Treatment of central pain syndromes by caloric vestibular stimulation

Background of the study: Central pain is caused by a dysfunction of the brain
and/or the spinal cord. The exact mechanism is unclear but usually there is an
incongruence between anticipated and actual somatosensory input. Treatment of
these patients is very complicated. Due to the widespread *neuropathic* pain
complaints combined with a treatment resistancy, this will lead to pain
*suffering* in both patients as well as relatives.
Recently, a non-invasive approach called caloric vestibular stimulation (CVS)
has been described and evaluated in these patients. CVS directly activates a
complex network of areas predominantly in the temporo-insular and
temporo-parietal cortex of both hemispheres. The activated areas receive
multisensory information (vestibular, visual, proprioceptive, tactile) and are
thought to be involved in body ownership and embodiment.
The effects of CVS on pain appear to be dramatic with a long lasting effect in
a number of patients. Studying the effects of this approach might lead to a new
way of treating these patients and these pain syndromes.
Study design: Pain scores of patients will be obtained before, immediately
following and a week after a single CVS treatment.
Study population: For this pilot, six adult patients with treatment-resistant
central neuropathic pain in the upper body on the non-dominant side will be
recruited in the Pain Center of UMC St Radboud. Patients will have to provide
written informed consent. Excluded from this pilot study are patients with the
following conditions: Other neurological disorders causing pain, significant
cardiac or respiratory disease (inadequately treated hypertension), ear disease
such as a perforated ear drum or otitis media/externa, vestibular disease or
significant motion sickness, or pregnancy.

Objective of the study: With this pilot study we attempt to explore the
possibility to treat patients suffering from intractable neuropathic pain with
CVS

Study design: Pain scores of patients will be obtained before, immediately
following and a week after a single CVS treatment.
Study population: For this pilot, six adult patients with treatment-resistant
central neuropathic pain in the upper body on the non-dominant side will be
recruited in the Pain Center of UMC St Radboud. Patients will have to provide
written informed consent. Excluded from this pilot study are patients with the
following conditions: Other neurological disorders causing pain, significant
cardiac or respiratory disease (inadequately treated hypertension), ear disease
such as a perforated ear drum or otitis media/externa, vestibular disease or
significant motion sickness, or pregnancy.

Intervention: The patient will be positioned in a supine position with head at
a 30° elevated angle. Patients will receive ear canal irrigation with ice water
(~4°C) on the dominant side (right ear for right handed people). The
irrigation (~30 ml) will continue until there are demonstrable signs of
nystagmus and reports of vertigo, but at least 30 s.

Nature and extent of the burden and risks associated with participation,
benefit and group relatedness: CVS with ice water is a safe technique that is
normally used for diagnostic purposes. The strong stimulation may acutely
result in a transient dizziness and nausea. The anticipated benefit is a much
longer lasting relieve of the neuropathic pain. The cold temperature of the
fluid might be uncomfortable.