the shunt reservoir. Ninety patients with a CSF shunt were examined. Fifty cases were studied both immediately after surgery (7-10 days) and at a later date (more than 2 months from surgery) in order to obtain a control group. In a further 38 cases with signs of intracranial hypertension, it was possible, by means of the air test, to distinguish surgical and non-surgical cases. In 2 cases with clinical signs of hypotension, it was possible, by means of the test, to demonstrate the hyperfunctioning of the shunt. The "Flitter test" proved to be useful in the early post-operative period only.