This paper reports five cases of aberrant cochlear implant electrode array insertion into the vestibular labyrinth. A review of the literature was conducted in order to clarify reasonable preventive and detection strategies and endorse the routine use of intra-operative plain skull X-ray.

The study entailed a clinical case series and literature review. The setting was a tertiary academic referral centre. The following data were evaluated: pre-operative temporal bone computed tomography, operative reports, intra-operative imaging, neural response telemetry/imaging and post-operative imaging.

There were no consistent pre-operative risk factors found on computed tomography scans and no reliable intra-operative signs of electrode array misdirection. All misdirections in our case series, and those in the literature, were easily detectable on intra-operative plain film X-ray.

These reported cases demonstrate implant misdirection without the surgeon's awareness. Aberrant insertion cannot be anticipated, and neural response telemetry/imaging is not a reliable indicator of misdirection. Routine intra-operative anteroposterior plain X-ray of the head is a reliable indicator of misdirection, and is fast and relatively inexpensive.

Professor Pietro Tullio was a director at the Laboratory of Experimental Physiology in Bologna during the early twentieth century. His experimental studies resulted in the description of the Tullio phenomenon, which is characterised by sound-induced vertigo and/or eye movements.

The experimental studies behind his contribution to vestibular physiology are described within this paper, as are some of the further developments that have been made.

To assess the incidence of vestibular disturbance in patients after cochlear implantation, and to evaluate the quality of vertigo symptoms.

Prospective, observational study.

Cochlear implant centre at a tertiary referral university hospital, Munich, Germany.

Forty-seven adult patients undergoing unilateral cochlear implantation between 2003 and 2007.

Patients were interviewed post-operatively about vertigo symptoms, using a specifically designed questionnaire. Questionnaire data were used to define patient subgroups based on probable vertigo aetiology. Cochlear implantation was performed via a retroauricular, transmastoidal approach. Thirty-six implants were Cochlear Nucleus 24 devices and 11 were MedEl devices.

Twenty-one (45 per cent) patients reported vertigo symptoms following cochlear implantation. The time of onset was directly post-operatively in the majority of patients. In 90 per cent, the symptoms suggested an otogenic origin. The majority of patients reported paroxysmal vertigo with a duration of seconds to minutes. Typical concomitant symptoms were tinnitus, fluctuating hearing loss and vegetative reactions. Serious disablement by vertigo was rare.

Exposing patients to the risk of possible balance disorders associated with cochlear implantation is justified in view of the hearing rehabilitation achieved, even with today's broader indications for cochlear implantation. However, patients should in any case be informed about the possibility and quality of post-operative vertigo symptoms.