7†Scoping review of homonymous hemianopia in childhood.

Cerebral visual impairment (CVI) encompasses a heterogeneous group of disorders and a spectrum of types of visual impairments. Research is needed to characterise the different forms of CVI and identify the specific needs of these groups to inform individualised patient care. Homonymous hemianopia (HH) is a definable visual field defect that affect some children with CVI. As part of a new research programme, we conducted a scoping review of the literature on HH in children and young people to map current knowledge and identify evidence gaps.We used the PRISMA extension for Scoping Reviews methodology. Multiple online databases were searched using terms associated with 'homonymous hemianopia' and 'children'. This yielded 1588 papers which were screened by two reviewers. Of these 1001 were excluded at abstract screen and a further 415 excluded after full text review, with full text unavailable for 15. Data were extracted and charted from 157 studies and additional grey literature.Interim analysis shows reported studies are predominantly from high income countries with a paucity of higher-level evidence, and a preponderance of case reports. Most papers reported causative pathology and diagnosis of HH. There was minimal attention to or evidence relating to intervention. Child-specific grey literature on HH was limited.This review collates the current evidence-base for HH in children. It demonstrates the important evidence-gap relating to intervention in these cases that would help inform more individualised care. Similar scoping reviews may be prove useful in assessing the evidence relating to other definable groups within the CVI umbrella.

NYX-related Congenital Stationary Night Blindness in Two Siblings due to Probable Maternal Germline Mosaicism.

Background: Congenital Stationary Night Blindness (CSNB) is a clinically and genetically heterogenous inherited retinal disorder associated with nystagmus, myopia, strabismus, defective dark adaptation, and decreased vision. Pathogenic variants in at least 17 genes have been associated with CSNB, where a hemizygous variant of NYX causing an X-linked form of the disorder is among the commonest causes.Materials and Methods: A retrospective chart review of a single pedigree was performed. Three pediatric patients underwent ophthalmic examinations, visual electrophysiology, and ocular imaging. Molecular genetic testing for CSNB was pursued where clinically indicated.Results: Two male siblings demonstrated clinical and electroretinographic evidence of complete CSNB. Genetic testing identified a NYX pathogenic, in-frame deletion in both children. Targeted variant analysis of the mother failed to identify the variant in two independent samples, most consistent with mosaicism.Conclusions: Clinical and molecular analyses within the described family demonstrate the possibility of maternal mosaicism in NYX-related CSNB. The importance of cascade molecular testing is highlighted. The prospect of somatic or germline mosaicism in NYX-related CSNB informs genetic counseling, genetic testing decisions, and risk assessment in affected families.

Evidence for a neurophysiologic auditory deficit in children with benign epilepsy with centro-temporal spikes.

Benign focal epilepsy in childhood with centro-temporal spikes (BECTS) is one of the most common forms of epilepsy. Recent studies have questioned the benign nature of BECTS, as they have revealed neuropsychological deficits in many domains including language. The aim of this study was to investigate whether the epileptic discharges during the night have long-term effects on auditory processing, as reflected on electrophysiological measures, during the day, which could underline the language deficits. In order to address these questions we recorded base line electroencephalograms (EEG), sleep EEG and auditory event related potentials in 12 children with BECTS and in age- and gender-matched controls. In the children with BECTS, 5 had unilateral and 3 had bilateral spikes. In the 5 patients with unilateral spikes present during sleep, an asymmetry of the auditory event related component (P85-120) was observed contralateral to the side of epileptiform activity compared to the normal symmetrical vertex distribution that was noted in all controls and in 3 the children with bilateral spikes. In all patients the peak to peak amplitude of this event related potential component was statistically greater compared to the controls. Analysis of subtraction waveforms (deviant - standard) revealed no evidence of a mismatch negativity component in any of the children with BECTS. We propose that the abnormality of P85-120 and the absence of mismatch negativity during wake recordings in this group may arise in response to the long-term effects of spikes occurring during sleep, resulting in disruption of the evolution and maintenance of echoic memory traces. These results may indicate that patients with BECTS have abnormal processing of auditory information at a sensory level ipsilateral to the hemisphere evoking spikes during sleep.

The achiasmia spectrum: congenitally reduced chiasmal decussation.

AIM: To describe the clinical spectrum of achiasmia, a congenital disorder of reduced relative decussation at the optic chiasm. METHODS: A retrospective case note and patient review of nine children (four boys). Achiasmia was defined by the combination of a characteristic asymmetry of the monocular visual evoked potential (VEP) response to flash and neuroimaging showing reduced chiasmal size. RESULTS: Three of the children had an associated skull base encephalocele with agenesis of the corpus callosum. In two patients achiasmia was associated with septo-optic dysplasia. Three patients had no neuroimaging abnormalities other than reduced chiasmal size and have no known pituitary dysfunction. One child had multiple physical deformities but the only brain imaging abnormality was reduced chiasmal size. CONCLUSIONS: Some children with disorders of midline central nervous system development, including septo-optic dysplasia and skull base encephaloceles, have congenitally reduced chiasmal decussation. Reduced relative decussation may co-exist with overall chiasmal hypoplasia. Children with an apparently isolated chiasmal decussation deficit may have other subtle neurological findings, but our clinical impression is that most of these children function well.

Adenoid-tonsillectomy to treat visual dysfunction in a child with craniosynostosis.

We report a child with isolated saggital synostosis where a gradual deterioration of the P100 component of the pattern reversal visual evoked potential recorded during the day was associated with episodes of upper airway obstruction during sleep that correlated with periods of ICP spiking. Adenoid-tonsillectomy reversed this deterioration with coincident increase in SaO2 and decreased sleep apnoea.

Auditory event-related potentials in the assessment of auditory processing disorders: a pilot study.

The aim of this pilot study was to investigate whether children with a suspected auditory processing disorder (sAPD) in the presence of normal hearing, differ significantly from normal age-matched controls on particular parameters of auditory event-related potentials. We assessed nine children (mean age 9.5 years) in whom the clinical profile and the results in a screening test for auditory processing disorder (SCAN/SCAN-A) suggested the presence of an auditory processing disorder, and nine age-matched normal control subjects, using auditory event-related potentials (ERP) to phonemes/ba/(standard) and/da/(deviant). Analysis of the auditory ERP recordings revealed an enlarged P85 - 120 and attenuated N1 and P2 in all sAPD children compared to controls. We also found significantly increased N1 peak latency, and a larger peak to peak amplitude of the P85 - 120-N1 and P2-N2 and smaller peak to peak amplitude of the N1-P2 in the sAPD children. Subtraction of the standard auditory ERP from the deviant revealed a mismatch negativity with no significant differences in duration, peak or onset latency between the control subjects and sAPD. Our results indicate that neurophysiological measures may identify a group of children with specific problems suggestive of an auditory processing disorder in the absence of an obvious structural or functional lesion who warrant further study in order to assess whether these findings reflect delayed CNS myelination.

Audiometric abnormalities in children with Gaucher disease type 3.

Exogenous enzyme replacement therapy achieves satisfactory biomedical correction in Gaucher type 1 disease and may halt or reverse neurological progression in type 3, while it does not appear to influence the outcome in type 2. In view of the therapeutic possibilities, early detection and monitoring of type 3 Gaucher disease, as well as evaluation of the effectiveness of enzyme therapy on neuronopathic involvement is necessary. The objective of this study was to evaluate the extent of brainstem disease in children with proven Gaucher type 3, by means of an audiological test battery. We studied 9 patients with Gaucher type 3 disease. The tests included baseline audiometric tests, as well as auditory brainstem evoked responses (ABR), acoustic reflexes and medial olivo-cochlear suppression by contralateral noise tests, that involve overlapping but not identical efferent and afferent pathways and brainstem structures. We found a constellation of abnormalities including bilaterally raised acoustic reflexes, poor medial olivo-cochlear suppression, and very poor brainstem evoked potentials. These abnormalities could be due to a single lesion in the dorsomedial brainstem, or to multiple lesions, and further study is needed to clarify this issue. Combined audiological tests may provide information on the severity of the neurological involvement and should therefore be part of a standard assessment for the diagnosis as well as for long term neurological monitoring of Gaucher type 3 patients.

Intracranial identification of an electric frontal-cortex response to auditory stimulus change: a case study.

The aim of the present study was to clarify whether ERPs recorded directly from the human frontal cortex contributed to the auditory N1 and mismatch negativity (MMN) elicited by changes in non-phonetic and phonetic sounds. We examined the role of prefrontal cortex in the processing of stimulus repetition and change in a 6-year-old child undergoing presurgical evaluation for epilepsy. EEG was recorded from three bilateral sub-dural electrode strips located over lateral prefrontal areas during unattended auditory stimulation. EEG epochs were averaged to obtain event-related potentials (ERPs) to repeating (standard) tones and to infrequent (deviant) shorter duration tones and complex sounds (telephone buzz). In another condition, ERPs were recorded to standard and deviant syllables, /ba/ and /da/, respectively. ERPs to vibration stimuli delivered to the fingertips were not observed at any of the sub-dural electrodes, confirming modality specificity of the auditory responses. Focal auditory ERPs consisting of P100 and N150 deflections were recorded to both tones and phonemes over the right lateral prefrontal cortex. These responses were insensitive to the serial position of the repeating sound in the stimulus train. Deviant tones evoked an MMN peaking at around 128 ms. Deviant complex sounds evoked ERPs with a similar onset latency and morphology but with an approximately two-fold increase in peak-to-peak amplitude. We conclude that right lateral prefrontal cortex (Brodmann's area 45) is involved in early stages of processing repeating sounds and sound changes.

Does the pre-frontal cortex contribute to movement-related potentials? Recordings from subdural electrodes.

The contribution of the pre-frontal cortex to movement-related potentials (MRPs) is unclear. We recorded MRPs from six subdural electrode strips placed over the frontal cortex in a 13-year-old girl being monitored prior to surgery for intractable epilepsy. MRPs were recorded prior to two types of movement: self-paced random joystick movements which involve 'what to do' and 'when to do' decision making on every trial and prior to joystick movements in a fixed forward direction triggered by a tone which does not involve any trial-by-trial decision making. Self-paced random joystick movements were associated with an increased subdural positivity starting from 1000 ms prior to onset of joystick movement at electrodes over the pre-motor cortex (BA 6) and dorsolateral and inferior pre-frontal cortex (BA 46/45/10), as evident from a magnetic resonance imaging scan. These results suggest that in addition to the pre-motor area, the pre-frontal cortex also contributes to the generation of MRPs in conditions involving decision making about the precise nature ('what to do') and timing ('when to do') of the movement. These preliminary results require replication in a larger series of patients.

Central auditory processing disorder as the presenting manifestation of subtle brain pathology.

The objective of this case-report study was to assess the presence of central auditory impairment in a patient with a normal neurological examination. This subject was a 45-year-old female with gradually deteriorating hearing difficulties over a period of 5 years and a borderline normal audiogram. Behavioural central auditory tests were used, including Dichotic Sentence Identification Test, Competing Sentences Test, and auditory event-related potentials (mismatch negativity). Behavioural central auditory tests and mismatch negativity results were abnormal and indicated disordered central auditory processing. Subsequent magnetic resonance imaging of the brain identified subtle changes consistent with small-vessel ischaemic disease. Adult patients who present with hearing difficulties that cannot be explained on the basis of their audiogram should undergo central auditory assessment, as the auditory symptoms may be the first and only manifestation of central nervous system pathology.

Intracranial evidence for differential encoding of frequency and duration discrimination responses.

OBJECTIVE: To identify cortical areas involved in auditory detection and discrimination of frequency and duration stimuli in an awake child. DESIGN: Single case study recording intracranial auditory event-related potentials to auditory odd-ball stimuli varying in duration and/or frequency. RESULTS: N1 wave to detection was recorded maximally just above the Sylvian fissure 1 cm posterior to the mismatch negativity (MMN) response to discrimination. Frequency MMN overlapped with the N1 whereas duration MMN appeared 100 msec later. MMN to both duration and frequency appeared as an additive bifid response. CONCLUSIONS: It is suggested that feature-specific neuronal networks are activated after changes in sounds, which may underpin a fast parallel preattentive process (MMN).

Intracranial auditory detection and discrimination potentials as substrates of echoic memory in children.

In children, intracranial responses to auditory detection and discrimination processes have not been reported. We, therefore, recorded intracranial event-related potentials (ERPs) to both standard and deviant tones and/or syllables in 4 children undergoing pre-surgical evaluation for epilepsy. ERPs to detection (mean latency = 63 ms) and discrimination (mean latency = 334 ms) were highly localized to areas surrounding the Sylvian fissure (SF). These potentials reflect activation of different neuronal populations and are suggested to contribute to the scalp recorded auditory N1 and mismatch negativity (MMN).