Acute cerebral blindness in childhood. Six cases studied clinically and electrophysiologically

Delayed-onset hypoxic cortical blindness: coming back from the abyss

PURPOSE

To report a case of typical delayed-onset hypoxic cortical blindness that occurred few days after resuscitation from drowning in a young male.

METHODS

Neurological and ophthalmological examination were performed including optical coherence tomography (OCT), Goldmann perimetry, pattern electroretinogram (pERG), pattern and flash visual evoked potentials (pVEP and fVEP) and brain magnetic resonance imaging (MRI).

RESULTS

At presentation, at day 12 post-hypoxic incident, best corrected visual acuity (BCVA) was reduced to hand motion OU with an abolished optokinetic nystagmus, a normal fundus and no relative afferent pupillary defect. Macular and peripapillary OCT were normal. Goldmann perimetry revealed bilateral centrocecal scotoma. pERG was normal while pVEPs were undetectable and fVEPs were abnormal with delayed, decreased and disorganized responses, without interhemispheric asymmetry. Brain MRI disclosed a bilateral cortical-subcortical occipital hypersignal with laminar necrosis and thus confirmed the diagnosis of delayed-onset hypoxic cortical blindness. Visual rehabilitation, including visual stimulation in the scotomatous areas, was associated with a dramatic and rapid visual improvement with a BCVA of 20/32 OU, an ability to read after 2 weeks (day 30 post-hypoxic incident), and a reduction in the size of the scotoma.

CONCLUSION

Delayed-onset hypoxic cortical blindness is a rare presentation of cortical blindness that develops few days after a cerebral hypoxic stress. While initial presentation can be catastrophic, visual improvement may be spectacular and enhanced with visual rehabilitation.

Cortical Visual Impairment in Young Children with Multiple Disabilities

Teachers of visually handicapped children are seeing an increased frequency in referrals of young, multiply handicapped children with cortical visual impairment. The use of the residual visual capacity in these children is related to their ability to neurologically process and understand environmental sensory information. The complex interaction of the visual process, central nervous system functioning, and environmental stimuli has major implications for effective educational planning.

The Effects of Brain Damage on Visual Functioning in Children

This article reviews the research literature on the direct effects of brain damage on the visual functioning of children and the electrodiagnostic tests used to diagnose them. Although the studies documented that brain damage affects visual functioning, they suggested that the prognosis for good functional vision after remedial intervention is more optimistic than was previously thought. They also found that electrodiagnostic testing is a valuable tool, but that the use of a combination of tests yields a more complete picture of the effects than does any single test.

Visual Deficits and Improvements in Children after Perinatal Hypoxia

This article reports on a study of the visual development of 38 infants, children, and youths who were neurologically impaired following perinatal hypoxia. All children showed impairments of one or more visual functions, indicating that perinatal hypoxia can have severe detrimental effects on visual development. However, in most patients visual development continued and visual improvements could be demonstrated up to age 16. The implications of these findings and suggestions for treatment are presented.

Delayed-onset Reversible Cortical Blindness after Resuscitation from Cardiac Arrest

We present a patient who presented with cortical blindness (CB) 1 week after repeated cardiac arrest while undergoing treatment for an acute myocardial infarction. He had been revived within 5 min in each instance and was apparently neurologically normal until presentation. Magnetic resonance imaging showed subtle hyperintensities on fluid-attenuated inversion recovery and diffusion-weighted imaging in both temporooccipital cortices. A rapid recovery over the next 2 weeks was remarkable for the appearance of metamorphopsia. CB may present even days to weeks after hypoxic-ischemic encephalopathy following cardiac arrest, even in patients apparently without immediate neurological sequelae. The pathogenesis of this phenomenon remains to be fully elucidated, but is likely to be due to delayed effects of anoxia on the occipital cortex and may be analogous to the previously described syndrome of delayed posthypoxic leukoencephalopathy. Prognosis for visual recovery appears to be good.

Is blindsight an effect of scattered light, spared cortex, and near-threshold vision?

Blindsight is the term commonly used to describe visually guided behaviour elicited by a stimulus falling within the scotoma (blind area) caused by a lesion of the striate cortex. Such “vision” is normally held to be unconscious and to be mediated by subcortical pathways involving the superior colliculus. Blindsight is of considerable theoretical importance since it suggests that destriate man is more like destriate monkey than had been previously believed and also because it supports the classical notion of two visual systems. It is also of potential clinical importance, since it has been claimed recently that systematic practice in blindsight can lead to the recovery of normal visual function in patients with cortical lesions. From a review of the literature it is concluded that all of the phenomena of blindsight can be attributed either to light scatter into unimpaired parts of the visual field or to residual vision resulting from spared striate cortex. The possible contribution f other factors is also considered. It is concluded that blindsight studies have generally failed to control for such nonblindsight interpretations partly because of poor methodology and partly because of difficulties in defining the term “blindsight.”

Experiments were carried out to investigate the extent to which subjects can exhibit performance similar to blindsight when they are using scattered light as a cue. This was done both with hemianopic subjects (by manipulating the amount of scattered and direct light coming from a stimulus) and with normal subjects (by presenting targets within their blind spots). Good blindsight performance was observed when only scattered light was available as a cue to the subjects. It is therefore concluded that an adequate case for blindsight has not been made. It is probably impossible to demonstrate the existence of blindsight on purely behavioural grounds. What is required is the establishment of relationships between visual function and independent anatomical evidence.

Paradoxical robust visual evoked potentials in young patients with cortical blindness

The objective of this study was to review retrospectively cases of clinically blind children in whom robust pattern visual evoked potentials (VEPs) were recorded. VEP records from a 10-year period (1990-2000) were reviewed. We searched for charts of children who were clinically cortically blind, but in whom assessment of visual acuity, using visual evoked potentials (VEPs), was normal or close to normal. The majority (77.5%) of VEP and behavioral acuity measures were concordant (subset analysis). Of the 1,113 VEP records, 9 cases (<1% of records reviewed) had clinically compromised vision with fair to good levels of visual function using VEPs. The commonality among the cases was the presence of suspected cortical visual impairment with seizures and developmental delay. VEP acuity cannot be correlated unequivocally with visually guided behaviour. In specific cases, particularly cases with developmental delay and neuroradiographic abnormalities, a child who is behaviorally blind with no clinical evidence of vision may show robust VEPs even to small patterns. This finding might be consistent with a defect of the visual association cortex.

Distinct early and late subcomponents of the photic blink reflex: response characteristics in patients with retrogeniculate lesions

To assess cortical contributions to the photic blink reflex, signal averaged electromyograms (EMG) were compared for responses to strobe flashes presented within the blind and sighted hemifields of 13 patients with occipital lobe lesions. Reflexes evoked by flashes within the scotoma were virtually identical to those evoked by flashes within the intact visual field. This suggests that both the early and late components of this reflex (R50 and R80, respectively) are mediated by subcortical structures that do not require, or benefit from, conscious visual processing. Additional findings included larger R80s at the eyelid contralateral to the lesion, regardless of stimulated hemifield. This presumably reflects the loss of a tonic descending influence of visual cortex onto the motor limb of the reflex arc. The R80 was also larger for stimuli activating the crossed (temporal hemifield) rather than the uncrossed (nasal hemifield) afferent pathway.

Infant visual development: an overview of studies using visual evoked potential measures from Harter to the present

Studies of sensory and perceptual abilities in infants require creative, innovative techniques. Although the young infant's response repertoire may appear limited to the naive individual, a number of highly refined procedures have been developed and implemented with these non-verbal humans over the last twenty years. The most successful protocols for evaluating visual development rely either on behavioral responses or on electrophysiological recordings. The first published report using visual evoked potentials to study the development of pattern vision in human infants was presented by M. Russell Harter. This work provided the impetus for a wealth of studies exploring issues of visual information processing abilities in early infancy. The available range of data and experimental techniques are now sufficiently refined that many clinical issues are currently being addressed. The purpose of this review is to document the evolution of scientific studies since Harter's seminal work. The selection of protocols presented focuses on those with either current clinical applications or those which hold promise for future applications in the evaluation and treatment issues of abnormal visual development.

Acuity card testing in children with cerebral palsy related to magnetic resonance images, mental levels and motor abilities

Visual acuity testing using Teller Acuity Cards was carried out on 78 infants and children affected by cerebral palsy (CP). Age of testing was between 3 and 109 months. The aim of the study was to investigate the usefulness of acuity cards in patients with CP, and to relate visual outcome with the type of CP, MRI findings, mental levels and motor disabilities. Visual acuity estimates were obtained for 60 children: acuity values were within normal values for age for 17 and below the 5th percentile for 43. Cerebral blindness was diagnosed in 10 patients. Eight infants were not testable, mainly because of behavioural problems. The overall success rate was 88%. Visual impairment in most infants with low acuity and in all blind children was not due to ophthalmological abnormalities. Visual outcome was significantly related to the type of CP, with hemiplegic children showing the best results and tetraplegics the worst. Cerebral blindness was significantly correlated with tetraplegia, the severity of lesions in the optic radiations, and visual cortex areas, as indicated by MRI, and the degree of mental, motor and oculomotor deficit. These correlations were mainly due to the blind subjects, who consistently showed major MRI abnormalities and severe motor, mental and oculomotor impairment. Longitudinal results obtained for 45 children showed visual outcome stable over time in 64.4% of cases, improvement in 6.6% and deterioration in 28.9%.

The visual-evoked response in infants with central visual impairment

We studied ten children with central visual impairment with a known neurologic defect and an abnormal visual-evoked response who had results of repeat electrophysiologic testing evaluated at the Children's Hospital of Philadelphia from December 1989 through July 1991. Central visual impairment is defined as poor visual function with a normal anterior visual pathway. Age at first examination ranged from 5 to 48 months with a followup of two to 31 months. Repeat visual-evoked response testing showed improvement in seven patients and no change in three. Grating acuity as measured by the Teller acuity card procedure, performed in nine of ten patients, improved in seven, showed no change in one, and declined in one. We found a potentially favorable prognosis for those infants with central visual impairment, despite an initially abnormal visual-evoked response. We used a clinical approach to this disorder to improve diagnostic categorization and prognostic capabilities in central visual impairment.

Post-traumatic transient cortical blindness

Five patients: three children, one adolescent, and one young adult, examined in an emergency room setting were diagnosed with post-traumatic transient cortical blindness. This syndrome is characterized by transient visual loss, normal pupillary response and normal funduscopic examination following minor head trauma. In each case, vision returned to normal within minutes to hours following injury, leaving no neurological sequelae. Headache, confusion, irritability, anxiety, nausea and vomiting were the most common related symptoms. While the mechanism responsible for the transient blindness is unknown, most authors propose an abnormal vascular response to trauma with resultant transient hypoxia and cerebral dysfunction. The similarity between the symptoms accompanying this syndrome and those seen during a classic migraine attack has led many investigators to suggest a common underlying pathophysiology. The purpose of this report is to highlight the salient clinical features and diagnostic approaches to this syndrome, thereby providing ophthalmologists and emergency room physicians a heightened awareness of this entity and the means to detect it.

Serial regional blood flow and visual evoked responses in transient cortical blindness

Normal regional blood flow was documented by Single Photon Emission Computed Tomograms 5 and 20 hours before the full recovery of cortical blindness in two patients, lending itself to the possibility of being a prognostic factor. Rubbing of the posterior cerebral arteries against the tentorial edges during trauma instead of traction was believed to cause blindness in one patient and embolization due to hammering bone grafts home during cervical spinal fusion, in the other. Pattern reversal visual evoked responses (PRVERs) were absent during blindness; upon recovery P 100 with full amplitude and normal latency appeared despite the presence of tunnel vision. These are consistent with the fact that the central 8-10 degrees of visual field represented in the posterior occipital poles being the main sources of P 100 in association with the x-cells in the centre of the retina.

Visual inattention in West syndrome: a neuropsychological and neurofunctional imaging study

Visual behavior is frequently impaired at onset of West syndrome (WS). We studied the neuropsychological outcome of eight children who had cryptogenic WS and moderate to severe visual impairment at the onset of epilepsy. At the last examination, a regional cerebral blood flow study using SPECT (single photon emission computed tomography) was performed. The behavior abnormalities observed initially evolved to various defects of cognitive function. Three patients had severe mental retardation with autistic features. Two had marked speech disorders but one had global cognitive impairment. Three patients had specific visual-spatial deficits. SPECT showed perfusion defects involving the parieto-occipital areas in 6 of 8 patients. These abnormalities were restricted to parieto-occipital regions in the three patients with selective visual-spatial deficits, whereas they were associated with other perfusion defects in the three remaining patients. This study demonstrates that the visual inattention observed at the onset of WS is frequently associated with long-term cognitive and/or perfusion defects involving the parieto-occipital regions.

Cortical visual impairment following bacterial meningitis: magnetic resonance imaging and visual evoked potentials findings in two cases

Cortical visual impairment (CVI) following bacterial meningitis is a very uncommon complication. Two children with CVI following bacterial meningitis are reported. Bacterial agents were Haemophilus influenzae type B in one and meningococci in the other child. Both children showed only insufficient recovery from CVI, mental retardation and residual neurological symptoms. Flash visual evoked potentials (VEP) showed preserved cortical response at onset of CVI. Re-evaluations several months later showed significantly reduced amplitudes, but normal latencies for P100. Thus, flash VEP does not allow prediction of visual outcome. MRI results have not been reported before. MRI at onset of diagnosis showed occipital parenchymal irregularities with enlarged sulci and subarachnoid spaces. Follow up MRI 15 months after onset of CVI in one patient showed marked atrophy of the occipital cortex, hyperintensities of the cortical white matter and no visible optic radiation. The MRI findings indicate hypoxic-ischaemic lesions in the border zone between the distribution of the great cerebral arteries.

Flash and pattern-reversal visual evoked potential abnormalities in infants and children with cerebral blindness

Visual evoked potentials (VEPs) were recorded of 60 infants and children with cerebral blindness, aged between six weeks and 10 years, and compared with age-matched normative data. Every patient had abnormal VEPs. 18 had absent flash and pattern VEPs and 13 had atypical or atypical and asymmetrical flash and pattern VEPs. Of the remaining 29, most had greater abnormality of pattern than of flash VEPs and greater abnormalities over parietal and temporal than occipital areas. Eight patients had normal occipital responses to flash and five others had delayed responses with normal morphology. One had normal occipital responses to pattern stimuli. All of these had abnormal late occipital responses or abnormal responses over the parietal and temporal areas. It is recommended that visual assessments using VEPs employ both flash and pattern stimuli, that pre-occipital as well as occipital recordings be made and that tracings be compared with age-specific normative data.

Cortical blindness in children: a study of etiology and prognosis

Thirty-four children (20 boys, 14 girls) with congenital and acquired cortical blindness were analyzed for visual outcome in relation to etiology, visual evoked potentials, electroencephalography, and cranial computed tomography. All 7 children with congenital cortical blindness remained blind on subsequent examination. Of the 27 children with acquired blindness, 16 (59%) had poor visual outcome. Poor visual outcome occurred in those with cardiac arrest, hypoxia, status epilepticus, intracranial hemorrhage, cerebral thrombosis, and head trauma. Good visual outcome occurred in children with hypotensive episodes after cardiac surgery. Of the 12 children with recovery of vision, the interval from acute loss of vision to partial or total recovery was 2 weeks to 5 months. Seven children had complete recovery of vision with no residual visual field defect. The majority of children (87%) had focal or multifocal spike-and-waves and slow sharp-wave discharges on electroencephalography. None had photic recruitment response or occipital spike-and-wave discharges. Flash visual evoked potential studies performed during acute episodes of cortical blindness documented 11 with absent response, 10 with bilateral increases in latency, and 6 with normal responses. There was no correlation between normal visual evoked potentials and a good visual outcome. Only 2 of 6 children with normal responses had normal vision. Abnormal or absent responses are more predictive of a poor recovery of vision because only 3 of 21 (14%) had normal vision on subsequent examination. Abnormal electroencephalographic findings with focal or multifocal spike-and-wave discharges or cerebral atrophy on cranial computed tomography are also poor prognostic signs.

Prognostic value of VEPs in young children with acute onset of cortical blindness

Visual evoked potentials (VEPs) were recorded in 32 children (ages 4 months to 5 years) who were clinically diagnosed as being cortically blind. None of the children had visual or neurologic abnormalities prior to the precipitating insult which included surgery (N = 15), trauma (N = 3), infectious disease (N = 5), hypoxia (N = 3), and other causes (N = 6). VEPs were recorded during the acute stage of cortical blindness in all children and were repeated in 24 of them. Either flash or pattern stimulation was used, depending upon the age and visual status of the child. All but one of the children who had normal flash VEPs while cortically blind, recovered normal visual function. All patients with abnormal VEPs had permanent visual impairment or blindness and all but one of those with absent VEPs remained blind. The recovery period was highly variable, ranging from 5 days to 3 years. Thus, flash VEPs recorded during the period of blindness were useful in predicting visual outcome, regardless of etiology. Repeat studies using pattern VEPs were valuable in monitoring recovery in many of these patients.

Effects of perinatal hypoxia on visual development during the first year of (corrected) age

Visual development was assessed in 124 infants (112 preterms and 12 fullterms) who had suffered from perinatal hypoxia and in 55 control preterm infants during the first year of corrected age. Using behavioural techniques, visual functions were tested during follow-up visits in the Sophia Children's Hospital. Corrected ages at testing ranged from 3 months to 1 year. During this period, infants with perinatal hypoxia showed more abnormalities in visual functions than preterm control infants. Gestational age at birth did not influence the outcome of visual development after perinatal hypoxia. Most visual impairments were demonstrated at 3 and 6 months of age. All infants with severe neuro-developmental handicaps showed visual deficits, although neuro-developmental abnormalities and visual deficits could be present as isolated phenomena. Ultrasound abnormalities related well with visual dysfunctions. Prospective studies of infants with visual deficits and a history of perinatal hypoxia are indicated.

Childhood prosopagnosia

K.D. has been unable to recognize people's faces since sustaining cerebral injury in infancy. Investigation of this disorder carried out when K.D. was aged 8 to 11 years showed that although her basic visual abilities were impaired, they were no poorer than those of other children who recognized faces without difficulty. K.D. had learned to read, but had not regained ability to recognize people's faces; instead she relied primarily on voices as a cue to person recognition. There was no evidence of any degree of overt or covert recognition of familiar faces, and K.D. also experienced problems in visual object recognition. She could, however, classify a visual input as a face, was able to perceive and imitate facial expressions, and was able to perform face matching tasks to an extent limited by her use of a feature by feature matching strategy. It is suggested that K.D.'s impairment affected higher order perceptual abilities, and is in a number of respects comparable to the impairments found in adult prosopagnosic patients.

Transient acute cortical blindness associated with hypoglycemia

A 7-year-old boy with glycogen storage disease type III developed transient acute cortical blindness associated with hypoglycemia on two separate occasions; the patient also demonstrated transient high-voltage slowing on the electroencephalogram over both occipital areas. This patient is the second examined in our pediatric department during a 5 year period with acute cortical blindness associated with hypoglycemia.

Cortical blindness: etiology, diagnosis, and prognosis

We examined 15 patients with cortical blindness, reviewed the records of 10 others, and compared these 25 patients to those in previous studies of cortical blindness. Although cerebrovascular disease was the most common cause in our series, surgery, particularly cardiac surgery, and cerebral angiography were also major causes. Only 3 patients denied their blindness, although 4 others were unaware of their visual loss. Electroencephalograms (EEGs) were performed during the period of blindness in 20 patients and all recordings were abnormal, with absent alpha rhythm. Visual evoked potentials recorded during blindness were abnormal in 15 of 19 patients, but did not correlate with the severity of visual loss or with outcome. Bioccipital lucencies were found in computed tomographic (CT) scans of 14 patients; none of the 14 regained good vision. Recovery of vision was poor in all 8 patients who had a spontaneous stroke, but fair or good in 11 of the other 17 patients. Prognosis was best in patients under the age of 40 years, in those without a history of hypertension or diabetes mellitus, and in those without associated cognitive, language, or memory impairments. We conclude that the prognosis in cortical blindness is poor when caused by stroke; EEGs are more useful than visual evoked potentials for diagnosis; and bioccipital abnormalities shown on CT scan are associated with a poor prognosis.

A case of cortical blindness due to carbon monoxide poisoning

We report a case of cortical blindness occurring 7 days after acute CO poisoning with no other neurological or psychic deficits apart from denial of the blindness with visual confabulation and slight loss of retentive memory. There was scant correlation between the course of the clinical pattern, which cleared completely within 6 days, and the electroencephalographic pattern with marked and diffuse slowing, which did not recede completely during 3 months observation. CT scanning of the skull, initially within normal limits, displayed 2 weeks later a faint but diffuse hypodensity of the white substance, more marked in the occipital region, which was no longer present 80 days after the first scan.

Objective techniques of visual acuity assessment in infancy

Three primary techniques for objective assessment of visual acuity in the preverbal infant are variations of optokinetic nystagmus, forced preferential looking and visual evoked potentials. Although these tests are useful, the clinician must be aware of their shortcomings. Failure to evoke optokinetic nystagmus may reflect the infant's lack of interest in the stimulus, an inherently uninteresting stimulus, or a defect in the motor system generating the nystagmus, other than failure to see the stimulus. Forced choice preferential looking has provided useful information about visual development in preverbal infants. The need for more complex stimuli to yield more precise estimates of acuity than the standard grafting stimuli, especially in cases of amblyopia, is discussed. Visual evoked potentials, like forced preferential looking, may grossly overestimate the acuity of the amblyopic patient. Of the techniques discussed, it holds the most promise.

Electroencephalograms of children with permanent cortical visual impairment

The electroencephalograms of 40 children with permanent cortical visual impairment (CVI) were studied. CVI was diagnosed in the presence of severe visual loss, normal or minimal ocular findings and clinical, electrodiagnostic and CT evidence of postgeniculate lesions involving the visual cortex. All patients had a multidisciplinary evaluation, including extensive neurological and ophthalmological investigations. The records did not contain any specific features which would be diagnostic of CVI. Isolated occipital spikes were rare and more commonly multifocal EEG disturbance was seen because of diffuse cerebral involvement. Photic stimulation was of little use in the diagnosis. Multihandicapped children with profound CVI tended to show multifocal abnormalities, no alpha rhythm and a suppressed posterior waking background in their EEGs, whereas those with more residual vision usually had an alpha rhythm. The presence or absence of alpha rhythm seemed to reflect the intactness of the striate cortex. However, the lack of alpha rhythm was not always associated with total blindness and not all children with useful residual vision had alpha rhythm.

Transient post-traumatic cortical blindness: brief v prolonged syndromes in childhood

Six children who sustained head trauma of varying degrees experienced self-limited cortical blindness--complete bilateral visual loss associated with normal pupillary responses to light. In five cases associated with relatively minor head trauma, full visual function returned within 24 hours. In the other case, associated with parietal and occipital contusions, the period of complete blindness was prolonged, lasting 1 week, followed by a striking recovery over an additional week. A bilateral inferior altitudinal visual field deficit has persisted over 6 years, with emergence of a complicated migraine syndrome. Sequential computed tomographic (CT) scans over a 4-year period demonstrate bioccipital and right parietal injury, correlating clinical and anatomic findings. This case is the first description of prolonged transient post-traumatic cortical blindness in a child with CT correlation. It underscores the clinical, radiographic, and pathophysiologic differences between syndromes of brief and prolonged transient post-traumatic cortical blindness in childhood.

Cortical visual impairment following birth asphyxia

Visual defects are often poorly recognized in children with multiple neurologic problems due to perinatal hypoxic-ischemic encephalopathy. We report the clinical, radiologic, and electrodiagnostic characteristics of 20 children with cortical visual impairment secondary to birth asphyxia. Clinical diagnosis often was delayed. Ten patients recovered vision during the first two years of life. Four infants had coexisting damage to the pregeniculate visual pathway. Useful investigations included cranial computed tomography and visual evoked potential mapping. Electroencephalographic abnormalities were nonspecific. The classical definition of cortical blindness must be modified for children.

Permanent cortical visual impairment in children

Fifty patients with permanent cortical visual impairment were evaluated. They had a characteristic behaviour profile, usually with residual sight but poor visual attention. 30 of the 50 also had damage to the anterior visual pathway. Visual evoked potential mapping was shown to have a clear advantage over visual evoked responses, and using that in conjunction with CT and clinical data enabled several subgroups of cortical visual impairment to be identified. The diagnosis probably is more common than previously recognised, and should be suspected when there is greater delay in visual development in other areas and the degree of visual loss is unexplained by ocular findings. Using traditional criteria for cortical blindness may mean that many children are not diagnosed, which has serious implications for their rehabilitation.