Abstract
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. 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. 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 < .001). The left and right side superior oblique muscle volumes were not significantly different in controls (P = .750), and the paretic and normal side superior oblique muscle volumes were not significantly different in the present group (P = .536). The cutoff value of the paretic/normal side superior oblique muscle volume ratio for diagnosing trochlear nerve absence was ≤0.75 (sensitivity 98.9%, specificity 95.0%) in patients with congenital superior oblique palsy. The ratio of paretic/normal side superior oblique muscle area and volume has an excellent predictability in diagnosing trochlear nerve absence in congenital superior oblique palsy.
Highlights
BACKGROUND AND PURPOSECongenital superior oblique palsy is known to relate to trochlear nerve absence and a variable degree of superior oblique muscle hypoplasia
774 Yang Apr 2015 www.ajnr.org ing MR imaging have consistently shown a variable degree of hypoplasia of the paretic superior oblique muscle (SO) and variable trochlear nerve absence.[1,2,3,4,5]
Patient Characteristics Of the 128 consecutive patients diagnosed with unilateral congenital superior oblique palsy (SOP) (88 patients with an ipsilateral trochlear nerve absence and 40 patients with normal anatomy of the trochlear nerve on both sides), 3 were excluded due to poor quality of MR images, with obscured SO margins in the midst of surrounding soft tissues and motion artifacts, or with an SO tendon extending more posteriorly than the optic nerve– globe junction in both eyes
Summary
The purpose of this study was to determine whether superior oblique muscle volume predicts trochlear nerve absence in congenital superior oblique palsy
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