Balint Syndrome

Etiology

Balint syndrome commonly results from ischemic infarctions in bilateral parietal and occipital areas.

There are also reports of Balint syndrome with other neurological disorders such as[2]:

• Posterior reversible encephalopathy syndrome (PRES)
• Alzheimer disease
• Creutzfeldt-Jakob disease (CJD)
• Posterior cortical atrophy (PCA)
• Corticobasal degeneration (CBD)
• Subacute HIV encephalitis
• Progressive multifocal leukoencephalopathy (PML)
• Head trauma
• Cerebral toxoplasmosis, and
• Brain metastasis

Two recent reports exist of cases of NMDA receptor encephalitis with a clinical presentation that was consistent with Balint syndrome.[3] There is also a case of idiopathic Balint syndrome.[4]

Epidemiology

Literature regarding Balint syndrome exists mostly in the form of case reports. There are no reports of the exact incidence and prevalence of Balint syndrome. Reports are usually in the adult population, but several case reports exist in the pediatric population as young as 4 years.[5]

Pathophysiology

Lesions involving bilateral parietal areas and occipital areas in some cases, due to the causes mentioned above, result in clinical features that present in Balint syndrome. Among the various etiological factors, ischemic infarction due to multiple causes appears to be the most common etiology of Balint syndrome.

History and Physical

Balint syndrome, as described initially, is a rare disorder associated with difficulties in visual and spatial coordination and is characterized by the three cardinal features:

1. Optic ataxia
2. Oculomotor apraxia
3. Simultagnosia

Optic ataxia is the lack of coordination between visual input and hand movements. For example, the patients can accurately touch their own body voluntarily, but when given a visually guided task, they are unable to complete it. However, once provided proprioceptive or auditory cues to reach for a target object, they can perform the task smoothly. Theories are that this deficit may arise due to damage to the superior parietal lobule, which is responsible for coordination between visual input and hand movements.[6] Isolated optic ataxia may occur from lesions in Broadman’s areas 5, 7, 19, 37, and 39.[7] Although existing literature suggests that parietal and occipital lobes are the primary areas of involvement in Balint syndrome, lesions in other areas of the brain such as the prefrontal cortex and frontal eye fields were reported to be associated with individual symptoms of Balint syndrome.[7]

Oculomotor apraxia is the inability to voluntarily shift gaze despite the intact function of extraocular muscles. Although described initially in patients with bilateral parietal lesions, later studies have shown that isolated lesions of frontal eye fields can also cause this deficit.[8]

Simultagnosia is the lack of ability to perceive more than a single object at a time. For example, when provided with a picture of a forest with trees, they are unable to see the forest, although they can see each individual tree. Because of their attentional visual deficit, they can appear to be functionally blind and will have difficulty reading and counting because these activities require viewing more than one object at a time. It further classifies as dorsal and ventral types. In the dorsal variant, the lesion is postulated to be in the bilateral parietal lobes, and the patient is often unable to see more than one object at a time. In the ventral type, the lesion is postulated to be in the left inferior occipitotemporal lobe, and the patient has a slower visual processing speed and is unable to identify individual parts of a multi-part object.[9]

The three defining features of Balint syndrome involve a lack of coordination between visual inputs and motor outputs, which causes an inability to use visual information to guide the patient’s hands or eyes. Patients with this syndrome have normal visual acuity, do not have paralysis of extraocular movement, and can name colors and objects.

Evaluation

Balint syndrome is suspected clinically based on the symptoms described above in the clinical features section. Lack of proper understanding of this syndrome often results in misdiagnosis of the presentation. No specific diagnostic criteria exist for imaging studies of the brain. Computed tomogram (CT) scan and magnetic resonance imaging (MRI) of the brain usually reveal atrophic changes in parietal and occipital lobes. However, Balint syndrome imaging studies may depict findings consistent with underlying etiology. Subsequent diagnostic studies are performed to delineate the etiology once there is clinical suspicion for Balint syndrome, and imaging findings are consistent with clinical presentation. In some cases, single positron emission computed tomography scan may be needed to evaluate for cerebral hypoperfusion of the involved areas.[4]

Treatment / Management

The core management of Balint syndrome relies on rehabilitation and reducing the extent of disability to a bare minimum. In some instances such as infarction, PRES, and infectious etiologies, secondary preventive measures can be employed to reduce the risk of recurrence. There are different approaches in occupational rehabilitation that have been proposed to help individuals limit their disabling symptoms. The adaptive approach is where the intact abilities are used effectively to reduce the extent of disability caused by the symptoms. The remedial approach aims to repair the damaged areas of the brain by training them in perceptual skills. The third and complex approach is a multi-context approach that involves strategic learning in an environment with multiple tasks.[10](B3)

Differential Diagnosis

Hemineglect, which usually results from lesions in the temporoparietal junction, should be distinguished from Balint syndrome. In patients with hemineglect defective eye movements may mimic ocular apraxia, difficulty in performing hand movements may mimic optic ataxia, and deficits in perception can mimic simultagnosia.[7]

Prognosis

The prognosis of Balint syndrome depends mostly on the underlying etiology. In acute etiologies such as stroke, infectious origin, or PRES, with appropriate management, a good prognosis may be seen in patients. On the other hand, Balint syndrome secondary to neurodegenerative etiologies such as corticobasal degeneration or posterior cortical atrophy correlates with poor prognosis.

Complications

Other than the disabling symptoms associated with the syndrome, there are no reports of significant complications in patients with Balint syndrome.