Chiasmal herniation following treatment of pituitary macroadenoma

Abstract

Purpose: To evaluate whether the occurrence of chiasmal herniation coincides with visual field (VF) deterioration and to compare the course of VF defects in patients with and without radiological chiasmal herniation following treatment of pituitary adenoma.

Methods: This retrospective cohort study included 48 pituitary macroadenoma patients with chiasm compression, divided into three groups: Group 1 (N = 12), downward displaced optic chiasm and deteriorated VFs; Group 2 (N = 16), downward displaced optic chiasm; Group 3 (N = 20), control-group matched for tumour size and follow-up VFs, in mean deviation (dB). VFs were compared over time and a severity index, Chiasm Herniation Scale (CHS), for herniation based on radiological parameters was designed.

Results: After treatment, all groups showed improvement of VFs (Gr1: 2.97 dB p = 0.097, Gr2: 4.52 dB p = 0.001 and Gr3: 5.16 dB p = 0.000), followed by long-term gradual deterioration. The course of VFs between patients with and without herniation was not significantly different (p = 0.143), neither was there a difference in the course before and after herniation (p = 0.297). The median time till onset of herniation was 40 months (IQR 6 month-10 years) and did not significantly differ (p = 0.172) between the groups. There was no relation between VFs and the degree of herniation (p = 0.729).

Conclusion: Herniation does not appear to have clinical relevance with respect to VF outcome. The newly designed CHS is the first scoring system to quantify the severity of herniation and, in the absence of alternatives, may be useful to describe MRI findings to serve future added value in larger sized outcome studies.

Keywords: Chiasmal herniation; Chiasmapexy; Optic chiasm; Pituitary adenoma; Visual deterioration; Visual field.

Fig. 1

MRI scan demonstrating a downward displaced optic chiasm classified with the Chiasm Herniation Scale (CHS). Line (a) connects the superior border of the superior carotid arteries at their entry point into the cavernous sinus. Line (b) connects the inferior border of the inferior carotid arteries at their entry point into the cavernous sinus. The mean distance between those lines is (e) (e = 13.7 mm), extracted from (c) (c = 13.9 mm) and (d) (d = 13.5 mm). The lowest point of the optic chiasm is (f). The distance from (f) to line (a) is (g) (g = 9.0). The proportional herniation is calculated with (e) and (g). Example: $\text{CHS}=100\times \text{g}/\text{e}\text{e}=\left(\text{c}+\text{d}\right)/2$, $\text{CHS}=100\times 9.0/13.7=65.7\text{e}=\left(13.9+13.5\right)/2$,$\text{CHS}=65.7\text{e}=13.7$

Fig. 2

MRI examples of the five categories on the CHS for ten different patients. For each of the five CHS categories two MRI’s are demonstrated with the exact CHS-value below. All MRI’s are obtained from different patients and include the same lines as used in Fig. 1 for calculation of the CHS-value. *With extrapolation of the optic chiasm. **With extrapolation of the line under lower carotid arteries. ***In the left lower corner, a tumour residual is visible. There is no compression on the optic chiasm. CAT category

Fig. 3

Flowchart of inclusion. From 156 patients, 48 patients are included into three groups, and from 3 of these included patients only 1 eye is included. Group 1 matches with Group 3 based on tumour size and follow-up, 20 patients are excluded because matching was complete

Fig. 4

Course of the visual fields around treatment. a Shows the MD scores before treatment, best achieved MD scores and latest MD scores for both eyes. b Shows the MD scores before treatment, best achieved MD scores and latest MD scores in the right eyes (OD). c Shows the MD scores before treatment, best achieved MD scores and latest MD scores in the left eyes (OS)

Fig. 5

Survival curves of time between treatment and moment of herniation and deterioration. On the left a survival curve showing time between treatment and development of a herniated optic chiasm in Group 1 and 2. On the right a survival curve showing time between treatment and moment of deterioration in Group 1, 2 and 3

Fig. 6

Course of visual fields. On the left the course of the VF around the moment of herniation (time = 0) for Group 1 and 2. On the right the long-term course of VF after treatment for Group 1, 2 and 3

Fig. 7

Relation between CHS and tumour size, MD and tumour size and MD and CHS. a Shows the relation between the CHS and tumour size, there is a trend to significance (p = 0.084). b Shows the relation between the best MD scores and the tumour size. There is no significant relation. c Shows the relation between the best MD scores and the CHS. There is no significant relation