A new study suggests that hearing problems could be an indicator for early autism screening. Many individuals with autism have difficulties with hearing, such as being hypersensitive to sound or struggling to focus on conversations in noisy environments. Neurological studies have found atypical brainstem auditory evoked potentials (BAEPs) in people with autism, with smaller and slower responses compared to neurotypical individuals. Brain imaging studies have also shown smaller brainstems in individuals with autism, possibly indicating a lack of neurons in specific areas. Further research is being conducted to understand how alterations in the brainstem and auditory system contribute to autism, with the aim of allowing for newborn screening and early diagnosis.
A study analyzed postmortem brainstem tissue from individuals with autism and controls and found that those with autism had fewer neurons in their auditory brainstem. Even children as young as 2 years old with autism had fewer auditory brainstem neurons compared to controls. The cluster of brainstem neurons called the medial superior olive was particularly affected in autism brains, with fewer and misshapen neurons. Some individuals with autism also had misplaced brainstem neurons during development.
The stapedial reflex, which measures a change in pressure in response to sound, was tested in children with autism and neurotypical children. Children with autism had a lower threshold, responding to quieter sounds, and a delayed stapedial reflex compared to controls. This delay could be due to fewer neurons or alterations in neuronal branches. Interestingly, in many children with autism, the stapedial reflex in the opposite ear was faster than in the ear that received the sound.
These findings suggest that auditory differences, such as faster reflexes in the opposite ear and differences in auditory function in the inner ear, could be used for noninvasive screening for autism. Researchers are currently evaluating the sensitivity of autism screening using these auditory differences in newborns. Animal models, such as rats exposed to valproic acid in the womb, have shown brainstem abnormalities associated with autism. These rats had fewer inhibitory neurons in the auditory brainstem and abnormal neuron appearance, as well as hyperactive responses to loud sounds. The aim of this research is to determine if the differences observed in animal models are also present in the brains of people with autism. Randy Kulesza, the director of anatomy at Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania, is involved in this research.
Randy Kulesza is director of anatomy at Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania.
