Reconsidering the Relationship Between Hand Preference and Cerebral Vascular Dominance: A Computed Tomography (CT) Angiography Study
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.344677
Source of Support: None, Conflict of Interest: None
Keywords: Cerebral dominance, computed tomography angiography, hand preference, internal carotid artery, vertebral artery
The concept of cerebral lateralization includes anatomical, embryological, pathological, chemical, and hormonal factors and mechanisms that affect the formation of asymmetric functions of the brain. It was first defined by Broca in 1860., Cerebral dominance can be defined as functional dominance in the brain., Hand preference is the most researched behavioral asymmetry among those described so far, and it is known as the most important indicator of hemispheric differentiation., Hand dominance is defined as a situation where a hand shows a distinct skill difference compared to the other hand, although there is no observable difference in power.
It was thought that the larger left vertebral artery (VA) diameter in people with right hand dominance was due to the need for more blood supply to the left VA, but a precise mechanism for this issue has not been defined. In some of the studies in the literature, a significant difference between right and left VA diameters could not be shown., Differently, it was found to be statistically significant in the study of Vural et al. In the same study, a significant correlation was not found between hand dominance and VA dominance.
In studies to date, VA diameter measurements were performed by using carotid and VA Doppler ultrasonography (USG), however none of them measured internal carotid artery (ICA) diameters.,, The ultrasonography method sometimes limits the evaluation of VA and ICA diameter measurement due to user-dependent and device-dependent reasons. In this study, we aimed to reevaluate the relationship between cerebral vascular dominance and hand preference, measuring VA and ICA diameters by using carotid and VA computed tomography (CT) angiography. Thus, by using the CT angiography method, that is superior to USG in many ways in VA and ICA diameter measurement, which gives more detailed and clear information and has higher sensitivity, we wanted to shed more light on this question, which was previously investigated in the literature.
The patients who were hospitalized in the Neurology clinic for any reason in the last 2 years and volunteered to participate in the study were included (n = 422). Seventy-one patients with carotid and VA occlusion, and six ambidextrous patients, and patients with a history of psychoactive substance use and active psychiatric illness were excluded from the study. The results of the CT angiographies taken during hospitalization were retrospectively reviewed. CT angiography was performed on a Canon TSX-036A tomography device (Rotation = 0.5; PF 0.813/HP 65.0). Afterward, the Edinburgh Hand Preference Questionnaire was used and the results were recorded. In the Edinburgh Hand Preference Questionnaire, the patients were asked which hand (s) they preferred to write, draw, grab, and throw an object, cut with scissors, brush teeth, use a knife (without a fork), use a spoon, broom, strike a match, open a box/lid. “Right hand,” “left hand,” and “both hands” were the responses recorded.
CT angiography images of the patients were evaluated by two radiologists, and VA and ICA diameter measurements were recorded. After evaluating the results for similarity with each other, the mean of the two values was accepted. VA diameters were measured and recorded by two radiologists such that the diameters of three different anatomical regions of the VA were V1, V2, and V3. V1 diameter measurement was defined as from the part where VA enters the transverse foramen, the V2 diameter measurement was defined as C5-C6 cervical vertebra level, and V3 diameter was measured from the level of the first cervical vertebra [Figure 1], [Figure 2] and [Figure 3].
Different classifications are used to evaluate the segmental anatomy of the ICA. One of the frequently used classifications is the classification created by Bouthilier et al. in which the ICA is divided into seven different segments. These are cervical, petrous, cavernous, clinoid, cisternal, ophthalmic, and communicating segments. In our study, measurements were made from the cervical segment of the ICA, [Figure 4].
Ethics committee approval was obtained for the study in accordance with the Declaration of Helsinki (Decision no: 2020/144). Signed consent was obtained from the patients who participated in the study.
The IBM SPSS Statistics 18 (IBM Corp., Armonk, NY, USA) was used for statistical analysis in the study. The normal distribution of the parameters was evaluated by the Shapiro–Wilk test. When there was normal distribution, parametric tests were used and when there was no normal distribution, non-parametric tests were used for comparison. In the evaluation of the study data, besides descriptive statistical methods (mean, standard deviation, frequency), Mann–Whitney U test was used to compare the quantitative data parameters of the two groups, and the Paired Samples T-test or Wilcoxon Signed Ranks test was used for intergroup comparisons. Significance was evaluated at P < 0.05.
In our study, 317 (90%) of the participants (n = 351) were right-handed, 28 (7.9%) were left-handed, and six (1.7%) were ambidextrous. The final evaluation was done for 345 cases, consisting of 197 (57.1%) males and 148 (42.9%) females. The mean age of the patients was 69 ± 13.04 years. The age range of the participants varied between 23 and 98. It was determined that 317 (91.9%) participants were right-handed and 28 (8.1%) were left-handed.
When the measurements of the radiologists were compared, there was high similarity between the two (Cronbach's alpha: 0.991 for VA; and 0.987 for ICA). While there was no difference between the genders in terms of right ICA, left ICA, and right VA, the diameter of the left VA was larger in males (p = 0.415; p = 0.296; p = 0.110; p = 0.048, respectively). There was no statistically significant difference between the genders in terms of right dominance, left dominance and ambidextrose (p = 0.649).
There was no difference between right-handed and left-handed patients in terms of right and left VA diameters (p = 0.617 and 0.673, respectively). In right-handed patients, the diameter of the left VA was significantly larger than the diameter of the right VA (p = 0.005). There was no significant difference between the diameter of the right and left VA in left-handed patients (p = 0.226) [Table 1].
There was no difference between right-handed and left-handed patients in terms of right- and left-handed ICA diameter (p: 0.094 and 0.980, respectively). In left-handed patients, the diameter of the left ICA was larger than the diameter of the right ICA, but the difference was not statistically significant (p: 0.055). There was no significant difference between the diameter of the right and left ICA in right-handed patients (p: 0.771) [Table 2]. In ambidextrous patients, there was no significant difference between the right and left ICA diameters and similarly between the right and left VA diameters (p: 0.344 and p: 0.058, respectively).
In this study, differently from previous studies, we reevaluated the relationship between cerebral vascular dominance and hand dominance using the CT angiography method, and we evaluated ICA measurements in addition to VA measurements.
Hand dominance is seen as left-handedness and right-handedness and ambidexterity, which means that both hands can be used without preference, although there is a slight difference in favor of right-handedness. In humans, it can be determined by the start of the retention of objects from the age of one and a half, and the development of the corpus callosum at this point is thought to be important. Subirana stated that 25% of people definitely use their right hand predominantly, approximately 40% of them primarily use their right hand; approximately 25% of them use both hands equally or almost equally without giving priority to any hand, and approximately 10% of them primarily use their left hand. In our study, 90% of the patients were right-handed, 7.9% were left-handed, and 1.7% ambidextrous.
The main inventories to show hand preference are the Geschwind, Edinburgh, Annet, and Wada tests. The Edinburgh inventory is therefore preferred in many studies because of its easy repeatability, rapidity, and universal appropriateness, and because it also allows comparative evaluation in both genders who might be different in terms of race, culture, and socioeconomics., This is why we used this inventory to determine hand preference in our study.
In previous studies, it has been suggested that there may be many factors affecting hand preference., Genetic and teratogenic factors, maternal age, babies born before 30 weeks, low birth weight, testosterone levels, birth-related factors, social environmental effects such as parents and teachers, and cultural influences have been addressed so far.
Studies have found that there are developmental anatomical differences between cerebral hemispheres in the human brain. While central sulcus in those with right hand dominance was deeper in the contralateral hemisphere of the preferred hand, it was observed that this pattern was absent in those with left hand dominance, and it was stated that gene expression in cortical (superior temporal sulcus and Heschl gyrus) and spinal areas could determine hand preference. Witelson and Pallie, as a result of their study on 14 neonatal and 16 adult brain samples, showed that the planum temporale on the left side was significantly larger than the right one in both groups. Chi, Dooling, and Gilles, examining the brains of 207 fetuses between the 10th and 44th week of intrauterine, stated that transverse temporal gyrus (Heschl gyrus) and planum temporale began to appear in both hemispheres after the 31st fetal week. They found that 54% of the brain samples showed the transverse temporal gyrus on the right and the planum temporale on the left developed better than the homologous areas in the opposite hemisphere. A transverse gyrus was found; however, they did not encounter any asymmetry between both hemispheres in 28% of their samples. Some studies have suggested that left planum temporale size variability may explain the difference in left hemisphere-language relationships.
Studies on the blood flow changes of the cerebral hemispheres have shown that the left brain has a greater blood flow. Orlandini et al. stated that the arteries on the left side of the circle of Willis are wider than those on the right, and that was related to the dominance of the left cerebral hemisphere. The faster blood flow in the left brain was associated with the fact that the left carotid artery emerges directly from the aorta, while the right carotid artery emerges from a separate artery in the aorta., Regional blood flow changes were investigated in the resting state of the cerebral hemispheres and after verbal and spatial materials were administered by the Xenon-133 inhalation technique. Gur and Reivich found that the left hemispheric blood flow was present in the lexical material in all 36 cases with right-hand dominance, and the right hemispheric blood in 17 cases and left hemispheric blood in 17 cases during spatial application, and they found resting-like blood flow in the remaining two cases.
In studies evaluating VA diameters, the left VA diameter was found to be greater than the right VA in those with both right and left hand dominance, but no statistically significant difference was found., Postmortem and angiographic studies have also shown the diameter of the left VA to be larger than the right. Zaina et al. tried to explain this situation with the vascular need of the brain and embryological development, but there is not enough evidence yet. Cagnie et al. suggested that the left VA is dominant for better blood supply in people with right hand dominance. Similar to these studies, the left VA diameter was found to be larger than the right, and it was significantly different from the others in the study conducted by Vural et al. However, no correlation was found between cerebral dominance and vertebral arterial dominance in the same study.
Subclavian artery originates from the brachiocephalic trunk on the right and aorta on the left. The VAs originate from the right aortic horn on the right and the left aortic horn on the left. Based on this, in the same study, VA and SCA diameters were evaluated together, whereas VA and SCAs of the same embryological origin were expected to show similar dominance; no correlation was found. In our study, similar to the study conducted by Vural et al., the left VA diameter was found to be larger at a statistically significant level compared to the diameter of the right VA. However, unlike their study, the left VA diameter was statistically significantly larger than the diameter of the right VA in patients with right-hand dominance in our study. Additionally, this result was not statistically significant in patients with left hand dominance and ambidextrous patients. Based on the idea that we can evaluate cerebral vascular dominance by studying both anterior and posterior system vessels, we also evaluated ICA measurements in addition to VA. However, there was no statistically significant relationship between right or left hand dominance and right and left ICA diameters. Based on these findings, we state that right-hand dominance is associated with left VA dominance, and the absence of significant diameter difference between both vertebral arteries can be associated with being left-handed or ambidextrous.
In carotid and VA imaging, the sensitivity of CT angiography, contrast-enhanced MR angiography and color Doppler USG is 95%, 93.3%, and 70.2%, respectively. USG is used as an inexpensive and non-invasive method for imaging the ICA and VA. However, the results may differ according to the experience of the person performing the USG. Furthermore, due to atherosclerotic and calcified vessels, technical deficiencies in imaging secondary to the deep and posterior localization of the VA, the curved structure of the artery, and the short neck, Doppler USG is inadequate in visualizing the V1 segment of the VA. Studies have shown that USG is also limited in showing small stenoses in the V2 segment. CT angiography is a method with high sensitivity and specificity used for imaging the VA. Radiation and the use of intravenous contrast agents are its disadvantages. In our study, the data of patients who underwent CT angiography for any reason in the past were used. Patients were not given a contrast agent again. In previous studies, the Doppler USG method was preferred as the imaging method for VA diameter measurement.,, In our study, the CT angiography method, which has higher sensitivity and enables us to measure VA diameter clearly by eliminating technical and anatomical limitations, was used. The evaluation of the images was made by two radiologists and it has further increased the objectivity of the measurement results by minimizing personal differences in evaluation.
Our study, unlike previous studies, revealed a significant relationship between right-hand dominance and left VA diameter. In this context, it has opened a new door to the evaluation of the literature information obtained from previous studies using a different diagnostic method, and to reconsider the results so far. Studies using CT angiography and involving a larger patient population may help us find an answer to our question in the future.
The limitations of our study are the small number of patients with left- handedness and ambidextrousness. Further studies with a larger number of patients may help us clarify this issue further.
In conclusion, in this study, we found a correlation between the dominant hemisphere VA diameter and hand preference. Perhaps, the main question to be asked is not the cause of cerebral dominance, but the cause of cerebral blood supply. Reevaluation of the theories about the need for more blood supply in the dominant hemisphere may be possible with the increase of anatomical and embryological researches on this subject.
We thank Aydan AÇIKALIN, Yagiz ÖZDAĞ, Rıfat Erdem TOĞROL and Ali Doğan ÖZDEMİR for their contributions to the article.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]