Differential Diagnosis and Medical Screening in Physical Therapy Practice Exam

The main idea here is recognizing a specific pattern of symptoms tied to vertebrobasilar insufficiency. The 3 N's are nausea, nystagmus, and numbness—signs that point to brainstem or cerebellar involvement from posterior circulation issues. Dizziness, while common in this condition, is not part of that particular three-symptom mnemonic. So dizziness is the symptom that does not fit the 3 N's.

Nausea reflects vestibular and brainstem processing perturbations, nystagmus shows abnormal eye movements from central vestibular or brainstem pathways, and numbness indicates sensory pathway disruption. In contrast, dizziness alone is a broader, nonspecific complaint that can arise from many non-vascular causes, making it less specific to vertebrobasilar insufficiency when you’re considering the 3 N's pattern.