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Naina Gupta, Cynthia J Roberts, Robert H Small, Andrew N Springer, Ashraf M Mahmoud, Jean Brian Kassem, Ami S Vira, Steven E Katz; Pilot Study of Physiologic Pressure-Volume Curves in Idiopathic Intracranial Hypertension. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5108. doi: https://doi.org/.
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Previous studies analyzing intracranial compliance have either used animal models, infusion studies in normal pressure hydrocephalus, or constant monitor of patients with traumatic brain injury. The purpose of this study is to present a physiologic representation of intracranial compliance in patients with idiopathic intracranial hypertension.
Four patients were followed from presentation. Duration of symptoms, visual acuity, grading of papilledema using Frisen grading, presence of relative afferent pupillary defect, Humphrey visual field with mean deviation, and medication regimen were recorded prior to lumbar puncture. Ultrasound guided lumbar punctures were conducted by a single anesthesiologist. Either a 4" 24 gauge Pencan pencil-point needle or a 4.75” or 6", 24 or 22 gauge Sprotte pencil-point needle was used, depending on the length needed. An electronic transducer was used to measure cerebrospinal fluid (CSF) pressure as fluid was removed in 2-4 mL increments.
Duration of symptoms ranged from 4 months to 2 years. Vision on presentation ranged from 20/20 to 20/200. Papilledema grade ranged from 1+ to 4+. Two subjects were noted to have a relative afferent pupillary defect. Mean deviation on Humphrey visual field ranged from -3.19 to -33.96. One patient was on medication prior to lumbar puncture with a regimen consisting of 1000mg acetazolamide daily. Opening pressure ranged from 27 to 34 mmHg. Intracranial pressure demonstrates a nonlinear relationship with volume of CSF removed during the lumbar puncture, as seen in Figure 1. Intracranial compliance can be determined from these curves based on the slope.
This preliminary study demonstrates the feasibility of measuring intracranial compliance in patients with idiopathic intracranial hypertension by removing CSF in steady increments. Compliance was noted to vary for each individual. Ongoing studies will assess possible correlations between intracranial compliance and symptom chronicity, papilledema grading, mean deviation on visual field, response to therapy, and need for surgical intervention.
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