Cochlear Implant in Klippel-Feil Syndrome: Challenges and Concerns

Abstract

Cochlear implantation (CI) can be safely performed in patients with syndromic hearing loss. Here we present a case of CI in a child with Klippel-Feil syndrome with various skeletal, extraskeletal, cochleovestibular and Arnold-Chiari malformations. Multidisciplinary approach and good preoperative imaging play a key role in planning for surgery.

Introduction

Klippel-Feil syndrome (KFS) is a rare congenital abnormality characterized by a clinical trial of short neck, low posterior hairline, and limited mobility of the neck. Various skeletal and extra-skeletal abnormalities are associated with KFS [1, 2]. External ear, inner ear and ossicular chain deformities have been reported to occur in about one-third of the patients, unilaterally or bilaterally. Inner ear anomalies related to KFS include an absence of semicircular canals, deformities of the vestibule and cochlea or even absence of IAC [3, 4]. Though ear deformities and hearing loss in KFS is well reported, cochlear implantation (CI) in a child with KFS and inner ear malformations is not previously documented in literature.

Case Report

A 5-year-old female child presented with bilateral severe to profound hearing loss for which she had been using hearing aid on the left side for 3 years with no significant benefit. Her Categories of Auditory Performance (CAP) [5] score was zero. She had undergone a cleft palate repair surgery at 2 years of age. Her gross motor developmental milestones were normal for age. She had short stature with a short, webbed neck and zero degrees of neck movement in the yaw, roll, and pitch planes. She had a cephalic index of 75% suggestive of dolichocephaly, a low posterior hairline, and Sprengel’s deformity. Asymmetry and downward slanting of both eyes were observed with a high arched palate and a residual defect in the hard palate. She had bilateral Marx Grade 1 microtia and narrow external auditory canals with normal tympanic membranes. The mastoid processes were underdeveloped but she had no facial assymetry. She also had an asymptomatic umbilical hernia and pectus cavum.

Magnetic resonance imaging (MRI) and high-resolution computed tomography (HRCT) of the temporal bone demonstrated bilateral underpneumatised mastoids with dysplastic ossicles. On the right side there was complete cochlear aplasia, cochleovestibular nerve aplasia and a stenotic IAC (Internal Auditory Canal). The left side had a Type 2 Cochlear Hypoplasia (CH) with dilated vestibule and lateral semicircular canal, absent posterior semicircular canal, and a widened cochlear aperture (Fig. 1a, d). The IAC directly opened into the small malformed cochlea (Fig. 1b). Bilaterally, round windows were not visualized and facial nerves had an anomalous more lateral course. On the left side, the IAC had only two undifferentiated nerves (Fig. 1c). The brain parenchyma was normal but the lateral ventricles were prominent and there was a dorsal deep cleft in the medulla with a large-sized cerebellum and low-lying cerebellar tonsils (Grade 1 Arnold-Chiari Malformation) (Fig. 1e). Imaging also revealed fusion of bodies of the cervical vertebrae (Fig. 3a) but no associated cardiac or renal abnormalities.

Fig. 1.

(a, b) HRCT of temporal bone axial view: a Left Type 2 cochlear hypoplasia and b short internal acoustic meatus with absent modiolus and absent lamina cribrosa (c, d) MRI Brain—T2 drive sequence: c oblique sagittal view showing cochleovestibular nerve (yellow arrow) and facial nerve, d axial view showing left Type 2 cochlear hypoplasia and e T1W sagittal view showing Grade 1 Arnold-Chiari Malformation with low lying cerebellar tonsils (green arrow).

Fig. 3.

Showing (a) fused cervical vertebrae, (b) intraoperative image intensifier scan with electrode array in place, (c) Sprengel's deformity and low posterior hairline (yellow arrow), and (d) postoperative NRT CI response in the left ear

A diagnosis of Klippel-Feil syndrome was made but targeted gene sequencing revealed no pathogenic/likely pathogenic variants for a syndromic cause. The parents were counselled regarding possible poor CI outcome and the risks of complications associated with anaesthesia and the surgical procedure, in view of the severe intracranial, upper spinal, and inner ear deformities. A preoperative lumbar drain was circumvented because of the pre-existing cerebellar tonsil herniation. Hyperextension of neck was avoided during laryngoscopy and intubation to avoid spinal injury.

Surgery

The head was placed on a soft head ring but fixed at midline due to the cervical spine anomalies. Facial nerve monitoring was carried out during the procedure. A transmastoid labyrinthotomy was created based on imaging, at the level of the lateral semicircular canals and in line with the short process of the dysplastic incus. An adequately sized, slit-like opening was drilled into the labyrinth encountering a high-pressure CSF gusher. A full banded 24 RE, straight electrode array from Cochlear Ltd. was guided into the labyrinth with 5 stiffening electrodes remaining outside. The labyrinthotomy was plugged with periosteal soft tissue and the CSF gusher was controlled by packing the mastoidectomy cavity with periosteal tissue, muscle and Surgicel (Ethicon from Johnson & Johnson) in layers with fibrin sealant (Fig. 2). Intraoperative imaging confirmed the placement of the electrode array in the cochlea (Fig. 3b).

Fig. 2.

Intraoperative images showing: a transmastoid labyrinthotomy (black arrow), b electrode insertion, c labyrinthotomy site sealed with tissue and fascia and d with fibrin sealant and surgicel

Intraoperative neural response telemetry (NRT) showed responses in the 7 basal electrodes while facial nerve stimulation occurred at the 11th, 16th, and 19th electrodes and no response was obtained at the 22nd (tip) electrode. Intraoperative impedances were good in all electrodes. Post-operative facial nerve and vestibular function were clinically normal.

The child was on absolute bed rest for 48 h and was started on intravenous ceftriaxone, dexamethasone and oral acetazolamide and discharged on the 3^rd postoperative day. On the 7th postoperative day, she presented with cough and mild grade fever and on examination, a nontender, fluctuant swelling without signs of cellulitis was noticed in the left supra-aural region. The child was readmitted and restarted on intravenous antibiotics and dexamethasone along with daily aseptic aspirations followed by pressure bandaging. The aspirated fluid was inconclusive for CSF, the swelling subsided by the third day and subsequently she was discharged.

The implant was activated at the end of the 3rd week. An objective programming was completed based on responses obtained intra-operatively and her auditory perception improved progressively reaching a CAP score of 6 at eight months after surgery. Her audiogram showed responses were just within the speech spectrum and post-operative NRT was good (Fig. 3d).

Discussion

Surgical intervention on a patient with an inner ear anomaly associated with other abnormalities such as Arnold Chiari malformation and fused cervical vertebrae are associated with greater anaesthetic and surgical risks. This may result from a compromised positioning of the patient’s head along with limited neck movements as well as other ear malformations. There are increased chances of facial nerve injury, labyrinthine fistula and CSF gushers. Patients with KFS also present a challenge when managing the airway and are more likely to have cervical instability, increasing their risk of neurologic damage with minor trauma during laryngoscopy, intubation, and positioning [6].

In Type II CH or cystic hypoplastic cochlea, the cochlea has smaller dimensions with defective modiolus and interscalar septa. There may be a complete absence of modiolus creating a wide connection with the IAC, making a gusher and misplacement of CI electrode into the IAC possible. The best option in these cases is to place the CI on the side with the better developed cochlear nerve or better audiological findings.

A transmastoid labyrinthotomy [3] approach may be considered in common cavity (CC) or cochlear hypoplasia (CH) deformities in which posterior tympanotomy may not be feasible. A larger than normal opening makes it easier to pack with tissue to seal the labyrinthotomy and a straight electrode is preferred, which can lie against the wall of the cavity. Absence of dizziness after surgery could be attributed to poor vestibular input from the common cavity and over reliance on visual and somatosensory information to maintain equilibrium [3].

A lumbar drain was avoided in our case as a preexisting cerebellar tonsil herniation could precipitate brainstem compression. However, anticipated high-pressure CSF gushers frequently encountered in CC, Type 2 CH, and incomplete partition anomalies pre-empt an intraoperative/ postoperative continuous lumbar drain [7, 8].

When the IAM opens directly into the inner ear there is more chance of the electrode entering the IAC unintentionally [8] causing facial or vestibular stimulation and an intraoperative imaging is necessary to confirm the presence of an intracochlear electrode.

Soft tissue complications following surgery may occur due to inflammatory reactions and lead to delay in implant use or extrusion of the implant. In our case the child developed a supra-aural seroma which was managed conservatively. The most probable cause of seroma in our case was an upper respiratory tract infection, likely following an abnormal immune response to viral infection. Another possibility considered was a reaction to silicone in the cochlear implant or to the Surgicel leading to inflammation and seroma [9, 10].

Conclusion

Cochlear implantation can be safely performed in patients with inner ear anomalies and complex syndromic skeletal and cranial anomalies. Preoperative imaging plays a key role in identifying anomalies and planning the surgery.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Consent

Informed consent was obtained from the patient.