Analysis of anomalous head posturing in patients with infantile nystagmus syndrome

Abstract

Purpose: To investigate anomalous head posturing in patients with INS.

Methods: This was a prospective, cohort analysis of clinical and anomalous head posture (AHP) data in 34 patients with INS and an AHP. Particular outcome measures included measurement of AHP in three dimensions of pitch (anterior posterior flexion/extension), yaw (lateral rotation), and roll (lateral flexion) during best-corrected binocular acuity testing and during their subjective sense of straight. Patients were also queried as to their subjective sense of head posture in forced straight position and in their preferred AHP. The paired t test was used to determine significance in differences between measures.

Results: A total of 34 patients (19 males [56%]) 9-56 years of age (mean, 16.5 ± 6) were included. Associated systemic or ocular system deficits were present in 30 patients (88%). AHP during best-corrected visual acuity testing averaged 16.5° ± 8.20° (range, 10°-51°), which was significantly different from the mean voluntary "comfortable" position only in the pitch and roll directions (P < 0.001). There was a significant noncongruous response during subjective response to head posturing with most sensing their head as "crooked" (76.5%) when manually straightened (P = 0.001).

Conclusions: The clinical AHP of patients with INS exists in all three spatial dimensions of pitch, yaw, and roll. Although the visual system may be causally related to the onset, amount, and direction of a compensatory AHP in patients with INS, its persistence over time or after surgical intervention is likely due to a combination of visual system (eg, nystagmus, strabismus) and nonvisual system (egocentric and musculo-skeletal) factors.