Bálint's syndrome

Bálint's syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments involving space representation (visuospatial processing). Its three major components are 1) simultanagnosia, i.e., the inability to perceive the visual field as a whole, 2) ocular apraxia, a deficit of visual scanning, and 3) optic ataxia, an impairment of pointing and reaching under visual guidance. The syndrome was named in 1909 for the Austro-Hungarian neurologist Rezső Bálint who had been the first to identify it. Since it represents impairment of both visual and language functions, it is a significant disability that can affect the patient's safety even in one's own home environment, and can render the person incapable of maintaining employment. Lack of awareness of this syndrome may lead to a misdiagnosis and resulting inappropriate or inadequate treatment. Therefore, clinicians should be familiar with Bálint's syndrome and its various etiologies.

Balint's syndrome occurs most often with an acute onset as a consequence of multiple bilateral strokes. The most frequent cause of complete Balint's syndrome is said by some to be sudden and severe hypotension, resulting in bilateral borderzone infarction in the occipito-parietal region. More rarely, cases of progressive Balint's syndrome have been found in degenerative disorders such as Alzheimer's disease or certain other traumatic brain injuries at the border of the parietal and the occipital lobes of the brain.

Symptoms
Bálint's syndrome is characterized by three visuo-ocular symptoms that sometimes occur following bilateral parieto-occipital lobe lesions. In many cases the complete trio of symptoms may not be noticed until the patient is in rehabilitation. Therapists unfamiliar with Bálint's syndrome may misdiagnose a patient's inability to meet progress expectations in any of these symptom areas as simply indicating incapability of benefiting from further traditional therapy. The very nature of each Bálint symptom frustrates rehabilitation progress in each of the other symptoms. Much more research is needed to develop therapeutic protocols that address Bálint symptoms as a group since the disabilities are so intertwined.

The three symptoms of Bálint's syndrome:


 * simultanagnosia—the inability to perceive simultaneous events in one's visual field
 * apraxia—inability to carry out familiar movements when asked to do so, and
 * optic ataxia—an impairment of target pointing under visual guidance.

Simultanagnosia
Simultanagnosia is the inability to perceive simultaneous events or objects in one's visual field. Victims of Bálint's syndrome perceive the world erratically, as a series of single objects rather than seeing the wholeness of a scene.

This spatial disorder of visual attention—the ability to identify local elements of a scene, but not the global whole—has been referred to as a constriction of the individual's global gestalt window—their visual "window" of attention. The article reinforces the notion that people fixate their eyes to specific images in social scenes because they are informative to the meaning of the scene. It suggests that any forthcoming recovery in simultanagnosia may be related to somehow expanding the restricted attentional window that characterizes this disorder.

Simultanagnosia is a profound visual deficit. It impairs the ability to perceive multiple items in a visual display, while preserving the ability to recognize single objects. One study suggests that simultanagnosia may result from an extreme form of competition between objects which makes it difficult for attention to be disengaged from an object once it has been selected. Patients with simultanagnosia have a restricted spatial window of visual attention cannot see more than one object at a time. They see their world in a patchy, spotty manner. Therefore, they pick out a single object, or even components of an individual object, without being able to see the global "big picture."

A study which directly tested the relationship between the restriction of the attentional window in simultanagnosia compared with the vision of healthy participants with normal limits of visual processing confirmed the limitations of difficulties of patients with simultanagnosia.

There is considerable evidence that a person's cortex is essentially divided into two functional streams: an occipital-parietal-frontal pathway that processes "where" information and an occipital-temporal-frontal pathway that provides "what" information to the individual.

Apraxia
Apraxia is a neurological disorder caused by damage to the brain. It is exemplified by the inability to carry out familiar movements when asked to do so. Persons with apraxia understand such commands, are willing to carry them out, but are physically unable to perform the task.

Apraxia of speech, also known as verbal apraxia or dyspraxia, is a speech disorder in which a person has trouble saying what he or she wants to say correctly and consistently. Apraxia of speech is often present along with another speech disorder called aphasia. At times, a completely different word or action is used than the one the person intended to speak or make. The person is often aware of the mistake.

Bálint referred to this as "psychic paralysis of gaze"—the inability to voluntarily guide eye movements, changing to a new location of visual fixation. The most frequent and disabling deficit is the syndrome of unilateral spatial neglect that manifests as a bias of spatial representation and attention on the same side as the lesion. Also significant is that the disturbances of space representation are more frequent and severe after traumatic damage to the right hemisphere.

There is no single factor or test that can be used to diagnose apraxia. In addition, speech-language experts do not agree about which specific symptoms are part of developmental apraxia.

In some cases, people with acquired apraxia of speech recover some or all of their speech abilities on their own. Otherwise, speech-language therapy, tailored to the individual and designed to treat other speech or language problems that may occur together with apraxia, is often helpful.

Optic ataxia
Optic ataxia is the inability to guide the hand toward an object using visual information where the inability cannot be explained by motor, somatosensory, visual field deficits or acuity deficits. Optic ataxia is seen in Balint's syndrome where it is characterized by an impaired visual control of the direction of arm-reaching to a visual target, accompanied by defective hand orientation and grip formation. It is considered a specific visuomotor disorder, independent of visual space misperception.

Optic ataxia is also known as misreaching or dysmetria (difficult to measure), secondary to visual perceptual deficits. A patient with Bálint's syndrome likely has defective hand movements under visual guidance, despite normal limb strength. The patient is unable to grab an object while looking at the object, due to a discoordination of eye and hand movement. It is especially true with their contralesional hand.

Dysmetria refers to a lack of coordination of movement, typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye. It is sometimes described as an inability to judge distance or scale.

The reaching ability of the patient is also altered. It takes them longer to reach toward an object. Their ability to grasp an object is also impaired. The patient's performance is even more severely deteriorated when vision of either the hand or the target is prevented.

Diagnosis
Lack of awareness of the syndrome may lead to misdiagnosis such as blindness, psychosis, or dementia. Symptoms of Bálint's syndrome are most likely to be noticed first by therapists providing rehabilitation following brain lesions. However, due to the scarcity among practitioners of familiarity with the syndrome, the symptoms are often explained away incorrectly without being considered as a possibility and followed by medical confirmation of clinical and neuroradiological findings. Any severe disturbance of space representation, spontaneously appearing following bilateral parietal damage, strongly suggests the presence of Bálint's syndrome and should be investigated as such.

Neuroanatomical evidence
Bálint's syndrome has been found in patients with bilateral damage to the posterior parietal cortex. The primary cause of the damage and the syndrome can originate from multiple strokes, Alzheimer's disease, intracranial tumors, or brain injury. Multifocal leukoencephalopathy and Creutzfeldt-Jakob disease have also been found to cause this kind of damage. This syndrome is caused by damage to the posterior superior watershed areas, also known as the parietal-occipital vascular border zone (Brodmann's areas 19 and 7).

Manifestations
Some telltale signs suggesting Bálint's syndrome following bilateral brain insults may include:
 * limitation to perceive only stimuli that is presented at 35 to 40 degrees to the right. They are able to move their eyes but cannot fixate on specific visual stimuli. (ataxia)
 * patient's field of attention is limited to one object at a time. making activities like reading difficult because each letter is perceived separately.(ataxia)
 * figure/ground defects in which a patient can see either the background but not the object residing somewhere in the whole scene, or conversely can see the background but sees no figure within it (simultanagnosia)
 * a patient, while attempting to put one foot into a slipper by trying to insert the foot into a nonexistent foot several inches from the slipper, even as the patient focuses on the actual slipper (oculomotor apraxia)
 * a patient raising a fork or spoon containing food to a point on the patient's face above or below the mouth, and possibly finding the mouth by trial and error by manually moving the utensil on the face (optic ataxia)

Treatment
In terms of the specific rehabilitation of visuoperceptual disorders, such as Balint’s syndrome, the literature is virtually silent. According to one study, rehabilitation training should focus on the improvement of visual scanning, the development of visually guided manual movements, and the improvement of the integration of visual elements. Very few treatment strategies have been proposed, and some of those have been criticized as being poorly developed and evaluated. Three approaches to rehabilitation of perceptual deficits, such as those seen in Bálint's syndrome, have been identified:
 * 1) The adaptive (functional) approach, which involves functional tasks utilising the person’s strengths and abilities, helping them to compensate for problems or altering the environment to lessen their disabilities. This is the most popular approach.
 * 2) The remedial approach, which involves restoration of the damaged CNS by training in the perceptual skills, which may be generalised across all activities of daily living. This could be achieved by tabletop activities or sensorimotor exercises.
 * 3) The multicontext approach, which is based on the fact that learning is not automatically transferred from one situation to another. This involves practicing of a targeted strategy in a multiple environment with varied tasks and movement demands, and it incorporates self-awareness tasks.

Some case studies
Symptoms of Bálint’s syndrome were found in the case of a 29-year-old migraine sufferer. In the aura before the migraine headache, she experienced an inability to see all of the objects in the visual field simultaneously; an inability to coordinate hand and eye movements; and an inability to look at an object on command. Symptoms were not present before the onset of the migraine or after it passed. A study of a patient with Corticobasal Ganglionic Degeneration (CGBD) also showed a development of Bálint’s syndrome. As a result of CGBD, the patient developed an inability to move his eyes to specific visual objects in his peripheral fields. He also was unable to reach out and touch objects in his peripheral fields. An inability to recognize more than one item at a time was also experienced when presented with the Cookie Theft Picture from the Boston Diagnostic Aphasia Examination.

A patient with congenital deafness exhibited partial Bálint’s syndrome symptoms. This patient experienced an inability to perceive simultaneous events in her visual field. She was also unable to fixate and follow an object with her eyes. In addition, her ability to point at targets under visual guidance was impaired.

Bálint's syndrome is rarely reported in children, but some recent studies provide evidence that cases do exist in children. A case involving a 10-year-old male child with Balint's syndrome has been reported. Similar results were seen in a 7-year-old boy. In children this syndrome results in a variety of occupational difficulties, but most notably difficulties in schoolwork, especially reading. The investigators encourage more careful recognition of the syndrome to allow adequate rehabilitation and environmental adaptation.

Criticism
The validity of Bálint's syndrome has been questioned by some. The components in the syndrome's triad of defects (simultanagnosia, ocular apraxia, optic ataxia) each may represent a variety of combined defects.