What condition refers to an acute unilateral infection or inflammation of the vestibular system?

The condition that refers to an acute unilateral infection or inflammation of the vestibular system is vestibular neuritis. This condition specifically affects the vestibular nerve, which is responsible for conveying balance and spatial orientation information from the inner ear to the brain.

In vestibular neuritis, inflammation typically occurs due to a viral infection, leading to symptoms such as vertigo, dizziness, balance issues, and sometimes nausea. Importantly, it is characterized by the sudden onset of these symptoms, which can significantly affect an individual’s ability to maintain balance and can lead to complications if not properly managed.

While labyrinthitis can also involve both auditory and vestibular dysfunction, it more broadly refers to inflammation of the entire inner ear structure, including the cochlea and the vestibular apparatus, and may commonly follow an upper respiratory infection. Mastoiditis, on the other hand, pertains to an infection of the mastoid process of the temporal bone, usually resulting from untreated otitis media. Otitis media itself is an infection of the middle ear, primarily affecting hearing.

Thus, the specificity of vestibular neuritis to the vestibular system makes it the correct answer.