Association of superior oblique muscle volumes with the presence or absence of the trochlear nerve on highresolution mr imaging in congenital superior oblique palsy

Abstract

BACKGROUND AND PURPOSE: Congenital superior oblique palsy is known to relate to trochlear nerve absence and a variable degree of superior oblique muscle hypoplasia. The purpose of this study was to determine whether superior oblique muscle volume predicts trochlear nerve absence in congenital superior oblique palsy. MATERIALS AND METHODS: A retrospective study of high-resolution MR imaging to evaluate the presence of the trochlear nerve and to measure superior oblique muscle areas and volumes with the image analysis tools of a PACS was performed in 128 consecutive patients with unilateral congenital superior oblique palsy and 34 age-matched healthy controls. RESULTS: Of the 128 patients with congenital superior oblique palsy, 88 had an ipsilateral trochlear nerve absence (absent group) and 40 had both trochlear nerves (present group). In patients with congenital superior oblique palsy, the paretic side superior oblique muscle volume was significantly smaller compared with the normal side only in the absent group (P