Cerebral Visual Impairment: Which perceptive visual dysfunctions can be expected in children with brain damage? A systematic review

Abstract

The current definition of Cerebral Visual Impairment (CVI) includes all visual dysfunctions caused by damage to, or malfunctioning of, the retrochiasmatic visual pathways in the absence of damage to the anterior visual pathways or any major ocular disease. CVI is diagnosed by exclusion and the existence of many different causes and symptoms make it an overall non-categorized group. To date, no discrimination is made within CVI based on types of perceptive visual dysfunctions. The aim of this review was to outline which perceptive visual dysfunctions are to be expected based on a number of etiologies of brain damage and brain development disorders with their onset in the pre-, peri- or postnatal period. For each period two etiologies were chosen as the main characteristic brain damage. For each etiology a main search was performed. The selection of the articles was based on the following criteria: age, etiology, imaging, central pathology and perceptive visual function test. The perceptive visual functions included for this review were object recognition, face recognition, visual memory, orientation, visual spatial perception, motion perception and simultaneous perception. Our search resulted in 11 key articles. A diversity of research history is performed for the selected etiologies and their relation to perceptive visual dysfunctions. Periventricular Leukomalacia (PVL) was most studied, whereas the main tested perceptive visual function was visual spatial perception. As a conclusion, the present status of research in the field of CVI does not allow to correlate between etiology, location and perceptive visual dysfunctions in children with brain damage or a brain development disorder. A limiting factor could be the small number of objective tests performed in children experiencing problems in visual processing. Based on recent insights in central visual information processing, we recommend an alternative approach for the definition of CVI that is based on functional visual processing, rather than anatomical landmarks. This could be of benefit in daily practice to diagnose CVI.

Introduction

When looking at visual dysfunction caused by brain damage or a brain development disorder, the medical term Cerebral Visual Impairment (CVI) is often used (Dutton & Jacobson, 2001). CVI is considered as the number one cause of visual deficit in children of developed countries (Fazzi et al., 2007). Since there has been a significant improvement in the peri- and neonatal care, the survival rate of preterm infants has increased (Stoelhorst et al., 2005). A negative consequence of this progress is an increase of children with brain damage in general and thereby of CVI. Although the term CVI is often mentioned, no sharp definition is available. Commonly, CVI includes all visual dysfunctions caused by damage to, or malfunctioning of, the retrochiasmatic visual pathways in the absence of damage to the anterior visual pathways or any major ocular disease (Fazzi et al., 2009, Khetpal and Donahue, 2007).

However, daily practice reveals that the above definition is not suitable for every patient. People from different disciplines debate about the applicability of CVI, but a distinct consensus is still not reached. This means it remains unclear which patient and for what reason receives a diagnosis of CVI. One of the main reasons that consensus has not been reached is the heterogeneity of causes and symptoms which can be included. In addition, for brain damage or brain development disorders causing CVI different periods of onset exist. This makes CVI an overall extensive non-categorized group, which include many different visual dysfunctions. Other reasons that make it difficult to work with the term CVI are the possible overlap or combinations of peripheral and central nervous system damage, and the high interconnectivity of different brain areas. In humans the visual system starts with the optical component from cornea to retina, followed by the retino-cortical component where neural signals travel from the retina to the primary visual cortex (V1) (Trobe, 2001). Several cortical areas are involved in processing different perceptive visual functions. The occipito-temporal lobes, known as the ventral stream, include object recognition, face recognition, orientation and visual memory. The occipito-parietal lobes, known as the dorsal stream, include visual spatial perception, motion perception and simultaneous perception which can be associated with crowding (Dutton, 2003, Trobe, 2001).

Finally, very few objective diagnostic instruments are available, especially for very young children and people with an intellectual disability who are a risk group for cerebral visual dysfunctions. Here fore CVI is a likely diagnosis or is diagnosed by exclusion if there is no other explanation. This situation will not benefit the patient for further follow-up and specified visual training.

The first objective of this review is to establish if perceptive visual dysfunctions are correlated to time, character and location of brain damage. Our second objective is to look at an alternative approach for the definition of CVI based on the different perceptive visual functions. To this end, a systematic review of the available evidence in the scientific literature was conducted to outline which perceptive visual dysfunctions are to be expected when focusing on a number of etiologies of brain damage and brain development disorders in the pre-, peri- and postnatal period.