42 Labyrinthitis

Labyrinthitis is an inflammation of the labyrinth and may be classified into perilabyrinthitis, paralabyrinthitis, serous labyrinthitis and suppurative labyrinthitis. Bacterial labyrinthitis is rare in our post-antibiotic era and is usually secondary to meningitis or acute otitis media. Cooksey–Cawthorne exercises will accelerate recovery and central compensation from reduced labyrinthine function caused by an episode of labyrinthitis but should only be commenced once the initial acute phase of symptoms has settled.

42.1 Labyrinthine Fistula

A labyrinthine fistula is a bony erosion of the labyrinthine capsule to expose and sometimes rupture the endosteum of the labyrinth. The endosteum is the thin layer of periosteum separating the membranous labyrinth from the dense cortical bone covering the semicircular canals. A breach results in a perilymph fistula and may cause vertigo and a dead ear. A fistula most commonly occurs in the dome of the lateral semicircular canal.

42.2 Tullio’s Phenomenon

The Tullio phenomenon is defined as vertigo in the presence of loud sounds. The phenomenon occurs when sound energy is transmitted from a mobile stapes footplate to the labyrinth which is distensible only when there is a fistula. Historically, the phenomenon occurred after a fenestration procedure was performed in the presence of a mobile footplate, this scenario arising in the 1950s in patients with so-called adhesive otitis. Adhesive otitis was a term applied to patients with a history of chronic middle ear disease without cholesteatoma, who had developed a conductive hearing loss in the presence of a mobile stapes and an intact ossicular chain but no obvious tympanosclerosis. Probably such patients had an undiagnosed ossicular erosion or otosclerosis. The Tullio phenomenon may also arise in those with endolymphatic hydrops when it is thought to be secondary to sound energy transmission from the footplate to the distended saccule which may be touching the undersurface of the footplate. It may also arise in patients who have had mastoid surgery when either the disease or the surgery has created a labyrinthine fistula, usually of the lateral semicircular canal.

42.3 Fistula Sign

In the presence of a labyrinthine fistula, raising the ipsilateral ear canal pressure may cause conjugate deviation of the eyes away from the affected ear. The mechanism is pressure transmission to the labyrinth causing endolymph movement and stimulation of the labyrinthine sense organs. This occurs either directly if there is labyrinth endosteum exposed to the ear canal after mastoid surgery or indirectly if endosteum is covered by disease (e.g., cholesteatoma) that can transmit the pressure wave. On occasion, it may occur by a similar mechanism to the Tullio phenomenon. Releasing the pressure allows the deviated eyes to return to the midline.

42.4 Perilabyrinthitis

Perilabyrinthitis is a syndrome caused by a labyrinthine fistula after mastoid surgery in the presence of retained labyrinthine function. The fistula may have been present, but silent, before surgery. For example, when secondary to cholesteatoma, the mass of the cholesteatoma sac prevents distension of the labyrinthine endosteum. Alternatively, the fistula may be iatrogenic. The hallmarks of perilabyrinthitis are the Tullio phenomenon and a positive fistula sign. Vertigo may also arise in perilabyrinthitis on windy days when the wind, which is cooler than air in the external ear canal, produces a thermal gradient across the labyrinth and a difference in the specific gravity of endolymph at each end of the semicircular canal to cause circulation of the endolymph within the canal (i.e., causes eddy currents).

Conservative treatment consists of occluding the meatus with cotton wool when outdoors. Surgical treatment involves covering the fistula with bone pâté or temporalis fascia and a temporalis muscle flap reinforced with fibrin glue, or a combination of these.

42.5 Paralabyrinthitis

This is vertigo occurring in the presence of chronic suppurative otitis media (CSOM) when inflammation close to the endosteum of the labyrinth causes an irritative nystagmus (nystagmus towards the affected ear because the irritation pushes the eyes away from the affected ear with a rapid correction—the nystagmus—towards the affected ear).

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