MAGNETIC RESONANCE IMAGING OF THE UPPER AIRWAY IN CHILDREN WITH DOWN SYNDROME

To the Editor :

Uong and colleagues (1) used magnetic resonance imaging to study the upper airway in children with Down syndrome who had no associated obstructive sleep apnea syndrome (OSAS). The patients with OSAS were excluded on the basis of a questionnaire developed by Brouillette and colleagues (2). These authors designed a clinical scoring system to differentiate 1 to 10 year-old children, with and without OSAS, without a background of adenotonsillectomy, neurological diseases, or craniofacial abnormalities. Considering the data of all the groups studied, we detected the following: (1) no child with an index under 1 had OSAS; (2) an index greater than 3.5 was highly predictive of OSAS; and (3) in children with an index ranging from 1 to 3.5, additional studies would be necessary in order to determine if there is obstruction of the upper airway or not.

We recently conducted a study in which we evaluated 192 consecutive children with adenotonsillar hypertrophy, without any associated diseases or craniofacial abnormalities (3). In every case, the Brouillette index was calculated and OSAS was confirmed by a polygraphic study (Apnoescreen II+; Jäeger-CNS, Minneapolis, MN). An apnea-hypopnea index (AHI) greater than or equal to five was considered diagnostic. Table 1 shows the results of the Brouillette index in our population of patients. From the patients having a Brouillette index less than 1, it can be seen that 41.1% really have OSAS. If these results are applied to the data of Uong and colleagues, the following results would be obtained: at least 5 of the 14 patients from the control group, all of them with a Brouillette index lower than 1, could have been poorly classified and could have OSAS.

More recently, we carried out a study on 108 patients with Down syndrome, with a mean age of 7.9 ± 4.5 years (4). The clinical history included a questionnaire answered by the parents, and all patients underwent cardiorespiratory polygraphy (Apnoescreen II+). An AHI greater than or equal to five was used for diagnosis. The results of the Brouillette index in our population of patients are listed in Table 1. Of the patients with Brouillette index under 1, 42.8% had OSAS. In the study by Uong and colleagues, 8 of the 11 children with Down syndrome had a Brouillette index under 1, so that no additional studies were performed to exclude OSAS. If our results are taken into consideration, at least three of them would have OSAS, so that they would have been poorly classified.

According to these results, it is possible that there may have been some deficiencies in the choice of non-OSAS patients in the study by Uong and colleagues. Thus, five subjects in the control group and three in the Down syndrome group may have been poorly classified. This selection bias may have influenced the results obtained. In fact, we think that at least one polygraphic study should have been performed in all the patients.

Hospital Clínico San Carlos, Madrid, Spain

José Ramón Villa-Asensi

Hospital Niño Jesús, Madrid, Spain

1. Uong EC, McDonough JM, Tayag-Kier CE, Zhao H, Haselgrove J, Mahboubi S, Schwab RJ, Pack AI, Arens R. Magnetic resonance imaging of the upper airway in children with Down syndrome. Am J Respir Crit Care Med 2001; 163: 731-736 [Abstract/Free Full Text].

2. Brouillette R, Hanson D, David R, Klemka L, Szatkowski A, Fernbach S, Hunt C. A diagnostic approach to suspected obstructive sleep apnea in children. J Pediatr 1984; 105: 10-14 [Medline].

3. Villa JR, De Miguel J, Romero F, Campelo O, Sequeiros A, Muñoz-Codoceo R. Utilidad del índice de Brouillette para el diagnóstico del síndrome de apnea del sueño infantil. An Esp Pediatr 2000; 53: 547-552 [Medline].

4. De Miguel J. Síndrome de apnea obstructiva del sueño en pacientes con síndrome de Down. Doctoral Thesis. Universidad Autónoma, Madrid; 2001.

From the Authors:

We read with interest the letter from Dr. de Miguel-Diez and colleagues who raise the question of a possible selection error in our study (1) by applying the Brouillette score (2) to our control subjects and subjects with Down syndrome. Based on their data (3), they raise a possibility that as many as 5 of 14 control subjects and 3 of 11 subjects with Down syndrome were incorrectly classified as free of obstructive sleep apnea (OSA).

It should be noted that the control group in our study was not similar to the group studied by Dr. de Miguel-Diez and colleagues (3), and therefore, inferring the possibility of OSA in our control group is inappropriate. We studied normal children who were referred to our Radiology Department to obtain a brain MRI, who had no risk factors for OSA by history and examination, and for whom the above scoring system was previously validated (2). In contrast, Dr. de Miguel-Diez and colleagues applied the Brouillette score to a group of patients with adenotonsillar hypertrophy who were referred for possible OSA. They found, as previously reported by Carroll and colleagues (4), that the Brouillette score was insufficient to discriminate between snoring and OSA in the latter subjects.

In regard to Down syndrome subjects, all subjects were recruited by advertisement and had no history of sleep-disordered breathing. Because the Brouillette score has not been validated in this particular group, we applied it with caution and performed polysomnography on children with indeterminate scores to rule out the existence of OSA. Moreover, as reported in our paper, all subjects, including those with negative Brouillette scores, were monitored continuously during the sedation period until full recovery (about 1 hour) and none experienced any snoring, apnea, or oxygen desaturations, suggesting no significant OSA.

The data Dr. de Miguel-Diez and colleagues present on subjects with Down syndrome (5) suggesting a limitation of the Brouillette score in determining the existence of OSA in this group is interesting and may have clinical relevance to these patients when published in full format. However, we were unaware of the above information at the time of our submission since it was not yet published.

The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania

1. Uong EC, McDonough JM, Tayag-Kier CE, Zhao H, Haselgrove J, Mahboubi S, Schwab RJ, Pack AI, Arens R. Magnetic resonance imaging of the upper airway in children with Down syndrome. Am J Respir Crit Care Med 2001; 163: 731-736 .

2. Brouillette R, Hanson D, David R, Klemka L, Szatkowski A, Fernbach S, Hunt C. A diagnostic approach to suspected obstructive sleep apnea in children. J Pediatr 1984; 105: 10-14 .

3. Villa JR, De Miguel J, Romero F, Campelo O, Sequeiros A, Muñoz-Codoceo R. Utilidad del índice de Brouillette para el diagnóstico del síndrome de apnea del sueño infantil. An Esp Pediatr 2000; 53: 547-552 .

4. Carroll JL, McColley SA, Marcus CL, Curtis S, Loughlin GM. Inability of clinical history to distinguish primary snoring from obstructive sleep apnea syndrome in children. Chest 1995; 108: 610-618 [Abstract/Free Full Text].

5. De Miguel J. Síndrome de apnea obstructiva del sueño en pacientes con síndrome de Down. Doctoral Thesis. Universidad Autónoma, Madrid; 2001.