According to Discovery Fit & Health, an inner ear dysfunction in children could cause neurological changes that lead to behavioral abnormalities related to attention deficit hyperactivity disorder (ADHD). Therefore, adolescents who suffer from inner ear problems could be at risk of developing ADHD, according to a recent study.
Findings published online in the journal Science reveal that children and adolescents with severe inner ear problems could develop behavioral problems, such as hyperactivity. When a Ph.D. student at Albert Einstein College of Medicine noticed that some mice in a laboratory were continuously chasing their own tails, researchers — including Dr. Jean Herbert, a neuroscience and genetics professor at the college — decided to examine if poor hearing and restlessness were caused by a faulty gene in animals and humans, reports the Daily Mail. Inner ear problems typically derive from genetic defects, though they can also stem from infection or injury.
The scientists took healthy mice and deleted the gene associated with poor hearing from either the inner ear, various parts of the brain that control movement, or the entire central nervous system (CNS). Patients of severe inner ear problems have a mutation of the gene Slc12a2, which mediates the transport of sodium, potassium, and chloride molecules in various tissues, including those in the inner ear and CNS, according to the Albert Einstein College of Medicine of Yeshiva University.
When the researchers deleted Slc12a2 from the inner ear, they were surprised by the results.
"To our surprise, it was only when we deleted the gene from the inner ear that we observed increased locomotor activity," said Herbert, lead author of the study.
The tests revealed increased levels of two proteins involved in a signaling pathway that controls the action of neurotransmitters — pERK (phosphorylated extracellular signal-regulated kinase) and pCREB (phospho-cAMP response-element binding protein). The increases in levels of these two proteins were only found in the central area of the brain controlling movement but not in other forebrain regions.
The researchers injected the mice who had the Slc12a2 mutation with SL327, a pERK inhibitor, to discover whether the protein was responsible for the abnormal increased movement in the mice. The injection restored the animals’ activity back to normal levels.
“Our study also raises the intriguing possibility that other sensory impairments not associated with inner ear defects could cause or contribute to psychiatric or motor disorders that are now considered exclusively of cerebral origin," said Herbert.
This study suggests that a sensory impairment, such as an inner ear dysfunction, can cause neurological changes that can induce behavioral problems in children.
“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 behaviours traditionally considered to originate exclusively in the brain,” Herbert said.
ADHD in children who suffer from inner ear disorders may be controlled with medications that inhibit the same pathway in the central area of the brain, according to the researchers of the study.
Approximately three to seven percent of school-age children have ADHD, with a total of 5.4 million children in the U.S. with an ADHD diagnosis, according to the Diagnostic and Statistical Manual of Mental Disorders.