Persistent geotropic direction-changing positional nystagmus: a systematic review

Persistent geotropic direction-changing positional nystagmus (DCPN) is a unique clinical phenomenon characterized by persistent nystagmus observed during the supine head roll test. Unlike other DCPNs caused by canalolithiasis or cupulolithiasis, this persistent geotropic form is not fully explained by conventional mechanisms. The “light cupula” hypothesis, introduced in the early 2000s, proposes that reduced cupula density relative to the surrounding endolymph is a key explanation for cases of peripheral origin. However, other mechanisms, such as heavier endolymph, light debris, utricular dysfunction, and perilymph-endolymph density difference have also been suggested. Persistent geotropic DCPN may also arise from central lesions, further complicating its diagnosis. This review examines persistent geotropic DCPN with a focus on the peripheral hypothesis, particularly the concept of the light cupula, exploring its origin, clinical characteristics, diagnostic approaches, proposed alternative mechanisms, and treatment. This review also explores cases of persistent geotropic DCPN linked to central lesions and coexisting conditions like vestibular migraine and Ménière disease, focusing on their distinctive characteristics as reported in the literature. The limited effectiveness of available treatments highlights the importance of advancing research to better understand and manage this condition.