Fran Lowry

June 19, 2014

HOLLYWOOD, Florida — Caloric vestibular stimulation (CVS), a test that is commonly used by ear, nose, and throat specialists and audiologists to test patients' balance, may transiently increase illness awareness in patients with schizophrenia.

"Poor insight into illness in schizophrenia is a huge problem and can have a direct impact on treatment adherence and clinical outcomes," lead author Philip Gerretsen, MD, a geriatric psychiatrist and clinical fellow at the Center for Addiction and Mental Health and the University of Toronto, Canada, told Medscape Medical News.

"This work is modeled on a number of different areas of prior research, starting with patients with anosognosia from right hemisphere stroke damage," said Dr. Gerretsen.

"According to that model, poor illness awareness, or not being aware that you have the neurological deficit of paralysis, tends to happen within the right hemisphere in the right parietal lobe frontal regions and insula. CVS is transiently effective treatment for anosognosia, and my thought was that you could use that as a template or starting point for looking at poor insight into illness in schizophrenia," he added.

Results of the pilot proof-of-concept study were presented here at the American Society of Clinical Psychopharmacology (ASCP) 2014 Annual Meeting.

CVS stimulates the vestibular ocular reflex and involves irrigating the ear canal with water. Depending on the temperature of the water and which ear is irrigated, the procedure can stimulate different areas of the brain, Dr. Gerretsen said.

"Warm water in the right ear stimulates the ipsilateral hemisphere, cold water stimulates the contralateral hemisphere. This has been shown by PET and functional MRI studies.

Dr. Gerretsen and coauthor David D. Pothier, MD, from the University of Toronto, tested CVS in 13 patients (10 men, 3 women) with a schizophrenia spectrum disorder and moderate to severe insight impairment, as defined by a score of 3 or greater on the Positive and Negative Syndrome Scale (PANSS) G12 scoring criteria.

Dr. Philip Gerretsen

"Research has also shown that cold water in the left ear of stroke patients with right hemisphere damage can reverse the anosognosia paralysis so that they gain awareness that they have neurological deficits anywhere from 30 minutes to as much as 2 hours afterwards," he noted.

Toward an Enduring Effect

The patients' mean age was 41 years, mean age at illness onset was 26 years, mean duration of illness was 16 years, and mean PANSS score was 4.5.

The patients were given, in a random order, left cold (4° C) CVS, right cold CVS, and sham CVS, in which the water was at body temperature and thus did not elicit a vestibular ocular reflex.

The investigators assessed the patients' insight into their illness 5, 30, and 60 minutes after CVS, using the University of Toronto Insight into Psychosis scale.

"This is an in-house measure that we had to design so that we could capture subtle changes. In my opinion, the currently valid measures of insight into illness are not designed to capture subtle changes over a short period of time but rather over an extended period of time," Dr. Gerretsen said.

Compared with the sham and right cold conditions, left cold CVS increased patients' insight and awareness of their illness (Cohen's d = 0.09) at 5 and 30 minutes. However, by 60 minutes, that insight had diminished.

"We think the effectiveness of left cold CVS is due to the stimulation of inactive right hemisphere circuits via vestibular neuclei projections to the contralateral hemisphere," Dr. Gerretsen said.

"Left cold CVS had a meaningful, significant effect in comparison with right cold CVS and sham. We now plan to do further research to find ways to make the transient period of awareness last longer," he said.

"Other researchers have used transcranial direct current stimulation and transcranial magnetic stimulation to stimulate the brain for longer periods of time and have had success in depression and hallucinations in schizophrenia, so our hope would be to move the CVS approach to perhaps 5 consecutive days of stimulation and see if we can have more enduring effects," he added.

New Insight

Commenting on the study for Medscape Medical News, Brendan Montano, MD, from Connecticut Clinical Research in Cromwell, described the research as a "breakthrough" with respect to providing insight into a common problem.

Dr. Brendan Montano

"If the researchers are able to prove that this works not only in the model of schizophrenia but in other disease states, such as with denial problems and substance abuse, or denial problems in severity of illness, so that patients are able to quickly have at least half an hour of improved insight with minimal side effects, and if you can repeat it enough for this insight to be enduring, or last, then you've got something worthwhile."

The study was funded by the Ontario Mental Health Foundation. Dr. Gerretsen and Dr. Montano report no relevant financial relationships.

American Society of Clinical Psychopharmacology (ASCP) 2014 Annual Meeting. Abstract 68. Presented June 17, 2014.

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