An inner ear infection is an inflammation or fluid build-up in parts of the ear that occurs when a microbe (bacterial or viral) enters the inner ear. Usually, the most common cause of this inflammation is a viral infection. In less common cases, a bacterial infection may be the cause.
It is commonly referred to as Labyrinthitis, which is the inflammation of part of the inner ear called the labyrinth. The part of the ear usually affected is responsible for hearing and balance.
Labyrinthitis  may occur when a cold, the flu, or a middle ear infection spreads to the inner ear and this can result in congestion and swelling of the nasal passages, throat, and eustachian tubes.
Inner Ear infections are usually painful as a result of inflammation and, unlike outer ear infections, they usually last longer. The infection can either be an acute or a chronic infection.
Acute infections span a shorter time and are painful while chronic ear infections are recurring and have the tendency to permanently damage  the inner ear. It is also likely that chronic ear infections clear up on their own.
Inner ear infections are very common among young people, especially adolescents and young children.
This article discusses the most prevalent signs of Inner ear infections.