Bilateral Cochlear Implantation in a Child With Galloway-Mowat Syndrome: A Case Report

Introduction

Galloway-Mowat syndrome (GAMOS) is an extremely rare genetic disorder characterized primarily by the early onset of steroid-resistant nephrotic syndrome, microcephaly, and diverse brain anomalies. The syndrome was first identified and described by Galloway and Mowat in 1968 [1]. The symptoms of GAMOS vary widely. In addition to the key features, affected individuals may have facial development abnormalities, hiatal hernia, short stature, and impaired psychomotor and intellectual development. In addition, GAMOS can present with hypotonia, micrognathia, pachygyria, and epilepsy [2–4].

Most cases of GAMOS are inherited in an autosomal recessive fashion. Mutations in multiple genes, including components of the KEOPS complex and WDR73, have been identified, reflecting the syndrome’s genetic heterogeneity [5,6]. Vision and hearing impairments are well recognized, yet they are often addressed separately in research and health care service planning. However, in children with congenital anomalies, these impairments frequently co-occur, a condition referred to as dual sensory impairment (DSI). The presence of DSI significantly affects daily functioning and presents challenges for professionals from various disciplines who must provide integrated therapeutic solutions to optimize their patients’ abilities [7,8].

In managing DSI, the development of auditory skills is crucial, as they are a foundation for communication and speech development. Research and clinical practice have consistently demonstrated that cochlear implantation offers significant auditory benefits for children with prelingual profound hearing loss, making it one of the most effective treatment options available [9–12]. Nevertheless, cochlear implantation can be particularly challenging in cases involving anatomical abnormalities of the inner ear. Such situations require a high level of surgical expertise, with a strong focus on preserving residual hearing and maintaining the cochlea’s anatomical integrity. Even in anatomically challenging cases, an atraumatic round window approach is preferred [13,14] because it minimizes damage to cochlear structures. This approach has been continually developed at the Institute of Physiology and Pathology of Hearing since 1997 in adults and since 2004 in children [15,16]. Clinical evidence suggests that in patients with inner-ear malformations, using soft electrodes helps preserve cochlear integrity and maximizes hearing outcomes [16,17].

To the best of our knowledge, this is the first description of bilateral cochlear implantation in a child with GAMOS. Here, we discuss the surgical, audiological, and rehabilitative implications of this intervention.

Case Report

We present the case of a young boy, born in April 2021 and diagnosed with Galloway-Mowat syndrome at another tertiary referral center, who was admitted to our Institute in November 2021 for evaluation of suspected profound hearing loss. Ethics committee approval was obtained for the intervention, and written informed parental consent was provided (IFPS: KB/Application 12/2024). ABR performed previously (July 2021) and reconfirmed at our Institute showed no responses in either ear. The pregnancy and perinatal history were unremarkable, and no exposure to ototoxic medications (eg, aminoglycosides) was documented during neonatal care. Additional clinical features included cerebellar hypoplasia, hypotonia (reduced muscle tone), and epilepsy. He also had severe visual impairment, likely due to optic nerve dysgenesis. The classification of “severe” visual impairment, along with the assessment of all other comorbidities, was made at a specialized clinical center. Our description of these findings is based on previously obtained medical documentation from that center. The patient had a healthy sibling with normal hearing. Magnetic resonance imaging confirmed the cerebellar hypoplasia, and high-resolution computed tomography (HRCT) revealed mild bilateral dysplasia of the cochlea’s middle and apical turns, with no other temporal bone abnormalities (Figures 1, 2).

Due to bilateral deafness and lack of response to hearing aids, cochlear implant (CI) surgery was recommended. The first procedure was performed in March 2023 on the left ear (at age 2 years). After the posterior tympanotomy, a partial bony overgrowth of the round window niche was encountered (Figure 3). After careful surgical exploration and removal of excess bone tissue, the round window membrane was found to be of normal size (Figure 4). A Med-El Flex 28 soft electrode was selected and inserted fully, without appreciable resistance, into the cochlea (Figure 5). The surgery was completed without complications, and the initial results were deemed satisfactory. The child was fitted with a Med-El Sonnet 2 behind-the-ear speech processor. He immediately demonstrated a noticeable improvement in auditory responsiveness. He began showing interest in sound-producing toys, consistently responded to sounds, and even had trouble falling asleep in noisy environments. Additionally, he showed sound source-searching behavior.

In January 2024, the right ear was implanted at age 2 years 9 months. In line with our program’s protocol, we applied structure-preserving partial deafness treatment (PDT) principles – a round window approach and soft-electrode insertion – which we use across the spectrum of hearing loss severity, including profound deafness. As with the first implant, a Med-El Flex 28 soft electrode was used, and the second surgery likewise proceeded without complications. The second surgery again required special attention to the round window area, which was partially obstructed by bone (similar to the first ear). Careful, staged removal of excess bone allowed clear access to the round window and enabled precise placement of the electrode array. Objective device checks were performed on both implants: Impedance and Field Telemetry (IFT) and Auditory Nerve Response Telemetry (ART ECAPs) were within expected limits across all electrodes bilaterally. To avoid additional radiation exposure to a young child, postoperative CT imaging was not performed. By the latest follow-up, the child showed clinically meaningful gains in auditory responsiveness and sound awareness. Approximately 6 months after activation of the second implant, a behavioral observation audiometry (BOA) test was performed at the follow-up visit. He responded to acoustic stimuli presented from various directions. During a speech therapy session, he listened and reacted to the therapist’s voice and to various musical instrument sounds. According to the mother, the child’s communication showed significant improvement, as reflected by a higher score on the adapted version of the LittlEARS Auditory Questionnaire at follow-up. He also started to communicate with his siblings using simple sounds, and he began attending a specialized kindergarten for children with special needs. An overview of key clinical events is presented in Table 1.

Discussion

SURGICAL CHALLENGES:

We present the first reported case of bilateral cochlear implantation in a child with Galloway-Mowat syndrome. The present case involved a child with profound bilateral deafness, cerebellar hypoplasia, dysplasia of the cochlea’s middle and apical turns, and visual impairment likely caused by optic nerve dysgenesis. A hearing impairment this profound has not (to our knowledge) been previously documented in GAMOS. Similarly, we know of no prior cases of cochlear implantation in GAMOS, whether unilateral or bilateral.

The surgery was carried out in accordance with established PDT principles. The round window approach used for this patient is a standard surgical technique at our Institute [15–17,19]. Although a bony overgrowth partially encroached on the round window niche, it did not prevent successful implantation. Importantly, this overgrowth did not extend into the cochlear interior, but was limited to the bony capsule. The round window approach is critical for minimizing trauma to inner-ear structures and for ensuring optimal electrode placement [17,19].

Use of a soft, lateral-wall array (Med-El Flex 28) facilitated full insertion in dysplastic anatomy while minimizing insertion forces. Soft electrodes minimize the risk of trauma to delicate inner-ear structures and lessen the chances of adverse auditory outcomes [20]. In cochlear dysplasia involving the apical or middle turns, soft electrodes can improve implantation outcomes by allowing a gentler, deeper insertion, which is an advantage when anatomical abnormalities are present. Research shows that children with Mondini dysplasia, a spectrum of inner-ear abnormalities that includes the dysplastic cochlear anatomy observed in our patient, can achieve hearing and speech outcomes comparable to those of children with normal inner-ear anatomy, demonstrating the effectiveness and safety of cochlear implantation in such cases. There is also a risk of an intraoperative cerebrospinal fluid leak, but it can generally be well controlled with appropriate precautions [21,22].

AUDIOLOGICAL OUTCOMES:

Before surgery, the child did not react to any sounds, even at 80 dB with fitted hearing aids. At early follow-up, BOA demonstrated reliable detection of acoustic stimuli from multiple directions; the therapist observed increased responsiveness to voice and musical instruments, and a caregiver report (an adapted version of LittlEARS) indicated clear improvements. Before implantation, at the metrical age of 2 years, the child scored 1 point on the LittlEARS questionnaire. Despite using hearing aids, auditory development did not progress. We repeated the LittlEARS assessment after bilateral cochlear implantation, when the child was 3 years 4 months old. Although the LittlEARS questionnaire is designed to assess auditory development up to a hearing age of 24 months, we administered it in this case due to the child’s complex medical background and delayed auditory development. The post-implantation score increased to 20 points, corresponding to an estimated hearing age of approximately 10 months. These benefits likely reflect the combined effects of bilateral stimulation, an atraumatic round window approach, and soft-electrode placement.

Interpretation of behavioral thresholds in this case requires caution. This patient’s combination of severe visual impairment, profound hearing loss, central nervous system anomalies, and global neurodevelopmental delay affects the reliability and repeatability of subjective measures such as BOA and lowers maximum attainable scores. Accordingly, results from any single test session are best viewed as trend indicators rather than as fixed benchmarks of performance.

In a child with dual sensory loss and neurodevelopmental impairment, expectations should not be too high, as dramatic improvements in open-set speech perception are unlikely. Instead, we believe that success should be defined in terms of consistent sound awareness, better environmental orientation, enhanced alertness and attention to sound, and stronger caregiver–child interaction. In this regard, the caregiver’s appraisal is essential; parent-reported outcomes should be the primary endpoints, together with objective measures and clinical observations.

REHABILITATION IN DUAL SENSORY IMPAIRMENT:

In a deaf child with a congenital complex malformation, and when vision is also markedly impaired, improved hearing is particularly important. In such circumstances, hearing becomes a critical sensory modality that allows the child to better navigate their environment and communicate effectively. In cases of dual sensory impairment, cochlear implantation can appreciably enhance quality of life by providing opportunities for interactions that would otherwise be severely limited [23–25]. The auditory input from a CI becomes a vital channel for learning and social interaction. It is worth noting that other very rare syndromes have also had successful cochlear implant cases (eg, Brown-Vialetto-Van Laere syndrome [26]), underscoring the value of shared clinical experience. Establishing a multicenter registry for similar cases could provide a long-term database to help guide future management.

Conclusions

This report describes the first case of bilateral cochlear implantation in a child with Galloway-Mowat syndrome. Although we encountered some intraoperative challenges, such as bony overgrowth in the round window region and cochlear dysplasia, these obstacles were successfully managed using minimally invasive surgery. At this relatively early stage, the patient showed meaningful functional gains in sound awareness, as assessed by BOA, the LittlEARS questionnaire, and caregiver observations, which is especially important given his severe visual impairment. However, the long-term effectiveness remains to be established.