Anomalies of Cochlea & their Management

Human ear consists of the outer, middle and inner ear and Inner ear complex that participates in Sensorineural hearing is the Cochlea. Birth related abnormalities in development of cochlea are called Anomalies/malformations of the Cochlea. Malformed inner ear complex are caused by interruption during various parts of development of the ear during the first 3 months of foetal development. They are the predominant causes of Sensorineural related hearing loss.

These malformations represent about 20% of all patients with sensorineural hearing loss. (1) From the first reported case in 1791 in Italy by Carlo Mondini, there has only been continual evolution in the world of inner ear impairments being discovered and discussions on their management have evolved in the last 230yrs. (2,3)

Sennaroglu and colleagues have extensively worked in this regard and the most accepted classification that is currently being followed in centres worldwide was given in 2017.(4)

Early identification of hard of hearing since birth becomes utmost important with newborn hearing screening having a major role. Early detection, workup and classification of disorder and thereafter planning for appropriate rehabilitation is necessary.

In the landmark article that talks about the latest classification 2017 (1), the authors propose the possible imaging findings to look for by clinicians, Facial nerve anomalous routes that may coexist and the possible treatment of such malformations in order to rehabilitate hearing (HA: Hearing aid, ABI: Auditory brainstem Implant, CI: cochlear implant) (1,4,5)

Of significance are the following considerations:

1. Classification of Inner ear malformation

2. Status of the cochlear nerve

3. Preoperative audiological findings.

The following tabular columns give the Indication of ABI and characteristic based management of inner ear malformations (1)

Management of Inner ear malformations

Predominant challenges in management are:

1. Cerebrospinal fluid gusher and risk for meningitis

2. Facial nerve anomalies

3. Decision making for the surgical approach and the type of electrode

4. Choosing the correct implantation method; CI vs ABI

5. Timing of surgery

Therefore, thorough preoperative assessment and counselling of the patient along with appropriate decision making based on universal guidelines becomes of utmost importance.

However, the final decision of rehabilitation in each patient must be done on a case-to-case basis on appropriate clinical evidence along with the experience of the surgeon in the accord of managing such cases.

One such case managed by our centre deserves a special mention where the child presented to Bangalore Head and Neck sciences at 2 years of age with a sensorineural deafness profile and was diagnosed with multiple anomalies being Incomplete partition II on one side and Absent cochlea on the other.

CT image 1: IPII with cystic apex of the cochlea and enlarged vestibular aqueduct

CT Image 2: Cochlear aplasia on the opposite side.

Child was told the need to undergo ABI and that the rehabilitation will be poor and challenging. At our centre the decision of CI was made. Right sided Meningoencephalic herniation into the site of the surgery was present. The course of the facial nerve was highly anomalous. The abnormal vascular malformation of the sigmoid dural venous sinus interfering with the surgical field along with middle fossa dura and posterior fossa dura left a very compact space for operating. The child underwent cochlear implantation of the right side along with Subtotal Petrosectomy.The child is now successfully able to vocalize sounds. Currently undergoing AVT sessions and is on follow up.

Hence, case-based decision making, and appropriate case selection based on thorough evidence based medicine along with expertise of the surgeon to manage complications associated with difficult anomalous Temporal bones with cochlear anomalies becomes extremely important.

Take home messages:

Early diagnosis and workup for status of hearing loss with inner ear malformation.

Thorough detailed pre operative assessment and anticipation of malformations and challenges on table to be accounted for.

Final decision on method of rehabilitation depends on the surgeon’s skill, clinical acumen, and the multitude of guidelines available are mere chalked out plans, and each case must be dealt with individually and successfully.

Here at Bangalore Head and Neck sciences, we regularly manage disorders of the inner ear with our detailed protocols and management techniques thereby having not only multiple difficult cases that have been managed meticulously but also multiple successful rehabilitative stories gone and ongoing. For further information, visit our clinic and meet our clinicians today!

References:

1. Sennaroğlu, L.; Bajin, M.D. Classification and Current Management of Inner Ear Malformations. Balk. Med. J. 2017, 34, 397–411.

2. Brotto, D.; Uberti, A.; Manara, R. From Mondini to the latest inner ear malformations’ classifications: An historical and critical review. Hear. Balance Commun. 2019, 17, 241–248.

3. Brotto, Davide, Flavia Sorrentino, Roberta Cenedese, Irene Avato, Roberto Bovo, Patrizia Trevisi, and Renzo Manara. 2021. "Genetics of Inner Ear Malformations: A Review" Audiology Research 11, no. 4: 524-536. https://doi.org/10.3390/audiolres11040047

4. Sennaroglu L, Saatci I (2002) A new classification for cochleovestibular malformations. Laryngoscope 112:2230–2241

5. Sennaroğlu L, Tahir E (2020) A novel classification: anomalous routes of the facial nerve in relation to inner ear malformations. Laryngoscope.