CSF Gusher and Its Management in Cochlear Implant Patient with Enlarged Vestibular Aqueduct

Abstract

Aim is to share our experience of CSF gusher and its management during cochlear implant surgery in patients with enlarged vestibular aqueduct. All cases underwent classic cochlear implant surgeries via Veria technique. It is a retrospective study done at Civil Hospital Ahmedabad from January 2013 to March 2018 with 415 patients. The study includes 39 children between age groups 2–8 years who have enlarged vestibular aqueduct. In all 39 patients with enlarged vestibular aqueduct during cochleostomy there was CSF gusher which was managed by the covering the cochleostomy site with temporalis fascia. There was no need for use of fibrin glue in any case. But it was kept in standby mode in case needed. And there was no post operative CSF otorrea in any patients. While preparing the patient for cochlear implant whenever you come across enlarged vestibular aqueduct via HRCT temporal bone and MRI of cochlea, be prepared for CSF gusher while doing the cochleostomy. Csf gusher is intra operative challenge rather than a bad prognostic determine for post operative audiologic out come. Keeping fibrin glue in stand by helps if major CSF leaks happens. Finally, we achieved a simple stepwise algorithm for the management of gusher during cochlear implantation.

Introduction

Cerebrospinal fluid (CSF) gusher means the profuse amount of flow of CSF during cochleostomy while doing cochlear implantation. Before the cochlear implant era, this condition was termed perilymphatic gusher which was found during stapedectomy in patients with an excessively wide internal auditory meatus (IAM) or the large vestibular aqueduct syndrome (LVAS). In cases of gusher, the fluid coming from the inner ear is the CSF and not the perilymph owing to it being a few microliters [1]. The first report of a gusher during cochlear implant surgery in an inner ear malformation was by Miyamoto et al. [2]. They experienced a gusher during cochleostomy in an ear with Mondini deformity. Normally, CSF is not there in the cochlea; the CSF in the subarachnoid space extends laterally into the internal auditory canal (IAC) up to the fundus, where it is separated from the perilymph by a bony plate termed the cribriform plate; however, it can access the cochlea and may be encountered during cochlear implantation either through an abnormal developmental pathway of the otic capsule, usually when there is deficient cribriform plate, or after traumatic disruption of the temporal bone.

Developmental abnormalities of the cochlea-vestibular apparatus in which there are high chance of CSF gusher include an abnormally wide IAC (IAM), LVAS, incomplete partition type II (Mondini) malformation, and common cavity malformation [3]. The majority of these anomalies usually can be found by preoperative imaging; however, unexpected CSF leaks may occur at the time of accessing the basal turn of the cochlea for insertion of the electrode array, whether through a round window or through the Veria technique anterior inferior to round window if no preoperative radiologic evidence available of any congenital inner-ear malformation.

Papsin [4] reported seven cases in a series of 103 patients with malformations; they also stated that the term gusher should be used only to describe the pulsatile egress of fluid that lasts for up to a minute and then subsides.

In known case of CSF gusher it was considered contradiction to cochlear-implant surgery. The first case with LVAS was first implanted in 1995 and since then, patients with a variety of preoperatively identified cochlear and labyrinthine abnormalities have been implanted with minimal complications and a reasonable post implantation audiologic profile gain [5].

Materials and Methods

It is a retrospective study done at Civil Hospital Ahmedabad from January 2013 to March 2018 with 415 patients. The study includes 39 children between age groups 2–8 years who have enlarged vestibular aqueduct. Incidence of CSF gusher, different management strategies for CSF gusher at the time of surgery, and also the postoperative CSF otorrhea was measured.

In Preoperative evaluation following was done.

Otologic examination, Audiologic evaluation, A high-resolution computed tomography (CT) scan of the temporal bone with bony cochlea and MRI brain with 7th 8th cranial nerve, Bill’s bar, Broca’s area and Internal Auditory meatus(IAM) was performed for all cases before surgery to detect the different types of congenital anomalies, which were classified according to Jackler et al. [6].

Surgeries were performed using a standard endaural incision (Fig. 1.) extending to squamous part of temporal bone. The superficial layer (skin and subcutaneous tissue) is elevated first followed by the deep layer of muscle and periosteum (Fig. 2). A suprameatal hollow is made measuring 5 mm × 5 mm × 5mm postero-superior to the bony canal (Fig. 3). Through the anterosuperior portion of hollow a tunnel is drilled in the posterior canal wall by 1.6 mm burr with a guard (Fig. 4). Cochleostomy was performed in all cases anteroinferior to the round window, Irrigation done inside the cochlea to remove bone dust and filled with gel foam (Fig. 5). Tympanomastoid portion of temporal bone is drilled to make the implant bed using the template. Tunnels are made above the bed and sutures passed through these tunnels and over the implant for anchoring and fixing the implant. Inserted implant secured in position by 2-0 prolene “double suture”. Rest of implant inserted between bone and periosteum. A groove is drilled from implant site towards the suprameatal hollow where in the end a tunnel is made connecting the hollow with the drilled.All cases with CSF gusher were detected at the time of surgery (Fig. 6). Electrode is passed through the tunnel, then through the suprameatal hollow in the postero-superior tunnel, through the middle ear finally into the cochlea (Fig. 7). The rest of the electrode array is placed like a loop in the suprameatal hollow and partly covred with bone dust (Fig. 8). Cochleotomy site was covered with temporalis fascia and gusher was stopped (Fig. 9). Tympanomeatalplap repositioned and gelfoam placed in canal. Working of implant confirmed with DIB (diagnostic interface box)-telemetry done. Electrode status checked and found ok. Wurzburg flap closed by interrupted 3-0 monocryl. Skin and subcutaneous tissue closed by interrupted 3-0 prolene. Neosporin wick kept in the canal. Mastoid bandage was given. No post op CSF otorrea or facial palsy.

Fig. 1.

Marking of incision

Fig. 2.

Incision and flap elevation

Fig. 3.

Making bed and suprameatal well

Fig. 4.

Making tunnel for electrode

Fig. 5.

Cochleostomy anteroinferior to RW

Fig. 6.

CSF gusher from cochleostomy

Fig. 7.

Insertion of electrode

Fig. 8.

Fixing Implant in bed with nylon suture

Fig. 9.

Sealing of cochleostomy with temporalis fascia graft

Results

Thirty nine cochleostomy gushers were identified among the 415 studied patients, at an incidence of 9.39%. The mean age of these nine patients was 4.5 years months (ranging from 2 to 8 years).

Table 1 shows that there was a significant difference regarding the occurrence of CSF gusher during cochleostomy among ears with congenital inner ear malformation when compared with others with no anomalies (the P value using Fisher’s exact test was 0.000005).

Table 1.

CSF gusher incidence

	CSF gusher at the time of cochleostomy		Total
	Yes [n (%)]	No
Congenital inner ear malformation	38 (9.15)	11	49
No congenital inner ear malformation	1 (0.24)	365	366
Total	39 (9.39)	376	415

In all thirty nine cases with CSF gusher, we didn’t needed lumbar drain or experienced postoperative meningitis; the gusher was fully controlled during surgery, and there was no postoperative leak encountered in any patients.

During surgery, when cochleostomy was d one CSF gusher occurred, and after waiting for its flow to decrease, a regular straight electrode array Cochlear Nucleus CI24RE(ST) was inserted into the cochleostomy. CSF continued to leak from the cochleostomy, so we stopped it by just sealing of the cochleostomy with the temporalis fascia graft winding around electrode.

Inner ear anomalies that developed gusher during cochleostomy in this study included all cases in which there was large vestibular aqueduct present.

Discussion

Although the occurrence of CSF gusher during cochlear implantation has been described by many authors in the literature, the incidence and the management of this surgical difficulty during surgery remains very variable among different institutes.

Packing the cochlea: Either sealing the cochleostomy site or whole packing the basal turn Firm packing around the electrode is important in patients with gusher. Continuous leak can cause, CSF rhinorrhea through the Eustachian tube or subsequent meningitis [7], and the risk of electrode extrusion [8, 9]. The fascia or the muscle can be applied around the cochleostomy site or packing of the basal turn around the electrode array may be carried out. In this study, sealing the cochleostomy site after electrode insertion was sufficient enough to stop CSF leak in all nine cases, and there was no need to obliterate the whole basal turn around the electrode array. Two cases needed further application of soft tissue into the cochlear lumen: one of these two cases was a common cavity and the soft tissue used was used not only to stop the gusher but also to align the electrode array against the wall of the common cavity so as to stimulate the largest possible number of spiral ganglion neurons, which is usually sparse in this type of deformity.

Excessive CSF can usually access the cochlea through patent developmental pathways of the otic capsule, the most common of which are a wide IAC, common cavity malformation, and a large vestibular aqueduct (LVAS), and any anomaly that results in incomplete turns in the cochlea increases the risk of a CSF gusher as in cases of incomplete partition type II termed after Mondini [1, 10]. In a review of the literature, most authors reported the incidence of gusher to be between 40 and 50% of their patients with inner-ear malformations; CSF leak from the cochlea can usually be anticipated as this occurs most often in cases of a congenitally abnormal inner ear [11–13].

It is important that the CT scan of the inner ear be reviewed carefully before surgery. That serves a two-fold purpose. One is to assess the ability to insert the whole array and the second is to be prepared for a possible gusher. The family and the patient can be counseled appropriately. They should be warned of potential complications, the potential for prolonged hospital stays, and the incidence of meningitis, despite the meningococal vaccine was given for all cases prior to surgery.

We classified CSF gusher during cochlear implantation into simple CSF ooze, which stops spontaneously by continuous suction, positioning of the patient in the anti-trendelenburg position, hyperventilation, and decreasing the end tidal CO₂ below 28. Simple gusher included cases in which the gusher stopped with simple insertion of the electrode array, whereas when gusher stopped on sealing the cochleostomy with muscles harvested from the temporalis muscle, it was termed mild gusher.

Hyperventilation causes a decrease in the cardiac output and subsequently decreases the intracranial pressure and the CSF pressure. Decreasing the end-tidal CO2 below 28 mmHg causes cerebral vasoconstriction.

Electrode insertion through the cochleostomy while CSF gusher increases the technical difficulty of the operation, because refraction through the clear fluid makes it difficult to visualize the electrode as it passes through the cochleostomy. At the same time, the surgeon may introduce the electrode array towards a bony structure, and the tip of the electrode may be damaged [14, 15]. During cochlear implantation in gusher-prone cases, there is a debate about the size of cochleostomy; some authors claimed that a small cochleostomy is the one of choice, allowing the electrode cable to partly block the flow of CSF, whereas others reported the importance of a slightly larger cochleostomy to allow extra mobility with the instruments to pack the cochleostomy reinforced with connective tissue, muscle, and fibrin [4, 16]. In this study, we used a 1-mm course diamond bur to create the cochleostomy anteroinferior to the round window. The tip of the suction was introduced at the edge of the cochleostomy, making a continual suction of CSF either totally or until suffi cient visualization was obtained to introduce the electrode array into the cochlear lumen without traumatizing the tip of the electrode array.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in this study involving human participant were in accordance with the ethical standard.