Which of the following might suggest central rather than peripheral vertigo?

Diplopia, or double vision, is a significant sign that suggests central vertigo as it can indicate involvement of the central nervous system, specifically where pathways for vision and balance integrate. Central vertigo arises from problems in the brain or brainstem, whereas peripheral vertigo usually originates from the inner ear or vestibular pathways.

In this context, the presence of diplopia may signify that the brain is affected by a central pathology such as a stroke, multiple sclerosis, or a tumor, which can disrupt the coordination between eye movements and balance. This neurological involvement stands in contrast to peripheral causes, which typically do not affect the visual pathways to this extent.

Other signs like sudden onset, horizontal nystagmus on extreme lateral gaze, and prominent vomiting and diaphoresis can occur in both central and peripheral vertigo, but they do not provide as direct an indication of central involvement as diplopia does. Therefore, the occurrence of diplopia alongside vertigo could prompt consideration of a more serious central condition requiring further investigation.