Drop attacks due to superior canal dehiscence

Brantberg K, Ishiyama A, Baloh RW. Drop attacks secondary to superior canal dehiscence syndrome. Authors describe 2 patients. They note drop attacks occur in late Meniere's syndrome but can be early as well with vestibular dysfunction and normal hearing. They are in these cases associated with a sensation of being pushed or environmental tilts.

SCD is a peripheral audivestibular disorder manifested by sound and pressure induced vertigo due to absent bone coverage at the apex of the semicircular canal. The diagnosis is by inducing vertical or torsional eye movements in the plane of the superior canal when exposed to sounds or pressure changes. High resolution CT shows bony dehiscence in canal. Audiological tests show increased threshold in the low frequency range for air but not bone conduction.

The 2 patients described with unprovoked drop attacks not provoked by coughing, straining or loud noises (Tullio phenomenon).