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Original Research |
1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333
Burnet Ave., MLC 5031, Cincinnati, OH 45229-3039.
2 Department of Pediatrics, Cincinnati Children's Hospital Medical Center,
Cincinnati, OH.
3 Division of Otolaryngology, Cincinnati Children's Hospital Medical Center,
Cincinnati, OH.
Received August 13, 2007;
accepted after revision October 17, 2007.
Address correspondence to L. F. Donnelly
(Lane.Donnelly{at}cchmc.org).
Abstract
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SUBJECTS AND METHODS. Seventy-one obese children (mean body mass index = 41.6 kg/m2) underwent sagittal fast spin-echo inversion recovery imaging. Lingual tonsils were identified and measured in the greatest anteroposterior diameter. Lingual tonsils > 10 mm were considered markedly enlarged. The subgroup with absent palatine tonsils (previous tonsillectomy) (n = 41) were compared with those with palatine tonsils present (n = 30).
RESULTS. Forty-four (62%) of the obese children had measurable lingual tonsils, which is greater than the frequency previously reported in normal subjects (0%), subjects with obstructive sleep apnea (33%), or subjects with Down syndrome and obstructive sleep apnea (50%). Ten (14%) had lingual tonsils > 10 mm. Obese subjects with absent palatine tonsils (previous tonsillectomy) had a higher prevalence of measurable lingual tonsils than those with palatine tonsils (78% vs 22%, respectively; p < 0.001) and a higher prevalence of lingual tonsils > 10 mm (90% vs 10%, p < 0.001).
CONCLUSION. Obese children have a high frequency of enlargement of the lingual tonsils with a significantly higher prevalence in those with previous tonsillectomy. Enlarged lingual tonsils may play a role in the pathogenesis of obstructive sleep apnea in obese children.
Keywords: adenoidectomy • childhood obesity • lingual tonsils • obstructive sleep apnea • pediatric imaging • tonsillectomy
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Enlargement of the lingual tonsils is increasingly being recognized as a cause of obstructive sleep apnea [1–4] and has been identified as a significant cause of obstructive sleep apnea, particularly in children with Down syndrome who have undergone palatine tonsillectomy and adenoidectomy. In this patient population, it is a cause of persistent sleep apnea in 35% [2]. It is important to identify enlargement of the lingual tonsils as a cause of obstructive sleep apnea because it is one of the surgically curable causes of obstructive sleep apnea [4]. We have subjectively recognized an increased incidence of lingual tonsillar enlargement in obese children. The purpose of this study was to evaluate the frequency of enlarged lingual tonsils in obese children.
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Subjects
Children were recruited for MRI as part of a research protocol. Subjects
were recruited from obese children seeking treatment at our institution's
sleep center. Children were imaged while well and without upper respiratory
illness.
The inclusion criteria were as follows: age of > 13 and < 21 years at evaluation visit and obesity, defined as body mass index (BMI) > 95th percentile for age and sex. The exclusion criteria were a craniofacial deformity, ongoing orthodontic problems requiring braces, pregnancy, weight > 375 lb (169 kg) or BMI > 55 kg/m2.
MRI Sequence
The size of the lingual tonsils was measured on fast spin-echo (FSE)
inversion recovery (IR) images. All imaging studies were obtained on a 1.5-T
unit (Signa Excite HD, GE Healthcare) with subjects positioned supine within a
head and neck vascular coil. The technical parameters for the sagittal FSE IR
images included a TR/TE, 5,000/34; echo-train length, 12; field of view, 22
cm; slice thickness, 6 mm; gap, 2 mm; matrix, 256 x 192; and 2 signal
acquisitions.
Lingual Tonsil Diameter
The maximum transverse diameter of the lingual tonsil was measured
perpendicular to the long axis of the lingual tonsil in an oblique
anterior-to-posterior plane. Measurements were made by a fellow in pediatric
radiology after training with a pediatric radiology faculty member (13 years'
experience). All measurements were reviewed by the fellow and faculty member
simultaneously and any issues were resolved by consensus. The lingual tonsils
were categorized as nonvisualized, present and measurable, or markedly
enlarged. Markedly enlarged was defined as a transverse diameter of greater
than 10 mm. "Nonvisualized" was defined as no bright-signal
tonsillar tissue was present in the expected location of the lingual
tonsils.
Previous Palatine Tonsillectomy and Adenoidectomy
The subjects were divided into those who had undergone tonsillectomy and
adenoidectomy with absent palatine tonsils and V-shaped surgical defect in the
adenoid tonsils on MRI and those who had not. There were 41 subjects in the
previous tonsillectomy and adenoidectomy group and 30 patients with no
previous tonsillectomy and adenoidectomy. Statistical evaluation was performed
to determine whether there was a difference in the frequency of lingual
tonsils being present (chi-square test) or markedly enlarged (Fisher's exact
test) between the two groups. A p value of less than 0.05 was
considered statistically significant.
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One of the complications of pediatric obesity is obstructive sleep apnea. It is well recognized that obese subjects are at increased risk for obstructive sleep apnea. One study found that 55% of obese adolescents had significant obstructive sleep apnea [5]. Furthermore, it has been shown that with increasing BMI there is a trend for ever higher prevalence of obstructive sleep apnea.
Although the relationship between obesity and obstructive sleep apnea is well established, the exact cause of obstructive sleep apnea in obese subjects is debated [5, 9, 10]. There are multiple potential contributing factors to the cause of obstructive sleep apnea in obese subjects. These include increased parapharyngeal fat impinging on the airway, increased prevalence of tonsillar tissue, increased elasticity of the walls of the airway related to decreased muscular tone, and poorly understood central effects related to things such as increased visceral adiposity [5, 9, 10].
Obstructive sleep apnea can occur from anatomic obstruction of the supraglottic airway, increased collapsibility of the airway, or some combination of the two [1]. One of the more common anatomic levels of obstruction is at the retroglossal airway [1]. Because of the anatomic position of the lingual tonsils in this region, enlargement of the lingual tonsils can contribute to significant obstructive sleep apnea [1–4]. It is important to recognize this potential cause of obstructive sleep apnea because it is easily rectified by surgical resection [4]. We have seen multiple cases in which significant obstructive sleep apnea has resolved after lingual tonsillectomy in a patient with enlarged lingual tonsils.
In this study, we found a high frequency of both measurable and markedly increased size of lingual tonsils in obese subjects. The frequency of lingual tonsils in obese subjects is greater than that previously seen in the normal population and in patients with Down syndrome and obstructive sleep apnea [2, 3]. The frequency of measurable lingual tonsils on MRI reported in the literature in asymptomatic children without obstructive sleep apnea is 0%, in children with obstructive sleep apnea in general is 33%, and in patients with Down syndrome and obstructive sleep apnea is 50% [3]. It is important to recognize that the increased size of the lingual tonsils may be one of many contributing factors to the development of obstructive sleep apnea in obese subjects. Further investigations into whether there is significant correlation between the presence of lingual tonsils and obstructive sleep apnea may be warranted.
Studies have shown that in patients with Down syndrome, previous palatine tonsillectomy and adenoidectomy are associated with an increased risk of overgrowth of the lingual tonsils [2]. Interestingly, in our study, there was a statistically significant increased rate of presence and marked enlargement of lingual tonsils in the children who had undergone palatine tonsillectomy and adenoidectomy. These findings suggest that in obese patients, previous palatine tonsillectomy and adenoidectomy are risk factors for enlargement of the lingual tonsils.
In summary, obese children have an increased incidence of both the presence and marked enlargement of the lingual tonsils. Enlargement of the lingual tonsils may be one of the contributing factors to the development of obstructive sleep apnea in obese subjects. This is particularly true in obese children who have previously undergone palatine tonsillectomy and adenoidectomy.
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