Preauricular Sinus: Clinical Course and Associations

Objectives  To evaluate the clinical course of congenital preauricular sinus (PAS) up until adulthood and to determine its association with congenital ear and renal abnormalities.

Design  Cohort survey.

Setting  Medical screening facility at a military base.

Participants  All individuals in a cohort of male subjects who were medically assessed for conscription into the army between September 1, 2003, and March 31, 2004.

Interventions  Subjects identified as having PAS were further evaluated with pure-tone audiometry and renal ultrasonography.

Main Outcome Measures  Presence of PAS and associated hearing and renal abnormalities.

Results  Of 10 734 male subjects (median age, 19 years; range, 16-26 years) screened, 121 (1.13%) were found to have PAS, all of which were isolated. The point prevalence of PAS in Chinese, Malay, and Indian subjects was 1.36%, 0.69%, and 0.17%, respectively. Of the 29 subjects (24.0%) who developed symptoms (mainly sinus discharge), most had recurrent symptoms, and 7 (24.1%) of the 29 had onset of symptoms after age 16 years. Only 1.7% and 2.6% of the subjects had associated hearing loss (sensorineural) and renal deformity (minor in nature), respectively.

Conclusions  In a study of young adult males with PAS, associations with ear and renal abnormalities were found to be rare, although PAS had widely been acknowledged to be associated with these congenital defects. Up until adulthood, about one quarter of all lesions became symptomatic. Of those who developed symptoms, almost one third did so after age 16 years. The most common symptom was sinus discharge, which tended to be recurrent.

Preauricular sinus (PAS) is a congenital malformation that manifests as small openings in the external ear, usually near the anterior limb of the ascending helix. The PAS may become symptomatic, necessitating surgical excision.^1,2 Because incomplete excision may lead to troublesome recurrent symptoms later on, there have been a number of articles dealing with surgical techniques to ensure complete removal of the lesions.^3,4

However, although PAS was described more than a century ago (in 1864), the understanding of it is far from complete. There remain a number of issues of clinical relevance that have not been adequately addressed. For example, although it is generally accepted that most sinuses remain asymptomatic, the actual prevalence of PAS is unknown. For those who present with sinus discharge, the likelihood of further episodes of discharge is also unclear. Although PAS is known to be associated with kidney and ear abnormalities, the extent of association is not well defined.

In Singapore, enlistment of all male citizens in the nation's army is compulsory. A cohort of these subjects provided us with a good opportunity to address some of these gaps in the knowledge of PAS. A relatively unbiased sample of the population could be retrospectively studied at an age when permanent congenital hearing loss can be reliably ascertained. The aim of this study was to identify subjects with PAS from such a cohort so as to chart its clinical course into young adulthood and to determine its association with hearing and renal abnormalities.

All male citizens undergo medical screening in the military facility at the Central Manpower Base (Singapore) prior to being conscripted into the nation's army. All subjects who were screened between September 1, 2003, and March 31, 2004, were examined for the presence of PAS.

Those identified as having PAS were further evaluated. A medical history relating to hearing loss and renal abnormalities was obtained. In those individuals whose sinuses were symptomatic, the details of symptoms were sought and recorded. Their ears were examined with the otoscope, and hearing thresholds were assessed by pure-tone audiometry performed by trained technicians in sound-attenuated booths. The subjects were considered to have hearing loss if their average air-conduction threshold higher than 0.5, 1, 2, and 4 kHz was worse than 25 dB. The renal status was evaluated by a consultant radiologist (G.K.-L.W.) using ultrasonography.

Quantitative variables are given as the mean with a 95% confidence interval (CI). Statistical analysis was performed with χ² testing using SPSS statistical software (version 12.0; SPSS Inc, Chicago, Ill). The criterion for statistical significance was P<.05.

A total of 10 734 males were screened for the presence of PAS. Of these, 7565 were Chinese; 2456, Malay; 594, Indian; and 119 from other minority ethnic groups, including white and Eurasian. The median age of the subjects screened was 19 years (range, 16-26 years).

A total of 121 individuals (1.13%) were found to have PAS. Of these, 103 were Chinese; 17, Malay; and 1, Indian. These differences in distribution by ethnic group were statistically significant (P = .003) (Table).

Of the 121 subjects with PAS, 33 (27.3%) had bilateral lesions; 52 (43.0%), left-sided lesions; and 36 (29.7%), right-sided lesions. This pattern of distribution of the laterality of PAS was present in each of the 3 main ethnic groups (Figure).

Twenty-nine (24.0%) of the 121 subjects had experienced symptoms related to PAS. The most commonly reported symptom was sinus discharge, which was present in 25 lesions. Eight subjects presented with fewer than 5 recurrent episodes of sinus discharge, 2 had 5 to 10 episodes, and 15 had more than 15 episodes. Seven subjects developed the first symptom after age 16 years.

Eight subjects experienced pain, for which 6 sought treatment; 2 of them required only treatment with antibiotic drugs, but another 2 developed abscesses that needed incision and drainage. Two subjects were eventually referred to the surgeon for excision of the lesion.

None of the subjects with PAS were found to have dysmorphic facial features, auricular defects, or other sinuses and fistulas in the head and neck region.

Only 2 subjects (1.7%) had associated hearing loss. The first was a 19-year-old Malay man with bilateral PAS, who had sensorineural hearing loss of 80 to 100 dB in his right ear. He did not have any symptoms relating to his PAS. The second was a 19-year-old Chinese man with a left-sided PAS who had concomitant bilateral mild to moderate sensorineural hearing loss. He also had had recurrent whitish discharge from his sinus since he was 6 years old, but this symptom was self-limiting and did not require any treatment. Both of these subjects had healthy external ear canals and tympanic membranes, with no clinical or audiometric evidence of conductive hearing loss. They did not have any other illnesses or physical deformities, and findings from their renal ultrasonographic studies were within reference range.

One hundred fifteen of the 121 subjects identified as having PAS consented to undergo renal ultrasonographic screening. Of those evaluated, the mean size of the right kidney was 10.3 cm (range, 8.3-12.3 cm; 95% CI, 10.1-10.4 cm). The mean size of the left kidney was 10.4 cm (range, 9.0-12.2 cm; 95% CI, 10.2-10.5 cm). Three subjects (2.6%) were found to have structural abnormalities. These were all minor, consisting of a partial or complete duplication of the pelvicalyceal system. These subjects were all asymptomatic, and findings from their urine dipstick tests were within reference range.

The auricle develops from the fusion of 6 mesenchymal proliferations, known as the hillocks of His. The most frequently cited and generally accepted theory attributes the development of PAS to incomplete or defective fusion of the 6 hillocks. The other, less well-known, published theory³ is that the sinus develops as a result of isolated ectodermal folding during auricular development.³

Although the incidence of PAS has been estimated to be 0.1% to 0.9% in the United States, 0.9% in England, 1.6% to 2.5% in Taiwan, and 4% to 10% in some areas of Africa,^3,4 its true prevalence remains unknown.⁵ The varying reported prevalence from different parts of the world suggests the possibility of differences according to ethnic group in the prevalence of PAS. This is confirmed by the results of the present study, wherein the prevalence was found to be 1.36%, 0.69%, and 0.17% in Chinese, Malay, and Indian individuals, respectively.

In studies conducted elsewhere, bilateral lesions had been found to occur in 25% to 50% of cases.⁴ Of the unilateral lesions, right-sided PAS occurred more frequently.³ Most of our cases were also unilateral, but left-sided lesions were more frequent than right-sided lesions. Similar laterality patterns existed in each of the 3 main ethnic groups studied. According to Paulozzi and Lary,⁶ differences in the lateral distribution of specific birth defects may be the result of subtle differences in morphogenesis on the left and right sides of the embryo brought about by establishment of left-right asymmetry prior to organogenesis.

Preauricular sinuses are known to be sporadic or inherited, and bilateral lesions are more likely to be inherited.³ When inherited, they show an incomplete autosomal dominant pattern with reduced penetrance and variable expression. They have also been described as part of a number of multiple congenital anomaly syndromes. The most well known of these is the branchio-oto-renal syndrome,⁷ an autosomal dominant condition that consists of PAS, other ear defects resulting in hearing loss; renal defects; lateral cervical fistulas, cysts, and sinuses; and nasolacrimal stenosis and fistulas. Besides genetic factors, environmental causes may also be important. For example, Merlob and Aitkin⁸ reported that PAS is a marker of teratogenic exposures and suggested that a decrease in their prevalence in Israel might be a marker for decreased exposure to teratogens.

Our present study found that up to a median age of 19 years, about 75% of subjects with PAS remained asymptomatic. Of those who develop symptoms, sinus discharge was the most common complaint and tended to be recurrent. Among the symptomatic subjects, 28% experienced onset of symptoms only after age 16 years. Although only 2 sinuses (1.7%) had been excised at the time of the study, there could be more lesions requiring excision in the future.

Deafness is known to be associated with PAS, especially when it is part of a syndrome such as branchio-oto-renal syndrome.⁷ However, in subjects with seemingly isolated PAS, the incidence of associated congenital hearing loss is unclear. From studies in children, the percentage of hearing impairment with isolated preauricular tags or pits has been estimated to be as high as 15% to 30%.⁹ Assessment of hearing in children can be difficult, and hearing loss from acquired middle ear infections is common. In the present study, only 2 (1.7%) of the 129 subjects studied were found to have hearing loss, both of which were sensorineural in nature. This is not any higher than the 3.7% prevalence rate of sensorineural hearing loss among young adult males in Singapore.¹⁰ None of our study subjects was found to have associated pinna, external ear canal or tympanic membrane defects, or conductive hearing loss, which are frequent sequelae of abnormal branchial development. On the other hand, in a study¹¹ of individuals born with branchial cleft anomalies, the presence of concomitant PAS was reported to be as high as 60%.

Studies of children have shown an association between PAS and renal structural abnormalities. The percentage of children with isolated PAS and associated major renal structural abnormalities was reported to be 2.2% to 4.3%.^12,13 Although routine renal ultrasonographic screening for all children born with isolated PAS has been advocated by Leung and Robson,¹² this view is not widely shared by others.² Instead, it has been recommended that renal ultrasonographic screening be conducted only if PAS is accompanied by 1 or more of the following: (1) another malformation or dysmorphic feature, (2) a family history of deafness and auricular and/or renal malformation, and (3) a maternal history of gestational diabetes mellitus.⁹ The results of our present study also do not support routine renal ultrasonographic screening in individuals with isolated PAS; only 3 (2.6%) of the 115 subjects in our study were found to have renal defects, all of which were minor. This figure is not higher than the prevalence rate of minor renal structural defects in the general population, which has been reported to be as high as 8%.¹³

One limitation of the present study is that only males were evaluated. Although sex differences in the prevalence of some human birth defects exist,¹⁴ significant sex differences in the prevalence and characteristics of PAS have not been reported.

In summary, in a study of young adult males, a difference in the prevalence of PAS according to ethnic group was found. Although PAS had widely been acknowledged to be associated with congenital hearing and renal abnormalities, these associations were found to be rare. Up until adulthood, about one quarter of all lesions became symptomatic. Of those subjects who developed symptoms, almost one third did so after age 16 years. The most common symptom was sinus discharge, which tended to be recurrent.

Correspondence: Wong-Kein Low, FRCS, Children's Medical Fund-SGH Centre for Hearing & Cochlear Implants, Department of Otolaryngology, Singapore General Hospital, Singapore 169608 (low.wong.kein@sgh.com.sg).

Submitted for Publication: May 18, 2006; final revision received August 3, 2006; accepted September 5, 2006.

Author Contributions: Dr Tay had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Huang, Tay, Wansaicheong, and Low. Acquisition of data: Tay and Low. Analysis and interpretation of data: Huang and Tay. Drafting of the manuscript: Huang. Critical revision of the manuscript for important intellectual content: Huang, Wansaicheong, and Low. Statistical analysis: Low. Administrative, technical, and material support: Tay and Low. Study supervision: Huang, Wansaicheong, and Low.

Financial Disclosure: None reported.

Acknowledgment: We thank Jayanthi d/o Arumugam, Rino bin Mohd Noor, and Tan Wen Jun Keith for their assistance.