Torsion and clinical features in patients with acquired fourth cranial nerve palsy

This retrospective study aimed to compare objective/subjective torsion and other clinical characteristics of patients with acquired trochlear nerve palsy. This study included 82 consecutive patients who were diagnosed with acquired fourth cranial nerve palsy between 2014 and 2021 and who were followed up for ≥ 6 months. The etiologies, ocular deviation, objective and subjective torsions were reviewed. The etiologies were classified as ischemic, traumatic, brain lesion, idiopathic, or other. The patients were classified into two groups according to the recovery state: full recovery and partial/no-recovery. We compared the torsion and clinical features based on the etiology and recovery state. The average age was 59.1 ± 11.1 years, and 58 (71.0%) of the patients were male. The most common cause was ischemic (n = 49, 59.7%) and other common causes included traumatic (n = 16, 19.5%), brain lesion (n = 8, 9.8%), idiopathic (n = 5, 6.1%) and others (n = 4, 4.9%). Of the 82 patients, 56 (68.3%) were assigned to the full recovery group, and 26 (31.7%) were assigned to the partial/no-recovery group. The average age and number of patients with ischemic causes of palsy were greater in the full recovery group (p = 0.026 and p < 0.000, respectively). The vertical deviation angle, tilted angle on the Lancaster red-green test (LRGT), proportion of patients who experienced subjective torsion on the LRGT, and head tilt were smaller in the full recovery group (p = 0.037, 0.042, 0.045, and 0.006, respectively). Ischemic trochlear nerve palsy, advanced age, a small deviation angle at the primary position, and few cases of excyclotorsion on LRGT were characteristic of the full recovery group of acquired unilateral trochlear nerve palsy patients.