How helpful are sleep studies in determining surgical need in infants with achondroplasia?
Clinical Genetics and Therapeutics
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Primary Categories:
- Clinical- Pediatric
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Secondary Categories:
- Clinical- Pediatric
Introduction:
Achondroplasia is the most common short stature skeletal dysplasia, occurring in 1:25,000-30,000 live births. It is characterized by impaired endochondral ossification which results in shortened long bones, midface retrusion, foramen magnum stenosis (FMS), varus deformity of the lower legs, and spinal stenosis. Children with achondroplasia (ACH) are at risk for sudden death in infancy due to sleep disordered breathing (SDB) and foramen magnum stenosis (FMS). Sleep studies and neuroimaging are performed in infants with ACH, but interpretation of infant studies is challenging. We sought to describe baseline data on polysomnography (PSG) indices in infants with achondroplasia as well as effects of age and surgery on these parameters.
Methods:
Retrospective data were abstracted from the 6-decade multisite CLARITY ACH REDCap database. Because the first standardized scoring manual for sleep studies was published by the American Academy of Sleep Medicine in 2007, data from PSGs was limited to those that were performed in 2008 or later in order to ensure consistency and comparability of scoring results across institutions. Both obstructive apnea hypopnea index (OAHI) and central apnea index (CAI) were extracted, and effects of age and surgical intervention (adenoidectomy [AD] or cervicomedullary decompression [CMD]) were analyzed. To identify the temporal effect of age on baseline indices (before any surgery), PSGs from surgically naïve (SN) patients were assessed over time using two separate generalized linear mixed models (LMM) which includes terms for age and also a quadratic term age2 to account for the non-linear change in indices over time during the first two years of life. To assess the influence of surgery, LMMs were limited to pre- and post-operative PSGs. Stata (v.17, College Station) was used in all analyses with significance set at a Type I error rate of 5%.
Results:
One hundred seventy-two PSGs from 86 infants met inclusion criteria. In SN children, OAHI decreased over the first year but then increased in the second year, while CAI was mostly stagnant over the first two years. There was no significant difference between age at first PSG for SN infants and patients who underwent any surgery. There were also no statistically significant differences between the indices from PSGs from SN patients and pre-op PSGs from patients that subsequently underwent surgery. Specifically, on average, the OAHI was 0.93 units higher (p=0.763) in the pre-op PSGs compared to the PSGs from SN patients. CAI was 0.58 units lower (p=0.157) on average in pre-op PSGs compared to SN but were not statistically different.
For patients who underwent an AD and/or tonsillectomy, there was a nonsignificant decrease in OAHI after the surgery (change in OAHI: -5.6, 95CI: -16.4 to 5.2), likely because of small numbers. However, when analysis was limited to patients who underwent an AD alone, a significant drop in OAHI was found (change in OAHI: -14.1, 95CI: -23.5 to -4.7). When adjusted for age, there was no significant difference in OAHI after CMD surgery (change in OAHI: 1.2, 95CI: -10.3 to 12.8). Among patients who underwent CMD, there was a significant drop in CAI (-3.3, 95CI: -5.1 to -1.5) independent of the patient’s age.
Conclusion:
The variability in OAHI and CAI in this population make them a poor benchmark in isolation for the need for surgery. We need to interpret sleep study findings of children with ACH in the context of age, particularly for obstructive indices. Improvement in OAHI after AD and the improvement in CAI after FMD suggest the surgeries did successfully treat the respective disorders of sleep. Re-evaluation of using PSGs to determine surgical risk in this population is likely needed.
Achondroplasia is the most common short stature skeletal dysplasia, occurring in 1:25,000-30,000 live births. It is characterized by impaired endochondral ossification which results in shortened long bones, midface retrusion, foramen magnum stenosis (FMS), varus deformity of the lower legs, and spinal stenosis. Children with achondroplasia (ACH) are at risk for sudden death in infancy due to sleep disordered breathing (SDB) and foramen magnum stenosis (FMS). Sleep studies and neuroimaging are performed in infants with ACH, but interpretation of infant studies is challenging. We sought to describe baseline data on polysomnography (PSG) indices in infants with achondroplasia as well as effects of age and surgery on these parameters.
Methods:
Retrospective data were abstracted from the 6-decade multisite CLARITY ACH REDCap database. Because the first standardized scoring manual for sleep studies was published by the American Academy of Sleep Medicine in 2007, data from PSGs was limited to those that were performed in 2008 or later in order to ensure consistency and comparability of scoring results across institutions. Both obstructive apnea hypopnea index (OAHI) and central apnea index (CAI) were extracted, and effects of age and surgical intervention (adenoidectomy [AD] or cervicomedullary decompression [CMD]) were analyzed. To identify the temporal effect of age on baseline indices (before any surgery), PSGs from surgically naïve (SN) patients were assessed over time using two separate generalized linear mixed models (LMM) which includes terms for age and also a quadratic term age2 to account for the non-linear change in indices over time during the first two years of life. To assess the influence of surgery, LMMs were limited to pre- and post-operative PSGs. Stata (v.17, College Station) was used in all analyses with significance set at a Type I error rate of 5%.
Results:
One hundred seventy-two PSGs from 86 infants met inclusion criteria. In SN children, OAHI decreased over the first year but then increased in the second year, while CAI was mostly stagnant over the first two years. There was no significant difference between age at first PSG for SN infants and patients who underwent any surgery. There were also no statistically significant differences between the indices from PSGs from SN patients and pre-op PSGs from patients that subsequently underwent surgery. Specifically, on average, the OAHI was 0.93 units higher (p=0.763) in the pre-op PSGs compared to the PSGs from SN patients. CAI was 0.58 units lower (p=0.157) on average in pre-op PSGs compared to SN but were not statistically different.
For patients who underwent an AD and/or tonsillectomy, there was a nonsignificant decrease in OAHI after the surgery (change in OAHI: -5.6, 95CI: -16.4 to 5.2), likely because of small numbers. However, when analysis was limited to patients who underwent an AD alone, a significant drop in OAHI was found (change in OAHI: -14.1, 95CI: -23.5 to -4.7). When adjusted for age, there was no significant difference in OAHI after CMD surgery (change in OAHI: 1.2, 95CI: -10.3 to 12.8). Among patients who underwent CMD, there was a significant drop in CAI (-3.3, 95CI: -5.1 to -1.5) independent of the patient’s age.
Conclusion:
The variability in OAHI and CAI in this population make them a poor benchmark in isolation for the need for surgery. We need to interpret sleep study findings of children with ACH in the context of age, particularly for obstructive indices. Improvement in OAHI after AD and the improvement in CAI after FMD suggest the surgeries did successfully treat the respective disorders of sleep. Re-evaluation of using PSGs to determine surgical risk in this population is likely needed.