erinc, you could ask Dr. Amir, the London-based dentist who posts here, who treats, by use of braces, imbalances in the teeth and jaw which theoretically help the C1 and C2 vertebra stay in proper alignment which allows for the proper flow of venous and arterial blood and CSF; impingement of the vagus nerve is also alleviated.
Cece, great thoughts... this line of thinking might also explain improvements in the sense of hearing, both immediate and longer term. If the auditory nerve isn't damaged, relieving congestion (and perhaps compression?), could allow for immediate improvement. If the auditory nerve is damaged, time for healing would be necessary dependent on the degree of damage. Also for the sense of smell, too.