Vestibular neuromodulation for the treatment of persistent pain: An open label case series

Caloric vestibular stimulation (detailed below) is administered by Dr Steven Miller (medical practitioner) at Monash University, Clayton, or Dr Murray Taverner (pain specialist) or trained pain specialists/pain fellows at Frankston Pain Management Clinic, on a non-randomised, convenience (patient-availability) basis, with one right ear CVS administration per attendance. CVS is administered for up to six sessions, with CVS never repeated on the same day. The usual frequency of administration is once per week, however can be increased to daily administration (3x/week over two weeks) and may occasionally be reduced to as infrequent as once per month for 6 months if required by patient availability or if each CVS session provides as much as 1 month’s relief. To reiterate though, the standard administration frequency is once per week for 6 weeks. The two instances in which more than 6 sessions of CVS is administered include: (i) if there is a change from right ear to left CVS if right ear CVS is not appearing to be of any benefit, and (ii) an option for patients to repeat the 6 sessions of right ear CVS for patients in whom the first six sessions delivered pain/function benefits and in whom the beneficial effects have worn off by the review date 6 weeks after the last CVS session. There is no control condition as this is an open-label case series. To prevent potential confounding from different interventions or medication changes, there is an expressed preference for patients to not undergo any other new pain intervention treatment or medication change during the course of their involvement in the study, but this is not mandated. CVS is administered with patients seated or lying with their head angled upward 30° from horizontal. Up to 50mls of cold water (16°C) is slowly irrigated into the right external ear canal using a syringe with attached plastic cannula tubing (with the needle removed) which is situated close to, but not touching, the tympanic membrane. To ensure maximal stimulation, irrigation is continued for 5–10 seconds after nystagmus onset. Nystagmus and vertigo are elicited in all patients and persists for 2–5 minutes. Occasionally if 50mls of cold water has failed to elicit vestibular stimulation, a second 50mls can be administered. Most often less than 50mls is required. Also occasionally, and only with the patient’s consent, a failure to elicit CVS with 16°C water can result in a further attempt to elicit the stimulation with iced water (0-4°C). The latter was the water temperature used in our previous research, however data exist that the CVS and nystagmus elicited is equivalent when using 16°C or 0-4°C water (and 16°C water is more comfortable to receive than 0-4°C water). One reason for failure to elicit CVS with either 16°C or 0-4°C water irrigation is ear wax blockage of the ear canal. If this is present and preventing CVS from occurring, there is the option to apply ear wax removal drops for several days prior to the second attendance. If CVS still does not occur, the patient may need to see their general practitioner for ear wax removal prior to attending for CVS again. Patients are advised that it is preferable that someone attend with them to drive them home after the CVS session, however if they are free from significant side effects, they are able to drive themselves home if required. The follow up sessions at 6 weeks after the last CVS session and at 6 months after the last CVS session are preferred to be conducted in person, however can be conducted via telephone or video calling if required. The administering medical practitioner will be responsible for determining that you are safe to leave. The first attendance will take around 2 hours given the history required to be elicited and the detailed questionnaire assessments. Subsequent CVS sessions will last closer to 1 hour given less time required for history taking and less outcome measure collection. The 3rd and 6th CVS sessions are closer to 1.25-1.5 hours due to longer assessments. Attendance will be during business hours Mon-Fri at a time of investigator and patient convenience.