Final answer:
The least common cause of dizziness in primary care geriatrics is an acoustic nerve tumor.
Step-by-step explanation:
Among the given options, the least common cause of dizziness in primary care geriatrics is An acoustic nerve tumor. Dizziness in the elderly population is commonly caused by conditions such as anxiety, vertebrobasilar transient ischemic attacks, cervical spine disease, and cerumen against the tympanic membrane.