Congenital Cholesteatoma of Mastoid Origin – a Multicenter Case Series Kongenitalni Holesteatom Mastoida – Multicentriþna Studija Sluþajeva

Background/Aim. The mastoid is the rarest site for the onset of congenital cholesteatoma (CC). The symptoms are atypical and minimal. The aim of this multicenter retrospective descriptive study was to define this extremely rare condition and its clinical presentation, diagnosis and management. Methods. We analyzed data files for a 15-year period in 4 tertiary otology centers and discovered 6 patients with the diagnosis of CC of the mastoid. Results. The clinical presentation of CC varied from incidental findings in patient to patient with otogenic meningitis. The most common findings during surgical procedures were mastoid cortex erosion, sigmoid plate dehiscence, dural exposure and external canal wall destruction. Conclusion. CC of mastoid origin tends to occur in adult patients probably because of minimal symptoms and the delayed diagnosis. It can exist for years in a nonaggressive state and develop to giant sizes. In children it is almost incidentally diagnosed. Early imaging is necessary in order to prevent serious complication.


Introduction
Congenital cholesteatoma (CC) is an epidermoid cyst arising from congenital remnants of keratizing squamous epithelium in the temporal bone 1 .The rarest site of origin within temporal bone is mastoid process and may go undiagnosed for years 2 .The symptoms are atypical and in reported cases the most common presentation was an incidental finding during radiologic evaluations 3 .CC of mastoid origin could be diag-nosed if the patient had intact tympanic membrane, intact skin of external canal, no ossicular erosion and no attic involvement of cholesteatoma in intraoperative and imaging findings.CC of mastoid origin can exist for years in a nonaggressive state, develop to gigantic size and, in some cases, rapidly cause bone destruction and serious complication 4,5 .
The purpose of this multicenter study was to better define this rare condition and its clinical presentation, diagnosis and surgical treatment.

Methods
Data files in six otology tertiary referral centers from Serbia were analyzed and patients with the diagnosis of CC of the mastoid origin were identified.All the patients were operated on by one of the authors of this article.Clinical information were compiled from the their histories.Demographics, symptoms and signs, otomicroscopic findings, audiometric data, and findings at the time of surgery were also analyzed.Computed tomography (CT) and magnetic resonance imaging (MRI) images were reviewed, as well.Follow-up length and recurrence of the disease were recorded.Audiometric data were presented as pure tone average air bone gap (ABG) preoperatively and postoperatively in four frequencies (500, 1000, 2000, 4000 Hz).

Results
Analyzing patient's data for the period of 15 years we recognized 6 cases of CC of the mastoid region in 4 otologic centers (Table 1).The mean age of patients was 23 years (range from 7 to 60 years).The clinical presentation of the disease varied.One of the cases (case 1) was with minimal and atypical otologic symptoms (retroauricular pain and mild hearing loss).Two of the cases (cases 2 and 5) were with ear discharge with normal tympanic membrane, but with swelling of the skin of meatus.One child (case 3) underwent MRI due to bilateral sensorineural hearing loss, and cholesteatoma was incidentally found.The oldest patient (case 6) was with otogenic meningitis and CC was displayed with CT scan only in the mastoid.There were 5 cases of the patients with few months' symptoms and the patient with a complication had one day history of headache, fever, dizziness and vomiting.All the patients had normal tympanic membrane findings.
Five out of 6 patients underwent CT scanning, whereas 2 of 6 patients underwent MRI.In the CT scan results, 2 of 5 patients had a well-circumscribed, expansive lesion into mastoid portion of the temporal bone.Three of 5 patients had external auditory canal wall destruction and 3 had sigmoid plate dehiscence and dural destruction, as well (Figure 1 and 2).In the MRI results, 2 of 2 patients had sharply circumscribed mass into mastoid process (Figure 3).Surgical approaches were 4-canal wall down mastoidectomies, and 2-canal wall up.The patients with sigmoid plate dehiscence had erosion of bony plate of the posterior fossa, as well (Table 2).Only one of the patients had exposed mastoid portion of the facial nerve.Two of the cases had spread into epitympanum without ossicular erosion.Two of the cases with hearing loss with intact ossicular chain had slight fixation of incudomalleolar and incudostapedial joint.None of them had erosion of the osseous labyrinth and 3 had external canal wall destruction but with intact skin of meatus.The most common findings in surgery were mastoid cortex erosion, sigmoid plate dehiscence, dural exposure and external canal wall destruction.
Five of 6 patients had audiometric data.Preoperative ABG ranged from 0 to 30dB and postoperative ranged from 0 to 20dB.Follow-up period was from 2 to 3 years, and only one patient had recurrence during this time.

Discussion
CC of mastoid origin is an extremely rare disease 2 .In the literature there are a few case reports about CC of mastoid origin 1, 2, 4, 5 and one case report with analysis of radiologic data in nine patients 3 .The symptoms are atypical and include neck pain, retroauricular swelling and pain, and dizziness 2 .CC of mastoid origin was diagnosed if a patient had intact tympanic membrane, intact skin of external canal, no ossicular erosion neither attic involvement of cholesteatoma.The most common presentation in our series was pain and ear discharge.Erosion of the mastoid cortex could be the reason of pain because the disease involves the periosteum.Intermittent ear discharge was a symptom in 2 cases due to inflammation of intact meatus skin.Hearing loss is an unusual symptom for CC and in our series was due to fixation into incudomalleolar and incudostapedial joint as another congenital anomaly in two cases.All the patients had normal otomicroscopic findings on ear drum.Everyone had a relatively short duration of symptoms.
Although CC of mastoid origin has a congenital origin, it tends to occur in adulthood probably because of minimal symptoms and delayed diagnosis.
Two of 3 children had only hearing loss as a symptom (case 3 -sensorineural loss and case 4 -conductive loss) and radiological imaging procedures were performed to differentiate reasons of hearing loss.Mastoid CC was the incidental finding in these cases.
The oldest, 60-year-old, patient (case 6) had expansive destructive mass into mastoid portion of temporal bone with 1-day duration headache, neck stiffness, vomiting and fever.Blood analysis and lumbar puncture confirmed the meningitis and CT scan showed a huge mass of the mastoid.The data of one patient in this descriptive case series (case 1) had already been published as a case report 5 .That patient had a giant cholesteatoma with complete exposure of the facial nerve with no facial weakness.Also, there was erosion of the perilabyrinthine space with no history of dizziness, and dural and jugular bulb exposures without intracranial or extracranial complication.
CC of mastoid origin can exist for years in a nonaggressive state and develop to giant size.It is possible that CC saves fine tissue of temporal bone and is very destructive for bone tissue, or the mastoid portion is silent region.
Early CC diagnosis is essential to prevent delayed treatment and serous complications.The most important tools in the diagnosis are CT and/or MRI 3,6 .CC gives minimal symptoms that might seem mild and nonspecific.It is not unusual to incidentally find CC on imaging 3 .Imaging is of essential importance for preoperative surgical planning as well.
Surgical management of these lesions is primarily directed by intraoperative and imaging findings.Surgical approaches were 4-canal wall down mastoidectomies, and 2canal wall up.Where the lesion was gigantic and where posterior canal wall was destructed, the canal wall down mastoidectomy was done.Giannuzzi et al. 7 considered that the management of the sigmoid sinus and the jugular bulb is the most demanding surgical key point.

Conclusion
Congenital cholesteatoma of mastoid origin can develop to huge sizes, can have minimal clinical presentation, and can be found not before causing serious complications.Sometimes the diagnosis is incidental.Otologists should keep this disease in mind in cases with normal otomicroscopic findings, unusual retroauricular pain and ear discharge.

Fig. 1 -
Fig. 1 -Case 1: Preoperative computed tomography of the right mastoid area.Coronal view of temporal bone showing the lesion destroying the posterior canal wall of auditory canal.

Fig. 2 -
Fig. 2 -Case 2: Preoperative computed tomography of the left mastoid area.Axial view showing an expansive mass eroding cortex of mastoid and the bony plate of the posterior fossa and the bony plate covering the sigmoid sinus.