The main objective was to describe spontaneous nystagmus characteristics during an episode of delayed endolymphatic hydrops (DEH), including an initial vertical upbeating nystagmus in one patient. The secondary objective was to highlight the contribution of chemical labyrinthectomy.

Episodic vertigo after a prolonged period of time of sensorineural hearing loss (profound or total) in one ear characterized ipsilateral DEH and was associated with the development of hearing loss in the opposite ear in contralateral DEH.

Ten patients met the criteria for DEH: 7 ipsilateral and 3 contralateral. Three (all ipsilateral DEH) were examined during a vertigo episode. Two patients had a typical horizontal-torsional nystagmus beating contralaterally to the hearing loss. One patient showed atypic initial vertical upbeating nystagmus with a slight torsional component, which secondarily became horizontal-torsional beating contralaterally to the hearing loss. Four patients had disabling vertigo with unilateral total deafness (ipsilateral DEH), successfully treated by 1-3 transtympanic gentamycin (Gentalline^®) injections.

Nystagmus direction during vertigo episodes varies, and may initially present as vertical upbeating nystagmus, which, to our knowledge, has not been previously reported in DEH or Menière's disease. This nystagmus might reflect an inhibition of the superior semicircular canal (on the hearing-impaired side), suggesting incipient hydrops in this canal. Chemical labyrinthectomy is a simple and effective procedure in unilateral DEH, especially as the patient often suffers from total deafness.