Hair mercury concentrations in cats and dogs in central Japan.

Hair mercury concentrations were measured in 41 cats and 34 dogs living in Kanagawa, Saitama and Tokyo Prefectures. Total mercury concentrations measured by atomic absorption spectrometry were significantly higher (P < 0.01) in cats [7.40 parts per million (ppm) in males and 7.45 ppm in females] than in dogs (0.99 ppm in males and 0.66 ppm in females). Mercury in cat hair was correlated with age (P < 0.01) and higher in cats fed with foods prepared by the owners than in those fed with commercial pet foods. Mercury concentrations in the animals' foods were markedly higher in fresh tuna (0.153 ppm) than in commercial pet foods (0.008-0.014 ppm).

Chronic otomastoiditis: a conceptual understanding of CT findings.

Inflammation of the middle ear cleft is a disease of great interest from both clinical and radiologic points of view. The attic floor (tympanic diaphragm), the tympanic isthmus, and the aditus ad antrum play important roles in inflammatory processes of the middle ear cleft. The anatomy of the temporal bone at this level was examined by studying microdissections of 250 fresh temporal bones and reviewing over 1,000 high-resolution computed tomography (CT) scans of the temporal bones. The pertinent anatomy is described, and the role of the tympanic diaphragm and isthmus in determining the degree to which middle ear disease may progress is stressed. The appearances on CT scans of chronic otomastoiditis, tympanosclerosis, cholesterol granuloma, attic retraction pocket, and acquired cholesteatoma are reviewed and illustrated.

Acute otomastoiditis and its complications: role of CT.

Acute bacterial (suppurative) otomastoiditis responds to antibiotic treatment; radiologic study is required only when there is clinical suggestion of coalescent mastoiditis, intracranial complications, or an underlying chronic disease. Computed tomography (CT) is the method of choice for evaluating otogenic intra- or extra-cranial complications. CT scans can show stages of disease progression when infection has spread by way of soft tissue, blood, and bone pathways into the dural venous sinuses, meninges, labyrinth, facial nerves, epidural and other intracranial spaces. When there is clinical suggestion of acute coalescent mastoiditis, a CT scan of the temporal bone can confirm the presence of rarefying osteitis, coalescence of the air cells, and subperiosteal abscess.

Computed tomography in the diagnosis of primary tumors of the petrous bone.

This paper constitutes an evaluation of 23 patients with signs and symptoms of 4 types of tumors: 6 congenital epidermoids, 3 cases of meningiomas presenting within the temporal bone, 2 cases of jugular fossa schwannomas, 3 cases of glomus tympanicum, and 9 selected cases of glomus jugulare tumors. Since these tumors occur insidiously and are located in an inaccessible region of the skull, they are usually not diagnosed until they reach considerable size and cause multiple cranial nerve deficits or intracranial complications. Assessment of these tumors and subsequent surgical management depend primarily on the preoperative radiographic findings. CT and dynamic CT study have proven to be extremely valuable and accurate in the diagnosis of these lesions. Epidermoids have a characteristic CT appearance. Dynamic CT is often helpful in differentiating glomus tumors from meningiomas and schwannomas. Involvement of the middle ear, labyrinth, intracranial, and extracranial components of these tumors can be best evaluated by CT. This paper places special emphasis on congenital cholesteatoma (epidermoid) and draws relevant conclusions about the diagnostic work-up.

Role of the tympanic ring in the pathogenesis of congenital cholesteatoma.

Topographic study of congenital cholesteatomas revealed that the majority of these congenital epidermal cysts occur near the tympanic isthmus of the middle ear. Since this is the junction of the first and second brachial arch, the origin of the cholesteatoma could be linked to the migration of the external canal ectoderm into the middle ear at the early stage of development. Embryologic study showed that the tympanic ring plays an important role in limiting the medial extent of the external canal to the level of the tympanic annulus. Migration of the ectodermal tissue into the middle ear beyond the annulus is likely to be caused by the failure of this inhibitory function of the tympanic ring. Microscopic sections of human fetuses were studied to determine the developmental relationships between the external canal ectoderm and the tympanic ring. A section from a 161/2-week fetus showed significant papillary ectodermal tissue projection into the mesenchyme near the tympanic isthmus, while the tympanic ring was absent in that site. Anatomical distance between the tympanic ring and the internal auditory canal is extremely short in these fetuses. This is suggestive of the source of petrous cholesteatomas from the canal ectodermal migration. These observations form the basis of the author's theory that the pathogenesis of congenital cholesteatomas is caused by migration of external canal tissue into the tympanic isthmus or into the petrous bone as a result of developmental error in which the advancing external canal ectoderm failed to receive stop signal of the tympanic ring that contains the ectoderm at the annular plane.

The tympanic isthmus: its anatomy and clinical significance.

The tympanic isthmus is a narrow passage between the tubotympanic cavity and the atticomastoid air space. Obstruction of the tympanic isthmus is frequent in various types of middle ear disease and causes significant air-diffusion disturbance within the temporal bone pneumatic system. Using large numbers of fresh temporal bone specimens, anatomical boundaries of the tympanic isthmus are defined and pathological variations are investigated. Embryological origin of the isthmus and pathophysiological implications of the tympanic isthmus block are discussed. Among factors that cause obstruction of the tympanic isthmus are mucosal folds variations, inflammatory webs and exudate, retracted tympanic membrane, diseased attic mucosa, and cholesteatoma. Each factor is analyzed with representative specimen photographs. Clinical signs due to tympanic isthmus block often simulate or coexist with symptoms of eustachian tube obstruction. Surgical management of the tympanic isthmus block requires clear recognition of these disease processes. Understanding of the tympanic isthmus as an anatomical entity is essential in the management of middle ear and attic disease.