Introduction to Cerebral Visual Impairment and Cerebral Palsy

Original Editor - Ewa Jaraczewska based on the course by Angela Kiger

Top Contributors - Ewa Jaraczewska, Jess Bell and Kim Jackson  

Introduction

Cerebral visual impairment (CVI) can occur in children with cerebral palsy (CP) or developmental delay. Children with CVI are frequently diagnosed with cerebral palsy. Despite the importance of early diagnosis, there is no standardised assessment tool to diagnose CVI. Nor is there one referral criteria guideline. The challenge in early diagnosis relates to the wide range of visual dysfunctions present in CVI. These include central and peripheral vision dysfunction, dysfunctions in movement perception, gaze control, visual guidance of movement, visual attention, attentional orientation in space, visual analysis and recognition, visual memory and spatial cognition. These impairments can all affect a child's learning and social interactions. This article presents an overview of CVI and its relationship with cerebral palsy.

Definitions

Cerebral Visual Impairment

Cerebral Visual Impairment (CVI) is “a verifiable visual dysfunction, which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment.”

Cerebral Palsy

Cerebral Palsy (CP) "describes a group of permanent disorders of the development of movement and posture causing activity limitation, which is attributed to non-progressive disturbances that occurred in the developing fetal or infant brain."

Brain Involvement in Vision

"It is estimated that over 50% of the brain is involved in vision processing." -- Angela Kiger

The following example of a child catching a ball explains how the brain controls eyesight.

• The child sees the ball.
• The frontal lobe decides on the action of catching the ball and its strategy.
• The occipital lobe processes the information received through the eyes. It passes the processed image data to the posterior parietal lobes via the superior longitudinal fasciculi.
• The middle part of the temporal lobe supports this process, with the posterior thalamus and superior colliculi, facilitating visual search and visual guidance of movement.
• The ball is identified and chosen as the target.
• The parietal lobe gauges the distance between the child's hands and the ball. If this is not the child's first time catching a ball, the temporal lobe takes part in the process as it controls memory. It subconsciously reminds the child that their hands are used to catch a ball, that they need to reach out, and that their body needs to adjust.
• The temporal lobes process local and detailed visual feedback via a bundle of nerve fibres on each side.
• The cerebellum helps the child adjust the timing of their actions and their balance.

Epidemiology

• CVI affect at least 3.4% of children. However, the number may be higher as many affected children go unidentified.
• More than 50% of children with learning difficulties who attend special schools have CVI.
• CVI is present in 2 per 1000 live births. It is present in 19 per 1000 live births for infants born at 20-27 weeks gestation; subcortical damage is more common in preterm infants.
• It is the most common cause of permanent vision loss in children aged 1-3 years old.
• Almost 50% of children diagnosed with a visual impairment have CVI.
• 56% of individuals with CVI have additional disabilities.

Aetiology

CVI in children can occur in the prenatal, perinatal or postnatal periods.

Prenatal (conception to birth):

• hydrocephalus
• congenital central nervous system malformation

Perinatal (starts at twentieth to twenty eighth week of gestation and ends one to fourth weeks after delivery) :

• hypoxic-ischaemic injury
• genetic/chromosomal disorders
• metabolic disorders
• infection during pregnancy
• neonatal hypoglycaemia
• medication during pregnancy

Postnatal (from birth to six to eight weeks after birth):

• meningitis
• encephalitis
• brain tumours
• cerebrovascular accident
• seizures
• periventricular leukomalacia
• cardiac arrest
• cranio-cerebral trauma

Brain Damage and CVI

Brain damage in patients with CVI can be categorised as subcortical, cortical or both. Brain lesions resulting in CVI can affect the following parts of the brain:

• the posterior visual pathways (the visual cortex of the occipital lobe)
• the optic chiasm ("part of the brain where the optic nerves cross")
• lateral geniculate bodies (a structure in the thalamus)
• optic radiations ("key white matter structures that cross the temporal lobe")
• primary visual cortices (part of the occipital lobe that processes visual information)
• the middle temporal lobes
• the visual association areas

The following video explains the role of the visual association areas:

Visual Impairments Associated with CVI

The symptoms of CVI and the severity of visual impairment vary in children. They can affect the following:

• sensory visual function (enables an individual "to be aware of colour, light level, contrast, motion and other visual stimuli")
• oculomotor function ("the ability to use the eyes systematically to efficiently scan and locate an object in the field of vision")
• visual-motor function ("integration between visual perception and motor skills")
• cognitive visual function (the ability to analyse and process visual information)

CVI can occur in isolation or in association with eye or optic nerve damage. The lack of vision tends to be profound when the thalamus is involved.

Children with CVI may present with the following:

• often have a normal or near-normal eye examination
• have a history or presence of a neurological disorder
• demonstrate behavioural responses to visual stimuli unique to CVI
• have difficulty sustaining gaze
• their head is often tilted slightly forward and to the side

Behavioural Changes

Children diagnosed with CVI can demonstrate specific behavioural signs, including:

• short visual attention span
• markedly fluctuating visual performances
• the need for time, environmental stability, and repetition of items to obtain the best response

CVI Classification

A medically-based CVI classification identifies three subgroups:

• A1: selective visual perception and visuomotor deficits
• A2: more severe and broader visual perception and visuomotor deficits and variable visual acuity
• B: unable to perform psychological testing due to significant visual acuity reduction

CVI and Cerebral Palsy

• CVI is common in children affected by CP
• In medically-based CVI classification, most children with CP belong to the B subgroup.
• The lesions which determine motor deficits in CP are "anatomically closely located to the distributed network of brain areas responsible for visual perception", and this helps explain the co-occurrence of CVI and CP.
• The clinical spectrum of visual problems in children with CP is broad, ranging from mild to severe. It may include ophthalmological, oculomotor, basic visual function, and cognitive-visual disorders.
• The intensity of visual impairment correlates with the severity of motor deficits:
  • children with tetraplegic CP present with:
    • markedly reduced or not-assessable visual acuity
    • highly impaired or absent oculomotor function
    • a high percentage of ocular abnormalities
  • children with diplegic CP present with:
    • moderately reduced visual acuity
    • altered contrast sensitivity
    • absence of stereopsis
    • impaired oculomotor abilities
    • refractive errors and cognitive-visual disorders (CVDs)
  • children with hemiplegic CP present with:
    • slightly reduced visual acuity
    • reduced visual field (frequently unilateral)
    • altered stereopsis ("the ability to appreciate depth, due to the lateral displacement of the eyes providing two slightly different views of the same object").
    • less frequent oculomotor involvement
    • less frequent refractive errors

Assessment and Diagnosis

Admission Referral

Children are often referred to a specialist or specialists for assessment of visual impairment because:

• the parents are concerned about the child's visual functioning
• they have an increased risk of CVI
• they have an intellectual disability or syndrome and can be screened for visual functioning

Multidisciplinary Team

A multidisciplinary team for CVI diagnostics is necessary for accurate and timely diagnosis. The team should include the following specialities at the minimum:

• paediatric ophthalmologist
• paediatric neurologist
• orthoptist or optometrist
• neuropsychologist

Follow-up Referral

The assessment results should be discussed with all members of the multidisciplinary team. Based on the outcome, the child can be referred to:

• vision teacher and developmental therapist with a vision specialisation in CVI
• a rehabilitation centre or a specialised centre
• school for children with visual impairments if there is evidence of CVI

Assessment Tools

There is no standardised assessment tool for the diagnosis of CVI. The following assessment tools are recommended:

• 

  Reproduced from reference: Moon JH, Kim GH, Kim SK, Kim S, Kim YH, Kim J, Kim JK, Noh BH, Byeon JH, Yeom JS, Eun BL, Eun SH, Choi J, Chung HJ. Development of the Parental Questionnaire for Cerebral Visual Impairment in Children Younger than 72 Months. J Clin Neurol. 2021 Jul;17(3):354-362.
  Questionnaires
  • Parental Questionnaire for Cerebral Visual Impairment (PQCVI) (see figure)
  • The CVI Questionnaire: 46-item screening questionnaire
  • The Five Questions completed by a parent. A 5-point Likert Scale describes if the child ‘always’, ‘often’, ‘sometimes’, ‘rarely’, or ‘never’ struggles with the described tasks
• Functional vision assessment (CVI Range)
  • "Behavioural assessment of functional vision, which defines the ability to interpret and react to visual information"
  • assessment based on observation, parent interview and direct assessment
  • the evaluator grades the child on ten characteristics of CVI:
    • colour preference
    • need for movement
    • visual latency
    • visual field preferences
    • difficulties with visual complexity
    • need for light
    • difficulty with distance viewing
    • atypical visual reflexes
    • difficulty with visual novelty
    • absence of visually guided reach
  • scores range from 0 to 10 when 0 represents no functional vision, and 10 means typical or near typical functional vision
• Neuropsychological assessment of children with possible CVI
  • no consensus in the diagnostic protocol
• Neuropsychological tests of visual perception
  • measurement of lower-level visual deficits (Judgment of Line Orientation test (JLO))
  • measurement of higher-level visual/cognitive deficits (Rey–Osterrieth Complex Figure test (ROCF))
• Eye tracking assessment
  • assessment of nystagmus, fixation, saccades, and pursuit
• Genetic assessment
• Neuroradiological evaluation and magnetic resonance imaging (MRI)
  • recording damage to those parts of the brain involved in visual processing

Multidisciplinary Team Approach in Rehabilitation

"Vision leads movement (....). Ask questions about motivating visual stimuli to initiate gross motor tasks." -- Erica Stearns

The role of the multidisciplinary team is to:

• establish a child's unique vision
• choose strategies to make sure that the child's overall needs are being met
• prioritise goals (physical or occupational therapy goals before vision goal)
  • example: working on balance or stabilisation prevents the child from visually fixating and attending to materials
• adjust the child's centre of vision and education materials as position changes
  • example: during pressure relief time when the wheelchair is tilted backwards, a desktop computer screen must be adjusted
• choose an environment where the child can visually attend to materials and objects

Resources

• Baranello G, Signorini S, Tinelli F, Guzzetta A, Pagliano E, Rossi A, Foscan M, Tramacere I, Romeo DMM, Ricci D; VFCS Study Group. Visual Function Classification System for children with cerebral palsy: development and validation. Dev Med Child Neurol. 2020 Jan;62(1):104-110.
• Prechtl HF, Cioni G, Einspieler C, Bos AF, Ferrari F. Role of vision on early motor development: lessons from the blind. Dev Med Child Neurol. 2001 Mar;43(3):198-201.
• CVI Range Assessment