[MRI in congenital Brown's syndrome: report of 16 cases]

Superior oblique retraction syndrome or Brown's syndrome is one of the so-called restrictive syndromes causing anatomic strabismus. It is characterized by active and passive limitation of upward gaze in adduction in the field of action of the superior oblique muscle (SO). The etiology of this congenital syndrome remains unknown. The purpose of this prospective study is to analyze brain and orbital magnetic resonance imaging (MRI) in patients with congenital Brown's syndrome.

Sixteen children (19 months - 9 years) underwent complete ophthalmologic evaluation followed by brain/orbital MRI with attention to the superior oblique muscle. Average age at time of MRI was 4.2 years old. Among patients included were eight girls and eight boys. MRI was performed on a 1.5T (Symphony TIM, Siemens, Erlangen) to visualize the orbit and specifically the SO.

Of 16 eyes, 13 demonstrated radiologic abnormalities of the SO muscle; six demonstrated tendon-trochlea complex hypertrophy, four demonstrated complete SO hypertrophy (tendon-trochlea-muscle belly), one demonstrated trochlear hypertrophy, and two demonstrated abnormalities solely of the tendons, of which one was longer and one was thinner with fibrosis.

MRI shows a high frequency of SO radiologic abnormalities in congenital Brown's syndrome. MRI permits the analysis of not only the tendon, but also the trochlea and muscle belly, whereas surgery only allows visualization of the tendon. MRI proved to be an interesting tool for investigation of these patients and for a better understanding of the pathogenesis.