[Post-traumatic disinsertion of the superior oblique muscle trochlea]

Ophthalmologic examination may rule out an ocular wound in the event of orbital traumatism. Some lesions are obvious but others may not be detected. We report a case of superior oblique muscle trochlea trauma. This infrequent pathology is illustrated with a scanned imagery and magnetic resonance imaging (MRI).

The initial penetrating trauma was caused by a hook in the medial canthus. The wound was sutured in the emergency unit. Three days later, oblique diplopia developed. Three weeks later, abnormal ocular movements appeared when contracting the frontal muscle. The patient then decided to consult. One month after the traumatism, the orthoptic assessment confirmed the presence of an acquired Brown syndrome suggesting a lesion of the superior oblique muscle. Orbital MRI could not find the trochlea and revealed a thickening by retraction of the posterior portion of the muscle and a hypotrophic aspect of the anterior portion. A fracture of the right orbital edge was revealed by the scanner. Surgical exploration was performed.

The trochlea is located very anteriorly and likely to be affected in the event of an internal palpebral wound. A direct traumatism of the pulley and/or the superior oblique muscle leads to an acquired Brown syndrome. This observation stresses the importance of surgical wound exploration for the supero-medial palpebral area as well as using MRI which allows proving the diagnosis.