Test-Retest Reliability of Outpatient Telemetric Intracranial Pressure Measurements in Shunt-Dependent Patients with Hydrocephalus and Idiopathic Intracranial Hypertension.

Background: Some patients with hydrocephalus and idiopathic intracranial hypertension treated for elevated intracranial pressure (ICP) with a cerebrospinal fluid shunt may continue to experience symptoms or develop new symptoms despite valve adjustments. Use of telemetric ICP measurements may help confirm clinical suspicion of cerebrospinal fluid underdrainage or overdrainage in these patients. However, point in time, duration, and activity during the measurements have never been standardized. We devised a simple, repeatable maneuver for outpatient telemetric ICP recording and evaluated its test-retest reliability.

Methods: Data of patients who underwent ventriculoperitoneal or ventriculoatrial shunt placement and subsequent telemetric ICP sensor implantation were retrospectively reviewed. Telemetric ICP recordings in patients were conducted in a standardized manner: The standing-supine-sitting paradigm requires postural changes in 10-minute intervals over 30 minutes. First, the patient is requested to walk; second, to lay down; third, to sit down with a headrest elevation of 60°. ICP data (in mmHg) were reported as mean ± SD values. Test-retest validity was assessed using Pearson correlation analysis.

Results: We evaluated 66 ICP datasets obtained repeatedly with a time difference of at least 24 hours. Overall test-retest reliability was excellent (Pearson correlation coefficient 0.99, P < 0.001), as were the scores for individual postures: standing (correlation 0.98, P < 0.001), supine (correlation 0.98, P < 0.001), and sitting (correlation 0.99, P < 0.001). The sum of square differences of the test-retest measures reflected a comparable validity of all tested positions.

Conclusions: We confirmed high test-retest reliability of the standing-supine-sitting paradigm for telemetric ICP measurements in the outpatient setting. High test-retest reliability should be considered as prerequisite for clinical decision making.