Eye Movements Induced by Stimulation to the Otolith Organs

Background: We have been performing a canalith repositioning procedure for benign paroxysmal positional vertigo. When we adopted the Epley maneuver for posterior semicircular canal type, and affected-ear-up 90° maneuver for lateral semicircular canal type, we noticed that no nystagmus occurred in the sitting position just after treatment. Despite direct excitation to the utricle by the pathological debris, none of the subjects complained of dizziness. Thus, we hypothesized that nystagmus and dizziness do not occur by stimulation of the otolith organs. Objective: The aim of the study was to observe and record the eye movements induced by the otolith organs to confirm our hypothesis. Materials and Methods: Twelve healthy humans were tested. In the sitting position, the head was tilted to the right ear by 45° and vice versa. Afterward, the head was bent forward by 90° (nose-down), and the subject’s seat was reclined to the head-hanging position. Each position was kept for five seconds. We interviewed the subjects to assess their dizziness. Results: None of the subjects showed nystagmus and complained of dizziness in every position. Conclusions: Nystagmus does not occur by the stimulation to the otolith organs;therefore, ocular counter-rolling is a semicircular canal ocular reflex.

Affected-Ear-Up 90°Maneuver Proves That Nystagmus Does Not Occur by the Stimulation to the Macula of the Utricle

Background: The utricular macula is located on the floor of the utricle, approximately in the plane of the lateral semicircular canal, and is oriented to respond best to lateral tilts and side-to-side or fore-and-aft translations of the head. However, the details of the otolith ocular reflex are unknown. Pathophysiology of transient direction-changing geotropic positional nystagmus is a canalolithiasis in the lateral semicircular canal. The principle of affected-ear-up 90° maneuver is moving debris from a long arm to the utricle, therefore debris stimulates the utricular macula in the sitting position after the treatment. Objective: To clarify whether nystagmus occurs by the stimulation to the macula of the utricle. Methods: The subjects were 10 patients with lateral semicircular canal canalolithiasis. After the diagnosis, we performed affected-ear-up 90° maneuver immediately. We observed eye movements in the sitting position (chin-down 30°) just after the treatment. Results: No one showed nystagmus in the sitting position after the treatment. In all patients, positional nystagmus disappeared within 7 days after the treatment. Conclusion: Nystagmus does not occur by the stimulation to the macula of the utricle. Hence, we cannot assess the function of the utricle by the analysis of eye movements, and ocular counter-rolling is considered to be a semicircular canal ocular reflex.

A 7-Year-Old Boy with Light Cupula of the Horizontal Semicircular Canal

Report of childhood positional vertigo is very rare. We present a 7-year-old boy who revealed persistent direction-changing geotropic positional nystagmus. In the supine position, horizontal nystagmus toward the left continued as long as the position was maintained. However, it ceased when the head was turned to the right side by 45°. With greater head turn (right-ear-down), nystagmus toward the right lasted for more than 1 minute. In the left-ear-down position, horizontal nystagmus toward the left occurred and lasted for more than 1 minute. After the disappearance of positional nystagmus, we detected canal paresis of the right ear by caloric test. We considered that the pathophysiology of the persistent type of geotropic nystagmus is a result of light debris cupulolithiasis of the horizontal canal.

Vestibular Rehabilitation for the Patients with Intractable Vestibular Neuritis

Objective: To clarify whether vestibular rehabilitation is effective in improving spontaneous nystagmus in patients with intractable vestibular neuritis. Methods: The subjects were 8 patients (6 females and 2 males) with vestibular neuritis who revealed long-lasting (more than 2 months since the onset) horizontal spontaneous nystagmus toward the healthy side. We used thumbs-up head shaking for vestibular rehabilitation. This exercise involves active head shaking (1 Hz) while staring at one’s thumb nail. One set is 10 cycles. We asked the patient to do 3 sets (morning, afternoon, and night) every day. Results: The mean value of the slow-phase velocity of spontaneous nystagmus before treatment was 4.1°/s, and that 3 months after vestibular rehabilitation was 4.1°/s. No improvement was observed. Conclusion: Vestibular rehabilitation is not always effective in improving spontaneous nystagmus in patients with intractable vestibular neuritis. Therefore, clinicians should consider the possibility of long-term incomplete central compensation.

水平半规管眼反射是否受耳石器传入的影响？

目的:探讨水平半规管眼反射是否受耳石器传入的影响。方法:7名健康受试者接受了右耳的冰水刺激。受试者保持左耳向下约20s,然后转为俯卧位、右耳向下和仰卧位,每个体位保持约20s。采用三维视频眼震图记录眼震。结果:仰卧位和俯卧位时以及左耳向下和右耳向下时的眼动不对称,提示不同头位时眼动轴向受重力影响。结论:耳石器传入能影响水平半规管眼反射的轴向,因此,水平半规管诱发的代偿性眼动可能不与水平半规管平面平行。