Neuroimaging studies in the evaluation of developmental delay/mental retardation

Chloral hydrate as a sedating agent for neurodiagnostic procedures in children

BACKGROUND

This is an updated version of a Cochrane Review published in 2017. Paediatric neurodiagnostic investigations, including brain neuroimaging and electroencephalography (EEG), play an important role in the assessment of neurodevelopmental disorders. The use of an appropriate sedative agent is important to ensure the successful completion of the neurodiagnostic procedures, particularly in children, who are usually unable to remain still throughout the procedure.

OBJECTIVES

To assess the effectiveness and adverse effects of chloral hydrate as a sedative agent for non-invasive neurodiagnostic procedures in children.

SEARCH METHODS

We searched the following databases on 14 May 2020, with no language restrictions: the Cochrane Register of Studies (CRS Web) and MEDLINE (Ovid, 1946 to 12 May 2020). CRS Web includes randomised or quasi-randomised controlled trials from PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, the Cochrane Central Register of Controlled Trials (CENTRAL), and the specialised registers of Cochrane Review Groups including Cochrane Epilepsy.

SELECTION CRITERIA

Randomised controlled trials that assessed chloral hydrate agent against other sedative agent(s), non-drug agent(s), or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated studies identified by the search for their eligibility, extracted data, and assessed risk of bias. Results were expressed in terms of risk ratio (RR) for dichotomous data and mean difference (MD) for continuous data, with 95% confidence intervals (CIs).

MAIN RESULTS

We included 16 studies with a total of 2922 children. The methodological quality of the included studies was mixed. Blinding of the participants and personnel was not achieved in most of the included studies, and three of the 16 studies were at high risk of bias for selective reporting. Evaluation of the efficacy of the sedative agents was also underpowered, with all the comparisons performed in small studies. Fewer children who received oral chloral hydrate had sedation failure compared with oral promethazine (RR 0.11, 95% CI 0.01 to 0.82; 1 study; moderate-certainty evidence). More children who received oral chloral hydrate had sedation failure after one dose compared to intravenous pentobarbital (RR 4.33, 95% CI 1.35 to 13.89; 1 study; low-certainty evidence), but there was no clear difference after two doses (RR 3.00, 95% CI 0.33 to 27.46; 1 study; very low-certainty evidence). Children with oral chloral hydrate had more sedation failure compared with rectal sodium thiopental (RR 1.33, 95% CI 0.60 to 2.96; 1 study; moderate-certainty evidence) and music therapy (RR 17.00, 95% CI 2.37 to 122.14; 1 study; very low-certainty evidence). Sedation failure rates were similar between groups for comparisons with oral dexmedetomidine, oral hydroxyzine hydrochloride, oral midazolam and oral clonidine. Children who received oral chloral hydrate had a shorter time to adequate sedation compared with those who received oral dexmedetomidine (MD -3.86, 95% CI -5.12 to -2.6; 1 study), oral hydroxyzine hydrochloride (MD -7.5, 95% CI -7.85 to -7.15; 1 study), oral promethazine (MD -12.11, 95% CI -18.48 to -5.74; 1 study) (moderate-certainty evidence for three aforementioned outcomes), rectal midazolam (MD -95.70, 95% CI -114.51 to -76.89; 1 study), and oral clonidine (MD -37.48, 95% CI -55.97 to -18.99; 1 study) (low-certainty evidence for two aforementioned outcomes). However, children with oral chloral hydrate took longer to achieve adequate sedation when compared with intravenous pentobarbital (MD 19, 95% CI 16.61 to 21.39; 1 study; low-certainty evidence), intranasal midazolam (MD 12.83, 95% CI 7.22 to 18.44; 1 study; moderate-certainty evidence), and intranasal dexmedetomidine (MD 2.80, 95% CI 0.77 to 4.83; 1 study, moderate-certainty evidence). Children who received oral chloral hydrate appeared significantly less likely to complete neurodiagnostic procedure with child awakening when compared with rectal sodium thiopental (RR 0.95, 95% CI 0.83 to 1.09; 1 study; moderate-certainty evidence). Chloral hydrate was associated with a higher risk of the following adverse events: desaturation versus rectal sodium thiopental (RR 5.00, 95% 0.24 to 102.30; 1 study), unsteadiness versus intranasal dexmedetomidine (MD 10.21, 95% CI 0.58 to 178.52; 1 study), vomiting versus intranasal dexmedetomidine (MD 10.59, 95% CI 0.61 to 185.45; 1 study) (low-certainty evidence for aforementioned three outcomes), and crying during administration of sedation versus intranasal dexmedetomidine (MD 1.39, 95% CI 1.08 to 1.80; 1 study, moderate-certainty evidence). Chloral hydrate was associated with a lower risk of the following: diarrhoea compared with rectal sodium thiopental (RR 0.04, 95% CI 0.00 to 0.72; 1 study), lower mean diastolic blood pressure compared with sodium thiopental (MD 7.40, 95% CI 5.11 to 9.69; 1 study), drowsiness compared with oral clonidine (RR 0.44, 95% CI 0.30 to 0.64; 1 study), vertigo compared with oral clonidine (RR 0.15, 95% CI 0.01 to 2.79; 1 study) (moderate-certainty evidence for aforementioned four outcomes), and bradycardia compared with intranasal dexmedetomidine (MD 0.17, 95% CI 0.05 to 0.59; 1 study; high-certainty evidence). No other adverse events were significantly associated with chloral hydrate, although there was an increased risk of combined adverse events overall (RR 7.66, 95% CI 1.78 to 32.91; 1 study; low-certainty evidence).

AUTHORS' CONCLUSIONS

The certainty of evidence for the comparisons of oral chloral hydrate against several other methods of sedation was variable. Oral chloral hydrate appears to have a lower sedation failure rate when compared with oral promethazine. Sedation failure was similar between groups for other comparisons such as oral dexmedetomidine, oral hydroxyzine hydrochloride, and oral midazolam. Oral chloral hydrate had a higher sedation failure rate when compared with intravenous pentobarbital, rectal sodium thiopental, and music therapy. Chloral hydrate appeared to be associated with higher rates of adverse events than intranasal dexmedetomidine. However, the evidence for the outcomes for oral chloral hydrate versus intravenous pentobarbital, rectal sodium thiopental, intranasal dexmedetomidine, and music therapy was mostly of low certainty, therefore the findings should be interpreted with caution. Further research should determine the effects of oral chloral hydrate on major clinical outcomes such as successful completion of procedures, requirements for an additional sedative agent, and degree of sedation measured using validated scales, which were rarely assessed in the studies included in this review. The safety profile of chloral hydrate should be studied further, especially for major adverse effects such as oxygen desaturation.

Chloral hydrate as a sedating agent for neurodiagnostic procedures in children

BACKGROUND

Paediatric neurodiagnostic investigations, including brain neuroimaging and electroencephalography (EEG), play an important role in the assessment of neurodevelopmental disorders. The use of an appropriate sedative agent is important to ensure the successful completion of the neurodiagnostic procedures, particularly in children, who are usually unable to remain still throughout the procedure.

OBJECTIVES

To assess the effectiveness and adverse effects of chloral hydrate as a sedative agent for non-invasive neurodiagnostic procedures in children.

SEARCH METHODS

We used the standard search strategy of the Cochrane Epilepsy Group. We searched MEDLINE (OVID SP) (1950 to July 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, Issue 7, 2017), Embase (1980 to July 2017), and the Cochrane Epilepsy Group Specialized Register (via CENTRAL) using a combination of keywords and MeSH headings.

SELECTION CRITERIA

We included randomised controlled trials that assessed chloral hydrate agent against other sedative agent(s), non-drug agent(s), or placebo for children undergoing non-invasive neurodiagnostic procedures.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for their eligibility, extracted data, and assessed risk of bias. Results were expressed in terms of risk ratio (RR) for dichotomous data, mean difference (MD) for continuous data, with 95% confidence intervals (CIs).

MAIN RESULTS

We included 13 studies with a total of 2390 children. The studies were all conducted in hospitals that provided neurodiagnostic services. Most studies assessed the proportion of sedation failure during the neurodiagnostic procedure, time for adequate sedation, and potential adverse effects associated with the sedative agent.The methodological quality of the included studies was mixed, as reflected by a wide variation in their 'Risk of bias' profiles. Blinding of the participants and personnel was not achieved in most of the included studies, and three of the 13 studies had high risk of bias for selective reporting. Evaluation of the efficacy of the sedative agents was also underpowered, with all the comparisons performed in single small studies.Children who received oral chloral hydrate had lower sedation failure when compared with oral promethazine (RR 0.11, 95% CI 0.01 to 0.82; 1 study, moderate-quality evidence). Children who received oral chloral hydrate had a higher risk of sedation failure after one dose compared to those who received intravenous pentobarbital (RR 4.33, 95% CI 1.35 to 13.89; 1 study, low-quality evidence), but after two doses there was no evidence of a significant difference between the two groups (RR 3.00, 95% CI 0.33 to 27.46; 1 study, very low-quality evidence). Children who received oral chloral hydrate appeared to have more sedation failure when compared with music therapy, but the quality of evidence was very low for this outcome (RR 17.00, 95% CI 2.37 to 122.14; 1 study). Sedation failure rates were similar between oral chloral hydrate, oral dexmedetomidine, oral hydroxyzine hydrochloride, and oral midazolam.Children who received oral chloral hydrate had a shorter time to achieve adequate sedation when compared with those who received oral dexmedetomidine (MD -3.86, 95% CI -5.12 to -2.6; 1 study, moderate-quality evidence), oral hydroxyzine hydrochloride (MD -7.5, 95% CI -7.85 to -7.15; 1 study, moderate-quality evidence), oral promethazine (MD -12.11, 95% CI -18.48 to -5.74; 1 study, moderate-quality evidence), and rectal midazolam (MD -95.70, 95% CI -114.51 to -76.89; 1 study). However, children with oral chloral hydrate took longer to achieve adequate sedation when compared with intravenous pentobarbital (MD 19, 95% CI 16.61 to 21.39; 1 study, low-quality evidence) and intranasal midazolam (MD 12.83, 95% CI 7.22 to 18.44; 1 study, moderate-quality evidence).No data were available to assess the proportion of children with successful completion of neurodiagnostic procedure without interruption by the child awakening. Most trials did not assess adequate sedation as measured by specific validated scales, except in the comparison of chloral hydrate versus intranasal midazolam and oral promethazine.Compared to dexmedetomidine, chloral hydrate was associated with a higher risk of nausea and vomiting (RR 12.04 95% CI 1.58 to 91.96). No other adverse events were significantly associated with chloral hydrate (including behavioural change, oxygen desaturation) although there was an increased risk of adverse events overall (RR 7.66, 95% CI 1.78 to 32.91; 1 study, low-quality evidence).

AUTHORS' CONCLUSIONS

The quality of evidence for the comparisons of oral chloral hydrate against several other methods of sedation was very variable. Oral chloral hydrate appears to have a lower sedation failure rate when compared with oral promethazine for children undergoing paediatric neurodiagnostic procedures. The sedation failure was similar for other comparisons such as oral dexmedetomidine, oral hydroxyzine hydrochloride, and oral midazolam. When compared with intravenous pentobarbital and music therapy, oral chloral hydrate had a higher sedation failure rate. However, it must be noted that the evidence for the outcomes for the comparisons of oral chloral hydrate against intravenous pentobarbital and music therapy was of very low to low quality, therefore the corresponding findings should be interpreted with caution.Further research should determine the effects of oral chloral hydrate on major clinical outcomes such as successful completion of procedures, requirements for additional sedative agent, and degree of sedation measured using validated scales, which were rarely assessed in the studies included in this review. The safety profile of chloral hydrate should be studied further, especially the risk of major adverse effects such as bradycardia, hypotension, and oxygen desaturation.

Global developmental delay in a 10-month-old infant boy

A 10-month-old boy was seen for the first time for a health supervision visit by a pediatrician. A brief review of the child's medical history did not reveal any specific problems. On physical examination, the pediatrician found an alert, smiling child, but she was surprised by the following observations: unable to sit without support, absent pincer grasp, no audible language, unilateral exotropia, and microcephaly. Expansion of the medical history revealed an uneventful full-term prenatal course and normal vaginal delivery. The mother denied use of alcohol or other drugs/medications during the pregnancy. She did not have a recent history of any infections, unexplained fevers, or high risks for sexually transmitted disease. The baby cried spontaneously and the parents reported no resuscitation efforts. There were early feeding problems associated with a poor suck and gastroesophageal reflux. The parents were healthy and this was their first child. Family history was negative for early problems in child development or any neurological conditions. Parents were high school graduates without any learning problems; they were both employed in retail sales with a steady employment history. The pediatrician then took a second look at the child and discovered truncal hypotonia, extremity hypertonia, tongue protrusion, and a broad mouth. She concluded that the child had a global developmental delay, including delays in motor, language, and social development.

Magnetic resonance imaging and proton magnetic resonance spectroscopy of the brain in the diagnostic evaluation of developmental delay

AIM

To assess the contribution of MRI and proton spectroscopy (1HMRS) in establishing an etiological diagnosis in children with developmental delay (DD) and to assess whether the chance of finding specific abnormalities correlates with the presence of neurological signs and/or abnormal head circumference (HC).

METHODS

Patients were derived from a cohort of 325 consecutive patients with DD receiving structured multidisciplinary evaluation in our centre. Patients had MRI/1HMRS if a diagnosis could not be made clinically and if additional neurological signs and/or abnormal HC and/or an IQ below 50 were present. The MRI protocol consisted of axial IR, T2, FLAIR, sagittal T1 and coronal T2 sequences. Multivoxel 1HMRS was located in a plane superior to the lateral ventricles with voxels in both grey matter and white matter.

RESULTS

One hundred and nine children were scanned, 80 of them because of neurological signs and/or abnormal HC. Although minor abnormalities were noted in the vast majority of patients, MRI and/or 1HMRS really contributed to an etiological diagnosis in only 10 (9%) patients, all of whom were scanned because of neurological signs. In these 10 patients, 1HMRS was diagnostic in one patient and of additional value to MRI findings in 3 patients.

CONCLUSIONS

MRI and 1HMRS may contribute to the diagnostic evaluation of DD, especially if applied specifically to patients with neurological signs, whereas its role is very limited in children without these signs.

Global developmental delay in a 10-month-old infant boy

A 10-month-old boy was seen for the first time for a health supervision visit by a pediatrician. A brief review of the child's medical history did not reveal any specific problems. On physical examination, the pediatrician found an alert, smiling child, but she was surprised by the following observations: unable to sit without support, absent pincer grasp, no audible language, unilateral exotropia, and microcephaly. Expansion of the medical history revealed an uneventful full-term prenatal course and normal vaginal delivery. The mother denied use of alcohol or other drugs/medications during the pregnancy. She did not have a recent history of any infections, unexplained fevers, or high risks for sexually transmitted disease. The baby cried spontaneously and the parents reported no resuscitation efforts. There were early feeding problems associated with a poor suck and gastroesophageal reflux. The parents were healthy and this was their first child. Family history was negative for early problems in child development or any neurological conditions. Parents were high school graduates without any learning problems; they were both employed in retail sales with a steady employment history. The pediatrician then took a second look at the child and discovered truncal hypotonia, extremity hypertonia, tongue protrusion, and a broad mouth. She concluded that the child had a global developmental delay, including delays in motor, language, and social development.

XLMR genes: update 2007

X-linked mental retardation (XLMR) is a common cause of inherited intellectual disability with an estimated prevalence of approximately 1/1000 males. Most XLMR conditions are inherited as X-linked recessive traits, although female carriers may manifest usually milder symptoms. We have listed 215 XLMR conditions, subdivided according to their clinical presentation: 149 with specific clinical findings, including 98 syndromes and 51 neuromuscular conditions, and 66 nonspecific (MRX) forms. We also present a map of the 82 XLMR genes cloned to date (November 2007) and a map of the 97 conditions that have been positioned by linkage analysis or cytogenetic breakpoints. We briefly consider the molecular function of known XLMR proteins and discuss the possible strategies to identify the remaining XLMR genes. Final remarks are made on the natural history of XLMR conditions and on diagnostic issues.

Neuroimaging of the child with developmental delay

Developmental delay (DD) affects approximately 1% to 3% of all children in the United States. This diagnosis significantly impedes quality of life and full participation in the life of the family, school, and community. In this setting, the clinician's ability to detect, diagnose, and possibly treat the cause for DD in a timely manner depends on a multimodality approach to neuroimaging and a robust understanding of the various imaging algorithms aimed at determining the etiology of disease, structural and/or anatomic defects, functional activity, metabolic profiles, and genetic characteristics. Taken separately and in combination, these features are effectively depicted and analyzed using an array of brain imaging modalities: ultrasound, computed tomography, nuclear medicine, magnetic resonance (MR) spectroscopy, and a growing mix of sophisticated MR imaging (MRI) techniques, including diffusion-weighted imaging, diffusion tensor imaging, perfusion MRI, and functional MRI. Thus, equipped with these advanced imaging capabilities, pediatric neurologists and neuroradiologists are now positioned to diagnose with greater accuracy and speed; this, in turn, results in more effective treatment plans and improved patient outcomes as measured by progress in reaching developmental milestones and in ameliorating secondary conditions such as seizures, poor motor control, incontinence, and impulsivity. The purpose of this article is to present the numerous causes of pediatric DD, describe their respective neuroimaging findings, discuss various neuroimaging approaches for elucidating etiology, and offer specific guidelines for optimizing imaging results in the setting of multimodality imaging capabilities.

The contribution of novel brain imaging techniques to understanding the neurobiology of mental retardation and developmental disabilities

Studying the biological mechanisms underlying mental retardation and developmental disabilities (MR/DD) is a very complex task. This is due to the wide heterogeneity of etiologies and pathways that lead to MR/DD. Breakthroughs in genetics and molecular biology and the development of sophisticated brain imaging techniques during the last decades have facilitated the emergence of a field called Behavioral Neurogenetics. Behavioral Neurogenetics focuses on studying genetic diseases with known etiologies that are manifested by unique cognitive and behavioral phenotypes. In this review, we describe the principles of magnetic resonance imaging (MRI) techniques, including structural MRI, functional MRI, and diffusion tensor imaging (DTI), and how they are implemented in the study of Williams (WS), velocardiofacial (VCFS), and fragile X (FXS) syndromes. From WS we learn that dorsal stream abnormalities can be associated with visuospatial deficits; VCFS is a model for exploring the molecular and brain pathways that lead to psychiatric disorders for which subjects with MR/DD are at increased risk; and finally, findings from multimodal imaging techniques show that aberrant frontal-striatal connections are implicated in the executive function and attentional deficits of subjects with FXS. By deciphering the molecular pathways and brain structure and function associated with cognitive deficits, we will gain a better understanding of the pathophysiology of MR/DD, which will eventually make possible more specific treatments for this population.

Higher harmonic generation microscopy for developmental biology

Optical higher harmonic generation, including second harmonic generation and third harmonic generation, leaves no energy deposition to its interacted matters due to an energy-conservation characteristic, providing the "noninvasiveness" nature desirable for biological studies. Combined with its nonlinearity, higher harmonic generation microscopy provides excellent three-dimensional (3D) sectioning capability, offering new insights into the studies of embryonic morphological changes and complex developmental processes. By choosing a laser working in the biological penetration window, here we present a noninvasive in vivo light microscopy with sub-micron 3D resolution and millimeter penetration, utilizing endogenous higher harmonic generation signals in live specimens. Noninvasive imaging was performed in live zebrafish (Danio rerio) embryos. The complex developmental processes within > 1-mm-thick zebrafish embryos can be observed in vivo without any treatment. No optical damage was found even with high illumination after long-term observations and the examined embryos all developed normally at least to the larval stage. The excellent 3D resolution of the demonstrated technology allows us to capture the subtle developmental information on the cellular or sub-cellular levels occurring deep inside the live embryos and larvae. This technique can not only provide in vivo observation of the cytoarchitecture dynamics during embryogenesis with submicron resolution and millimeter penetration depth, but would also make strong impact in developmental and structural biology studies.

Supratentorial functional disturbances in two children with cerebellar cortical dysplasia

When evaluating children with mental retardation, subtle cerebral and cerebellar morphologic anomalies are often noted at Magnetic Resonance Imaging (MRI). Some, such as cerebellar cortical dysplasia (CCD), have been considered as subtle markers of cerebral dysgenesis. Their functional significance and their effect on brain function, remain unknown. To study supratentorial functional disturbances related to CCD we performed Positron-Emission-Tomography (PET) studies in two children with isolated CCD, in order to investigate the degree of involvement of supratentorial structures. One had developmental delay, motor disturbances and ataxia, and the other one only had mental retardation. PET studies revealed hypoperfusion and hypometabolism within the vermis, thalamus and the right striatum in one case, and hypometabolism in the basal ganglia and cerebellar deep grey nuclei in the other case. Our results could lead to a hypothesis explaining motor disturbances as well as cognitive impairment, and could suggest a pathological functional significance of CCD. Nevertheless, the relationship between these findings and mental retardation needs further investigation.

Diagnostic evaluation of developmental delay/mental retardation: An overview

Mental retardation (MR) is one of the few clinically important disorders for which the etiopathogenesis is still poorly understood. It is a condition of great concern for public health and society. MR is currently defined as a significant impairment of cognitive and adaptive functions, with onset before age 18 years. It may become evident during infancy or early childhood as developmental delay (DD), but it is best diagnosed during the school years. MR is estimated to occur in 1-10% of the population, and research on its etiology has always been a challenge in medicine. The etiopathogenesis encompasses so many different entities that the attending physician can sometimes feel a "virtual panic," starting a wide-range diagnostic evaluation. The Consensus Conference of the American College of Medical Genetics has recently established guidelines regarding the evaluation of patients with MR [Curry et al., 1997], emphasizing the high diagnostic utility of cytogenetic studies and neuroimaging in certain clinical settings. However, since then there has been substantial progress in molecular cytogenetics and neuroimaging techniques, the use of which has allowed recognition and definition of new disorders, thus increasing the diagnostic yield. This review will focus on the most appropriate investigations shown to be, at present, necessary to define the etiology of DD/MR, in the context of recommendations for the clinical evaluation of the patient with undiagnosed MR.