Sternocleidomastoid muscle asymmetry in unilateral congenital superior oblique palsy

To determine whether there is an asymmetry in bilateral sternocleidomastoid muscle (SCM) thickness in patients with unilateral congenital superior oblique palsy (SOP) and its association with surgical results.

The medical records of 186 patients with head tilt secondary to unilateral SOP, who were evaluated for the status of the SCM with neck ultrasound or magnetic resonance imaging, were reviewed. The SCM asymmetry index was calculated as a bilateral difference in the maximal muscle thickness divided by each tilted-side SCM thickness. The presence of SCM asymmetry, defined as an index of >10%, and its relationship to residual torticollis ≥5° after SOP surgery were assessed.

Of 186 patients with a median age of 1.2 years, SCM asymmetry was present in 102 (54.8%) patients (6.8 ± 1.9 mm for the SOP side vs. 6.6 ± 2.1 mm for the tilted side). The SCM asymmetry did not differ according to age, amount of head tilt or hypertropia. In the patients with SCM asymmetry, more patients (87.3%) underwent physiotherapy than those without asymmetry (61.9%) (P = 0.021). In 99 patients who underwent surgery for SOP, the resolution of torticollis was not significantly different between patients with and without SCM asymmetry (87.2% vs. 76.9%, P = 0.184).

Nearly half of the patients with congenital SOP had SCM thickness asymmetry that was already determined at a young age. However, the surgical results did not differ significantly with respect to SCM asymmetry when physiotherapy was combined. Thus, SOP surgery can be considered despite preoperative SCM asymmetry.