Graeme Clark Collection
Permanent URI for this collection
Search Results
1 - 3 of 3
-
ItemThe postnatal growth of the temporal bone and its implications for cochlear implantation in children( 1993)The postnatal growth of the human temporal bone was examined by direct anatomical measurements on 60 cadaver specimens of all ages. The bones were dissected as one would perform cochlear implant surgery using a posterior tympanotomy approach. Nineteen anatomical /surgical landmarks with implications for cochlear implant surgery were identified on each bone and the distance between these points measured. The temporal hone was found to be a complex structure, phylogenetically, anatomically and functionally consisting of four different parts with independent postnatal development. The inner and middle cars were adult size at birth. The external auditory canal and most parts of the temporal hone were subject to significant lateral growth. The size of the pneumatised mastoid increased in all directions. In the facial recess, however, no postnatal growth was observed. Between birth and adulthood an average of 12 mm (SD 5 mm) of growth was seen directly between the sino-dural angle and the round window, the landmarks approximating the Implantation site for the receiver-stimulator and the electrode entry point into the inner car. However, if an electrode leadwire is fixed at a cortical fixation site such as the posterosuperior point of Macewen's triangle, the leadwire would be subject to approximately 20 mm of growth. These results indicate that a paediatric cochlear implant design incorporating an expandable leadwire to accommodate this growth should allow up to 25 mm of leadwire lengthening. The fossa incudis showed no growth relative to the round window and was found to be a convenient fixation site for the electrode array close to the cochlea. From an anatomical and surgical point of view, cochlear implantation in very young children is feasible, provided the electrode array is secured and the design accommodates for controlled leadwire lengthening.
-
ItemThe postnatal growth of the temporal bone and its implications for cochlear implantation in children( 1993)The growth of the human temporal bone is of practical concern if young children are implanted. It is feared that the normal development of the temporal bone after implantation may displace the electrode array and jeopardize the success of the device. To evaluate the extent of growth 60 cadaver specimens of all ages were examined by direct anatomical measurements. The bones were dissected by imitating the cochlear implantation surgical procedure in the temporal bone laboratory. 19 anatomical/surgical landmarks with implications for cochlear implant surgery were identified and the distance between them measured. The inner ear and middle ear are adult size at birth. The external auditory canal and most parts of the temporal bone are subject to significant lateral growth. The size of the pneumatised mastoid was found to increase in all directions. In the facial recess however, no postnatal growth could be noted. Between birth and adulthood a considerable amount of growth is to be expected between the sino-dural angle and the round window, the landmarks representing the implantation site for the receiver/stimulator and the electrode entry site respectively. From an anatomical and surgical point of view, cochlear implantation in very young children proved to be feasible, provided the electrode array is secured close to the cochlea and the design accommodates for controlled leadwire lengthening.
-
ItemThe postnatal growth of the temporal bone and its implications for cochlear implants in children( 1993)An understanding of the postnatal growth of the temporal bone is an important prerequisite for the development of cochlear implantation in very young children. Such information will have an important bearing on both the design of the implant and the surgical procedure. We have measured the postnatal growth of the temporal bone by direct anatomical measurements on 60 cadaver specimens with ages ranging from 2 months to 84 years. Nineteen anatomical landmarks with implications for cochlear implant surgery were identified on each bone and the distance between these points measured. The inner and middle ears were adult size at birth. The external auditory canal and most parts of the temporal bone were subject to significant lateral growth. The size of the pneumatized mastoid increased with age in all directions. Significantly, no postnatal growth was observed in the facial recess. The fossa incudis showed no growth relative to the round window and was found to be a convenient fixation site for the electrode array close to the cochlea. However, with the electrode leadwire fixed at a cortical site such as the osterosuperior point of McEwan's triangle, the leadwire would be subject to approximately 20 mm of growth between this point and the cochlea. These anatomical results indicate that a paediatric cochlear implant would require an expandable leadwire to accommodate these growth changes.