Evaluating optic system compression in sellar tumors: A novel application of quantitative pupillometry
Authors: Lenga Pavlina , Grutza Martin , Kühlwein Daniel , Walter Johannes , Krieg Sandro M. , Beynon Christopher 
Published: December 2024

Abstract

Introduction
Tumorous growths in the sellar region pose significant clinical challenges due to their proximity to critical visual structures such as the optic chiasm and optic nerves. Given their proximity to the optic system, these tumors are often diagnosed due to a progressive decrease in visual acuity. Thus, surgical intervention is crucial to prevent irreversible damage, as timely decompression can halt the progression of edema and subsequent optic atrophy. Although Quantitative Pupillometry (QP) has been employed in various clinical settings, its application in patients with sellar region neoplasms remains unexplored. This study aims to evaluate the utility of QP to enhance treatment approaches in patients undergoing surgical resection of these tumors.

Methods
Pupillometry assessments were conducted prospectively using the automated NPi 200® Pupillometer on 45 patients who underwent surgical resection of tumors in the sellar region at our institution. The Neurological Pupil Index (NPi) was measured pre- and post-operatively, with a focus on correlations with visual acuity and tumor volume. Concurrently, MRI findings were analyzed to assess optic chiasm compression.

Results
Of the patients, 73.3% were diagnosed with pituitary tumors, 22.2% with tuberculum sellae meningiomas, and 4.4% with craniopharyngiomas. 66.7% of patients presented with decreased visual acuity, and 42.2% demonstrated paresis of the third cranial nerve (CN III). Compression of the optic chiasm was noted in 55.6% of cases. Patients with visual disturbances and CN III paresis exhibited significantly reduced NPi scores compared to unaffected individuals. In patients with pituitary adenomas, pathological NPIs were observed exclusively in cases of optic chiasm compression; compression of cranial nerve III (CN III) did not significantly affect the NPIs. Conversely, in patients with tuberculum sellae meningiomas, pathological NPIs were associated specifically with CN III compression, while optic chiasm compression tended to show a difference, however the results are not significant. Postoperatively, NPi values normalized among those who had presented with decreased visual acuity.

Conclusions
This study contributes to the field of skull base surgery by evaluating the utility of QP as a diagnostic tool for neurological assessment in patients with sellar region tumors. The findings suggest that QP may help in assessing the extent of tumor-related compression on the optic system. It particularly points to differences in the effects of optic chiasm and CN III compression, with observed variations in NPI scores corresponding to the type of compression in specific tumors, such as pituitary adenomas and tuberculum sellae meningiomas. By providing rapid and non-invasive assessments, QP supports enhanced correlation with clinical and radiological evaluations, potentially improving targeted interventions for these complex conditions.