Diagnosis and etiologic classification of optic tract lesions.

Existing literature regarding optic tract syndrome, which arises from lesions affecting the optic tract(s), is limited. The objective of this retrospective cohort study was to elucidate the diverse clinical and imaging manifestations of the optic tract syndrome relative to the causative lesion. The study population comprised of all patients with optic tract syndrome who were seen at two tertiary neuro-ophthalmology practices from 2014 to 2024. Inclusion criteria were (i) signs associated with optic tract syndrome (homonymous hemianopia and/or relative afferent pupillary defect and/or characteristic findings on peripapillary optical coherence tomography or ganglion cell analysis) and (ii) radiographically confirmed optic tract lesion. Patient records were ascertained through medical databases and reviewed. Statistical analysis was performed to identify relationships between clinical/imaging manifestations and lesion type. Fifty-six patients with optic tract syndrome were identified. The mean age was 49.4 ± 16.7 years, and 37 were female patients. Aetiologies included space-occupying lesions (n = 25), demyelination (n = 11), ischaemia/haemorrhage (n = 9), non-specific optic tract atrophy (n = 8), perinatal insult (n = 2) and trauma (n = 1). At presentation, visual field defects were observed in 98% of patients (n = 55). Of these patients, 20% (n = 11) demonstrated complete field loss while 80% (n = 44) demonstrated partial field loss, of which 95% (n = 42) were incongruent and 5% (n = 2) were congruent. Of the 40 patients with homonymous hemianopia, 78% (n  = 31) demonstrated incongruous defects. Of the 54 patients with peripapillary optical coherence tomography findings, 41% (n = 22) had contralateral band atrophy and ipsilateral hourglass atrophy. Of the 51 patients with available data, 29% (n = 15) had contralateral relative afferent pupillary defect. Patients with demyelinating lesions were most likely to present within 2 weeks of symptom onset (P = 0.0180) and least likely to exhibit band/hourglass atrophy (P = 0.0112). In contrast to previous studies that found a significant percentage of optic tract lesions to produce congruent homonymous hemianopia, most patients in this study demonstrated incongruent homonymous hemianopia. As such, optic tract lesions should be considered in patients with incomplete, incongruous and subtle homonymous defects. Peripapillary optical coherence tomography should be examined for the presence of band and hourglass atrophy in these patients but may be less commonly observed, especially in those with a demyelinating aetiology.