The purpose of this study was to determine the normal variations of cochlear nerve canal dimensions, which is useful information to have when assessing congenital malformations, i.e. during the preoperative evaluation of cochlear implant candidates. The length and diameter of the cochlear nerve canal were measured in 117 casts from randomly selected temporal bone specimens obtained from the Uppsala Temporal Bone Laboratory. In 16 of the casts the dimensions were correlated with those obtained from CT scans of the same temporal bone. Measurements were also made from CT examinations of the temporal bone of 50 patients referred for evaluation of cholesteatoma or chronic otitis media. The mean length and diameter in the axiopetrosal plane measured in casts were 1.17 and 2.58 mm, respectively. The mean diameter in the axial plane was 2.59 mm. The mean length and diameter determined from CT scans of the specimens were 1.19 and 1.98 mm, respectively. The mean length and diameter determined from CT examinations of patients were 1.08 and 1.91 mm, respectively. In conclusion, the cochlear nerve canal is short, with a circular cross-section. If the diameter of the canal is < 1.4 mm then the possibility of cochlear nerve abnormality should be considered; if it is > 3.0 mm then other anomalies may coexist.

Stjernholm C. Aspects of temporal bone anatomy and pathology in conjunction with cochlear implant surgery. Stockholm 2002.Cochlear implantation is a treatment for patients with severe sensorineural hearing loss/deafness, who get no help from ordinary hearing aids.The cochlear implant is surgically placed under the skin near the ear and a very thin electrode array is introduced into the cochlea of the inner ear, where it stimulates the remaining nerve fibers (1,2). The operation is complicated; it is performed with the aid of a microscope, and involves drilling very close to vital vessels and important nerves.The method was introduced in Sweden in 1984 by Professor Göran Bredberg, then at Stockholm Söder Hospital.High resolution computed tomography (CT) of the temporal bone is a part of the preoperative evaluation preceding cochlear implantation. It is a method for visualizing the bony structures of the middle and inner ear -to diagnose pathology and to describe the anatomy.In Stockholm, these examinations have usually been performed at the Radiology Department of Stockholm Söder Hospital. Examinations of cochlear implant candidates from other parts of Sweden and from abroad are also sent there for special reviewing.The first work concerns CT of the temporal bone and cochlear implant surgery in children with CHARGE association. This is a rare condition with multiple congenital abnormalities, sometimes lethal. Children with CHARGE have different combinations of disabilities, of which impairments of vision and hearing, as well as balance problems and facial palsy can lead to developmental delay. There have been few reports of radiological temporal bone changes and none of cochlear implant surgery for this group. The work includes a report of the findings on preoperative CT and at surgery, as well as pos-timplant results in two children. A review of the latest diagnostic criteria of CHARGE and the temporal bone changes found in international literature is also included.The conclusion was that certain combinations of temporal bone changes in CHARGE are, if not specific, at least extremely rare in other materials. CT can visualize these changes and be used as a diagnostic tool. This is important, since some of the associated disabilities are not so obvious from the start. Early treatment is vital for the child's development. This work also shows that cochlear implantation may help some of these often very isolated children to communicate.The second work is a radioanatomic study of one of the structures of the inner ear -the bony canal for the cochlear nerve. It involves measurements of the dimensions of the canal on 117 silicone rubber casts of the temporal bone (from a unique collection of casts at Uppsala temporal bone laboratory) and on 50 clinical CT-studies (100 ears). The purpose was to show the normal variation, which is of use in the appraisal of congenital temporal bone malformations on CT.Based on our results we propose that if the canal is less than 1.4 mm, as measured on CT, the possibility of cochlear nerv...

Stjernholm C. Aspects of temporal bone anatomy and pathology in conjunction with cochlear implant surgery. Stockholm 2002.Cochlear implantation is a treatment for patients with severe sensorineural hearing loss/deafness, who get no help from ordinary hearing aids.The cochlear implant is surgically placed under the skin near the ear and a very thin electrode array is introduced into the cochlea of the inner ear, where it stimulates the remaining nerve fibers (1,2). The operation is complicated; it is performed with the aid of a microscope, and involves drilling very close to vital vessels and important nerves.The method was introduced in Sweden in 1984 by Professor Göran Bredberg, then at Stockholm Söder Hospital.High resolution computed tomography (CT) of the temporal bone is a part of the preoperative evaluation preceding cochlear implantation. It is a method for visualizing the bony structures of the middle and inner ear -to diagnose pathology and to describe the anatomy.In Stockholm, these examinations have usually been performed at the Radiology Department of Stockholm Söder Hospital. Examinations of cochlear implant candidates from other parts of Sweden and from abroad are also sent there for special reviewing.The first work concerns CT of the temporal bone and cochlear implant surgery in children with CHARGE association. This is a rare condition with multiple congenital abnormalities, sometimes lethal. Children with CHARGE have different combinations of disabilities, of which impairments of vision and hearing, as well as balance problems and facial palsy can lead to developmental delay. There have been few reports of radiological temporal bone changes and none of cochlear implant surgery for this group. The work includes a report of the findings on preoperative CT and at surgery, as well as pos-timplant results in two children. A review of the latest diagnostic criteria of CHARGE and the temporal bone changes found in international literature is also included.The conclusion was that certain combinations of temporal bone changes in CHARGE are, if not specific, at least extremely rare in other materials. CT can visualize these changes and be used as a diagnostic tool. This is important, since some of the associated disabilities are not so obvious from the start. Early treatment is vital for the child's development. This work also shows that cochlear implantation may help some of these often very isolated children to communicate.The second work is a radioanatomic study of one of the structures of the inner ear -the bony canal for the cochlear nerve. It involves measurements of the dimensions of the canal on 117 silicone rubber casts of the temporal bone (from a unique collection of casts at Uppsala temporal bone laboratory) and on 50 clinical CT-studies (100 ears). The purpose was to show the normal variation, which is of use in the appraisal of congenital temporal bone malformations on CT.Based on our results we propose that if the canal is less than 1.4 mm, as measured on CT, the possibility of cochlear nerv...