Neuro-otological examinations are important in the diagnosis of subtentorial lesions, because there are sometimes no other neurological signs in the early stage. Recent progress in radiologic imaging, especially MRI, has made it possible to diagnose intracranial lesions more easilly, but the functional assessment of abnormal lesions seen with MRI must be confirmed by neurological examinations. A cerebellar tumor was diagnosed by neuro-otological examinations and MRI in an 18-year-old male who complained of dizziness. He had received radiation therapy for a pineal tumor seven years earlier. Neuro-otological examinations such as positioning down beat nystagumus and dysmetria of eye movement suggested tumor in the cerebellum. After radiation therapy, the tumor signs disappeared on MRI, and the neuro-otological signs also improved. Two months later, neurological symptoms appeared again, and recurrence of the tumor was confirmed by MRI. As the tumor grew, the symptoms grew worse. Finally the tumor was removed surgically and identified as anaplastic astrocytoma. During the clinical course the severity of the neuro-otological findings corre-sponded to the extent of the tumor in the cerebellum. It was very helpful to follow this patient with neuro-otological examinations as well as radiologic imaging, to predict the prognosis.
An 81-year-old female complained of double vision and oscillopsia. Right medial longitudinal fasciculus (MLF) syndrome associated with convergence, trochlear and abducent palsies, and counterclockwise rotatory nystagmus was diagnosed. Her MR image showed infarction in the right tegmental portion of the pons. Symptoms of MLF syndrome and associated palsies resolved two weeks later, and the electronystagmography then revealed reduction of the quick phase of caloric nystagmus on the right and of transient ocular deviation (TOD) in head torsion to the right. These findings suggested that the primary lesion might be in the paramedian pontine reticular formation (PPRF) and have affected the MLF and nuclei of cranial nerves III, IV and VI for two weeks from the onset. The rotatory nystagmus recognized for two months was believed to have been caused by an ischemic lesion in the medulla which could not be seen in the MR image.
Three patients treated with microvascular decompression to relieve severe disabling rotatory vertigo were followed for two years. All patients had relief of symptoms. The results show that microvascular decompression is an effective way to treat disabling severe vertigo, but two of them complained of occasional brief episodes of floating sensation. Vestibular function tests of these two patients showed biphasic head-shaking nystagmus in one patient and paralytic nystagmus in the other. Caloric responses were not abnormal. Possible neural mechanisms related to neurovascular compression of the eighth cranial nerve are discussed with special reference to vestibular symptoms.
Spontaneous nystagmus was examined in 38 patients with lateral medullary infarct syndrome. Although horizontal nystagmus is commonly observed in this syndrome, the direction of nystagmus is not always consistent with the side of the lesion. Horizontal nystagmus beats away from the side of infarction in 79% of patients. Meanwhile, torsional nystagmus which is characteristic of this syndrome beats away from the side of infarction (ipsilateral slow phase beats) in all cases. In an investigation of the mechanism of torsional nystagmus, patients were assigned to one of two groups: typical form (lesions of the descending root of the trigeminal nerve) and ventral form (no or incomplete involvement of the root of the trigeminal nerve). Although horizontal nystagmus occurred in both the typical and the ventral form, torsional nystagmus was observed only in the typical form. Furthermore, cerebellar signs were more common within patients with torsional nystagmus than in those of horizontal nystagmus. There-fore, it is suspected that torsional nystagmus in the lateral medullary infarct syndrome may originate not in ventral but in rostral and dorsal lesions of the medulla, including the vestibular nucleus, which is related to torsional and vertical eye movements.
In this study conditions necessary for inducing horizontal positioning nystagmus were investigated. These conditions were the speed of head rotation (slow or quick), the plane of head rotation (frontal, sagittal or horizontal), the angle of the axis of head rotation with gravity (head rotation in the horizontal plane in the sitting position or in the supine position) and the direction of head rotation. The results suggest that an essential condition is the velocity of head rotation in the perpendicular plane to provoke horizontal positioning nystagmus and that lesions in the cupulo-endolymph system are not responsible for horizontal positioning nystagmus. It was speculated that unilateral utricle dysfunction (such as separation of otoconia from the otolithic membrane) might be the primary cause of the pathophysiology. So head rotation in the perpendicular plane might send a mistaken velocity signal to the central nervous system and finally provoke horizontal positioning nystagmus related to head velocity. It may be that a velocity signal is formed in the central nervous system when one detects a moving pattern that occurs as utricular afferents with different polarization vectors are excited sequentially by a rotating gravity vector (Raphan T and Cohen B 1981).
Two kinds of experimental endolymphatic hydrops were produced:one was induced by obstruction of the endolymphatic sac, and the other was induced by systemic KLH immunization and secondary KLH challenge into the endolymphatic sac. Vascular permeability of the stria vascularis was compared in the two models by light and electron microscopy using the tracer horseradish peroxidase (HRP) method. The ratios of capillaries showing HRP leakage to capillaries observed were 7/33 in the endolymphatic sac obliteration model, 36/39 in the secondary challenged side, and 13/37 in the non-secondary challenged side of the immunologically induced model. Permeability to HRP was significantly higher in the secondary challenged side than in either the endolymphatic sac obliteration model or the non-secondary challenged side. The present study raises the possibility that endolymphatic hydrops is induced by overproduction of endolymph.
Thirty five patients with congenital horizontal nystagmus (except nystagmus alternans and latent nystagmus) were examined electronystagmographically. All patients underwent the following tests of eye movements:gaze test, optokinetic pattern test (OKP), eye tracking test (ETT) and pendular rotation test (PRT) while gazing at a stationary target point. If the nystagmus had the element of saccade at least in the uni-directional gaze test, we defined it as "jerky type", and when the nystagmus had no saccade in the bilateral gaze test, we defined it as "pendular type". 1. Five patients had pendular type and 30 patients had jerky type nystagmus. 2. One patient who showed no response in the OKP test had pendular type nystagmus and another with inversion of OKP clearly had jerky type. 3. We considered that lateral gaze nystagmus and inversion or no response in the OKP test are related to the direction of eye movement. 4. Disorders of smooth pursuit in ETT were much better compensated in PR T while gazing at a stationary target point in patients with jerky type than in those with pendular type congenital nystagmus. 5. Rehabilitation is considered to be of value for patients with congenital nys-tagmus, especialy of the jerky type.
The effects of optokinetic stimulation (OKS) on postural control were investigated by recording the sway of the center of gravity with OKS at a constant velocity of 30°/sec in 8 patients with cerebello-pontine angle tumor with on unsteadiness or vertigo and in 32 normal subjects. In the patients, small tumors had been demonstrated by MRI. 1. In the normal subjects, there was no laterality in OKS tests, and body sway was almost the same with the eyes closed. 2. In the patients tested with OKS, sway velocity was significantly faster than in the controls (P<0.01). 3. In the patients, sway ares, RMS and SDY were greater on the side of the tumor. The relationship between OKS and body sway is discussed.
In order to demonstrate equilibrium ataxia during motion sickness, we examined 12 normal adult volunteers with sharpened Romberg tests and standing on one leg with eyes closed. They underwent the tests before riding and after riding in a car 10 times on course A with straight streches and unidirectional curves, and after riding 10 times on course B with straight streches, S-shaped curves, and right and left turns. The eight subjects who became sick showed a significant decrease in the duration of steady standing after driving on course B. No significant change was noted in the four subjects who did not become sick. The results support the theories that motion sickness, whether it occurs during walking while wearing horizontally reversing goggles or during riding in a car, is evoked by spatial disorientation which produces not only autonomic nervous symptoms but also equilibrium ataxia.
Infrasound below 50 Hz at 100 to 110 dB SPL, generated by an instrument for ear drum massage, was applied for 60 sec. through a rubber tube to each ear canal in 14 normal adults and 25 patients with endolymphatic hydrops. The normal group showed no notable increase in the area of body sway or in nystagmus during infrasound application. The mean value of the sway area in the hydrops group showed no marked difference from that of the normal group or between before and during infrasound application; however, 17.6% and 11.8%, respectively, had a marked increase in the sway area and in horizontal nystagmus toward the exposed side during exposure to infrasound. This study confirms that some patients with certain features of endolymphatic hydrops may manifest infrasound effects on vestibular function.
Two patients with anterior inferior cerebellar artery syndrome and cerebellar infarction due to compression of the vertebral artery, caused by atlantoaxial dislocation were treated successfully. Case 1 : a 56-year-old male began having vertigo with sudden sensorineural hearing loss. Case 2 : a 28-year-old female had Ménière's disease-like symptoms. Both patients were treated surgically with reposition and fixation of the atlantoaxial joint. Compression of the vertebral artery was confirmed at surgery. No attacks of vertigo have occurred since surgery.
To clarify the mechanism of the development of equilibrium skills, a study was done of subjects standing on a freely movable balance-board who practiced maintaining their balance while moving freely in a left-right direction. Swayings of the head and of the body's center of gravity (BCG), activities of both soleus muscles and the inclination of the balance-board before and after training were recorded with a polygraph and analyzed with the use of a 5-dimensional feedback model. We observed acquisition, maintenance and transfer gained by training. (1) Acquisition was manifested by the effects of training on four healthy adults using a balance-board for 30 minutes daily for two months. (2) Maintenance was mani-fested in two of the subjects by grades of acquisition after a rest period of a month. (3) Transfer was manifested by the effects of training in two separate healthy adults standing on one foot for 20 minutes daily for two months instead of using a balance-board. Results : (1) Acquisition training using a balance-board led to regular swayings of the head and BCG, and steady activities of both soleus muscles without burst discharge, with subsequent horizontal maintainability of the balance-board. Swa-yings of the head and BCG and muscle activity corresponded to the movement of the balance-board. Muscle activity, especially, showed high power and fine control up to a high frequency. (2) Maintenance acquired balance-board training effects were decreased, but maintained. (3) Transfer : the ability to maintain balance acquired by training in standing on one foot to some degree equalled that acquired by using a balance-board. We noted that maintenance of a steady standing posture was possible because labyrinthine and proprioceptive postural regulations became precise with pre-dominant improvement in spinal proprioceptive reflexes.
Endolymphatic hydrops was produced in guinea pigs, and the inner ear microvasculature was observed morphologically. Then inner ear circulatory disturbance was induced by noise exposure in ears with endolymphatic hydrops and the changes were observed morphologically. Glycerol was administered to the animals before and after noise exposure and the differences were compared. 1) Examination of the inner ear vessels by the casting method revealed slight vasoconstriction-like changes in the vessels of the cochlear lateral wall and narrowing in the capillary of the saccular macula, which suggested the presence of slight inner ear circulatory disturbance. 2) In ears with endolymphatic hydrops exposed to noise, blood cell sludge was observed around the upper turn of the cochlea from the upper coiled arteriole to the capillary of the stria vascularis under light and electron microscopy by the cracking method. Observation by the casting method also revealed the vasoconstriction-like changes of the capillary of the stria vascularis around the upper turn of the cochlea. Even when the frequency of the noise applied was changed, similar inner ear circulatory disturbances occurred around the upper turn of the cochlea, which suggests that this region is the site most liable to injury in ears with endolymphatic hydrops. 3) When glycerol was administered to ears with endolymphatic hydrops under noise exposure, distension of Reissner's membrane was decreased, blood cell sludge was diminished and vasoconstriction-like changes of the capillary of the stria vascularis were not observed. Compared to ears with endolymphatic hydrops under noise exposure without glycerol administration, the severity of hydrops and the circulatory disturbance were clearly reduced. These results suggest that improvement of the inner ear circulatory disturbance as well as the osmotic force of glycerol are involved in the relief of endolymphatic hydrops.
Pendular optokinetic nystagmus(P-OKN) was studied with the use of a rotating optic cylinder, artificial visual field defects and a rotating chair. The optokinetic stimuli consisted of twelve stripes rotating with a variable velocity (pendular rotation). The pendular rotation was applied at a frequency of 0.1 Hz and a peak velocity of 120 degrees/sec. Artificial visual field defects were made with contact lenses to simulate foveal vision, peripheral vision, and hemianopsia. Rotation of the chair was applied at 2 and 8 degrees/sect at a uniform angular acceleration and a peak angular velocity of 100 and 160 degrees/sec. 1. At the same absolute speed of the optical cylinder, nystagmus was larger in the accelerating phase than in the decelerating phase. The P-OKN field was on the quick phase side during cylinder acceleration and on the slow phase side during cylinder deceleration. 2. Foveal and peripheral vision had the same effect on P-OKN. With foveofugal optokinetic stimulation, P-OKN showed good release in the accelerating phase but poor release in the decelerating phase. With foveo-petal optokinetic stimulation, P-OKN release showed no relationship between acceleration and deceleration. With artificial visual field defects, the P-OKN field was on the quick phase side when visual function was good and shifted to the slow phase side when visual function was reduced. 3. P-OKN was promoted when the head was rotated in the direction opposite to that of optical cylinder rotation. On the other hand, when the head and the optical cylinder both rotated in the same direction, P-OKN was inhibited. With head rotation at 2 degrees/sec2, promotion of P-OKN was stronger than inhibition. On the other hand, promotion was weaker than inhibition at 8 degrees/sec2. The field of optokinetic nystagmus was biased to the quick phase side (promotion) compared with the slow phase side (inhibition).
In a previous report the anthor described a new air caloric test with continuous thermal change. In this study, 19 patients with vestibular disorders were examined with this technique, and the results were compared with the results of the water caloric test (30°, 50ml, 20seconds) in the same subjects. A difference in interaural response to the air caloric test with continous thermal change was noted in nine of the 19 patients (47.4%), greater than with the water caloric test, five of 19 (26.3 %). The detectability of vestibular disorders with the air caloric test with continuous thermal change (28 of 38 ears ; 73.7 %), was significantly higher than that with the water caloric test (8 of 38 ears ; 21.1 %) (P<0.01). The air caloric test with continuous thermal change seems to estimate vestibular function more precisely, because stimulation by this method is too weak to cause vestibular recruitment.
Angular acceleration of head movement was measured with the Watson angular accelerometer which is based on piezoelectric vibrating beam technology. The angular accelerometer fixed on the head can detect the action of the 3 semicircular canals, measuring movement in the coronal plane (right and left direction : R-L), sagittal plane (anterior and posterior direction : A-P), and axial plane (horizontal direction : HOR) of the head. In static postures, angular acceleration registrography is greatly influenced by the pulse in sitting and Romberg positions. In normal subjects, averaged amplitude was larger when blindfolded than with eyes open, and larger in unstable than in stable postures. According to the direction measured, averaged amplitude was larger on the HOR than A-P plane and larger on the A-P than R-L plane. Averaged frequency was lower when blindfolded than with eyes open, and lower in unstable than in stable postures except in the one leg position It was significantly lower on the HOR than R-L or A-P plane. In artificial disequilibrium models, averaged amplitude increased as the frequency of nystagmus increased under caloric stimulation and with the eyes blindfolded, it also increased when galvanic stimulation was either on or off. Averaged frequency decreased as averaged amplitude increased. Angular acceleration registrography as used in this study detected dysfunction of the semicircular canals more clearly than did linear acceleration registrography reported previously. Angular acceleration registrography was also measured during stepping. The parameter was amplitude of "specified angular acceleration" which was significant angular acceleration of the head toward the opposite site when one leg was elevated. In normal subjects, amplitude of specified angular acceleration with left leg elevation was almost equal to that with right leg elevation. It seemed that specified angular acceleration acted on the semicircular canals, and this modulated bilateral muscle tension in the legs to make stepping performance smoother. In artificial disequilibrium models, a significant difference in the amplitude of specified angular acceleration between right and left was seen in proportion to stimulation intensity similar to the deviation of body sway. These findings suggest that the function of the right and left semicircular canals can be demonstrated by this difference.