This benign malformation on the outside part of the ear characterized by a small piece or clump of skin is referred to as preauricular sinus infection. It is congenital abnormality of the preauricular soft tissues. This condition was described first by Van Heusinger in 1864. In the Uited States, the estimated incidence is 0.1% up to 0.9%. It is slightly higher in Africa with 4% up to 10%.
Most of the time, this condition only affects one ear, although some instances show that it can affects both ears. In females, it is commonly found outside the right ear. Theoretically, preauricular sinus infection is attributed to the incomplete or abnormal fusion of the six auditory hillocks of His. A less common theory is that during auricular development, the ectodermal folding caused the sinus to develop. Preauricular sinus does not involve branches of the facial nerve although it can be placed at risk during treatment. This condition seldom happens and it is inherited.
Preauricular sinus is commonly seen on the right ear and is often sporadic. Bilateral occurrences (both ears) are most likely inherited. General changes during gestation may cause the defect to occur, based on the family history of an individual. Mucus buildup and bacteria can cause sinus infections as well as genetic.
A study has shown that among those with preauricular sinus infection, 52% had inflammation in their sinuses, 34% drained their sinus abscess and 18% had infected sinuses. Infectious agents that were identified were Staphylococcus epidermidis with 31%, Staphylococcus aureus which is also 31%, Streptococcus viridians with 15%, Peptococcus species is also 15% and Proteus species with 8%. One must be treated with systemic antibiotics once you acquire infection of the sinus. In the presence of abscess, incision and drainage is required. Exudate must be sent to the lab or culturing and Gram staining for appropriate antibiotic coverage.
There has been no associated fatality due to preauricular sinus infection. Morbidity associated with preauricular sinus includes ulceration, recurrent infection on the site, scarring, facial cellulitis and pyoderma. Specific conditions may arise such as malar ulceration, unilateral facial cellulitis, abscess on the anterior of the involved ear, recurrent and chronic sinus orifices drainage and otitis externa. Post operative recurrence may occur because the sinus tract was not completely removed.
Both men and women can be equally affected with preauricular sinus infection. It has 0.0% to 0.6% incidence in whites while in Africans and in Asians, its incidence is 1% to 10%. This condition arises during antenatal period and is present at birth usually but becomes apparent later in life. Infants affected with this congenital defect are usually asymptomatic and does not pose any problems, however, there is a possibility of sinus infections.
Preauricular sinus infection can sometimes be confused with branchial ceft anomalies. These anomalies are related intimately to the ear drum or external auditory canal and angle of the mandible, on the other hand, preauricular sinuses are not. It does not in any way involve the facial branches or the facial nerves, although surgery may put them at risks.
Preauricular sinus infection occurs either sporadic or inherited. About 50% of the cases occur on the right side and they are sporadic. Bilateral cases are most commonly inherited and are autosomal dominant with different degrees of penetration (about 85%). Studies in China show the 8q11 chromosome is the site of abnormal gene transmitting preauricular sinus.
It has been described that preauricular sinus has been a part of multiple syndromes such as:
- Branchio Oto Renal Syndrome
- Branchio Oto Urethral Syndrome
- Brancio Otic Syndrome
- Branchio Oto Coastal Syndrome
- Cat Eye Syndrome
- Trisonomy 22
Preauricular sinus infection is a small opening usually located at the anterior margin of the ascending limb of the helix. This pit can also be found along the postero superior margin of helix. In very rare cases, it can be located close to the lobule or the tragus. Part of the tract commonly blends with the auricular cartilages’ perichondium in almost all the patients.
The preauricular sinus is differentiated from branchial cleft anomalies because the sinus tract is lateral and superior to the parotid gland and the facial nerve in preauricular sinus. This condition may sometimes lead to subcutaneous cyst formation that is related intimately to the crus of helix and tragal cartilage. Patients affected with preauricular sinus usually presents discharge on the infected area. The discharge can be caused by infection or desquamating epithelial debris. According to studies, the common pathogens that cause the infection are staphylococcus, streptococcus, peptococcus and proteus.
Ruling out syndromes associated with preauricular sinus is always good practice. Oftentimes, kidney is involved in the symptoms. According to Wang’s criteria, ultrasound examination should be performed in patients with preauricular sinus if:
- Another malformation or dysmorphic feature is present
- Deafness in the family
- Malformations that involve the pinna.
- History of gestational diabetes.
Another routine investigation that should be performed is the puretone audiometry to determine hearing impairment in patients affected with preauricular sinus.
Incision and drainage is necessary in the acute phase of preauricular sinus where abscesses is present. The lacrimal probe as described by Coatesworth et al. is a technique used for draining preauricular abscess. This technique involves the use of topical anesthesia on the overlying skin ad a blunt ended lacrimal probe is inserted into the sinus, this allows the draining of the abscess. This procedure can be repeated if necessary.
Persistent or recurrent preauricular sinus is due to incomplete excision. According to the comparison done in 1990 by Prasad et al. and in 2001 by Lam et al. the supra-auricural approach or the wide local excision has a lower recurrence rate compared to the standard technique. The supra-auricural approach uses dissection to determine the temporalis fascia as the medial limit of dissection and continues to the cartilage of anterior helix which is the posterior margin of dissection. The preauricular sinus is removed together with the superficial tissue to the temporalis fascia. To ensure that preauricular sinus infection will not recur, a portion of the perichondrium of the helix should be excised.