The Tongue and Airway

Skeletal and Dentoalveolar Changes in Growing Patients Treated with Rapid Maxillary Expansion Measured in 3D Cone-Beam Computed Tomography

The skeletal and dental effects of rapid maxillary expansion (RME) have been extensively studied, but high-quality research is still needed to determine the three-dimensional (3D) effects of RME. The aim of this study was to compare skeletal and dentoalveolar parameters through cone-beam computed tomography (CBCT) pre- (T1) and post-treatment (T2) with respect to RME. Twenty growing patients (mean age 10.7 years) were treated with a Hyrax-type expander. A 3D CBCT was performed at T1 and T2, measuring nasal width, maxillary width, palatal height, maxillary arch perimeter, angulation of the upper first molar, and intermolar width. The mean palatal suture opening was 2.85 ± 0.62 mm (p < 0.0001). Nasal width increased 1.28 ± 0.64 mm and maxillary width 2.79 ± 1.48 mm (p < 0.0001). In contrast, palatal height was reduced 0.65 ± 0.64 mm (p < 0.0001). Regarding arch perimeter, the radicular perimeter increased 2.89 ± 1.80 mm, while the coronal perimeter increased 3.42 ± 2.09 mm (p < 0.0001). Molar angulation increased 5.62 ± 3.20° for the right molar and 4.74 ± 2.22° for the left molar (p < 0.0001). Intermolar width increased 5.21 ± 1.55 mm (p < 0.0001). Treatment with Hyrax produced a significant opening in the mean palatal suture. Also, a significant increase in nasal width, maxillary width, arch perimeter, molar angulation, and intermolar width, and a decrease in palatal height, were observed.

Assessment of Nutrition and Feeding Interventions in Turkish Infants with Cleft Lip and/or Palate

PURPOSE

The present study aimed to highlight the feeding challenges of infants with cleft lip and/or palate (CLP) that caregivers encounter and analyze the alternative interventions they perform based on their experiences in the preoperative period.

DESIGN AND METHODS

Parents of 200 infants with CLP were asked to complete our questionnaire. The prenatal feeding preparations, preoperative processes, and feeding challenges and modifications to overcome these difficulties were evaluated.

RESULTS

One-third of the caregivers stated that they had received feeding education prenatally. Sixty-five percent of the parents stated that they were not successful in breastfeeding. Infants with isolated cleft lip had minor feeding difficulties, whereas the ones with cleft palate had some major challenges such as aspiration, choking, and inadequate growth. Parents also reported that 59.5% of the infants with cleft had stayed in the intensive care units following birth. Moreover, 42% of the infants were initially fed by nasogastric or orogastric tube. Out of the 166 infants with cleft palate, 31.9% used palatal obturators.

CONCLUSIONS

We have reviewed the various feeding difficulties of the infants with clefts and highlighted the results of the interventions performed to overcome these difficulties for better nutrition and growth.

PRACTICE IMPLICATIONS

In the light of our findings, further studies should be conducted and additional educational programs should be implemented for both healthcare providers and parents to increase families' awareness regarding cleft feeding, prevent unnecessary and improper feeding interventions in infants with clefts, and alleviate the burden of feeding difficulties for both parents and infants.

Genioglossus Advancement and Hyoid Surgery

The structure and dimensions of the mandible, tongue, and hyoid complex are important variables in the pathophysiology of obstructive sleep apnea at the hypopharyngeal level. Genioglossus advancement is based on mandibular osteotomy, which brings the genioglossus muscle (GGM) forward and prevents posterior collapse during sleep. The genioglossus advancement technique has recently undergone several modifications; each has attempted to minimize surgical morbidity while improving the incorporation and advancement of the GGM. The hyoid bone has been of interest in sleep apnea and apnea-related surgical procedures because of its integral relationship with the tongue base and hypopharynx. Hyothyroidopexy is illustrated.

Effects of targeted activation of tongue muscles on oropharyngeal patency in the rat

Laboratory rats were acutely implanted with an electrode array composed of eight independently controllable contacts applied to ventral and dorsal aspects of the left and right hypoglossal nerves (HGNs) and their branches. Bipolar intramuscular electromyographic (EMG) electrodes were implanted into the left and right genioglossus, hyoglossus and styloglossus muscles to identify which muscles were activated during stimulation via the contacts. Elicited movements, including changes in the position of the tongue and in the size and the shape of the airway, were documented video-graphically through a surgery microscope and an endoscope. Constant current electrical stimulation activated various combinations of electrode contacts and the stimulation patterns were correlated with corresponding oral movements, airway sizes, and EMG activities. Results demonstrate that graded responses and differential activation of the various tongue muscles are achievable by stimulation of specific contacts in the electrode array. These effects are interpreted to result from the targeted activation of regions of the nerve lying under and between the electrodes. Further testing established that the muscle responses elicited by unilateral electrical stimulation with the present approach can be smoothly graded, that the muscle responses resulted in opening of the airway and could be reliably maintained for long durations.

Activation of upper airway muscles during breathing and swallowing

The upper airway is a complex muscular tube that is used by the respiratory and digestive systems. The upper airway is invested with several small and anatomically peculiar muscles. The muscle fiber orientations and their nervous innervation are both extremely complex, and how the activity of the muscles is initiated and adjusted during complex behaviors is poorly understood. The bulk of the evidence suggests that the entire assembly of tongue and laryngeal muscles operate together but differently during breathing and swallowing, like a ballet rather than a solo performance. Here we review the functional anatomy of the tongue and laryngeal muscles, and their neural innervation. We also consider how muscular activity is altered as respiratory drive changes, and briefly address upper airway muscle control during swallowing.

Tongue anatomy and physiology, the scientific basis for a novel targeted neurostimulation system designed for the treatment of obstructive sleep apnea

INTRODUCTION

 Obstructive sleep apnea (OSA) is a chronic condition that affects millions adults. The effective standard treatment is positive airway pressure (PAP). However, approximately half of the patients that are prescribed PAP are unable or unwilling to comply with this therapy. Untreated OSA ultimately leads to very serious comorbidities. An alternative therapy for this patient population, therefore, is desirable. Hypoglossal nerve (HGN) stimulation is under investigation by multiple groups as a possible alternative therapy for OSA.

OBJECTIVE

To understand the underlying mechanisms of actions related to HGN stimulation, and the implication of this knowledge for specifying and designing a neurostimulation system for the treatment of OSA.

RESULTS

 Loss of lingual and pharyngeal tone within a narrow airway is the primary mechanism for OSA. Posterior and anterior tongues are different in their anatomy and physiology. Muscle fibers in the posterior tongue are predominantly fatigue resistant that are responsible for the long sustained tonic activities required for maintaining the tongue's position and preventing its mass from falling into the retroglossal airway. The human tongue is a muscular hydrostat and hence would benefit from a sophisticated HGN stimulation system that is capable of achieving a concerted spatio-temporal interplay of multiple lingual muscles, including retrusors.

CONCLUSION

 Targeted neurostimulation of the proximal HGN presents as a viable system approach that is far more versatile and physiologic and quite different than prior systems.

Reoperative treatment of obstructive sleep apnea

Over the last several decades, various surgical treatments have been advocated and used to treat obstructive sleep apnea. Treatments ranging from aggressive procedures, such as tracheostomy, to the least-invasive procedures, such as radioablation, have not yielded satisfactory results. One of the major causes for surgical failures and lower success rates lies in the inadequate understanding and appreciation of the anatomic and pathophysiologic factors that contribute to upper airway obstruction. In some cases, combinations of various surgical techniques may help improve the conditions. This article reviews several major types of surgical procedures, their complications, and the recommended approaches for retreatments.

Is the tongue position influenced by the palatal vault dimensions?

The influence of the palatal vault dimensions on tongue position is here studied through evaluation of the in-mouth air cavity (IMAC) volume when the mandible is in maximal intercuspal position. A sample of 35 women (mean age 21.2 +/- 1.0) and 15 men (mean age 22.1 +/- 0.9) was selected. The sagittal cross-section area of the IMAC, which is modulated by the tongue position, was measured on lateral cephalograms. Dental casts were used to measure the palatal vault volume, which was defined by the occlusal plane, the hard palate and the posterior face of the second molars. Palatal vault volume allowed deduction of the IMAC volume through a rule of three procedure relating volume to area ratios. No IMAC could be calculated from cephalograms of 10 subjects who had the tongue stuck to the palate. For the 40 other subjects, the IMAC volume was 8.9 +/- 4.8 mL. It was 2 mL larger in men (n = 14) than in women (n = 26) and was the largest in skeletal Class III and the smallest in skeletal Class II (P > 0.05). IMAC volume was strongly correlated with palatal vault height but neither with palatal width nor length. It was thus assumed that the height of the palatal vault could influence the most observed position of the tongue but this does not exclude a possible growth influence of the tongue on its surrounding skeletal structures.

Dental arch morphology in children with sleep-disordered breathing

The aim of the present study was to examine the effects of nocturnal breathing disorders such as obstructive sleep apnoea (OSA) and snoring on developing dental arches. The study group comprised 41 children (22 males, 19 females, mean age 7.2 years, standard deviation 1.93) with diagnosed OSA. Age- and gender-matched groups of 41 snoring and 41 non-obstructed control children were selected. Orthodontic examination was carried out and dental impressions were taken. Malocclusions were diagnosed clinically and 13 linear variables were measured from the dental casts. The differences between the dental arch measurements of the OSA, snoring, and control groups were studied using analysis of variance followed by Duncan's multiple comparison method. Children with diagnosed OSA had a significantly increased overjet, a reduced overbite, and narrower upper and shorter lower dental arches when compared with the controls. Snoring children had similar but not as significant differences as OSA children when compared with the controls. There were more children with an anterior open bite (AOB) in the OSA group (P=0.016) and with a Class II or asymmetric molar relationship in the groups of OSA (P=0.013) and snoring (P=0.004) subjects compared with the non-obstructed controls. There were more subjects with mandibular crowding (P=0.002) and with an AOB (P=0.019) with an increasing obstructive apnoea-hypopnoea index (AHI). These findings are in agreement with previous studies of the effects of increased upper airway resistance on dental arch morphology and can be explained by long-term changes in the position of the head, mandible, and tongue in order to maintain airway adequacy during sleep.

The role of malocclusion in non-obese patients with obstructive sleep apnea syndrome

OBJECTIVE

The maxillofacial characteristics of patients with obstructive sleep apnea syndrome (OSAS) have previously been analyzed using standard cephalometric analysis. Malocclusion influences the occurrence of sleep apnea, but the pathology of malocclusion in OSAS has not yet been fully investigated. Therefore, we investigated malocclusion in patients with OSAS using cephalometric and dental analysis.

METHODS

Cephalometric and dental analyses were performed to evaluate malocclusion in 97 male patients with OSAS (49.7+/-11.7 years). The number of apnea and hypopnea episodes per hour (apnea-hypopnea index: AHI) was determined by standard polysomnography.

RESULTS

The overall prevalence of severe overjet (the horizontal distance between the upper and lower incisors of >or=6 mm) was 43.3%. AHI was significantly correlated with body mass index (BMI) in obese OSAS patients (r=0.385, p=0.010), whereas it was significantly correlated with overjet in non-obese OSAS patients (BMI<25 kg/m2) (r=0.313, p=0.022). Multiple regression analysis revealed that BMI was the significant factor contributing to increased AHI in all patients, and overjet was in non-obese OSAS patients. There were no significant differences between non-obese and obese OSAS patients in the angle of protrusion of the superior alveolar base (SNA) or in the angle of protrusion between the superior and inferior alveolar bases (ANB). The angle of protrusion of the inferior alveolar base (SNB) was significantly smaller in non-obese than in obese OSAS patients.

CONCLUSION

We have shown that overjet was associated with the severity of OSAS in non-obese patients. Our findings suggest that malocclusion may play an important role in the development of sleep apnea/hypopnea.

Effect of pacifier use on mandibular position in preterm infants

AIM

It has been hypothesized that the association of pacifier use with reduced risk of sudden infant death is mediated by forward movement of the mandible and tongue that helps open the upper airway. Our aim was to examine whether the mandible is moved forward when an infant is sucking on a pacifier, and if so, whether the mandible remains advanced after the pacifier is removed.

METHODS

In sixty clinically stable premature infants (corrected gestation age 36.5 +/- 0.3 weeks, mean +/- SEM) the distance from each ear where the pinna met the cheek to the most prominent point of the chin was measured bilaterally, and the average was used as an index of mandibular position. Mandibular position was determined before and after allowing the infants to suck on a pacifier for 10-15 min, and after removing the pacifier.

RESULTS

There was a significant forward movement of the mandible when the infants were sucking on the pacifier (59.5 +/- 0.7 vs. 58.6 +/- 0.7 mm, p = 0.001), with no significant change after the pacifier was removed.

CONCLUSIONS

Pacifier use in preterm infants was associated with a small significant forward displacement of the jaw. These data suggest that pacifier use may help protect the upper airway.

Long-term sequellae of oral appliance therapy in obstructive sleep apnea patients: Part 2. Study-model analysis

INTRODUCTION

Side effects observed in the occlusion and dental arches of patients using an oral appliance (OA) to treat snoring or sleep apnea for more than 5 years have not yet been investigated.

METHODS

Stone casts trimmed in centric occlusion before appliance placement and after an average of 7.4 +/- 2.2 years of OA use in 70 patients were compared visually by 5 orthodontists.

RESULTS

Of these patients, 14.3% had no occlusal changes, 41.4% had favorable changes, and 44.3% had unfavorable changes. Significant changes in many variables were found. Patients with greater initial overbites and Class II Division 1 and Class II Division 2 malocclusions were more likely to have favorable or no changes. More favorable changes in overbite occurred in subjects with large baseline overbites. A greater baseline overjet and more distal mandibular canine relationship were correlated to favorable changes. A greater initial overjet was correlated to a more favorable change, a decrease in mandibular crowding, a smaller change in anterior crossbite, and a greater change in overjet.

CONCLUSIONS

OA wear after a mean of 7.4 years induces clinically relevant changes in the dental arch and the occlusion.

Cephalometric and fiberoptic evaluation as a case-selection technique for obstructive sleep apnea syndrome (OSAS)

In order to obtain relatively simple and useful parameters to estimate the severity of obstructive sleep apnea syndrome (OSAS), cephalometric and fiberoptic studies were performed in 64 clinical cases previously diagnosed with either OSAS or snoring. Fourteen cephalometric parameters, 13 parameters derived from physical examination and 18 fiberoptic parameters were compared with the apnea index (AI), the apnea-hypopnea index and lowest SaO2 values. Statistically significant correlations were found between the Al and the shortest linear distance from the posterior line of the soft palate to the posterior pharyngeal wall measured along a line parallel to the supramentale-Gonion line (PAS-epipharynx distance), the distance from the mandibular plane to the most anterior and superior point on the body of the hyoid bone obtained from cephalometry (MP-H distance) and the degree of redundancy of mucosa in the arytenoid/aryepiglottic fold obtained from videoendoscopy. An increased Al was observed when the PAS-epipharynx distance was < 7 mm and there was 100% obstruction in Muller's maneuver at the palate level (supine), the MP-H distance was > 27.4 mm and the mucosa of the arytenoid/aryepiglottic fold was markedly redundant. As these three parameters are relatively easy to obtain on an outpatient basis, it is suggested that they could be used in an outpatient setting to provide a good prediction of the severity of OSAS.

A practical method for describing patterns of tongue-base narrowing (modification of Fujita) in awake adult patients with obstructive sleep apnea

PURPOSE

The purpose of the present study was to evaluate a clinically practical classification system for tongue-base narrowing and to assess intrarater and interrater reliability of the proposed system.

PATIENTS AND METHODS

A population of 248 consecutive patients with polysomnographically proven upper airway obstructive pathology were evaluated (using the hypotonic method) for evidence of upper airway narrowing with the commonly available techniques of fiberoptic nasopharyngoscopy, clinical examination and lateral cephalometric analysis.

RESULTS

Four basic patterns of tongue-base narrowing have been discerned to occur in awake adult patients with diagnosed obstructive upper airway pathology. These include type A (high tongue base), type B1 (high tongue base with retroepiglottic narrowing), type B2 (diffuse tongue-base narrowing), and type 3 (isolated retrogepiglottic narrowing). These recognized patterns have been found to have high intraexaminer and interexaminer reliability. No statistical correlation was found between tongue-base pattern and severity of obstructive sleep apnea, age, or facial skeletal pattern. Males had a higher percentage of type C pattern, and the type A pattern patients tended to have a higher body mass index.

CONCLUSIONS

Potential future uses of this classification system include the ability to more practically assess and describe anatomic locations of tongue-base narrowing and to permit an improved means of comparing the results of various surgical and nonsurgical therapies.

Differential diagnosis of obstructive sleep apnea syndrome patients and snorers using cephalograms

Severe snoring is thought by many to be an early stage of obstructive sleep apnea syndrome (OSAS), but the anatomical relation between snoring and OSAS, if any, has remained unclear. To compare the morphology of the airway between snorers and OSAS patients for possible similarities, we conducted a cephalometric analysis of Japanese OSAS patients (n=10), habitual snorers (n=10), and non-snoring controls (n=50). There was no significant difference in SNB (the angle formed by the sella, nasion and point B) between OSAS patients and the control subjects. Obstructive sleep apnea syndrome patients tended to have an anteriorly positioned maxilla, and an anteroposterior misalignment between the maxilla and mandible. There was also a tendency toward skeletal openbite. Both OSAS patients and snorers had large tongues and large soft palates, thus causing constriction of the airway with resultant smaller airway diameter and smaller airway surface area. Significant differences between OSAS patients and snorers were found in thickness and length of soft palate surface area, and thickness, length, and position of the hyoid bone. These results suggest that cephalographic measurements may be of considerable use in determining the seriousness of a patient's condition.

Physical findings and the risk for obstructive sleep apnea. The importance of oropharyngeal structures

In this study, we hypothesized that anatomic abnormalities of the oropharynx, particularly narrowing of the airway by the lateral pharyngeal walls, tonsils, and tongue, would be associated with an increased likelihood for obstructive apnea among patients presenting to a sleep disorders center. To test this hypothesis, we used data from a cohort of 420 patients presenting to the Penn Center for Sleep Disorders. Associations between individual variables in the clinical evaluation model and sleep apnea as defined by a respiratory disturbance index greater than or equal to 15 events per hour were characterized by odds ratios (ORs) with 95% confidence intervals (CIs). Multivariable logistic regression was used to simultaneously estimate ORs for multiple variables and to control for other relevant patient characteristics. Results showed that narrowing of the airway by the lateral pharyngeal walls (OR = 2.5; 95% CI, 1.6-3.9) had the highest association with obstructive sleep apnea (OSA) followed by tonsillar enlargement (OR = 2.0; 95% CI, 1.0-3.8), enlargement of the uvula (OR = 1.9; 95% CI, 1.2-2.9), and tongue enlargement (OR = 1.8; 95% CI, 1.0-3.1). Low-lying palate, retrognathia, and overjet were not found to be significantly associated with OSA. Controlling for BMI and neck circumference, only lateral narrowing and enlargement of the tonsils maintained their significant (OR = 2.0 and 2.6, respectively). A subgroup analysis examining differences between male and female subjects showed that no oropharyngeal risk factor achieved significance in women while lateral narrowing was the sole independent risk factor in men. These findings suggest that enlargement of the oropharyngeal soft tissue structures, particularly the lateral pharyngeal walls, is associated with an increased likelihood of OSA among patients presenting to sleep disorders centers.

State-related changes in upper airway caliber and surrounding soft-tissue structures in normal subjects

State-dependent changes in upper airway caliber were studied with magnetic resonance imaging (MRI) techniques. We hypothesized that changes in airway caliber during sleep in normal subjects would result from positional and dimensional changes in upper airway soft-tissue structures, including the lateral pharyngeal walls, tongue, and soft palate. We used MRI to study 15 normal subjects during wakefulness and sleep. Sleep was facilitated by one night of sleep deprivation prior to MRI. During sleep, the volume of the retropalatal (RP) airway was reduced by 19% (p = 0.03). The volume of the retroglossal (RG) airway was not significantly reduced during sleep, suggesting that the RP region may be more likely to collapse. The mean minimal cross-sectional airway area was reduced by 228% (p = 0.004) in the RP and by 22% (p = 0.02) in the RG region during sleep as compared with values in anatomically matched axial images during wakefulness. Airway anteroposterior (AP) and lateral dimensions were also significantly reduced in the RP region. Airway narrowing in the RP region was associated with a 7% increase in thickness of the lateral pharyngeal walls (p = 0.04). In nine subjects, sagittal data showed significant posterior displacement of the soft palate during sleep as compared with wakefulness. Multiple linear regression analyses indicated that reduction in the RP airway area during sleep resulted from posterior movement of the soft palate, thickening of the lateral pharyngeal walls, and an increase in tongue oblique distance. We conclude that the lateral pharyngeal walls play an important role in upper airway narrowing during sleep in normal subjects.

Oropharyngeal fatty infiltration in obstructive sleep apnea patients: a histologic study

It has been suggested that due to fatty infiltration, obstructive sleep apnea (OSA) patients have a narrower pharyngeal airway than normal persons. To identify potential fatty infiltration of pharyngeal tissues that may contribute to OSA, a histologic study of the distal soft palate was performed. Histologic sections of 46 oropharyngeal specimens were evaluated. This included 25 overweight OSA patients (25/31), 6 normal-weight OSA patients (6/31), and a control group of 15 healthy (non-OSA) individuals. A semiquantitative analysis of the fatty tissue was performed. In all 31 OSA patients an excess of fatty infiltration was found in the histologic oropharyngeal specimens in comparison to the control group. No correlation was found between the pharyngeal fatty infiltration degree, the body mass index, and the apnea index. Irrespective of their body weight, in none of the patients without OSA was excessive fatty infiltration seen. It is suggested that excessive pharyngeal fatty infiltration plays a role in upper airway obstruction in OSA and that it can be associated with the development of apnea.

A method to evaluate upper airway mechanics following intervention in snorers

PURPOSE

To describe a method that measures multisegment upper airway changes following intervention for snoring and obstructive apnea that controls for physiological fluctuations during sleep.

PATIENTS AND METHODS

Retropalatal, retroglossal, and retrohyoid airway segments were evaluated before and after application of an oral appliance (OA) in four snoring subjects. Twelve airway segments were evaluated. Physiological fluctuations during sleep were controlled with variably applied nasal continuous positive pressure (CPAP), benzodiazepam-induced sleep, and obtaining measures at zero flow on the first test breath. Airway area was measured endoscopically.

RESULTS

The methodology identified that following intervention with an OA, maximum retroglossal airway size increased 23.3% +/- 7.5% (P < .05) and retrohyoid size decreased -63.5% +/- 16.0% (P < .05). No changes in retropalatal area (-2.5% +/- 3.0%) or closing pressure were observed. The level of primary obstruction shifted inferiorly in one patient. Airway measures prior to intervention showed small alterations of applied pressure (1 cm H2O) changed retropalatal and retroglossal area an average of 10% +/- 0.9%/cm H2O.

CONCLUSION

The mechanical effects of limited airway intervention can be measured with a hypotonic, pressure-controlled methodology. At small airway areas, the airway is highly collapsible and airway size fluctuates. Small changes in applied or physiological forces may alter the airway as significantly as the effects of the intervention being evaluated. The hypotonic upper airway method provides a method to control airway collapse and evaluate interventions, such as OA or surgery, for snoring and obstructive sleep apnea syndrome.

Cephalometric comparisons of craniofacial and upper airway structure by skeletal subtype and gender in patients with obstructive sleep apnea

To investigate whether patients with obstructive sleep apnea (OSA) have abnormalities in their craniofacial and upper airway (UA) structures compared with normal subjects, cephalometric comparisons were systematically performed in both the upright and the supine positions in subjects with and without OSA, who were then grouped according to their craniofacial skeletal type and gender. A total of 347 patients with OSA and 101 control subjects were divided into male and female groups and then classified into Class I (CI), Class II, Division 1 (CII/1), Class II, Division 2 (CII/2), and Class III (CIII) skeletal subtypes. In the upright position, the most atypical craniofacial and UA structure was shown in male patients with CI OSA. In patients with OSA, the degree of UA abnormalities was less in the supine position regardless of skeletal subtype. In the supine position, the most atypical craniofacial and UA structure was also shown in male patients with CI OSA; there were no significant differences between male patients with CII/2 OSA and control subjects or between female patients with CI OSA and control subjects. With a change in body position from upright to supine, distinctive changes in the UA structure in both patients with OSA and control subjects occurred, according to skeletal subtype and gender. We conclude that there are a series of characteristics of craniofacial and UA structure that differ between patients with OSA and control subjects matched for skeletal subtype and gender. These differences may predispose to UA obstruction during sleep in patients with OSA.

Diagnostic difficulties in cases of sudden death in infants with mandibular hypoplasia

Infants with mandibular hypoplasia are at risk of sudden death from cardiorespiratory arrest secondary to upper airway obstruction. To evaluate diagnostic difficulties that may occur at autopsy in such infants, the autopsy files at the Adelaide Children's Hospital (ACH) for 36 years, 1959 to 1994, were reviewed. Eight cases were identified (age range, 2 days to 10 months; mean age, 2.2 months; male/female ratio, 5:3). In all cases, death was considered most likely due to airway obstruction related to mandibular hypoplasia or its treatment. Although death occurred in the hospital in five cases, one infant suddenly collapsed at home while feeding and died, and two infants were unexpectedly found dead in their cribs at home. Three infants had defined genetic syndromes. Although all the infants had histories of antemortem airway obstruction, one infant had normal oxygen saturation studies before hospital discharge, and one infant had a tracheostomy. Acute bronchopneumonia was an exacerbating factor in one case. Assessment of mandibular size is important in any infant who dies unexpectedly; and if hypoplasia is found, careful review of the clinical details for evidence of airway obstruction is necessary to help distinguish these cases from sudden infant death syndrome (SIDS). Sudden death may, however, occur in infants with mandibular hypoplasia in spite of apparent clinical stability before death with no significant recent episodes of oxygen desaturation.

Effects of electrical stimulation to the soft palate on snoring and obstructive sleep apnea

Obstructive sleep apnea (OSA) is a disorder and has been associated with social and physical problems. Many treatments of OSA have been proposed with various levels of success. Seven patients with histories of snoring and OSA participated in this pilot study to evaluate the effects of electrical stimulation to the soft palate. Each patient slept with a palatal appliance that delivered a weak electrical stimulus to the soft palate on activation. A 3 milliampere stimulus in the range of 9 to 10 volts was found to be effective in terminating snoring without causing patient arousal. The effects of the stimulus on OSA were variable. The results of this study indicated that electrical stimulation of the soft palate may be effective as a treatment for snoring and OSA and warrants further investigation.

Thyrotropin-releasing hormone inputs are preferentially directed towards respiratory motoneurons in rat nucleus ambiguus

In the present study, we assessed the extent of the thyrotropin-releasing hormone (TRH) input to motoneurons in the ambigual, facial, and hypoglossal nuclei of the rat using a combination of intracellular recording, dye filling, and immunohistochemistry. Twelve motoneurons in the rostral nucleus ambiguus were labelled by intracellular injection in vivo of Neurobiotin (Vector). Seven out of 12 ambigual motoneurons displayed rhythmic fluctuations of their membrane potential in phase with phrenic nerve discharge, whereas the other five had no modulations of any kind. Seven facial motoneurons and seven hypoglossal motoneurons were also filled with Neurobiotin. All three motor nuclei contained TRH-immunoreactive varicosities, with the largest numbers found in the nucleus ambiguus. Close appositions were seen between TRH-immunoreactive boutons and every labelled motoneuron. Respiratory-related motoneurons in the nucleus ambiguus received the largest number of TRH appositions with 74 +/- 38 appositions/neuron (mean +/- S.D.; n = 7). In contrast, nonrespiratory ambigual motoneurons received significantly fewer TRH appositions (11 +/- 5; n = 5; P < 0.05; Mann-Whitney U test). Facial motoneurons received about the same number of TRH appositions as nonrespiratory ambigual motoneurons, with 13 +/- 4 (n = 7). Hypoglossal motoneurons received the fewest appositions from TRH-containing boutons, with 8 +/- 2 (n = 7). There were no differences in the TRH inputs to respiratory and nonrespiratory motoneurons in the facial and hypoglossal nuclei. These results demonstrate that, among motoneurons in the medulla, respiratory motoneurons in the rostral nucleus ambiguus are preferentially innervated by the TRH-immunoreactive boutons.