For the first time ever, a group of researchers from Massachusetts Eye and Ear have deployed electrodes to successfully induce sense of smell in humans by stimulating neurons in the olfactory bulb – a part of the brain involved in communicating inputs from the nose to deeper regions within the same organ.
“Our work shows that smell restoration technology is an idea worth studying further,” said corresponding author Dr Eric Holbrook, MD. “The development of cochlear implants, for example, didn’t really accelerate until someone placed an electrode in the cochlea of a patient and found that the patient heard a frequency of some kind.”
Needless to say, a good sense of smell makes a significant contribution to our safety and well-being by helping us navigate the world, detect fire, gas leaks, spoiled food, and much more. And yet roughly 5 percent of the global population (and over 50 percent of people over the age of 65) suffer from the loss of this valuable faculty.
Even though some cases of smell loss, or anosmia, can be treated by addressing a relatively harmless underlying cause, such as nasal obstruction or sinus disease, in other cases it results from more severe conditions, like damage to sensory neurons, for which there are currently no effective treatments.
With this in mind, and taking inspiration from the work conducted by their colleagues at Virginia Commonwealth University’s School of Medicine, the research team wanted to figure out the consequences (or the lack thereof) of subjecting the olfactory bulb to electrical stimulation.
In a paper out in the journal International Forum of Allergy & Rhinology, Holbrook and his team managed to induce sensations of smell (including reports of onions, antiseptic, sour, and fruity aromas) in five patients with intact ability of smell by placing electrodes in their sinus cavities with endoscopes.
Naturally enough, these findings give hope for an eventual “cochlear implant for the nose”, yet authors emphasise that devices which stimulate the olfactory neurons could be more difficult to make than those which do the same to auditory neurons.
“There’s currently so little that we can do for these patients, and we hope to eventually be able to re-establish smell in people who don’t have a sense of smell,” said Holbrook. “Now we know that electrical impulses to the olfactory bulb can provide a sense of smell – and that’s encouraging”.