Which of the following conditions may NOT impact HGN results?

The correct choice suggests that seasonal allergies may not significantly impact HGN results. Horizontal Gaze Nystagmus is a test used to assess a person's ability to follow a stimulus with their eyes and can indicate impairment, particularly related to alcohol consumption or certain drug influences. While neurological disorders and inner ear problems can directly affect eye movement and balance, potentially skewing the results of the HGN test, seasonal allergies typically do not lead to the same degree of impairment in ocular function. Although allergies can cause discomfort or mild effects on vision, they usually do not disrupt the neurological pathways or vestibular functions as markedly as the other conditions listed.

In context, both neurological disorders and inner ear issues can create significant ocular movement abnormalities, which are crucial factors considered in an HGN assessment, whereas seasonal allergies are less likely to introduce such impairments.