Clinical and radiological characteristics of Graves' orbitopathy patients showing spontaneous decompression

To investigate clinical implications and radiological characteristics of spontaneous decompression in patients with Graves' orbitopathy (GO).

The medical records and images of GO patients showing spontaneous decompression in computed tomography (CT) scans without any other cause, such as orbital surgery or trauma were retrospectively reviewed. Clinical parameters, including clinical activity score (CAS), modified NOSPECS score, exophthalmometry results, extraocular muscle involvement, and the presence of optic nerve compression were evaluated. Paired orbit analyses of maximum recti muscle diameters, area of lamina papyracea, and number of ethmoid air cell septa were determined quantitatively in the unilaterally decompressed group.

77 orbits of 55 patients were found to present spontaneous decompression, which was observed only in the medial orbital wall in all cases. In the paired orbit comparison, maximal diameters of medial (P = 0.009) and lateral recti muscles (P = 0.023) were significantly larger in decompressed orbits than in non-decompressed orbits. However, the incidence of optic neuropathy was not significantly different (P = 0.500). There was no difference in anatomic features of lamina papyracea or ethmoid air cells between decompressed and non-decompressed orbits.

Spontaneous decompression occurred in the medial wall, associated with enlarged horizontal recti muscles, but not with structures of lamina papyracea or the ethmoidal sinus. Orbital bone remodeling by spontaneous decompression by lowering intraorbital pressure, might have provided a protective effect against the development of optic neuropathy.