Attitudes

Attitudes to left-handedness, which is of course only one aspect of human laterality, have eased over the last 100 years in the developed world. In previous generations, there was considerable pressure to conform and to use the right hand to write. Jimi Hendrix may well have written with that hand, but could any right-hander play naturally the inverted electric guitar like he did? There is a tendency to oversimplify, which must be resisted, or at the very least be understood. The quoted figure of 10 per cent left-handed prevalence will vary depending on sample size and when handedness was measured, as well as attitudes to handedness. This variation is reflected in studies of hand usage rather than preference in the older population, where the pressure to conform was higher.

The causes of handedness are multifactorial, but it is thought to occur more than expected in some families.^{Reference McManus12} Of the second author's immediate family and their partners (n = 19 in three generations) there are six who have a left-handed preference (1:3). In the first author's immediate family and partners (n = 13), there are four left-handers (prevalence of 1:3).

Laterality and usage

The preference of a paired organ, eye, ear, foot or hand varies naturally from adult to adult. Even the simplest task, for example throwing a ball, requires the use of the hand, eye, balance and co-ordination. The right eye, ear, foot and hand may dominate in some. It is natural to ask if there is an association between eye and hand preference, for example, although the central processing for the task is complex, and it must integrate sensory inputs and motor functions.

As mentioned, the dominance of the right-handed world is easy to recognise: the layout of a mobile telephone, the position of a mouse on a desk, the buttons of a Bluetooth headset on the right speaker and the exit of an electrical cable on the left speaker to leave the right hand unencumbered. Even an adult who has strong preference for the right hand may listen to the telephone with the left ear and hold the telephone with the non-dominant hand. An electric drill spins clockwise as this makes it easier for the right-handed members of both sexes to use. Many left-handers utilise a mixed-handed approach as they negotiate this world.

Measuring hand preference scientifically is fraught with difficulties, as learnt usage and the input of other paired organs confound. When listening to music, an individual may subconsciously tap one foot. Early footage of the four Beatles shows the two right-handers, John Lennon and George Harrison, tapping time with different feet: John used his left whereas George used his right. Even posture is affected, for when sitting, the legs may be crossed with the preferred leg on top. Although laterality is more complex than handedness, emphasis on handedness extends into customs and beliefs that may well influence how life is interpreted.

Laterality and culture

Some societies are less developed materially and hold different cultural beliefs. In such societies, a hand dips into the communal food bowl. The skin around an emptied bowel is cleaned with the contralateral hand, whilst custom dictates that the right hand is used for feeding and the left for cleaning, even if a left-hander naturally does the opposite. Use of the left hand is discouraged, and such attitudes may extend to left-handed surgeons.^{Reference Zaghloul, Saquib, Al-Mazrou and Saquib13}

Each side of the body may be given a moral value. The right is ‘good’ and the left is ‘bad’ or ‘evil’, and such views are found from antiquity. The Hamsa, an amulet of the right hand, warded off the evil eye. The dichotomy of left and right extends into political ideology: right, for conservatism and left, for change.

When writing using the Latin (or Roman) alphabet, accepted practice is to move from left to right. This is also true when evaluating information on a graph, or a comic strip. This is contrary to Chinese characters, which begin at the top right and descend the page from right to left. In all different forms of writing, the implement is pulled by the right hand and pushed by the left. Theories surrounding the directionality of languages are lacking in evidence, although in East Asian languages, traditionally recorded on bamboo scrolls, it was easier to write top to bottom and right to left, with the left hand managing the bamboo. As Middle Eastern languages favoured stone, chiselling right to left was thought to be easier. With the use of ink in modern-day society, moving left to right as a right-hander prevents smudging.¹⁴ Left-handed writing is still forbidden in some cultures.

The fewer characters of the Latin alphabet facilitated both printing and the widespread literacy that occurred in Europe. Colonial expansion was aided by technology produced by the Industrial Revolution. Now, English is the current language of science. With the advent of technology, a computer keyboard permits the use of both hands for typing, and dictation software overcomes the limitations of many different languages and scripts. In addition, the introduction of the electronic patient record is making handwriting redundant, potentially taking away this challenge for the left-hander.

Laterality and sensory input

Laterality and learning

It would be straightforward to explain laterality if the brain were programmed this way, but there seem to be multiple factors at play. It is easy to focus on one aspect of laterality, for example hand preference, and link it to another issue, for example the ability to read fluently. Dyslexia is more complicated than a simple link, as there is a visual element as well as central processing. Even so, being left-handed has been connected over the years to children with special needs, stuttering and stabismus.^{Reference Kushner25–Reference Tønnessen, Løkken, Høien and Lundberg27} In adults, it has been associated with criminality, alcoholism, heavy smoking, epilepsy, asthma, autoimmune conditions, cancers and social deprivation.^{Reference Bogaert28–Reference Zverev and Chisi31}

Clinical environment

The clinic room is set up for the right-eye dominant and right-handed doctor.^{Reference Drake-Lee32} A bull's eye lamp was commonly found in the otolaryngology clinic over the past few decades, whereby a parallel light source originated from behind the left shoulder of the patient. The parabolic head mirror had a focal length of 7 inches (18 cm), which allowed the clinician to move freely around the clinic and to use both hands, but the mirror had a central hole positioned for the right eye to use. A headlight gets around this limitation, and when powered by a battery, it overcomes the restriction of the light box. However, when an otoscope is used, it is customary to hold it with the left hand for the left ear, and the right hand for the right ear: eye preference is not important.

In the past, the laryngoscope or mirror used to view the post-nasal space was held with the right hand, and the tongue was covered in a gauze swab and held with the left hand. Patients often found this unpleasant, and views were incomplete. Modern endoscopes (both rigid and flexible) often include a camera attachment for an image to be portrayed on an adjacent screen. Eye preference is therefore not important, but the controls are usually set up for right-handed use. In practice, this means that far fewer direct laryngoscopies are now required in the operating theatre.

When a monocular microscope is used, a right-hander might well prefer to use the left eye. Even in medicine, binocular operating microscopes are usually set up for the right eye. When the teaching arm or camera is attached, it is usually on the right side.

Whilst there are left-handed instruments, these are not commonly found within UK operating theatres or clinical environments. Most instruments are made for the right hand, and the floor pedals are usually placed for right-foot usage. The problem with using scissors with the left hand has been mentioned, and many left-handed surgeons have developed manoeuvres to cut sutures.^{Reference Al Hussainy and See8}

Medical training and handedness

Training and practice appear to differ around the world for hand usage. When sutures are tied by hand, both hands are used to tie the knot. In the UK, otolaryngologists are expected to not cross their hands to allow an adequate view. This is particularly pertinent in a tonsillectomy procedure, where the left hand is used for the dissection and diathermy application for the left tonsillectomy, and the right hand for the right side. This is also relevant to endoscopic laryngeal surgery, where there is relative symmetry with regard to anatomy. Hand choice is often dictated by the laterality of the lesion, as opposed to handedness or preference, to obtain sound surgical results. In one study of simulated endoscopic laryngeal surgery performed by 19 surgeons, of whom 1 was left-handed, it was demonstrated that in only a third of the cases was the non-dominant hand used appropriately.^{Reference Naunheim, Le, Dedmon, Franco, Anderson and Song33}

Kim et al.'s study on the incidence of intra-operative complications in cataract surgery performed by left-handed residents revealed that although left-handed residents (n = 3) performed 9.2 per cent (n = 170) of the operations over a five-year period, they had a statistically significantly lower rate of complications.^{Reference Kim, Ali, Cremers, Yun and Henderson34} Several theories exist to explain this finding, including better use of the right hand when required, or that left-handed surgeons may just be more talented. Although this is a bold, generalised claim to make, years of suppression and having to conform may mean that left-handed surgeons, when allowed to flourish in the perfect environment, could be naturally more technically gifted.

One study on psychomotor skills comparing left- and right-handed medical students found little difference between them.^{Reference Alnassar, Alrashoudi, Alaqeel, Alotaibi, Alkahel and Hajjar35} The study of 27 students in each group compared suturing skills, cannulation techniques, urinary catheterisation and laparoscopic skills. The only difference was in laparoscopic peg removal, which was performed more quickly by the left-handers, but both groups completed the task in the targeted time.

There is a need for ambidexterity in laparoscopic surgery. A study of 16 trainees found that the 4 left-handed trainees used their right hand frequently. These four trainees were able to use both hands better and had a shorter operating time compared with those who were right-handed.^{Reference Nagaraj, AbdelFattah and Farr36}

One study compared 50 right- and 50 left-handers using the O'Connor tweezer dexterity test.^{Reference Lombana, Naeger, Padilla, Falola and Cole37} This compared the time taken to complete a task using both hands sequentially, and showed that left-handers performed significantly better and had a greater degree of ambidexterity than right-handers (97.2 vs 71.6 per cent congruity). The authors’ summary that ‘these results suggest that any perceived difference between left-handed and right-handed surgical residents may not be due to innate skill or dexterity, but rather a combination of external influences’ rings true to what we have summarised so far in this review.

In addition, Mehta and Lotke reviewed the outcomes of total knee replacements performed by a right-handed surgeon, where the surgeon stood to operate on the ipsilateral side, and found poorer outcomes associated with left total knee replacement compared to right total knee replacement.^{Reference Mehta and Lotke38} This further qualifies that external influences could be causation for a worse outcome.

With regard to otology surgery, a small retrospective study investigated whether the results of surgery performed on ipsilateral and contralateral ears were similar for both left and right-handed surgeons. Only surgeon experience was associated with shorter operative times and a slightly better hearing outcome (although these findings were not statistically significant).^{Reference Barzaga39}

A literature search published in 2010 revealed 19 studies on handedness and surgical training, and although many were in the form of surveys, numerous issues were apparent. A lack of mentoring, anxiety for both trainers and trainees, and the need for a trainee to have a degree of ambidexterity were observed.^{Reference Tchantchaleishvili and Myers40} Additionally, trainers can become impatient, and do not know how to train a left-handed trainee.^{Reference Lieske41}

Handedness and ENT conditions

Otolaryngologists treat a range of conditions, from rare genetic diseases to commonly acquired ones. The relationship between dextrocardia and ciliary dysfunction has been explored.^{Reference Afzelius and Stenram42,Reference McManus, Davison and Armour43} The conclusion is that there is probably no relationship between left-handedness and situs inversus or ciliary dysfunction. Moreover, in patients with situs inversus requiring abdominal surgery, the laparoscopic approach is much more ergonomic and comfortable, with ambidexterity employed by the left-handed surgeon.^{Reference Oms and Badia44} Much more common is otitis externa: the dominant hand scratches the external ear, and in patients with necrotising otitis externa, there is a strong correlation between handedness and affected side.^{Reference Migirov, Lipshitz, Dagan and Wolf45} The same has also been shown to be true for acquired cholesteatoma.^{Reference Migirov46} Carcinoma of the external ear is rare, but habitual ear picking is common in Japan. Again, there is some evidence that handedness is related to side of the carcinoma.^{Reference Tsunoda, Sumi, Terasaki and Kishimoto47} Tinnitus, noise-induced hearing loss and acoustic trauma are more common on the left side, but do not seem to be related to handedness.^{Reference Reiss and Reiss48,Reference Nageris, Raveh, Zilberberg and Attias49}