Equilibrium Research Vol. 76(2017) No. 2
APRIL

　　Research into spatial orientation in the field of sports medicine is progressing very slowly. The reasons for this are the difficulties in recruiting top athletes with superior spatial orientation and in quantitatively evaluating spatial orientation during sports performance. We had the opportunity to perform a spatial orientation experiment on a top gymnast, and our results are presented in this report. Spatial orientation was evaluated using the head tilt perception gain (HTPG) derived from the subjective visual vertical when the head was in either an upright or tilted position. We measured the HTPG when the head alone was tilted, when the entire body was tilted, and when the body was subjected to a centrifugal force in a horizontal direction in the dark or with the aid of a static image that was not tilted from the perspective of the subject. Our results showed that the HPTG of the top gymnast was very accurate, compared with the results for normal individuals, under all the conditions examined. The top gymnast exhibited superior spatial orientation based on information obtained from an otolith, which is a gravity sensor in the inner ear. These results showed that the athlete did not depend on visual information to any significant degree. In addition, we have also discussed previous research regarding spatial orientation, in which eye movement and posture control were used as indicators. We hope that these previous reports, along with the results of the present study, become references for future spatial orientation research in the field of sports medicine.

　　Vestibular compensation after acute unilateral vestibular loss plays an important role in reducing uncomfortable symptoms, such as strong rotatory vertigo, nausea, and vomiting. In most cases of acute unilateral vestibular loss, the vestibular functions of the healthy side are temporally reduced but subsequently recover. This phenomenon is well known as vestibular compensation. In addition, the vestibular functions of the affected side also recover in some cases. To obtain an overall understanding of the vestibular function in cases with acute unilateral vestibular loss, vestibular function must be tested several times. However, the caloric test is not suitable for repetitive evaluations of vestibular function because it is time-consuming, labor-intensive, and tends to cause nausea.
　　The video Head Impulse Test (vHIT), a novel semicircular canal function test that was developed in 2009, is suitable for repetitive evaluations of vestibular function. The vHIT can be performed relatively quickly and is unlikely to cause nausea.
　　Here, we report a case of Ramsey-Hunt syndrome with frequent changes in the direction of gazed-nystagmus. We were able to evaluate the patient's complicated clinical course of vestibular function using vHIT in detail. We concluded that vHIT is a useful test for evaluating the clinical course of bilateral vestibular function in cases of acute unilateral vestibular loss.

　　Dizziness and vertigo are common symptoms associated with minor head trauma or whiplash. Although these symptoms improve within a few weeks in many patients, the symptoms can last much longer in some patients. Furthermore, patients with minor trauma often suffer from other symptoms such as hearing loss, tinnitus, olfactory dysfunction, or taste disorder. The aim of the present study was to clarify the process by which dizziness following trauma arises. We investigated 254 patients (115 males and 139 females, with an average age of 44.2 years) who suffered from chronic dizziness following trauma but who did not have any abnormal head CT or MRI findings. In each of the patients, we evaluated the vestibular function and hearing, taste and smell by performing a spontaneous or gaze nystagmus test, an ENG evaluation (eye tracking test, optokinetic nystagmus test, caloric test), a stabilometer test, standard pure tone audiometry, a speech discrimination test, taste test (electrogustometry, filter-paper disk assay using taste solutions), and a smell test (intravenous olfaction test, odor-identification card test for Japanese). Accordingly, we investigated the relation between body sway and other sensory functions. We found a larger sway area than usual in 60% of the patients undergoing a stabilometer test with their eyes open and with their eyes closed. The results of the nystagmus and ENG evaluations suggested a vestibular disorder in 15% to 20% of the patients and a brainstem or cerebellum disorder in 10% or less of the patients. A significant correlation between the body sway area and smell identification was observed. However, smaller correlations were observed between body sway and the hearing threshold, the laterality of the hearing, the taste function, and the smell threshold. According to this study, we speculated that chronic dizziness following minor trauma might arise from related to central nervous system disorders, such as disorders of the hippocampus, hypothalamus, entorhinal cortex or other olfactory-related cognitive areas.

　　The differential diagnosis for positional dizziness/vertigo, such as vertigo upon waking up or standing up, includes benign paroxysmal positional vertigo (BPPV), orthostatic hypotension (OH), autonomic dysfunction, and so on. A correct and efficient diagnosis of this condition is important. The purposes of this study were to clarify in which cases is a Schellong test the optimal means of diagnosing OH among patients with positional vertigo and to obtain specific answers to our original questionnaire on dizziness/vertigo among OH patients. All the patients who visited our office complaining of dizziness/vertigo between 2012 and 2015 were asked to perform the Schellong test and to complete our questionnaire. We used a conventional BPPV diagnostic maneuver to diagnosis BPPV. The results were analyzed statistically. A total of 309 cases returned analyzable questionnaire results. Overall, 38 cases were finally diagnosed as having certain BPPV based on the observation of positional nystagmus; 104 cases tested positive using the Schellong test. None of the items in the questionnaire were correlated with either a positive or negative Schellong test result. When 13 Schellong test-positive cases were excluded from the certain BPPV group, three answers to the questions in the questionnaire differed significantly between the certain BPPV group and the Schellong test-positive group. These answers were as follows: a waking up/lying down movement or rolling over in a supine position triggers vertigo, and a specific head position exacerbates vertigo. In conclusion, when a patient complains of vertigo upon waking up or standing up, the following two specific questions should be asked: “Is your vertigo triggered by waking up/lying down or by rolling over in a supine position?” and “Does a specific head position exacerbate your vertigo?” If a patient answers ‘yes’ to either of these questions and positional nystagmus is not observed, a Schellong test should be performed to diagnose OH.

　　The characteristic symptoms of Meniere's disease are recurrent vertigo, fluctuating hearing loss and tinnitus, and the principal underlying pathology is endolymphatic hydrops (ELH). Imaging of endolymphatic hydrops is now possible by 3-Tesla MRI after intratympanic (IT) or intravenous injection (IV) of gadolinium (Gd). 3D-FLAIR and 3D-real IR are obtained in the case of IT injection of contrast, while heavily T2-weighted 3D-FLAIR and HYbriD of Reversed image Of Positive endolymph Signal and native image of positive perilymph signal (HYDROPS) are obtained in the case of IV injection of contrast, to visualize the endolymphatic space. Higher concentrations of the contrast agent can be introduced into the perilymph by IT injection than by IV injection. However, the IV method is preferable in the clinical setting, as the endolymphatic spaces of both ears can be evaluated after a single intravenous injection of Gd. ELH is observed more frequently in patients with definite Meniere's disease than in those with possible Meniere's disease. ELH is observed in both the cochlea and the vestibule in patients with atypical Meniere's disease. The vestibular Meniere's disease patients show significant vestibular predominance in the distribution of ELH. ELH is observed more frequently in patients with fluctuating tinnitus than in patients with stable tinnitus. Examination of ELH can be performed as part of preoperative evaluation prior to stapes surgery in patients with otosclerosis; the presence of ELH is a risk factor for the development of severe vertigo after stapes surgery. Examination to detect vestibular ELH can be helpful in the differential diagnosis between vestibular migraine and vestibular Meniere's disease. MRI is a sensitive technique for detecting ELH and the relationships between ELH and clinical symptoms are expected to be widely investigated using this technique.

　　Visualization of endolymphatic hydrops (EH) by magnetic resonance imaging (MRI) is becoming increasingly important and popular for the diagnosis of various inner ear diseases, such as Meniere's disease. However, most studies have been performed using Siemens scanners. At Osaka University, we have been using General Electric (GE) scanners at 3 Tesla for imaging EH since 2007. Both the scanning protocols of 24h after intratympanic administration of gadolinium (Gd) and 4h after intravenous injection of Gd are used. In contrast to the Siemens system, in which MRI sequences specific for EH imaging are available, we use the conventional two-dimensional fluid-attenuated inversion-recovery (2D-FLAIR) and three-dimensional fast imaging sequences employing steady state acquisition (FIESTA, also known as “cisternography”) to acquire axial images of the inner ear of 2-mm and 0.5-mm thickness, respectively. Written informed consent is obtained from the patients before the imagings. The examinations are performed in compliance with the Declaration of Helsinki and are approved by the institutional ethics committee. In total, 76 patients have undergone MRI under various clinical situations, such as before and after sac surgery, and before intratympanic administration of gentamycin to treat Meniere's disease. The presence of hydrops is clearly detected by T2-FLAIR images in most patients with clinical EH. Unlike the MRI sequences obtained using the Siemens system, it is currently difficult to distinguish the area of the inner ear with no enhancement (either perilymph with no contrast or endolymph) from bony areas surrounding the inner ear in our T2-FLAIR images obtained using the GE system. Comparison between T2-FLAIR and FIESTA sections at the same level is recommended. Three-dimensional volumetric co-registration of FIESTA images to T2-FLAIR images is also helpful when the patient's head movements during the MRI scanning are not negligible.

　　For patients presenting to the ER or clinics with sudden onset of vertigo and dizziness, immediate medical attention for suspected stroke is critical, as immediate treatment can minimize the long-term functional outcome after stroke and prevent death. Patients with cerebellar or brainstem stroke because of compromised vertebral and/or basilar arterial supply often present not only with vertigo/dizziness and nystagmus, but also with dysarthria/dysphagia, ataxia, disturbed consciousness, restriction of eye movements and hemiparesis. There are two broad types of stroke: hemorrhagic and ischemic. An ischemic stroke occurs as a result of obstruction of the blood vessel supplying blood to the brain. Atrial fibrillation can cause cardiogenic embolism, and the risk factors such as hypertension, diabetes, dyslipidemia and smoking induce arterial occlusion to lead to atherothrombotic or lacunar infarction. Hemorrhagic stroke occurs when a weakened blood vessel ruptures and blood leaks into the cerebellum and brainstem. The most common cause of such blood vessel rupture is uncontrolled hypertension or anti-thrombotic treatment. CT and MRI with diffusion-weighted imaging and MR angiography play critical and essential roles in the definitive diagnosis of ischemic or hemorrhagic stroke. The gold standard treatment for ischemic stroke is administration of a tissue plasminogen activator (t-PA) by intravenous injection via through vein in the arm. The t-PA works by dissolving the clot and improving the blood flow to the part of the brain that is deprived of blood flow. If administered within 4.5 hours of the onset, t-PA may improve the chances of complete recovery from a stroke. Another treatment option is an endovascular procedure called mechanical thrombectomy using the stent or suction after detection of the ischemic penumbra by MRI. To attenuate the brain damage caused by the intraparenchymal hematoma and its expansion, intensive blood-pressure lowering, optional hemostasis against anti-thrombotic agents or surgical removal of the hematoma could be performed immediately after serial CT. The concept that “Time is Brain” in the treatment strategy of acute stroke strongly depends upon quick triage for stroke using the A²B²C²D² score, and an attempt at immediate diagnosis based on an accurate medical history for ABC-DEMON, neurological examination, immediate CT followed by MRI, and face-to-face cooperation and collaboration between specialists in otorhinolaryngology and cerebrovascular neurology.