This paper presents two patients with chronic progressive hearing disturbance. Each patients had an intrameatal tumour, part of which extended to the cerebellopontine (CP) angle. In both cases, the patients were initially diagnosed with an acoustic neurinoma. A 63-year-old male experienced a hearing disturbance in the left ear for 1.5 years prior to visiting our hospital. Magnetic resonance (MR) imaging revealed a mass which was surgically resected. The tumour originated from the intrameatal dura mater. Histologically, the tumour was a meningioma. Similarly, a 53-year-old male presented with systemic lymphoma diagnosed 10 months earlier, and a hearing disturbance in the right ear that began 3 months prior to visiting our hospital. MR imaging prior to chemotherapy revealed a mass which extended to the CP angle. Part of the tumour in the CP angle disappeared after chemotherapy, suggesting a secondary lymphoma. Another tumour appeared later in Meckel's cave on the left side; however, it decreased in size following repeated chemotherapy. The present results indicate that differential diagnosis of intrameatal tumours and acoustic neurinomas may be difficult due to the small tumour size. Recent progress in neuroradiology may allow distinction of intrameatal tumours as a separate tumour classification. Our second patient is the sixth reported case of a CP angle lymphoma in the literature.

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Three-dimensional images of the incudostapedial joint (I-S joint) were reconstructed using helical computed tomography (CT). The images of the joint were most often reconstructed when threshold values were selected at −500 to −700 Hounsfield Units. These shapes were changed by choosing various threshold values. Histological examinations of the cadaver specimen indicate that these changes are due to structure of the I-S joints. We conclude that these 3-D images may be useful in assessing pathology of the I-S joint.

Three-dimensional (3-D) computed imaging was applied before surgery in 16 patients with nasal or paranasal disease. The images obtained by computed tomography (CT) were scanned by a personal computer. The contours of the organs were outlined on the scanned images, and the images were then reconstructed using 3-D imaging software. The resulting 3-D images were evaluated and compared with actual surgical images. The 3-D images were found to be useful for surgical procedures, because they facilitated recognition of the topologic relation between structure and lesion. Although this method requires a personal computer and an image scanner, it is cheaper than, and in some respects even superior to, a 3-D CT system.

We examined the shape of the jugular fossa and its protrusion into the tympanic cavity in 51 human skulls and in 355 various monkey skulls. All human specimens had a dome-shaped fossa, and the right fossa was larger than the left in 60 per cent of the specimens. Fossae protruded into the tympanic cavity in 20 per cent of these specimens.In contrast, none of the monkey specimens had a dome-shaped fossa. Some monkeys had saucershaped jugular fossa; the frequency of such fossa became higher as phylogeny progressed. Furthermore, the jugular fossae in monkeys did not protrude into the tympanic cavity. The shapes of both the jugular fossa and sulcus of the transverse sinus were generally symmetrical.The shape of the jugular fossa and its positional relationship to the tympanic cavity were considered from the viewpoint of the influence of phylogeny and the possible relationship to various otological problems.