Utility of Transcranial Doppler in Idiopathic Intracranial Hypertension

Abstract

INTRODUCTION: Idiopathic intracranial hypertension (IIH) can be an elusive diagnosis, and poor visual outcomes may occur. Currently, the only means of accurately diagnosing and following these patients is with repeated lumbar puncture. Previous work has shown that transcranial doppler measurements of pulsatility correlate accurately with elevated intracranial pressure (ICP). This study is designed to assess whether pulsatility index (PI) correlates with ICP in patients newly diagnosed with IIH. METHODS: Seven patients with clinical suspicion of IIH were included in this study. Clinical suspicion was based on history of recurrent headaches and papilledema. All patients had otherwise normal examinations and imaging. Middle cerebral arteries were insonated to obtain average PI values. Cerebrospinal fluid (CSF) was then withdrawn, and closing pressures were recorded. Pulsatility index values were then obtained again, within ten minutes after completing CSF withdrawal. PI values were correlated with ICP values, and pre and post CSF withdrawal values were compared. RESULTS: All seven patients had elevated opening pressures (average 39 cm H2O, range 27-70). The average closing pressure after approximately 30 cc of CSF withdrawal was 11.9 cm H2O. The average PI before CSF withdrawal was 0.95, which dropped to 0.70 after CSF withdrawal (p = 0.02). The change in ICP was found to be correlated with a change in PI (p = 0.004). CONCLUSIONS: These findings suggest that PI may be useful for following patients with IIH non-invasively. Further study with larger groups and blinded assessments should be useful in better characterizing the accuracy of this technique.