8Beyond Sound: Non-Auditory Percepts and Pain

FThe menu of off-target percepts

Beyond facial-nerve twitching, recipients can report pain or a pulling, pressure or throbbing sensation on stimulation; body, tingling or needle-like sensations; and vestibular percepts such as dizziness or a sense of movement when specific electrodes are stimulated. These are non-auditory side effects: the percept is felt rather than heard, and it is typically time-locked to stimulation of particular electrodes or to loud levels. The common thread is current spread to a non-auditory structure, the facial nerve, vestibular afferents, or somatosensory and dural fibres near the cochlea, or an electrode-specific problem at one contact. Customised mapping strategies can reduce or eliminate these side effects in most affected recipients without abandoning the device.[2025][2023]

CWhy a single electrode goes rogue

Current spread is the dominant mechanism: high levels and broad monopolar stimulation spread charge beyond the target neurons to nearby sensitive structures. Position matters: an electrode lying close to a sensitive structure (the facial nerve at the basal turn, vestibular afferents near the cochleovestibular junction, or dura at an eroded wall) is more likely to evoke a non-auditory percept. An electrode-specific fault, partial extracochlear migration, contact with bone or fibrosis, or an out-of-range impedance, can make one contact uniquely uncomfortable or painful while its neighbours behave normally. High comfort levels set during programming can push otherwise quiet electrodes into the range where current spread reaches non-auditory fibres, so percepts may emerge as the map is made louder.[2025][2020]

TTroubleshooting: find the culprit, then balance

Step one is to localise the offending electrode by stimulating contacts individually and asking the patient to describe and rate any non-auditory sensation; impedance telemetry and integrity testing help flag a faulty contact. Step two is to remap: lower the comfort level and current on the culprit electrode, lengthen pulse width to maintain loudness, reduce rate, and trial a focused configuration; many percepts resolve without losing the electrode. Step three, if remapping fails, is to deactivate the offending electrode, accepting the loss of one spectral channel but eliminating the percept. Every change is balanced against speech outcome: deactivating or softening electrodes narrows the frequency map, so the goal is the minimum intervention that removes the percept while preserving as much speech benefit as possible.[2025][2019][2023]

CDevice problem or biological cause?

A key fork in the road is distinguishing a device or electrode problem (faulty contact, migration, short or open circuit) from a biological cause (current spread to the facial or vestibular nerve, an anatomically close structure, or a sensitive ear). Clues to a device problem: a single electrode behaving abnormally, abnormal impedance or integrity-test results, percept onset after a fall or head trauma, or imaging showing electrode migration. Clues to a biological cause: a pattern across several adjacent electrodes (e.g. all basal contacts twitching), known otosclerosis or malformation, or percepts that scale smoothly with loudness across the array. When a hard device fault is confirmed, the path may be integrity testing and, if needed, revision; when the cause is biological, the answer is mapping. Getting this distinction right avoids both unnecessary surgery and futile reprogramming.[2020][2025]