Cerebrospinal fluid leaks can either be caused by trauma, can pre-exist congenitally, or can appear spontaneously. In cases of CSF leaks, a reliable detection of its origin is needed in order to seal the leaks efficiently, and to prevent complication such as meningitis. With this video, we aim to present a method to identify a temporal basal cerebrospinal fluid leak.
The case of a child with a bilateral temporal bone malformation was chosen in order to demonstrate how the intrathecal application of fluorescein can assist the orientation in anatomical variations or malformations, especially in temporal bone surgery, where a precise work, and also a good knowledge about the anatomical structures, is mandatory. The safety can be increased to a large extent by applying this method. This video protocol was approved by the local Ethics Committee in accordance with the Helsinki declaration.
Informed consent was obtained from all the participants.Protocol. Preparation for surgery. Make sure to obtain audiological testing, high-resolution computer tomography, and MRI of the skull base.
Obtain written informed consent about the off-label use of fluorescein. In a first step in preparation for surgery, perform lumbar puncture and place a lumbar drain for later application of the dye. Use fluorescein sodium with a 10%concentration.
For lumbar application, dilute the fluorescein to a 5%concentration with aqua. Apply 0.1 milliliter of the dilution per each 10 kilograms of body weight, with a maximum of one milliliter intrathecally. Perform the application immediately before surgery in order to achieve intraoperative visualization.
When applying the method in children, the application should be performed in general anesthesia. General anesthesia is performed according to the patient's individual clinical history and risk factors according to the decision of the anesthesiologist. Cover the microscope with a blue light filter to visualize the fluorescein, or use a fully digital microscope.
Use sterile draping to cover the patient.Surgery. For the transmastoid approach, perform mastoidectomy and posterior tympanotomy. Expand the surgery according to the expected origin of the leak.
As a first land mark, expose the dura to the middle cranial fossa. Thin out the posterior canal wall of the outer ear canal. Expose the short incus process in the antrum, and identify the lateral semicircular canal.
As the next surgical step, expose the chorda facial angle, where the chorda tympani leaves the facial nerve. Open the facial recess. Leave the facial nerve with a bony coverage.
Access the middle ear through posterior tympanotomy. The origin of the fluid leak can easily be identified in the stapes footplate. Use fascia from the temporal muscle and absorbable collagen-fibrin sealant patches to seal the CSF leak until no more fluid leaves the footplate.
The stapes superstructure is stabilizing the sealant.Results. In the presented case, minor trauma has led to a CSF leak from the nose in a ten month old child. MRI revealed bilateral temporal bone malformation, with aplasia of the right cochlea and a dilatation of the left cochlea and vestibule, with absent interscalar septum.
Identical to an incomplete partition type I.Brainstem-evoked audiometry was performed and confirmed bilateral deafness. Since high-resolution computer tomography did not reveal the origin of the CSF, fluorescein assisted transmastoidal auto-basal exploration with simultaneous cochlea implantation was indicated. During primary surgery, the trans-mastoidal approach was used to identify the CSF in the stapes footplate, to seal the leak, and to perform cochlear implantation for hearing restoration.
Six months after prior surgery, the child suffered from meningitis caused by mastoiditis. The implant was removed and the electrode array was left as a spacer. Postoperatively, the oral smell detected beta transferrin.
Revision mastoidectomy was performed, showing a dislocated coverage of the leak in the stapes footplate. The stapes was completely removed, and the oval window was sealed using temporal muscle, temporal fascia, and absorbable collagen-fibrin sealant patches. The stapes was investigated under the electron microscope, showing the malformated footplate with perforation.
In order to reduce the pressure onto the leak, lumbar puncture was performed daily. Five days after revision, no more beta transferrin was detected. During cochlear implant revision six months later, the coverage of the oval niche was intact.
The presented case shows that the intrathecal application of fluorescein can be used for the intraoperative identification of auto-basal CSF leaks. It facilitates the orientation in malformations or in a complicated or unknown anatomical variation of the temporal bone. This method has been used in several of our clinical cases, and the results confirm the visibility of safely accessing the origin of the leak.
