Akihiro Ikai

Dangerous angles and depths for middle ear and middle cranial fossa injury during arthroscopy of the temporomandibular joint

PURPOSE Several reports have suggested a risk of injury to the middle cranial fossa and middle ear during arthroscopic procedures in the superior joint space of the temporomandibular joint (TMJ). However, there has been no anatomic study of directions and distances of the TMJ from the posterior portal in relation to the risk of mandibular fossa injury. In this study, the angles and depths at which the risk is greatest for injury to the deepest point of the mandibular fossa (DP) and to the middle ear during arthroscopy were analyzed. MATERIALS AND METHODS Three-dimensional measurements of 96 mandibular fossae in 48 dry skulls were made. RESULTS It was found that the distance from the lateral rim of the fossa to DP and Hugiers canal was 9.50 +/- 2.07 mm and 17.04 +/- 3.09 mm, respectively. The most dangerous angle for DP injury in the Frankfort horizontal plane (FH plane) was an inclination of the instrument base of -8 degrees dorsad and 17 and 19 degrees caudad in the frontal plane. The most dangerous angle for Hugiers canal injury was a tilting of the instrument base of 15 degrees ventrad in the FH plane and -2 degrees craniad in the frontal plane. However, these values showed a wide range. CONCLUSION It was concluded that great care must be exercised in manipulation of instruments near the DP and Hugiers canal to avoid injury to the middle ear or penetration into the middle cranial fossa.

Localised Amyloidosis of the Palate: Multislice Helical Computed Tomography and Magnetic Resonance Imaging Findings

Abstract Localised amyloidosis in the head and neck is a rare disease. This report presents a 43-year-old woman with localised amyloidosis of the hard palate. Multislice helical computed tomography and magnetic resonance imaging findings are discussed. Computed tomography findings are non-specific with various degrees of contrast enhancement resulting from the degree of vascularity in the lesion. Signal intensities on both T1 and T2-weighted magnetic resonance images resemble those of skeletal muscle, and significant enhancement on enhanced T1-weighted magnetic resonance imaging is noted.