May 30 2012
By Joanna Lyford
Certain tumors of the pituitary gland are associated with glaucomatous abnormalities of the optic nerve head, such as enlarged beta zone, an international research team reports.
Their discovery relates to tumors within the parasellar or suprasellar regions of the pituitary gland and could shed light on the pathogenesis of optic neuropathy in people with glaucoma.
The research involved 34 patients with intrasellar or perisellar tumors and disc glaucoma and 129 age-matched healthy individuals, all of whom were participating in the population-based Beijing Eye Study. The mean age of participants was 41.0 years.
Of the patients with tumors, the mean tumor dimensions on neuroradiology were 30.3x28.1x29.7 mm, and histologic classifications were pituitary adenoma with extrasellar extension in 26 patients, meningiomas in four patients, and craniopharyngiomas in four.
All patients underwent fundus photography, which revealed that beta zone of parapapillary atrophy - a hallmark of glaucoma - was significantly more common among patients than controls, at 79% versus 46%.
Where present, beta zone was also significantly larger in patients than controls, as indicated by both circumference (135 vs 57 units) and area (1856 vs 759 units).
Among patients, tumor width positively correlated with both the circumferential extent and the area of beta zone, at r-values of 0.36 and 0.37, respectively.
Furthermore, tumor width, height, and depth were all significantly greater among patients with beta zone of parapapillary atrophy than in those without this feature.
The researchers comment that patients with intracranial tumors compressing the optic nerve or nearby structures may develop either glaucomatous optic neuropathy or nonglaucomatous nerve damage.
While the same is true for patients with pituitary tumors located in the intrasellar region, the present study, together with some previous reports, supports a causal relationship between a "typically glaucomatous appearance" and the presence of large perisellar tumors.
"Taking into account that an enlargement of parapapillary atrophy has not been described in any other than glaucomatous optic neuropathy, the results of our study may give reason to assume a glaucoma-like pathogenesis in these patients with a glaucoma-like appearance of the optic nerve head," write Jian Wang (Capital Medical University, Beijing, China) and co-authors in Acta Ophthalmologica.
They add: "It supports the notion that the pathogenesis of glaucomatous optic neuropathy may partially be influenced by intracranial parameters."
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