Obstructive Apneas in a Mouse Model of Congenital Central Hypoventilation Syndrome.

Rationale: Congenital central hypoventilation syndrome (CCHS) is characterized by life-threatening sleep hypoventilation and is caused by PHOX2B gene mutations, most frequently the PHOX2B27Ala/+ mutation, with patients requiring lifelong ventilatory support. It is unclear whether obstructive apneas are part of the syndrome. Objectives: To determine if Phox2b27Ala/+ mice, which present the main symptoms of CCHS and die within hours after birth, also express obstructive apneas, and to investigate potential underlying mechanisms. Methods: Apneas were classified as central, obstructive, or mixed by using a novel system combining pneumotachography and laser detection of abdominal movement immediately after birth. Several respiratory nuclei involved in airway patency were examined by immunohistochemistry and electrophysiology in brainstem-spinal cord preparations. Measurements and Main Results: The median (interquartile range) of obstructive apnea frequency was 2.3 (1.5-3.3)/min in Phox2b27Ala/+ pups versus 0.6 (0.4-1.0)/min in wild types (P < 0.0001). Obstructive apnea duration was 2.7 seconds (2.3-3.9) in Phox2b27Ala/+ pups versus 1.7 seconds (1.1-1.9) in wild types (P < 0.0001). Central and mixed apneas presented similar significant differences. In Phox2b27Ala/+ preparations, the hypoglossal nucleus had fewer (P < 0.05) and smaller (P < 0.01) neurons, compared with wild-type preparations. Importantly, coordination of phrenic and hypoglossal motor activities was disrupted, as evidenced by the longer and variable delay of hypoglossal activity with respect to phrenic activity onset (P < 0.001). Conclusions: The Phox2b27Ala/+ mutation predisposed pups not only to hypoventilation and central apneas, but also to obstructive and mixed apneas, likely because of hypoglossal dysgenesis. These results thus demand attention toward obstructive events in infants with CCHS.

Progressive gray matter changes in patients with congenital central hypoventilation syndrome.

INTRODUCTION: Patients with congenital central hypoventilation syndrome (CCHS) show brain injury in areas that control chemosensory, autonomic, motor, cognitive, and emotion functions, which are deficient in the condition. Many of these abnormal characteristics are present from the neonatal period; however, it is unclear whether tissue injury underlying the characteristics progressively worsens with time. We hypothesized that several brain areas in subjects with CCHS would show increased gray matter volume loss over time. METHODS: We collected high-resolution T1-weighted images twice (4 years apart) from seven subjects with CCHS (age at first study, 16.1 ± 2.7 years; four males) and three control subjects (15.9 ± 2.1 years; three males) using a 3.0-Tesla magnetic resonance imaging (MRI) scanner, and evaluated regional gray matter volume changes with voxel-based morphometry (VBM) procedures. RESULTS: Multiple brain sites in CCHS, including frontal, prefrontal, insular, and cingulate cortices; caudate nuclei and putamen; ventral temporal and parietal cortices; and cerebellar cortices showed significantly reduced gray matter volume over time. Only limited brain areas, including sensory, temporal, and medullary regions, emerged with increased gray matter at the later age. DISCUSSION: Patients with CCHS show reduced gray matter volume with age progression in autonomic, respiratory, and cognitive regulatory areas, an outcome that may contribute to deterioration of functions found in the syndrome with increasing age.

A case of congenital central hypoventilation syndrome.

We encountered a 2-year-old female infant with congenital central hypoventilation syndrome (CCHS) who underwent an abdominal operation for strangulated ileus. Prior to the surgery, at home, the infant had been receiving non-invasive positive-pressure ventilation (NPPV) support only during sleep. However, after postoperative extubation, the blood oxygen saturation (SpO(2)) decreased to approximately 90 % with NPPV during sleep alone, necessitating the use of biphasic cuirass ventilation (BCV) along with NPPV for 2 days. The infant was weaned from the BCV on hospital day 9, and was discharged from the intensive care unit (ICU) on hospital day 13. Although it has been said that CCHS is not under the control of the respiratory center, there are no reports of the true CO(2) response curves in these patients. Therefore, during respiratory management in the ICU post-surgery, we examined (with the consent of the mother) the relationship of the end-tidal carbon dioxide (ETCO(2)) to the tidal volume and respiratory rate, for a period of 6 min in the absence of sedation, using a respiratory profile monitor. Electrocardiographic and SpO(2) monitoring was also conducted at the same time, to ensure the patient's safety. In this patient, while the ETCO(2) increased, the tidal volume and respiratory rate remained unchanged. No relationship was found between the tidal volume and the respiratory rate. Various modalities have been used for the treatment of CCHS (tracheotomy, NPPV, and diaphragmatic pacing). Treatment of these patients in the ICU should be tailored to the needs of individual patients and their families.

Rostral brain axonal injury in congenital central hypoventilation syndrome.

Brain injury underlying the state-related loss of ventilatory drive, autonomic, cognitive, and affective deficits in congenital central hypoventilation syndrome (CCHS) patients appears throughout the brain, as demonstrated by magnetic resonance (MR) T2 relaxometry and mean diffusivity studies. However, neither MR measure is optimal to describe types of axonal injury essential for assessing neural interactions responsible for CCHS characteristics. To evaluate axonal integrity and partition the nature of tissue damage (axonal vs. myelin injury) in CCHS, we measured water diffusion parallel (axial diffusivity) and perpendicular (radial diffusivity) to rostral brain fibers, indicative of axonal and myelin changes, respectively, with diffusion tensor imaging (DTI). We performed DTI in 12 CCHS (age 18.5 + or - 4.9 years, 7 male) and 30 control (17.7 + or - 4.6 years, 18 male) subjects, using a 3.0-Tesla MR imaging scanner. Axial and radial diffusivity maps were calculated, spatially normalized, smoothed, and compared between groups (analysis of covariance; covariates, age and gender). Significantly increased radial diffusivity, primarily indicative of myelin injury, emerged in fibers of the corona radiata, internal capsule, corpus callosum, hippocampus through the fornix, cingulum bundle, and temporal and parietal lobes. Increased axial diffusivity, suggestive of axonal injury, appeared in fibers of the internal capsule, thalamus, corona radiata, and occipital and temporal lobes. Multiple brain regions showed both higher axial and radial diffusivity, indicative of loss of tissue integrity with a combination of myelin and axonal injury, including basal ganglia, bed nucleus, and limbic, occipital, and temporal areas. The processes underlying injury are unclear, but likely stem from both hypoxic and developmental processes.

Cerebral MRI abnormalities in a premature infant with later confirmed congenital central hypoventilation syndrome.

We present a premature infant with an inability to ventilate spontaneously during sleep periods. In addition, the patient showed general hypotonia. The child had a delayed passage of stool and increased anal muscle tone, indicating Hirschsprung's disease. The combination of these symptoms suggested congenital central hypoventilation syndrome, which was confirmed postmortem by DNA analysis showing a mutation in the PHOX2B gene. MRI of the brain showed damage to the white matter, including the internal capsula. This type of damage to the white matter has not been described before in a premature infant, who did not experience birth asphyxia.

Mammillary body and fornix injury in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) is accompanied by reduced ventilatory sensitivity to CO2 and O2, respiratory drive failure during sleep, impaired autonomic, fluid, and food absorption regulation, and affective and cognitive deficits, including memory deficiencies. The deficits likely derive from neural injury, reflected as structural damage and impaired functional brain responses to ventilatory and autonomic challenges. Brain structures playing essential memory roles, including the hippocampus and anterior thalamus, are damaged in CCHS. Other memory formation circuitry, the fornix and mammillary bodies, have not been evaluated. We collected two high-resolution T1-weighted image series from 14 CCHS and 31 control subjects, using a 3.0-Tesla magnetic resonance imaging scanner. Image series were averaged and reoriented to a standard template; areas containing the mammillary bodies and fornices were over sampled, and body volumes and fornix cross-sectional areas were calculated and compared between groups. Both left and right mammillary body volumes and fornix cross-sectional areas were significantly reduced in CCHS over control subjects, controlling for age, gender, and intracranial volume. Damage to these structures may contribute to memory deficiencies found in CCHS. Hypoxic processes, together with diminished neuroprotection from micronutrient deficiencies secondary to fluid and dietary absorption issues, may contribute to the injury.

Cor pulmonale due to congenital central hypoventilation syndrome presenting in adolescence.

OBJECTIVE: To report the first case of congenital central hypoventilation syndrome (CCHS) presenting with severe cor pulmonale in an adolescent. METHODS AND DESIGN: Case report and literature review. Our Institutional Review Board waived the need for consent. SETTING: Pediatric intensive care unit in a tertiary care children's hospital. PATIENT: A 12-year-old girl who developed profound hypoxia following routine dental extraction under intravenous opiate sedation and became progressively obtunded due to marked hypoventilation without hypoxic arousal, requiring mechanical ventilation. She had evidence of severe right heart failure, but no cardiac, pulmonary, neurologic, or neuromuscular cause was identified. The diagnosis of CCHS was suspected and subsequently confirmed by blood polymerase chain reaction analysis that revealed a heterozygous polyalanine expansion mutation of the PHOX2B gene (five polyalanine repeats). CONCLUSIONS: This report describes the unusual presentation of severe cor pulmonale in an adolescent with so-called "late-onset" CCHS. CCHS was previously thought to be a disease affecting only neonates, but the late-onset phenotype has now been well described in adults. It should be considered in any child presenting with unexplained right heart failure without an identifiable cause, particularly if central sleep apnea is present, because early initiation of ventilatory support can prevent cardiac and neurologic sequelae and improve outcome.

Later-onset congenital central hypoventilation syndrome due to a heterozygous 24-polyalanine repeat expansion mutation in the PHOX2B gene.

AIM: to describe a family with later onset congenital central hypoventilation syndrome (LO-CCHS) and heterozygosity for a 24-polyalanine repeat expansion mutation in the PHOX2B gene, rendered phenotypically apparent with exposure to anesthetics. CASE SUMMARY: An otherwise healthy 2.75-year-old boy presented with alveolar hypoventilation after adenoidectomy and tonsillectomy for obstructive sleep apnea, requiring invasive ventilatory support during sleep. He had a heterozygous 24-polyalanine repeat expansion in the PHOX2B gene (20/24 genotype), a genotype that has not been previously described in association with CCHS or LO-CCHS symptoms. Clinical findings in members of the family with the same 20/24 genotype ranged from asymptomatic to prolonged sedation after benzodiazepines. CONCLUSION: CCHS should be suspected in individuals presenting with unexplained hypoventilation and/or seizures after anesthetics or sedatives. This is the first report of LO-CCHS in a kindred with the PHOX2B 20/24 genotype. The incomplete penetrance observed in this family suggests a gene-environment interaction.

Parental origin and somatic mosaicism of PHOX2B mutations in Congenital Central Hypoventilation Syndrome.

Heterozygous polyalanine repeat expansions of PHOX2B have been associated with Congenital Central Hypoventilation Syndrome, a rare neurocristopathy characterized by absence of adequate control of respiration during sleep. Here we report a PHOX2B mutational screening in 63 CCHS patients, 58 of whom presenting with poly-A expansions or frameshift, missense and nonsense mutations. To assess a somatic or germline occurrence of poly-A length variations, the relative amounts of mutant and wild type alleles have been quantified in 20 selected CCHS patients presenting with an expansion, and in their parents. Somatic mosaicism was shown in four parents, while no mosaic was found among CCHS patients. Moreover, while co-segregation analysis of the PHOX2B poly-A expansions with selected marker alleles in the same 20 CCHS trios has not demonstrated any parent-of-origin effect of the mutations, it has provided further clues to clarify the molecular mechanism underlying the expansion occurrence. Finally, the segregation of PHOX2B poly-A anomalous tracts within family members has allowed us to exclude tendency of polymorphic variations towards expansion. This strengthens the notion that expanded polyalanine tracts, identified as frequent disease-causing mutations also in other human diseases, are mitotically and meiotically stable.

Diffusion tensor imaging demonstrates brainstem and cerebellar abnormalities in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) patients show reduced breathing drive during sleep, decreased hypoxic and hypercapnic ventilatory responses, and autonomic and affective deficits, suggesting both brainstem and forebrain injuries. Forebrain damage was previously described in CCHS, but methodological limitations precluded detection of brainstem injury, a concern because genetic mutations in CCHS target brainstem autonomic nuclei. To assess brainstem and cerebellar areas, we used diffusion tensor imaging-based measures, namely axial diffusivity, reflecting water diffusion parallel to fibers, and sensitive to axonal injury, and radial diffusivity, measuring diffusion perpendicular to fibers, and indicative of myelin injury. Diffusion tensor imaging was performed in 12 CCHS and 26 controls, and axial and radial diffusivity maps were compared between groups using analysis of covariance (covariates; age and gender). Increased axial diffusivity in CCHS appeared within the lateral medulla and clusters with injury extended from the dorsal midbrain through the periaqueductal gray, raphé, and superior cerebellar decussation, ventrally to the basal-pons. Cerebellar cortex and deep nuclei, and the superior and inferior cerebellar peduncles showed increased radial diffusivity. Midbrain, pontine, and lateral medullary structures, and the cerebellum and its fiber systems are injured in CCHS, likely contributing to the characteristics found in the syndrome.

[Clinical and neuropsychological characteristics in congenital central hypoventilation syndrome]. / Aspectos clinicos y neuropsicologicos del sindrome de hipoventilacion central congenita.

INTRODUCTION: Congenital central hypoventilation syndrome (CCHS) syndrome is a rare disease caused by mutations in the PHOX2B gene. Patients show a reduced response to hypercapnia and hypoxia accompanied by diffuse disturbances of the autonomic nervous system and occasionaly also disturbances in neuroimaging. A specific neuropsychological profile has not been described in children and adolescents with CCHS. CASE REPORTS: We describe three cases (aged between 4 and 19 years) with different profiles of affectation in cognitive and functionality. These profiles are compared with the features described in the literature about neuropsychology in CCHS. CONCLUSIONS: The profile of functional impairment in the CCHS is variable: in case 1, a severe global developmental delay with autistic features and marked functional involvement is described. In case 2, bilateral atrophy of the hippocampus is associated with involvement in social cognition and in executive functions with moderate functional repercussion. Case 3 shows difficulties in some cognitive executive functions (planning and non-verbal fluency), but without functional repercussion. Neuropsychological assessment can help in the clinical management of these patients by determining and guiding the need for rehabilitation treatments.

TITLE: Aspectos clinicos y neuropsicologicos del sindrome de hipoventilacion central congenita.Introduccion. El sindrome de hipoventilacion central congenita (SHCC) es una enfermedad rara producida por mutaciones en el gen PHOX2B. Los pacientes muestran una reducida respuesta a la hipercapnia e hipoxia acompañada de alteraciones difusas del sistema nervioso autonomo y ocasionalmente alteraciones en neuroimagen. No se ha descrito un perfil neuropsicologico especifico en los niños y adolescentes con SHCC. Casos clinicos. Se presentan tres casos (de edades comprendidas entre 4 y 19 años) con diferente perfil de afectacion cognitiva y funcional. Se comparan los perfiles de los tres casos con los hallazgos descritos en la bibliografia sobre neuropsicologia en el SHCC. Conclusiones. El perfil de afectacion funcional en el SHCC es variable: en el caso 1 se describe un grave retraso global en el desarrollo con rasgos autistas y acusadas implicaciones funcionales. En el caso 2, la atrofia bilateral del hipocampo se asocia a deficit en cognicion social y alteraciones en funciones ejecutivas con moderada repercusion funcional. El caso 3 muestra dificultades en algunas funciones ejecutivas cognitivas (planificacion y fluidez no verbal), pero sin repercusion funcional. La evaluacion neuropsicologica puede ayudar en el manejo clinico de estos pacientes determinando y orientando la necesidad de tratamientos rehabilitadores.

Alcohol use in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) is a rare disorder where there is failure of automatic control of breathing. With improved recognition of CCHS, more children are appropriately diagnosed and treated in infancy, allowing survival into adult years. Because most of these children are able to participate in regular school, they are exposed to common adolescent behaviors, such as abusing alcohol and drugs. Alcohol and many illicit substances are known respiratory depressants. We report on 3 cases of adolescents/young adults with CCHS who had severe adverse events related to alcohol, including coma and death. This series illustrates the dangers of alcohol abuse in CCHS. We speculate that adolescents with CCHS may be less able to perceive the risks of substance abuse and impulsive behavior, leading to increased morbidity and mortality. Patients with CCHS appear to lack anxiety and the awareness that their inability to perceive physiologically dangerous levels of hypercarbia and hypoxia deprives them of important protective mechanisms.

Neuroanatomic deficits in congenital central hypoventilation syndrome.

Congenital Central Hypoventilation Syndrome (CCHS) patients exhibit compromised autonomic regulation, reduced breathing drive during sleep, diminished ventilatory responses to chemoreceptor stimulation, and diminished air hunger perception. The syndrome provides an opportunity to partition neural processes regulating breathing and cardiovascular action. No obvious lesions appear with conventional magnetic resonance imaging; however, T2 relaxometry procedures can detect reduced cell or fiber density or diminished myelination not found with routine evaluation. High-resolution T1, proton density, and T2-weighted brain images were collected from 12 patients and 28 age- and gender-matched controls. Voxel-by-voxel T2 maps were generated from the proton density and T2-weighted images and evaluated by voxel-based-relaxometry procedures. Normalized and smoothed T2 maps were compared between groups using analysis of covariance at each voxel, with age and ventricle size included as covariates. Patients showed damaged or maldeveloped tissue, principally right-sided, including white matter from the level of the anterior cingulate cortex caudally to the level of the posterior cingulate and laterally to the posterior superior temporal cortex. Portions of the posterior, mid, and anterior cingulate, as well as the internal capsule, putamen, and globus pallidus and basal forebrain extending to the anterior and medial thalamus were affected. Deficits in the cingulum bundle and mid-hippocampus and ventral prefrontal cortex appeared, as well as the right cerebellar cortex and deep nuclei. Neuroanatomic deficiencies in limbic structures suggest a structural basis for reduced air hunger perception, thermoregulatory and autonomic deficiencies in the syndrome, while cerebellar deficits may also contribute to breathing and cardiovascular dysregulation.

Autonomic function in children with congenital central hypoventilation syndrome and their families.

STUDY OBJECTIVES: Congenital central hypoventilation syndrome (CCHS) is a genetic disorder characterized by failure of automatic control of breathing in the absence of obvious anatomic lesions. There have been several reports suggesting that CCHS patients display autonomic dysregulation. Pulse arterial tonometry (PAT) is a novel technique that provides noninvasive moment-to-moment measurements of sympathetic tone changes to the cutaneous vascular bed. We hypothesized that autonomic function as measured by PAT would be altered in children with CCHS. DESIGN: Prospective study. SETTING: CCHS Family Conference, Orlando, FL, and the local community in Louisville, KY. PARTICIPANTS: Nineteen CCHS patients and 31 parents as well as 24 control children and 15 adult control subjects. INTERVENTIONS: Children with CCHS and their parents underwent sympathetic challenges (vital capacity sigh and cold hand pressor test) and a test of reactive hyperemia (brachial artery occlusion) while PAT was continuously monitored from the right hand. Control children and control adults underwent the same procedure. MEASUREMENTS AND RESULTS: The maximal change of the PAT signal compared to the preceding baseline was averaged and expressed as percentage change for each of the challenges. The magnitude of sympathetic discharge-induced attenuation of PAT signal following a sigh was reduced in CCHS children compared to control subjects for both the vital capacity sighs and the cold hand pressor test. There were no differences observed in the magnitude of PAT attenuation between parents of children with CCHS and control adults. No differences were observed between either CCHS and control subjects or CCHS parents and adult control subjects for the brachial artery occlusion test. CONCLUSION: CCHS patients show an attenuated response to endogenous sympathetic stimulation, supporting the presence of autonomic nervous system dysfunction as a consistent feature of this condition. No differences were found in parents of children with CCHS compared to control adults, consistent with the finding that CCHS is primarily the result of a de novo gene mutation.

Hypoxia reveals posterior thalamic, cerebellar, midbrain, and limbic deficits in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) patients show deficient respiratory and cardiac responses to hypoxia and hypercapnia, despite apparently intact arousal responses to hypercapnia and adequate respiratory motor mechanisms, thus providing a model to evaluate functioning of particular brain mechanisms underlying breathing. We used functional magnetic resonance imaging to assess blood oxygen level-dependent signals, corrected for global signal changes, and evaluated them with cluster and volume-of-interest procedures, during a baseline and 2-min hypoxic (15% O(2), 85% N(2)) challenge in 14 CCHS and 14 age- and gender-matched control subjects. Hypoxia elicited significant (P < 0.05) differences in magnitude and timing of responses between groups in cerebellar cortex and deep nuclei, posterior thalamic structures, limbic areas (including the insula, amygdala, ventral anterior thalamus, and right hippocampus), dorsal and ventral midbrain, caudate, claustrum, and putamen. Deficient responses to hypoxia included no, or late, changes in CCHS patients with declining signals in control subjects, a falling signal in CCHS patients with no change in controls, or absent early transient responses in CCHS. Hypoxia resulted in signal declines but no group differences in hypothalamic and dorsal medullary areas, the latter being a target for PHOX2B, mutations of which occur in the syndrome. The findings extend previously identified posterior thalamic, midbrain, and cerebellar roles for normal mediation of hypoxia found in animal fetal and adult preparations and suggest significant participation of limbic structures in responding to hypoxic challenges, which likely include cardiovascular and air-hunger components. Failing structures in CCHS include areas additional to those associated with PHOX2B expression and chemoreceptor sites.

Neurotrophic factor expression in three infants with Ondine's curse.

This study investigates the expression of some neurotrophic factors (brain-derived neurotrophic factor, glial-derived neurotrophic factor, and nerve growth factor) in the cerebrospinal fluid of infants suffering from idiopathic congenital central hypoventilation syndrome and determines their correlations with this syndrome. Cerebrospinal fluid samples were collected from three infants suffering from idiopathic congenital central hypoventilation syndrome and 15 control subjects with obstructive hydrocephalus to measure the expression of brain-derived neurotrophic factor, glial-derived neurotrophic factor, and nerve growth factor using an immunoenzymatic assay. In the cerebrospinal fluid of patients, analysis of neurotrophic factors expression indicated a reduction, not statistically significant, of brain-derived neurotrophic factor compared with the mean level of the control group (1554 pg/mL, 1509 pg/mL, and 1582 pg/mL respectively, in comparison to 1954 +/- 103 pg/mL), whereas nerve growth factor and glial-derived neurotrophic factor did not undergo significant variations in either group. Neurotrophic factors, namely brain-derived neurotrophic factor, regulate the maturation and differentiation of respiratory neurons. The reduced expression of brain-derived neurotrophic factor in the cerebrospinal fluid samples of infants with Ondine's curse, although not statistically significant, is suggestive of a dysregulation in the brain-derived neurotrophic factor synthesis that could play an important role in the breathing disorders observed in patients with idiopathic congenital central hypoventilation syndrome.

Diaphragm pacers as a treatment for congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome is a rare syndrome present from birth, and is defined as the failure of automatic control of breathing. All patients with congenital central hypoventilation syndrome require life-long ventilatory support during sleep, although approximately a third of patients require ventilatory support 24 h per day. Diaphragm pacers offer a modality of ventilatory support that affords congenital central hypoventilation syndrome patients with maximal mobility for full-time ventilatory patients, and they may allow for a more normal lifestyle in the appropriate patient. They may permit tracheostomy decannulation in those requiring only support during sleep. Diaphragm pacing entails surgical placement of an electrode onto the phrenic nerve, connected to a subcutaneous receiver. There is an external battery-operated transmitter and antenna placed on the skin over the receiver. The transmitter emits energy, similar to radio transmission, which is converted into an electrical current by the receiver. This stimulates the phrenic nerve resulting in a diaphragmatic contraction. Settings on the transmitter include respiratory rate and electrical voltage, and are adjusted to give enough tidal volume to allow for adequate oxygenation and ventilation. Therefore, diaphragm pacing is an attractive alternative mode of mechanically assisted ventilation for many patients with congenital central hypoventilation syndrome.