new research shows.
Results from one of the largest studies of its kind show the auditory brainstem response (ABR) test, which is carried out on most newborns, represents “a huge untapped potential” to detect autism, lead author Oren Miron, research associate, department of biomedical informatics, Harvard Medical School, Boston, and a PhD candidate at Ben Gurion University in Beersheba, Israel, said in an interview.
“The findings further reinforce our understanding that autism, in many cases, has a sensorial and auditory aspect to it,” said Mr. Miron, adding that an adverse response to sound is one of the earliest behavioral signs of autism.
The research was published online Oct. 31 in Autism Research.
Early intervention critical
Autism spectrum disorder (ASD), which involves problems in social communication and interaction, affects an estimated 1 in 59 children. Early identification and intervention are critical for improving outcomes and decreasing the economic burden associated with ASD.
The ABR test, which is used for Universal Newborn Hearing Screening (UNHS), uses surface electrodes to measure auditory nerve and brainstem responses to sound.
Previous studies identified abnormal ABR amplitude in children with ASD. However, it’s unclear whether healthy newborns who later develop autism also show ABR differences vs those who don’t develop the disorder.
Researchers used UNHS data, which allowed them to examine a larger, younger, and healthier sample compared with previous studies. The study included 321 newborns later diagnosed with ASD and 138,844 controls without a subsequent ASD diagnosis.
The mean ABR testing age was 1.76 days for newborns later diagnosed with ASD and 1.86 for those in the non-ASD group.
The ASD group was 77% male and the non-ASD group was 51% male. The rate of neonatal intensive care unit admission was 8% in the ASD group and 10% in the non-ASD group.
The hearing test involves placing an earpiece in the baby’s ear and delivering a click sound at 35 dB above normal hearing level (nHL) at a rate of 77 clicks per second in the right ear and 79 clicks per second in the left ear.
The clicks create electrical activity, which is recorded by a surface electrode and used to extract the ABR waveform. When a sound reaches the brain stem, it creates five consecutive waveforms – waves I, II, III, IV, and V.
Previous studies focused on wave V, which is easiest to detect. The current study used low intensity sound that resulted in a weaker signal.
To overcome this low intensity issue, researchers focused on the negative drop (latency) after the wave V (Vn), which is easier to detect, and on the ABR phase, or entire waveform. They illustrated the differences between the ASD and non-ASD groups in a series of graphs.
Results showed that the ABR phase in the right ear was significantly prolonged in the ASD vs non-ASD group (P < .001). ABR phase in the left ear was also significantly prolonged in the ASD group (P = .021)
Vn latency in the right ear was significantly prolonged in the ASD group compared with the non-ASD group (P = .048); however, this was not the case in the left ear.
The prolongation could mean that the V-negative wave might appear after 8 ms in normally developing children compared with 8.5 or 9 ms in children with autism, said Mr. Miron.
The new study is the first to show V-negative and phase abnormalities are associated with ASD, the authors note. The brainstem prolongation could be due to anatomical abnormalities in the brainstem in individuals with ASD, the researchers added.