Crossed Laterality
Laterality is the expression of the asymmetrical distribution established between the functions of the two cerebral hemispheres and is defined approximately around five years of age. This does not mean that each hemisphere has a specific function; in fact, both participate to a greater or lesser extent in all complex functions.
The right hemisphere is responsible for perception, global comprehension, and the extralinguistic aspect. The left hemisphere, on the other hand, deals with interpretation, information coding, and the linguistic aspect. Both are connected by the corpus callosum, which activates or inhibits contralateral areas depending on the task to be performed. In other words, each hemisphere receives both motor and sensory information from the contralateral side of the body.
Depending on how body functions are distributed in our brain (between the two hemispheres), we will preferentially use one side or the other of the body (right or left) to perform various daily actions. Through various exercises such as: writing, throwing a ball, opening a door, winding a ball of yarn, looking through a kaleidoscope, holding cutlery, etc., we can determine the dominance of the hand, foot, eye, and ear. If the person presents a different laterality for hands, feet, etc., we are dealing with crossed laterality.
An individual’s laterality is classified based on manual (hand), pedal (foot), visual (eye), and auditory (ear) preference. Homogeneous laterality refers to these four previously mentioned parts being defined on the same side of the body. If not, it is referred to as crossed laterality.
In this expression, there is a non-homogeneous lateral dominance, meaning hand, foot, ear, and eye are not established on the same side of the body, with right-hand and foot dominance and left-eye and ear dominance being common.
In this case, there is a visual preference in the left eye. Visual information from the left eye is processed by the right hemisphere (which handles global and non-linguistic aspects), and the motor response occurs with the right hand, which is dominant. Therefore, it makes sense that in these cases, reading and writing difficulties appear, as letters are differentiated by their lateral orientation, leading to a different hemispheric dominance between the visual information perceived and the graphomotor response.
Crossed Laterality: Consequences
Crossed laterality can also be caused by genetic factors; it is a neurophysiological disorder that affects a person’s cognitive development.
In the case of crossed laterality in the school environment, the child will be dealing with symbols (letters and numbers) where the spatial and temporal coordinates they use are relevant for their comprehension (the position of a letter within a word or a number in a longer digit, etc.). If the child does not have this naturally acquired ability, it will be more difficult for them to handle these new codes.
All of this can lead to performance below the actual intellectual level (referring to the child’s potential), showing difficulties in reading, speech, and calculation, writing deficiencies, difficulties in concentration and comprehension, also causing school integration problems, family conflicts, and demotivation.
If detected in adulthood, laterality can show the following symptoms: physical, mental, and emotional exhaustion, insomnia and slowness, imbalance and clumsiness, concentration or language problems, and can lead to relational conflicts in the workplace and family.
Therapy
It is important to treat crossed laterality in time, as the longer its diagnosis is delayed, the greater and more severe the consequences will be. Starting treatment as soon as it is detected allows the disorder to be reduced by 80%, with possibilities of achieving a recovery success close to 100%.
Being a neurophysiological treatment, relapses will not occur. The first step towards recovery is early diagnosis, which should be carried out from four and a half or five years of age.
Types and Treatment of Crossed Laterality
Contrariated Laterality: for this type of laterality, changes in the hand used can be distinguished, for example, using the right hand when the patient was previously left-handed.
Crossed Laterality in Ambidextrous Individuals: Depending on the case, different hands are used. They write and eat with the right hand but cut with the left.
Oppositional Laterality: In this case, psychological and emotional elements need to be considered. Here, the child shows discomfort towards school or family,
Indiscriminate Use of Both Hands: Performing actions like cutting or brushing teeth can be a problem because laterality needs to be individualized.
Finally, it is important to evaluate laterality properly, as over-diagnoses and labels of dyslexia are observed solely due to mirror writing or confusion between p, d, q, b. However, it must be made clear that not all children with crossed laterality develop dyslexia; nevertheless, it is an important risk factor to consider.
ISEP’s Master’s in Educational Speech Therapy includes knowledge of functional neuroanatomy applied to speech therapy to correctly detect, evaluate, and intervene in possible alterations of language, speech, communication, and voice globally, taking into account the characteristics of child neuropsychology.