Dorsolateral pontine lesions produce distinct ocular motor abnormalities with anatomical correlations

The dorsolateral portion of the caudal pons contains the vestibular nucleus (VN) and inferior cerebellar peduncle (ICP) that play important roles in conveying and processing vestibular and ocular motor signals. This study aimed to characterize ocular motor abnormalities along with their anatomical correlations in dorsolateral pons (DLP) lesions.

We analyzed clinical features, and results of neuro-otological evaluations and neuroimaging of 18 patients with unilateral DLP lesions (17 with DLP infarction and 1 with cavernous malformation) from among 506 patients with pontine infarction in a stroke registry.

Most of the patients (n = 16) presented with isolated acute vestibular syndrome (AVS). The involved structures within the DLP were the ICP in four patients and the VN in the remaining 14. The unilateral ICP lesions were associated with consistent abnormalities in vestibular and ocular motor tests, including ipsilesional nystagmus without gaze-evoked nystagmus (GEN), and normal head impulse tests (HITs) and caloric response. In contrast, lesions of the VN were associated with a broader range of eye-movement abnormalities, including ipsi- or contralesional nystagmus with GEN, positive HITs, normal or abnormal caloric responses, and fixation nystagmus. Initial diffusion-weighted magnetic resonance imaging (within 48 h) was falsely negative in 41% (n = 7) of the DLP infarction cases.

This study demonstrates that unilateral DLP lesions frequently present with isolated AVS and diverse ocular motor abnormalities. These characteristics may be due to the complex involvement of afferent or efferent fibers to and from the VN.