Sternocleidomastoid muscle asymmetry in unilateral congenital superior oblique palsy

Abstract

Background: 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.

Methods: 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.

Results: 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).

Conclusions: 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.

Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1. Measurement of head tilt and facial angle using the toriCAM application on the frontal photographs.

a Original frontal photograph. b The degree of head tilt measured as the difference between the midline and the median line passing through the nose of the face, showing 25° of leftward head tilt. The facial angle is calculated as the intersection of c the inter-palpebral line and d the inter-labial line, showing 4°. Parental informed consent was obtained for publication of this figure.

Fig. 2. The sternocleidomastoid muscle (SCM) asymmetry index according to age.

The SCM asymmetry index was calculated by the following equation: SCM asymmetry index (%) = (SCM tilted − SCM opposed) ÷ SCM tilted × 100. The vertical dotted line is indicated at the age of 2 years and horizontal dotted lines indicate bilateral differences of ±10 percentages.