J Clin Neurol.  2018 Jan;14(1):66-72. 10.3988/jcn.2018.14.1.66.

Diagnostic Utility of the Three-Step Test According to the Presence of the Trochlear Nerve in Superior Oblique Palsy

Affiliations
  • 1Department of Ophthalmology, Maryknoll Medical Center, Busan, Korea.
  • 2Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. hjm@snu.ac.kr
  • 3Department of Radiology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.

Abstract

BACKGROUND
AND PURPOSE: To determine the diagnostic utility of the three-step test in unilateral superior oblique palsy (SOP) according to the presence of the trochlear nerve using high-resolution thin-section magnetic resonance imaging.
METHODS
In total, 166 patients with congenital and acquired unilateral SOP were included, comprising 87 with a normal trochlear nerve (present group) and 79 without a trochlear nerve (absent group). The sensitivity of each component of the three-step test was evaluated as well as factors related to the sensitivity.
RESULTS
All three steps were positive in 78% of those in the present group and 72% of those in the absent group, demonstrating no intergroup difference (p=0.471). Superior rectus muscle (SR) contracture was more frequent in patients who exhibited at least one negative step (incomplete group) (p=0.014). The incomplete group was significantly related to larger hypertropia in ipsilateral gaze (p < 0.001), smaller hypertropia in contralateral gaze (p < 0.001), and smaller differences in hypertropia between ipsilateral head tilt and the primary position (p=0.012).
CONCLUSIONS
The diagnostic utility of the three-step test in unilateral SOP did not differ according to the presence of the trochlear nerve. SR contracture was the main cause of exceptions of the three-step test in unilateral SOP.

Keyword

superior oblique palsy; trochlear nerve; Parks-Bielschowsky three-step test
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