Inner ear dysfunction may contribute to symptoms of ADHD
Story source: http://www.bbc.co.uk/news/health-23972137
A new study (2013) has suggested that inner-ear problems could be a cause of hyperactive behaviour.
A study on mice, published in Science, said such problems caused changes in the brain that led to hyperactivity. Although no causal link has been established, the team from the Albert Einstein College of Medicine of Yeshiva University in New York noticed some mice in the lab were particularly active - constantly chasing their tails.
“They were found to be profoundly deaf and have disorders of the inner ear - of both the cochlea, which is responsible for hearing, and the vestibular system, which is responsible for balance.
The researchers found a mutation in the Slc12a2 gene, also found in humans.
Blocking the gene's activity in the inner ears of healthy mice caused them to become increasingly active.
The researchers then examined the striatum, an area in the centre of the brain area that controls movement.
Researchers found higher-than-normal levels of two proteins, pERK and pCREB. Mice with the gene flaw were given injections of haloperidol, a medicine already used to treat tics - uncontrollable movement - in humans.
It was seen to counteract the high protein levels, and mouse activity patterns returned to normal.
The researchers suggest the same process could be targeted in people, and that medications could be developed to help manage hyperactivity in children with inner-ear disorders.
Prof Jean Hebert, the lead scientist, said: "Our study provides the first evidence that a sensory impairment, such as inner-ear dysfunction, can induce specific molecular changes in the brain that cause maladaptive [counterproductive] behaviours traditionally considered to originate exclusively in the brain.”
Comment by Sally Goddard Blythe
These findings mirror both scientific and empirical evidence obtained from clinical practice, which have demonstrated a link between vestibular disorders and attention deficit/hyperactivity disorder.
For many years Dr Harold Levinson has used a combination of anti-motion sickness, anti-histamine and vitamin preparations in the treatment of dyslexia, attention deficit/hyperactivity disorder and phobic disorders, based on the theory that a disturbance in the functioning of the inner ear and the cerebellum result in a range of symptoms linked to perception, arousal and affect.
The work of A Jean Ayres, the inspiration behind the therapeutic treatment know as Sensory Integration, suggested that different types of vestibular stimulation could influence different levels of arousal.
These most recent scientific findings, although derived from experiments on mice, and caution should always be exercised in applying such findings to human subjects, appear to add weight to existing therapeutic techniques which aim to improve behaviour by concentrating on the functioning of the vestibular system and related pathways. While the recent research focused on the use of pharmacological agents (haloperidol for example) to ameliorate symptoms, existing clinical practice suggests that non-pharmacological interventions are also of value.
Unfortunately the latter do not attract large scale funding for research from pharmaceutical companies.