Oculomotor apraxia or apraxia of gaze can occur both acquired and congenital This second form is a hereditary disorder that affects the eye and is generally present from birth.
It consists of an alteration in brain function characterized by the inability to execute horizontal eye movements voluntarily, or under the verbal command of another person.
It is a condition, of still unknown causes, generally considered a sporadic disorder, although cases with autosomal dominant inheritance have been described (when a single copy of the gene allele is enough for the disease to be expressed).
The patient suffering from oculomotor apraxia cannot voluntarily change the direction of gaze to the sides, nor does it present the rapid phase of the vestibulo-ocular or optokinetic reflexes (responsible for stabilizing the gaze to obtain sharp images).
Causes
Although the causes responsible for the appearance of a condition such as oculomotor apraxia in newborn children have not yet been identified, It has been suggested that most of them may have developed Joubert syndrome a genetically transmitted disorder.
This syndrome would cause partial metabolic alterations or defects in neurological development, such as hypoplasia (incomplete development) of the cerebellar vermix, aplasia (absence of development) of the corpus callosum, heterotopias of the gray matter, Kallman syndrome or chromosomal alterations.
To establish an accurate diagnosis of oculomotor apraxia Other causes, such as fixation defects and abnormal head movements, must be ruled out: visual deficits due to eye problems, mobility disorders, spasms or psychomotor delay.
Furthermore, the patient must preserve vertical saccades (both voluntary and vestibulo-ocular and optokinetic reflexes). However, it should be noted that in acquired oculomotor apraxia, secondary to other lesions of the central nervous system, vertical movements are also affected.
Main features
Cogan identified several key features characteristic of congenital oculomotor apraxia.
First of all, it highlights the sudden turn of the head in the direction of the object of fixation and deviation of the gaze to the opposite side followed by a slow movement of the eyes towards the desired location.
They are also given occasional spasms when fixating your gaze and a movement of the head towards the object of fixation while the gaze remains fixed in the first position, followed by a closure of the eyelids and a subsequent slow movement of the eyes towards the new place of fixation.
On the other hand, there are preservation of spontaneous eye movements and gaze in the vertical plane
Finally, the alteration of attraction movements and, sometimes, gaze-following movements stands out.
Oculomotor apraxia type 2
One of the most studied oculomotor apraxias is type 2, caused by a mutation in the SETX gene This apraxia is usually accompanied by ataxia, which is the lack of muscle control or coordination of voluntary movements.
This type of apraxia is a characteristic symptom of Gaucher disease a rare and degenerative condition, resulting from the accumulation of certain fatty substances in organs such as the spleen or liver.
This disease usually causes early death in children who suffer from it, although in recent years an enzymatic treatment has been carried out that replaces inactive enzymes with new ones to try to stop its progression. In the most severe cases, a bone marrow transplant is usually needed.
Treatment
Some health professionals recommend vision therapy to deal with a condition such as oculomotor apraxia and the consequences that arise from its condition.
In this type of therapy Non-surgical visual exercises are performed, personalized and prepared by a behavioral optometrist always under the supervision of a specialist ophthalmologist in the field.
There seems to be evidence that the problem improves over the years if the exercises are performed correctly and for the specified time.
However, It has also been suggested that this disease has no cure and that the only solution is to adopt compensatory measures so that the person adapts to their new disability situation.
Other types of apraxias
Oculomotor apraxia is a specific type of apraxia that involves difficulties in eye movement, but There are other types of apraxias with symptoms that generate another series of complications of similar nature. We will see, below, what they are:
1. Ideomotor apraxia
Ideomotor apraxia is the most common apraxia of all and is characterized because people who suffer from it They cannot copy movements or perform everyday gestures such as waving or nodding.
Patients suffering from ideomotor apraxia are able to describe the steps to follow to perform a specific action, but have severe difficulties in performing said action or imagining that they are carrying it out.
This type of apraxia is the second most common. People with construction apraxia are incapable of carrying out motor actions that involve spatial organization ; For example, they cannot make a drawing, make shapes with blocks, or make a grimace with their face.
3. Ideatory apraxia
Ideatory apraxia is a type of apraxia characterized by the difficulty in carrying out complex actions that require some type of planning such as sending an email or making food.
Patients with ideatory apraxia generally produce incoherent, inappropriate and disorganized gestures.
4. Apraxia of speech
Apraxia of speech is characterized by the inability to reproduce motor sequences necessary with the mouth to be able to speak intelligibly. This apraxia Both adults and children of the age of learning to speak can suffer from it although in childhood patients this disorder is usually called dyspraxia.
5. Kinetic limb apraxia
People who suffer from this type of apraxia have a deficit in the fluid movement of the extremities, both upper and lower. Likewise, they suffer a loss of dexterity or ability to make both fine and precise movements with their hands and fingers (fine motor skills) and movements with their arms and legs (gross motor skills).
6. Orofacial apraxia
In orofacial apraxia there is a manifest inability to properly control the muscles of the face, tongue, and throat and therefore, problems chewing, swallowing, sticking out the tongue, etc.
This inability manifests itself when the person makes voluntary and purposeful movements – and not involuntary -, that is, it only occurs when a movement is executed after having previously thought about and planned it.
