I had absolutely no clue that the patient was using clicking sound for echolocation to help with ambulation . It is now well-known that humans can learn echolocation 2 which has the potential to become an invaluable asset for a visually challenged person . Daniel Kish ,
Image by Nan Knighton blinded in early childhood from retinoblastoma was exceptionally skilled in echolocation , so much so he was nicknamed “ real life Batman .” He has contributed enormously to increase the awareness of human echolocation ; he has helped many visually handicapped children to “ see with sound ” by teaching the technique of echolocation . 3 There has also been significant insight into the neural basis of echolocation ( functional MRI studies show that a blind person surprisingly uses the visual cortex for echolocation ). Echolocation is also the basis for the development of the “ UltraCane ” a walking stick which emits ultrasound signals and analyzes the echoes to provide feedback to the person , a major achievement in the development of gadgets to help the visually handicapped to ambulate safely .
Credit goes to Lazzaro Spallanzani , an 18th century Italian physiologist and Charles Jurine , a Swiss naturalist whose experiments eventually led to the concept of echolocation ( a blinded bat can fly in the dark , a deaf bat cannot ). Centuries later , Harvard students Griffin and Galambos coined the term echolocation 4 and figured out that bats utilized ultrasound waves , generated through their larynx , looking out for echoes . Numerous technological advances eventually led to medical use of ultrasound to generate tissue images from waves reflected by different underlying structures . Ian Donald in 1956 introduced ultrasound in medicine when he used the one-dimensional A-mode ( amplitude mode ) waves to measure the biparietal diameter of the fetal head . From this humble beginning , the field of ultrasonography blossomed with the addition of B mode ( brightness mode ) and M mode ( motion mode ) as well as Doppler imaging . Newer technologies include ultrasound elastography , 3D ultrasound and contrast agent enhanced ultrasonography .
Diagnostic ultrasonography has applications in almost every specialty , and I am sure that each of you use it in some context or other . However , the more exciting development is the rapidly expanding field of therapeutic ultrasonography . I can ’ t help sharing with you the story of one of my patients as an illustration . The patient started experiencing hand tremor about five years ago which gradually worsened . His grandfather had a similar problem and could “ steady his hand with a glass of wine .” Examination showed a combination postural and kinetic tremor of hands , right more than left . The clinical picture was one of essential tremor and pharmacotherapy was tried for two to three years and later botulinum toxin injections into selected forearm muscles . Though initially successful , it became clear that he needed more effective treatment . Stereotactic thalamotomy was offered as an option . He was quite reluctant to have a burr hole placed in the skull , as the initial step for the procedure . Eventually he was referred to a center which just started doing thalamotomy using high intensity focused ultrasound ( HIFU ) guided by MRI , a procedure which did not need surgical incision / placement of burr hole . The patient greatly benefited from the procedure .
High intensity focused ultrasound ( HIFU ) combined with MRI has the potential to transform many surgical procedures , starting with stereotactic brain surgery . The FDA has already approved its use for thalamotomy for treatment-resistant essential tremor , tremor-dominant Parkinson disease ( PD ) and pallidotomy for other PD symptoms . It has also been approved for treatment of prostate cancer , thyroid adenoma and uterine fibroid . HIFU is an effective technique for reversible disruption of blood brain barrier , highly useful for drug delivery into selected areas of brain parenchyma . The scientists who developed HIFU must be thrilled and gratified to realize that it won ’ t be long before this technology will have an important role in managing a vast number of disorders affecting many different organs .
Let me conclude my thoughts of Flaco and ultrasonography with a quote from the beloved two-time Nobel laureate , Marie Curie : “ I am among those who think that science has great beauty . A scientist in his laboratory is not only a technician : he is also a child placed before natural phenomena which impress him like a fairy tale .”
References
1
Greif S et al Acoustic mirrors as sensory traps for bats . Science 2017 357 1045-47
2
Kish D , Hook J . Echolocation and FlashSonar . 2016 . American Printing House for the Blind , Louisville , KY
3
Thaler L et al . Human click-based echolocation of distance : Superfine acuity and dynamic behavior . JARO 2019 20 499-510
4
Gareth J . Echolocation . Current Biology . 2005 15 ( 5 ) 484-488
Dr . Iyer practices at the Neurodiagnostic Center of Louisville and is a retired professor of neurology at the University of Louisville School of Medicine .
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