The aims of the study were to clarify whether persistent direction-changing geotropic positional nystagmus contains vertical and torsional components, and to quantify the asymmetry. We analyzed nystagmus in four positions (healthy-ear-down, affected-ear-down, supine, nose-down) using three-dimensional video-oculography. Subjects were 18 patients with persistent direction-changing geotropic positional nystagmus, 16 females and 2 males, with a mean age of 55 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured maximum slow-phase velocity (MSV) of three components. Positional nystagmus was not purely horizontal. Eight (44%) patients revealed a vertical component (upward) and 15 (83%) patients had a torsional component in the healthy-ear-down position. Seven (39%) patients revealed a vertical component (downward) and 10 (56%) patients showed a torsional component in the nose-down position. The mean value of MSV of the horizontal component in the supine position was 9.3°/s and that in the nose-down position was 15.7°/s. The latter was significantly greater than the former (p < 0.05). Eye movements in the supine position and the nose-down position were not mirror images. These results suggest that vertical and torsional components occur from the horizontal semicircular canal, and that horizontal canal ocular reflex is influenced by input from the otolithic organs.
The aim of this study was to measure the neutral position of direction-changing apogeotropic positional nystagmus (heavy cupula of the horizontal semicircular canal) and persistent direction-changing geotropic positional nystagmus (light cupula of the horizontal semicircular canal). We conducted a prospective case series study on 31 patients with heavy cupula (12 males, 19 females; mean age, 64.3 years) and 33 patients with light cupula (10 males, 23 females; mean age, 60.9 years). We measured the angle of the neutral position in patients with heavy cupula (θ 1) and that in patients with light cupula (θ 2) using a large protractor. The mean value and standard deviation of θ 1 was 31.6 ± 22.4°, minimum value was 5°, and maximum value was 89°. The mean value and standard deviation of θ 2 was 44.4 ± 20.5°, minimum value was 5°, and maximum value was 85°. θ 2 was significantly greater than θ 1 (p < 0.05). The neutral position varies widely. Some patients exhibit a great angle (more than 40°); therefore, examiners should make patients adopt a completely lateral position in the supine head roll test and should confirm the direction of nystagmus in order to avoid mistaking positional nystagmus for spontaneous nystagmus.
Using high-resolution computed tomography, we measured the cross-sectional area of mastoid air cells and the shortest distance between the external auditory canal and the anterior edge of the sigmoid sinus (DIST), and then compared the right-left difference in 70 patients with unilateral chronic otitis media and 23 cases without middle ear disease. DIST was significantly short where there was poor mastoid pneumatization (P < 0.0001), regardless of whether it was the right or left ear. Furthermore, on the well-pneumatized temporal bone, the increase in size of the cross-sectional area was closely correlated with the increase in DIST (r = 0.495). We suggest that the relative position of the external auditory canal and the sigmoid sinus is affected by middle ear inflammations in childhood.
Whether or not the shape and size of the sigmoid sinus are affected by middle ear inflammation is still controversial. Using high-resolution computed tomography (CT), we examined the shape and cross-sectional area of the sigmoid sinus in 80 patients with unilateral chronic otitis media. Forty patients had right otitis media, and the others left otitis media. Whether chronic inflammation involved the right or left ear, a protrusive type of sigmoid sinus was found more frequently on the right than the left, while the cross-sectional area was significantly greater on the right. These findings suggest that a side difference affecting the sigmoid sinus would thus appear not to be caused by postnatal otitis media, but to originate in fetal life. The shape of the sigmoid sinus greatly varies among individuals and according to whether it is on the right or the left. Findings also indicate that a temporal bone CT is desirable to optimize surgical safety.
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