MRI of nasopharyngeal adenoid hypertrophy

Abstract

Nasopharyngeal adenoid hypertrophy (NAH) is a typical benign lesion. Due to involution, nasopharyngeal lymphatic tissue usually is not found in adults beyond the 30th to 40th year of life. However, occasionally NAH has been recognized after the 50th or 60th year. The aim of this study is to identify the frequency of NAH and to analyze its MRI findings in different age groups. From 2007 to 2011, 6693 MR investigations of the head were performed at our institution. MRI was obtained with a 1.5 T MRI device. NAH was identified in 18.0% of the patients. The frequency of NAH varied from 60.3% to 1.0% in the different age groups. The mean size of NAH was 23.2 ± 4.5 mm in cranio-caudal, 31.1 ± 5.2 mm in left-right, and 14.2 ± 4.1 mm in the anterior-posterior direction. The left-right and cranio-caudal sizes of NAH were largest in the 0–9 age group and decreased with age. On T1-w images most lesions (95.4%) were hypointense in comparison to the adjacent musculature. On T2-w fat-saturated images 82.4% of the lesions were hyperintense. After intravenous administration of contrast medium most lesions showed a slight enhancement (58.6%). Moderate enhancement was seen in 32.4% and a marked enhancement was identified in 9.0%. In the 0–9 age group most lesions showed a slight enhancement. Cysts within NAH were identified in 433 cases (35.9%). The frequency of cysts increased continuously with age, namely from 10.9% to 65.2%.

Introduction

Nasopharyngeal adenoid hypertrophy (NAH) is a typical benign lesion in childhood and may often be detected incidentally on imaging.^1–3 Because of involution, nasopharyngeal lymphatic tissue usually is not found in adults beyond the 30th to 40th year of life.^2,3 However, occasionally NAH has been recognized after the 50th or 60th year.^3,4 At this age, a differentiation between NAH and malignant nasopharyngeal lesions may be difficult. Previously, magnetic resonance imaging (MRI) appearances of NAH have been described in only a few series.¹ In addition, the frequency of NAH has not been reported previously. Typically, NAH manifests as a symmetrical lesion with stripes and retention cysts.^1,5 However, NAH can also present with asymmetrical mucosal thickening and may be misdiagnosed as malignancy.⁶

Therefore, our aim was to identify the frequency of NAH and to analyze its MRI findings in different age groups.

Methods

Patients

In the time period from 2007 to 2011 in 6693 patients, MR investigations of the head were performed at our institution. There were 3447 women and 3246 men. NAH was identified in 1205 patients (628 women and 597 men) with a median age of 20 years, range 0–82 years, mean age, 22.8 ± 16.8 years.

MRI

MRI was obtained with a 1.5 T device (Magnetom Vision Sonata Upgrade, Siemens, Germany). The imaging protocol included axial T2-weighted (T2-w) fat-suppressed (FS) short tau inversion recovery (STIR) images (repetition time (TR)/echo time (TE) of 6130/88 ms; 5 mm section thickness; field of view (FOV) of 250 × 200 mm; acquisition matrix of 320 × 210), and axial T1-weighted spin echo (T1w SE) images (TR/TE of 562 × 16 ms; FOV of 250 × 200 mm; 5 mm section thickness; acquisition matrix of 320 × 192). In all patients T1w SE and/or T1w SE fat-suppressed and/or T1 three-dimensional (3D) gradient echo volumetric interpolated breath-hold examination (VIBE) with fat suppression (TR/TE of 7.17/3.62 ms; FOV of 250 × 250 mm; section thickness of 1 mm; acquisition matrix of 256 × 256) images were repeated after intravenous administration of contrast medium (gadopentate dimeglumine, Magnevist, Bayer Schering Pharma, Leverkusen, Germany) at a dose of 0.1 mg/kg. Contrast-enhanced T1-w images were available at least in the axial and coronal plane.

All images were available in digital form. MR images were re-evaluated by two radiologists (AS and SK with 10 and 25 years of experience, respectively). In different readings, the decision was made on the basis of consensus.

Statistical analyses

For statistical analysis the SPSS statistical software package was used (SPSS 17.0, SPSS Inc, Chicago, IL, USA). Collected data were evaluated by means of descriptive statistics (absolute and relative frequencies). Categorical variables were expressed as percentages. Analyses of lesion-specific outcomes (size, signal intensity, and enhancement characteristics) were performed by means of generalized linear mixed models. P < 0.05 was taken to indicate statistical significance in all instances. P values were adjusted for multiple testing by using the Bonferroni correction.

Results

Frequency and size of NAH

NAH was identified in 1205 of 6693 patients (18.3%). The frequency of NAH varied from 60.3% to 1.0% in the different age groups (Table 1).

Table 1.

Frequency and size of the identified nasopharyngeal adenoid hypertrophy (NAH) in different age groups.

	Age groups (years)
	0–9	10–19	20–29	30–39	40–49	50–59	60–69	>70
Number of patients	516	524	749	646	949	1083	1078	1140
Frequency of NAH (%)	60.3	52.1	34.6	21.7	12.5	6.3	2.1	1.0
Size of NAH (mm)
Cranio-caudal direction	22.2	23.7 p = 0.001 vs 0–9 years	23.8	23.9	24.9 p = 0.001 vs 0–9 years	24.2	22.0	21.7
Left-right direction	30.5 p = 0.001 vs 10–19 years	32.4 p = 0.001 vs 30–39 years	31.4 p = 0.013 vs 30–39 years	29.5 p = 0.001 vs 0–9 years	31.1	31.0	29.6	28.5
Anterior-posterior direction	16.6	16.8 p = 0.001 vs 20–29 years; p = 0.001 vs 30–39 years	13.1 p = 0.001 vs 0–9 years	11.8 p = 0.001 vs 0–9 years	11.7 p = 0.001 vs 0–9 years; p = 0.001 vs 10–19 years	12.2 p = 0.014 vs 0–9 years; p = 0.009 vs 10–19 years	11.6 p = 0.001 vs 0–9 years	10.6 p = 0.001 vs 0–9 years

The mean size of NAH was 23.2 ± 4.5 mm in cranio-caudal, 31.1 ± 5.2 mm in left-right, and 14.2 ± 4.1 mm in the anterior-posterior direction. The size of NAH dependent on age is listed in Table 1. The left-right and cranio-caudal sizes of NAH were largest in the 0–9 age group and decreased with age (Table 1).

MRI features of NAH

On T1-w images, most lesions (n = 1109, 95.4%) were hypointense in comparison to the adjacent musculature. Fifty-four of them (4.6%) were iso- to slightly hyperintense (Figures 1 and 2).

Figure 1.

MRI appearance of NAH (arrows) in a 6-year-old child. (a) T2-w image (STIR) showing a nasopharyngeal mass slightly hyperintense in comparison to the pterygoid muscles. Small cysts are seen within the lesion. (b) The lesion is isointense to the musculature on T1-w image. (c) On contrast-enhanced T1-w image the lesion demonstrates a slight enhancement. Additionally longitudinal septa are seen in the mass. MRI: magnetic resonance imaging; NAH: nasopharyngeal adenoid hypertrophy; T1-w: T1-weighted; T2-w: T2-weighted; STIR: short tau inversion recovery.

Figure 2.

MRI appearance of NAH (arrows) in a 16-year-old patient. (a) On T2-w fat-saturated image the mass is hyperintense in comparison to the pterygoid muscles. (b) On T1-w image it is isointense. (c) On contrast-enhanced T1-w image, the NAH demonstrates a moderate enhancement with septa within the lesion. MRI: magnetic resonance imaging; NAH: nasopharyngeal adenoid hypertrophy; T1-w: T1-weighted; T2-w: T2-weighted.

On T2-w FS images, 947 (82.4%) lesions were hyperintense (Figures 1–3). The signal intensity in the age groups increased from the 0–9 age group to the 20–29 age group and further decreased in the older age groups. In this context the signal intensity was higher in the 20–29 age group vs the 0–9 age group (p = 0.028). The signal intensity on T2-w FS images of NAH lesions did not differ between the other age groups (Table 2).

Figure 3.

NAH (arrows) in a 36-year-old man. (a) The lesion is marked hyperintense on T2-w fat-saturated image. Small cysts are seen in the lesion. (b) On contrast-enhanced T1-w image, NAH shows a moderate enhancement. NAH: nasopharyngeal adenoid hypertrophy; T1-w: T1-weighted; T2-w: T2-weighted.

Table 2.

MRI features of NAH.

MRI features	Age groups (years)
	0–9	10–19	20–29	30–39	40–49	50–59	60–69	>70
T1-w images
Isointense (%)	95.4	90.7	97.2	97.1	97.1	97.0	95.2	90.9
Slightly hyperintense (%)	4.6	9.3	2.8	2.9	2.9	3.0	4.8	9.1
T2-w FS images
Moderate hyperintense (%)	28.0	15.1	13.8	16.0	20.6	25.8	30.0	33.0
Marked hyperintense (%)	72.0	84.5	86.2 p = 0.028 vs 0–9 years	84.0	79.4	74.2	70.0	67.0
Enhancement
Slight (%)	82.1	63.3 p = 0.014 vs 0–9 years	39.6 p = 0.014 vs 0–9 years	40.0 p = 0.014 vs 0–9 years	39.2 p = 0.014 vs 0–9 years	50.0 p = 0.014 vs 0–9 years	55.6 p = 0.014 vs 0–9 years	75.0
Moderate (%)	16.6	31.7	41.0	48.9	44.3	38.9	27.7	25.0
Marked (%)	1.3	5.0	19.4	11.1	16.5	11.1	16.7
Frequency of cysts (%)	10.9	31.9 p = 0.014 vs 0–9 years	44.8 p = 0.014 vs 0–9 years	52.1 p = 0.014 vs 0–9 years	51.3 p = 0.014 vs 0–9 years	55.9 p = 0.014 vs 0–9 years	65.2 p = 0.014 vs 0–9 years	63.6 p = 0.014 vs 0–9 years

MRI: magnetic resonance imaging; NAH: nasopharyngeal adenoid hypertrophy; T1-w: T1-weighted; T2-w: T2-weighted; FS: fat suppressed.

After intravenous administration of contrast medium most lesions showed a slight enhancement (n = 482, 58.6%) (Figures 1–3). Moderate enhancement was seen in 267 cases (32.4%) and a marked enhancement was identified in 74 lesions (9.0%). In the 0–9 age group most lesions showed a slight enhancement (Table 2). There was an increase of signal intensity in the 0–9 age group to the 30–39 age group (Table 2).

Cysts within NAH were identified in 433 cases (35.9%). The frequency of cysts increased continuously with age, namely from 10.9% to 65.2% (Table 2).

Septa could be identified in 29.8% of the cases.

Discussion

NAH is a common incidental finding on head, skull, and base of the neck imaging.² It is known that the size of NAH reduces with age and finally it disappears in almost all adults.³ However, NAH can persist in adults and elderly. Our study showed a decrease of NAH frequency with increasing age from 60.3% to 1%.

Only a few reports described MR appearance of NAH.^1–3 According to the literature, it presents as a symmetric nasopharyngeal mass with slight hyperintensity on T2-w images, isointensity on T1-w images and a slight enhancement after administration of contrast medium.¹ However, previous reports investigated a relatively small number of patients.^1,3 In addition, age-related changes of MR appearances of NAH have been not reported previously. As seen, in adults a more moderate or marked enhancement was seen in comparison to children and adolescents. This may be related to the fact that NAH develops more connective tissue with age.

Often, cysts are seen in NAH.^1–3 Bhatia et al. reported a frequency of cysts in 41% of the lesions.¹ In our study, cysts were detected in 36% of the cases. Furthermore, the frequency of cysts increased in adults suggesting increasing regressive changes of NAH with age.

According to the literature, NAH often shows septa on T1-w images after contrast administration.¹ In our study septa were identified in 29.8% of the cases.

In conclusion, NAH as a frequent benign lesion both in children and adults can be found in 18% of all MRI investigations of the head. Furthermore, a decrease of NAH frequency with increasing age from 60.3% to 1% is seen. MRI shows an increase of regressive changes of NAH with age.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.