Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery
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Results of shunt tap were studied in 224 clinically or radiologically suspected instances of shunt malfunction. In 130 retrospectively studied patients the results of the tap had reported the opening pressure and ease of aspiration. In 94 prospectively studied instances the shunt tap parameters described were (i) the opening pressure, (ii) the drip interval, i.e., the interval between the drops of cerebrospinal fluid when the open end of the butterfly used for tapping was placed 5 cm below the level of the valve, and (iii) the closing pressure. ⋯ The opening pressure, closing pressure, and the drip interval recorded at surgery were not significantly different from the values obtained by shunt tap. The results suggested that shunt tap accurately provides information otherwise obtained at surgery and the drip interval is most useful for evaluating a proximal malfunction. The subjective impression of the distal flow may be more helpful in diagnosing distal malfunction rather than the absolute level of opening or closing pressures.