Hiroaki Ichijo

Differences in size and shape between the right and left sigmoid sinuses

SummaryWhether 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.

Positional nystagmus of horizontal canalolithiasis

Abstact Conclusion: Vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal flow is greater than that to ampullofugal flow in every component. Objectives: To clarify whether positional nystagmus of horizontal canalolithiasis contains vertical and torsional components, and to quantify the asymmetry of nystagmus. Methods: Twenty patients with transient direction-changing geotropic positional nystagmus were examined, and we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components. Results: Positional nystagmus was not purely horizontal. Fifteen (75%) patients revealed a vertical component and 19 (95%) patients had a torsional component. The mean value of MSV of the horizontal component in the affected-ear-down position was 51.5°/s and that in the healthy-ear-down position was 19.1°/s. The mean value of MSV of the vertical component in the affected-ear-down position was 8.7°/s and that in the healthy-ear-down position was 3.0°/s. The mean value of MSV of the torsional component in the affected-ear-down position was 12.8°/s and that in the healthy-ear-down position was 6.5°/s. For every component, MSV in the affected-ear-down position was significantly greater than that in the healthy-ear-down position (p < 0.01).

The relationship between mastoid pneumatization and the position of the sigmoid sinus

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.

The second and third phases of caloric nystagmus

Abstract Conclusion: The second and third phases of caloric nystagmus occur at a high rate. We can explain this phenomenon based on the hydrostatic pressure theory involved in perilymph. Objectives: To clarify the incidence of the second and third phases of caloric nystagmus, and to measure their intensity. Methods: The subjects were 12 healthy humans. The right ear was stimulated using iced water. The first phase of caloric nystagmus was recorded in a supine position. Immediately after the cessation of the first phase, each subject was repositioned to a prone position, and the second phase was recorded. Immediately after the halt of the second phase, each subject was repositioned to a supine position, and the third phase was recorded. Nystagmus was analyzed using three-dimensional video-oculography. Results: The mean value of maximum slow-phase velocity (MSV) of the first phase was 27.2°/s. All subjects revealed the second phase, and the direction was toward the right. The mean value of MSV was 7.2°/s. Nine subjects (75%) showed the third phase, and the direction was toward the left. The mean value of MSV was 2.7°/s.

Can caloric testing evaluate the function of vertical semicircular canals

Abstract Conclusion: Neither posterior nor superior semicircular canal receives a caloric effect; therefore, caloric testing cannot evaluate the function of vertical semicircular canals. Objective: To clarify whether caloric stimulation reaches the posterior and superior semicircular canals. Methods: The subjects were 10 healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a supine position for 40 s and then repositioned to a sitting position until horizontal nystagmus stopped; afterwards, a nose-down position was adopted. Nystagmus was analyzed by three-dimensional video-oculography. Results: In the supine position, four subjects revealed a vertical component and five subjects showed a torsional component. In the sitting position, neither a vertical nor a torsional component occurred when the horizontal component stopped. Three subjects revealed a vertical component and four subjects showed a torsional component in the nose-down position.

Asymmetry of positioning nystagmus in posterior canalolithiasis

Abstract Conclusions: Ewalds third law is correct in the posterior semicircular canal and the intensity of stimulatory nystagmus is 2.7 times as strong as that of inhibitory nystagmus. Objectives: Ewalds third law states that a flow of endolymph away from the ampulla causes more stimulation than a flow toward the ampulla in the posterior canal. The aims of this study were to quantify the asymmetry of positioning nystagmus in posterior canalolithiasis and to confirm the validity of Ewalds third law. Methods: Subjects were 20 patients who revealed typical vertical/torsional positioning nystagmus in the Dix–Hallpike test, 14 females and 6 males, with a mean age of 55.2 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 of three components (horizontal, vertical, and torsional). Results: The mean value of maximum slow-phase velocity (sum of three components) in the head-hanging position was 42.3°/s and that in the sitting position was 15.6°/s. The former was significantly greater than the latter (p < 0.01).

Comparative Study of Computerized Trapezoid Rotation Test and Sinusoidal Harmonic Acceleration Test

By using the Contraves computerized rotary chair system, trapezoid rotation (TR) test and sinusoidal harmonic acceleration (SHA) test were performed on each subject on the same day. The results in 25 normal volunteers and 145 patients with peripheral vestibular disorders were as follows: 1) As regards directional preponderance, the results of two rotation tests agreed in 75.9% of all patients, but a discrepancy was found in the rest. Abnormality was detected by TR test in 57.2% of all patients, and, less frequently, in 45.5% by SHA test. 2) In normal subjects, the maximum slow phase velocity of nystagmus provoked by TR test was greater than that of nystagmus provoked by SHA test using angular acceleration of a magnitude comparable to that in TR test. 3) As to the detection of abnormal VOR gain, the results of two rotation tests agreed in 100% of patients with bilateral vestibular disorders. However, in patients with unilateral vestibular disorders, the detection rate was higher for SHA test than that for TR test.

Onset time of benign paroxysmal positional vertigo.

Abstract Conclusion: Benign paroxysmal positional vertigo (BPPV) is strongly related to sleep. This study proposes a micro-otoconia accumulation theory in which the pathological debris is an aggregate of micro-otoconia over a long time period, and which begins to slide by its own weight during sleep. Objectives: To examine the onset time of idiopathic BPPV and to investigate its etiology. Method: Patients (n = 351) were classified as posterior canalolithiasis (PC), horizontal canalolithiasis (HC), and horizontal heavy cupula (HHC) according to nystagmus findings. This study examined the medical records, and categorized the onset times into the following four groups; (1) during sleep, (2) at the time of rising, (3) morning, and (4) afternoon. Results: PC (n = 135): In 33 patients, vertigo occurred during sleep, in 69 patients at rising, in 10 patients in the morning, and in 23 patients in the afternoon. HC (n = 87): In 38 patients, vertigo occurred during sleep, in 30 patients at rising, in eight patients in the morning, and in 11 patients in the afternoon. HHC (n = 129): In 27 patients, vertigo occurred during sleep, in 59 patients at rising, in 15 patients in the morning, and in 28 patients in the afternoon.

Is horizontal semicircular canal ocular reflex influenced by otolith organs input

Abstract Conclusion: Otolith organs input influences the axis of horizontal semicircular canal ocular reflex; therefore, the plane of compensatory eye movements induced by the horizontal canal stimulation is not always parallel to the canal. Objective: To clarify whether horizontal canal ocular reflex is influenced by otolith organs input. Methods: The subjects were seven healthy humans. The right ear was stimulated using ice-water. Each subject was kept in a left-ear-down position for 20 s and then repositioned to a prone position, a right-ear-down position and a supine position with 20 s intervals. Nystagmus was analysed using three-dimensional video-oculography. Results: Eye movements in the supine position and the prone position were not in a symmetric fashion. Nystagmus in the left-ear-down position and the right-ear-down position were not symmetric either. These phenomena indicate that the axis of the eyeball rotation was affected by the shift of the direction of gravity exerted on the head.

Vestibular Function in Bilateral Progressive Sensorineural Hearing Loss

To investigate the vestibular function in patients with bilateral progressive sensorineural hearing loss, we examined 5 cases using electronystagmography. Cases 1, 2 and 3 were adult type, and Cases 4 and 5 juvenile type. All patients had dizzy spells in the early stage of the disease, and showed spontaneous nystagmus. Bilateral reduction of caloric response and very low vestibulo-ocular reflex (VOR) gain on rotation testing were observed in Cases 1, 2 and 3. Case 4 showed right canal paresis upon the caloric test and left directional preponderance upon the rotation test. Case 5 showed good responses to both tests. Optokinetic afternystagmus (OKAN) in Cases 2, 3 and 5 was not brisk, and Cases 1 and 2 showed directional preponderance of OKAN. OKAN was useful for detecting directional preponderance. We believe there are two types of this disease which correlate with vestibular function. One type is associated with high grade vestibular dysfunction while, in the other, vestibular function is reasonably good.