Decreased Optic Disc Cup Volume with Increased Intracranial Pressure
Duncan Mackay, MD MBA, Christopher L. Kalmar, MD MBA, Laura S. Humphries, MD, Giap H. Vu, BA, Carrie E. Zimmerman, BS, Scott P. Bartlett, MD, Jesse A. Taylor, MD, Jordan W. Swanson, MD.
Children's Hospital of Philadelphia, Philadelphia, PA, USA.
BACKGROUND: Craniosynostosis can result in increased intracranial pressure, which has traditionally been screened using fundoscopy to detect papilledema. Unfortunately, papilledema is a subjective and late finding, resulting in poor sensitivity at 14%. Clinicians need a reliable quantitative screening assessment of elevated intracranial pressure in this population. The purpose of this study is to demonstrate whether three-dimensional changes at the optic disc can be quantified to accurately predict elevated intracranial pressure in children with craniosynostosis.
METHODS: Spectral-domain optical coherence tomography of the optic nerve head was performed preoperatively for patients undergoing initial corrective surgery for craniosynostosis. Measurements of the optic nerve head including rim area, disc area, cup volume, and multiple measurements of the retinal nerve fiber layer (RNFL) including the maximum RNFL thickness when the nerve head is split into octants and into quadrants. These measurements were automatically calculated by the algorithm of the iVue software (Optovue; Fremont, CA).
RESULTS: During the study interval, 232 patients underwent OCT scans, with 69 patients having ICP measured intraoperatively, of which 39 patients met inclusion criteria for having adequate quality measurements. Cup volume was significantly correlated with ICP (p= .004, B=-61.9 mmHg/mm3, r2=.252). Cup volume was significantly decreased (p=.003) in patients with ICP above 15 mmHg (median .0040 mm3, 95%CI .0000-.0140) compared with patients with ICP below 15 mmHg (median .0225 mm3, 95%CI .0100-.1095). Max quartile and Max octant RNFL were significantly increased (p=.041 and .021 respectively) in patients with ICP above 15 mmHg (median values 136 and 151, 95%CI 129-147 and 142-159) compared with patients with ICP below 15 mmHg (127 and 141, 95%CI 121-137 and 134-147).
CONCLUSIONS: Increased intracranial pressure significantly decreases decreases the optic disc cup volume in patients with craniosynostosis and patients with increased intracranial pressure had significantly thicker max octant and max quadrant retinal nerve fiber layers. Further research is needed to develop cut points to optimize the sensitivity and specificity of this diagnostic modality, which could then be applied prospectively to patients, in order to validate this modality as a novel quantitative assessment of intracranial pressure. These automated measurements allow rapid data acquisition and analysis for convenient implementation in the clinic setting to better understand need for urgent intervention.
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