Abstract
Purpose: :
To analyse the horizontal rectus extraocular muscles (EOM) and abducens nerve (VI) by magnetic resonance imaging (MRI) in patients with Duane syndrome (DRS).
Methods: :
A prospective study on 40 patients with DRS was performed. The morphology of the horizontal rectus EOMs was analyzed in orbital images perpendicular and parallel to the long axis of the orbit. The cisternal segment of the VI was explored by 3D T2 CISS weighted images (slice thickness 0.5-0.7 mm). All participants underwent a complete ophthalmologic examination at the time of diagnosis.
Results: :
Of 40 patients we noted 28 type I (70%), 5 type II (12.5%), 7 type III (17.5%). Absence of VI was observed in 93% of type I, 60% of type II and 57% of type III, and hypoplasia in 7% of type I, 20% of type II and 43% of type III (p=0.017).The lateral EOM (LR) was split or hypertrophic in 93% of type I, 80% of type II and 28% of type III and hypotrophic in 0% of type I, 20% of type II and 29% of type III (p=0.001). The medial EOM was normal in 43% of type I, 80% of type II and 71% of type III, abnormal MR were hypertrophic (p>0.05).
Conclusions: :
This study confirm the maldevelopment of abducens nerve in 97.5% of DRS patients and highlight the possibility of a total agenesis in 3 cases of 5 patients with type II. The law rate of LR atrophy suggests some other innervation arising from oculomotor nerve wich prevents the LR from denervation atrophy. In this regard, MRI became an extremely precious tool for guiding the diagnosis and the management of difficult clinical features of oculomotor disorders.
Keywords: strabismus: diagnosis and detection • extraocular muscles: structure • imaging/image analysis: clinical