If you’ve ever found yourself in an MRI machine, you know keeping still isn’t easy. For newborns, it’s nearly impossible. Now, a portable, ultrasonic brain probe about the size of a domino could do similar work, detecting seizures and other abnormal brain activity in real time, according to a new study. It could also monitor growing babies for brain damage that can lead to diseases like cerebral palsy.
“This is a window of time we haven’t had access to, and techniques like this are really going to open that up,” says Moriah Thomason, a neuroscientist at Wayne State University in Detroit, Michigan, who wasn’t involved in the new study.
Researchers have long been able to take still pictures of the newborn brain and study brain tissue after death. But brain function during the first few weeks of life, which is “utterly essential to future human health,” has always been something of a black box, Thomason says. Two techniques used in adults—functional magnetic resonance imaging (fMRI), which can measure blood flow; and electroencephalography (EEG), which measures electrical activity in the outer layers of the brain—have their drawbacks. FMRI doesn’t work well with squirmy tots, is expensive, and is too big to haul to a delicate baby’s bedside. EEG—which only requires attaching a few wires to someone’s head—can’t penetrate deeper brain structures or show where a seizure begins, critical information for doctors weighing treatment options, says Olivier Baud, a developmental neuroscientist at the Robert Debré University Hospital in Paris.
Seeking to develop something small, yet powerful, Baud and colleagues turned to ultrasound, an imaging technology that uses high-frequency sound waves to capture moving images of structures inside the body. Previous studies have shown that extremely fast ultrasound waves—10,000 frames per second, compared with the 50 frames per second in conventional medical imaging—can detect tiny changes in blood volume within blood vessels in rodent and human brains. As in fMRI, scientists use these changes in blood flow to approximate electrical activity in neurons. But because ultrasound does not easily pass through bone, these studies required that the skull be filed down or cracked open.
So Baud’s team aimed for a soft spot: the anterior fontanelle, a membrane-covered gap between the bones of an infant’s skull, which hardens as the bones fuse around age 2. The researchers attached a 40-gram ultrasonic probe to the anterior fontanelles of six healthy babies. A flexible silicon mount kept the device in place, while a wire transmitted data to a computer.
Despite their small size, the probes are 50 times as sensitive at measuring blood flow as conventional ultrasound. Like an EEG machine, they could easily distinguish between two phases of sleep in napping newborns: “active” sleep, in which the brain displays continuous electrical activity; and “quiet” sleep, in which brain activity waxes and wanes. When combined with EEG, the probes detected seizures in two infants whose cortexes had developed abnormally. The researchers were even able to identify where in the brain the seizures started by tracking the waves of increased blood flow that occur during such an event, they report today in Science Translational Medicine.
The probe, which runs custom software on commercially available hardware, is not yet sensitive enough to monitor brain activity outside the fontanelle area. With refinement, however, Baud believes the device will be able to detect abnormal brain activity caused by conditions like early onset sepsis, an infection of the bloodstream that can cause brain damage. It could also help distinguish healthy and unhealthy brain activity in young babies, a vitally important aspect of clinical trials for drugs aimed at protecting the brain from infection.
The new technique is equally important for neuroscientists who want to study normal brain development and the developmental origins of diseases such as autism, Thomason says. If researchers could acquire more data about brain development during this early stage, she says, “we could make much stronger predictions in the future.”