David C. Johnsen

Genioglossus Response to Airway Occlusion in Apneic Versus Nonapneic Infants

ABSTRACT. The ability to maintain pharyngeal patency is compromised in infants who have apneic episodes associated with airway obstruction. Since the genioglossus (GG) muscle is thought to be important in maintaining pharyngeal patency, we measured the GG EMG with sublingual surface electrodes during unobstructed breathing and in response to end-expiratory airway occlusion. Studies were performed in nine premature infants with mixed and obstructive apnea and in eight nonapneic control infants. Phasic GG EMG was usually absent during normal tidal breathing in both groups of infants, however, GG activity typically appeared during airway occlusion. The response of the GG muscle during airway occlusion differed between control and apneic infants. During the first three occluded inspiratory efforts, control infants had 42 ± 5, 74 ± 5, and 80 ± 5% (mean ± SEM) of their occlusions associated with a GG EMG response, respectively. In contrast, apneic infants had significantly fewer (13 ± 4, 38 ± 9, and 52 ± 9%) occlusions associated with a GG EMG response. There was a delay in onset of the GG EMG when compared to the onset of the diaphragm EMG and initial negative esophageal pressure swing, but this delay decreased with each subsequent appearance of the GG EMG in both infant groups. Infants with mixed and obstructive apnea thus have decreased activation of their GG in response to occlusion which may reflect their inability to recruit dilating muscles of the upper airway during spontaneous airway obstruction.

The role of the pediatrician in identifying and treating dental caries.

Although dental caries has been reduced greatly in the last two generations, this infectious disease persists. The pediatrician can play a direct and indirect role in preventing dental caries. The pediatrician can provide counseling on feeding practices to prevent baby bottle tooth decay as well as identify children at risk. Dental caries of the grooves of molar teeth now accounts for dental caries in more children than any other form of caries. Dental sealants are recommended to coat the grooves and prevent dental caries. Restoration of decayed teeth is the most direct means of treating dental caries.

Hearing and neurologic impairment: insult timing indicated by primary tooth enamel defects.

The association between hearing loss, neurologic impairment, and primary tooth enamel defects was examined in a group of 88 children presenting for hearing evaluation at a tertiary care childrens hospital. Forty-one had classifiable enamel defects, reflecting the time and duration of prenatal or perinatal insult. Hearing loss was more prevalent and severe in 19 children with enamel defects of the incisal tooth edge (mean = 61 dB) reflecting a systemic insult at 14 to 16 weeks gestation, than in 7 children with cervical third tooth defects (mean = 23 dB) reflecting insult near term (X2 = 4.08; p less than 0.05). Audiometric findings among the 15 children with incisor defects of the middle third varied; 7 had significant hearing loss and 8 were normal. A correlation was observed between severity of hearing loss (in dB) and estimated time of systemic insult (in weeks gestational age) determined by tooth defect site (r = -0.48; p less than 0.01). The neurologic data revealed similar trends. The group with early systemic insults more frequently had moderate or severe neurologic deficits known to originate early in fetal development. The two groups with third trimester or term insults tended to have mild or no neurologic impairment. A differential susceptibility for developing auditory and neurologic structures based on insult timing is supported.

Hearing deficits correlated with the timing of systemic disturbance as indicated by primary incisor defects

A correlation of hearing deficits and enamel defects was investigated in 18 children presenting to a pediatric neurology service for hearing evaluation. Eleven had enamel defects. Five had defects consistent with a systemic insult occurring as early as 14 weeks gestation, two between 29 to 33 weeks gestation, and four near term. Hearing loss was more severe-in the five with enamel defects occurring in the mid-trimester (&OV0398; = 70 dB) than in the four subjects with defects occurring around term (&OV0398; = 23 dB) (t = 3.8; p <0.01). Of the remaining two subjects, one had normal hearing and the other had a moderate loss. A correlation was found between the average degree of hearing loss (in dB) versus the estimated time of systemic insult in weeks gestational age as indicated by position of the tooth defect (r = −0.78; p <0.01). Neurological profiles also differed with those having early defects being more severe. These findings suggest a differential susceptibility for developing audiological (and possibly other neurological) structures based on insult timing.

1307 HEARING LOSS AND NEUROLOGIC IMPAIRMENT: TIMING OF SYSTEMIC INSULT AS INDICATED BY TOOTH DEFECTS

Hearing loss and primary tooth defects have been separately associated with neurological impairment, but have not been systematically examined in the same population. To investigate the association of these defects and to explore their potential use as prenatal biological markers, 18 children presenting for hearing evaluation were examined. 11 had enamel defects. 5 had defects consistent with a systemic insult occurring in the 2nd trimester, 2 between 29-33 wks gestation, and 4 near term. Hearing loss was more severe in the 5 with enamel defects occurring in the mid-trimester x=70 dB), than in the 4 subjects with defects occurring around term x=23 dB) (t=3.1; p<.05). Of tne remaining two subjects, one had normal hearing and the other had a moderate loss. A correlation was found between the average degree of hearing loss (in dB) vs. the estimated time of systemic insult (in wks gestational age) as indicated by position of tooth defect (r=-.78; p<.01). Neurological profiles also differed. Developmental delay was more prevalent and more marked in the group with defects occurring in the mid-trimester vs. term; 4/5 children in the former group had visual/occulomotor defects compared to none in the latter group. These findings suggest a differential susceptibility for developing neurologic structures such that a given systemic insult occurring in the mid-trimester of pregnancy appears to have more serious ramifications regarding subsequent auditory and neurologic function, than those occurring late in gestation.