[Stilling Duane syndrome and MRI: 2 preliminary results]

Dynamic mode magnetic resonance imaging (DMMRI) allows good visualization of the oculomotor muscles and allows their dimensions to be measured both when they contract and when they relax. The accuracy of this method has been checked and the measurements of the cross section of medial and inferior recti and of superior obliques can be considered to be valid. Measurements of length are inaccurate and the other muscles are not perpendicular to the sectional planes generally used in MRI of the head. By means of a fixation scale situated in the tunnel of the machine, the maximum diameter of medial recti in their thickest part was evaluated in two girls affected by a Stilling Duane retraction syndrome of the left eye. Two direction of the gaze were explored: 25 degrees at the right, then 25 degrees at the left, these angles being obtained by the fixation of particular points of the tunnel scale. The measurements have been made on axial sections, then on coronal sections, both medio-orbital and apical. The first finding is that the diseased medial rectus is much bigger than the healthy one. When relaxed, its thickness is about the same as that of the contracted normal muscle. Coronal orbital cross sections clearly show recession of the belly of the diseased muscle towards the back of the orbit. When contracted it stays in the apical plane and when relaxed in the medio-orbital plane. Lastly the relaxation is much weaker for the pathological muscle than for the healthy one.(ABSTRACT TRUNCATED AT 250 WORDS)