The caloric test has been used worldwide for many years. It is a clinical test that is performed to evaluate the function of the lateral semicircular canal, by irrigation of the external auditory canal with warm or cold water. This irrigation generates a convective flow in a duct of the lateral semicircular canal, stimulating or suppressing the canal, and inducing nystagmus and vertigo. Robert Bárány termed the neurologic response to the irrigation of water of different temperatures, the “caloric response.” The duration or the maximum angular velocity of the slow phase of the nystagmus is used as the evaluation index. Caloric stimulation is the only test in which the right ear and the left ear can be stimulated separately. When the caloric response is weak, canal paresis is diagnosed. The caloric test was established by Bárány, who was awarded the 1914 Nobel Prize in Physiology/Medicine for it. To obtain a strong response, the recording must be done while the subject is in complete darkness. During the caloric test, a visual suppression test is also performed to check the activity of the central vestibular system. During the caloric response, the subject looks at a visual target for 10 seconds in light. The slow phase eye velocity of the caloric nystagmus should reduce, and the reduction ratio is used as the evaluation index in the visual suppression test. In this review, the history, basic neurophysiological findings, recording methods, data interpretation, and future of the caloric and visual suppression tests are described.

　A-43-year-old woman with bipolar disorder who was receiving combined therapy with lithium carbonate (400 mg/day) and lamotrigine (100 mg/day) visited us with a history of having recently experienced, on two occasions, sudden wobbling with a fainting sensation, nausea, and vomiting on her way to work. She had no other symptoms, including auditory symptoms. A few hours after she vomited, the symptoms gradually disappeared on both occasions. Subsequently, she has occasionally felt a faint sensation, for instance, when she abruptly stopped to walk. She was also worried about falling while climbing down stairs. MRI revealed no remarkable findings. The serum level of lithium was 0.29 mEq/L, which was within the therapeutic range (0.3-1.2 mEq/L). The characteristic findings on the ENG were as follows: (1) both in light and in the dark, square wave jerks (SWJs) were clearly recognized at the primary eye position; (2) downbeat nystagmus (DBN) was observed mainly at the primary eye position or downward gaze in the dark; (3) the vertical pursuit, especially upward, consisted of saccadic pursuits, while the horizontal pursuit was well preserved; (4) the horizontal and vertical saccades were relatively well preserved. However, post-saccadic drift (glissade) was observed after the upward saccade, and the latency of the downward saccade was slightly delayed; (5) the peak slow phase velocities and frequencies of the horizontal/vertical OKN were reduced; (6) the OKAN was preserved bilaterally, although the SWJs were remarkably intermingled with the OKAN; (7) caloric nystagmus was induced bilaterally; (8) the visual suppression (VS) ratio was reduced bilaterally. These ENG findings mainly suggested dysfunction of the cerebellar systems and deterioration of the neural integrator in the brainstem. The symptoms subsided after discontinuation of the lithium carbonate, and the DBN and postsaccadic drift in the ENG disappeared gradually.

　The present report suggests that lithium intoxication should be considered in the differential diagnosis in a patient taking lithium carbonate presenting with dizziness, whose ENG shows DBN, SWJs and abnormalities of smooth pursuit, OKN, and OKAN.

　Purpose: Optokinetic nystagmus (OKN) testing is an important oculomotor function test for differentiating between central vertigo and peripheral vertigo. Bárány's hand-rolled OKN drum has been used for qualitative screening. An optokinetic stimulator that projects a visual pattern on a large screen and an installation space equivalent to it is necessary for quantitative laboratory testing. The recent advances in programming technologies have enabled the development of a mobile application (app) that allows optokinetic stimulation with controllable stimulus speed and visual pattern. We investigated the effectiveness of a locally-designed OKN app for screening oculomotor function and compared its efficacy with that of Bárány's hand-rolled OKN drum. A questionnaire survey was conducted to evaluate the test burden on the examinee.

　Methods: The iPad was placed in front of the subject's eyes, so that the black-and-white striped pattern of the locally-designed OKN app was at 30° with the visual angle in the horizontal direction. OKN was induced with the OKN app on the iPad or by rotating Bárány's black-and-white striped drum in either the horizontal or vertical direction. Qualitative evaluation of the ability to induce OKN was performed using ENG recordings.

　Results: The eye tracking of a small visual target that moved horizontally on the iPad was smooth in 11 of the 13 healthy subjects. The OKN evoked by the OKN app was sufficient for evaluation in both stimulus directions. No subject reported any autonomic symptoms such as nausea or cold sweats. Only one subject developed mild dizziness during the optokinetic stimulation. The OKN evoked by Bárány's OKN drum was also sufficient for evaluation; however, the stimulus speed was occasionally difficult to control.

　Conclusions: The OKN app can have a variety of uses, including in diagnosis, medical education, and vestibular rehabilitation.

　Postoperative vertigo is one of the common complaints after cochlear implantation (CI). Recently, development of new electrode designs and minimally invasive surgery have enabled preservation of residual hearing. At our department, an atraumatic electrode, FLEXSOFT^® of MED-EL, is inserted via the round window approach (RWA) and dexamethasone is administered intraoperatively and postoperatively to preserve vestibular function, regardless of the level of residual hearing ability. This retrospective study was aimed at determining the frequency of equilibrium dysfunction after minimally invasive CI.

　Between April 2018 and March 2019, 10 adult patients underwent minimally invasive CI surgery at our institution. The equilibrium function in these patients was assessed based on the symptom of vertigo, nystagmus, results of the caloric reflex test, measurement of vestibular evoked-myogenic potential (VEMP), and static stabilometry, before surgery and at various intervals after the surgery. One year after the surgery, 1/10 patients (10%) reported dizziness, and nystagmus was observed in 2/10 patients (20%). There were no abnormal results of the caloric reflex test after the surgery (0/4 side). Examination of the ocular VEMP (oVEMP) showed abnormal values before surgery on all sides. Examination of cervical VEMP (cVEMP) showed abnormal values after surgery on 5/9 sides (56%). In the static stabilometer test, there was no significant deterioration in either the Romberg's ratio of velocity with foam rubber or the foam ratio of velocity with eyes closed after the surgery.

　Our study showed that the functions of the saccule can become impaired after minimally invasive CI. cVEMP may be most sensitive for detection of problems after CI surgery, since the saccule is anatomically closer to the implanted cochlea as compared to other vestibular organs.

　Paraneoplastic neurological syndrome (PNS) is a rare syndrome representing the remote effect of a cancer, that is often associated with the presence of specific serum antibodies. PNS can affect the central, peripheral, and autonomic nervous systems at various levels. Clinically, it is characterized by subacute progression of neurological dysfunction and substantial refractoriness to therapies. Herein, we report a case of PNS with dizziness and bilateral progressive sensorineural hearing loss. A 65-year-old woman complaining of numbness in the left upper extremity, abnormal sensation in the limbs, and dizziness and light-headedness during walking visited our otolaryngology department. At the first visit, she showed pure rotatory nystagmus, and in the stepping test, she almost fell over to the right within a few steps. Thereafter, the right sensorineural hearing loss was recognized, and the nystagmus changed to a left-beating horizontal-torsional nystagmus; the hearing loss progressed even after oral steroid treatment. At week 14 after the first visit, the muscle weakness in her limbs worsened and the patient became unable to move or walk herself, and sensorineural hearing loss developed on the left side. She was admitted to the department of neurology for closer examination. Finally, the diagnosis of PNS was made based on the detection of a squamous cell carcinoma of the lung and positive test result for anti-Ma1 antibody and anti-Ma2 (Ta) antibody. After the steroid pulse therapy and chemotherapy, the tumor shrank, but the neurological symptoms persisted, with only slight improvement. The patient died ten and a half months after her first visit to our department.