The vestibular nucleus receives sensory signals from the vestibular periphery as well as visual and proprioceptive information, and then sends afferents to regions controlling posture and ocular movements. In this network, the vestibular nucleus neurons play a role in not only relaying signals or switching between excitatory or inhibitory transmission, but also modifying the signals by their intrinsic membrane properties. Since the late 80's, in vitro electrophysiological recording in rodent brainstem slices has revealed detailed neuronal membrane properties. Medial vestibular nucleus neurons (MVNn) were classified into types A and B by the shape of their action potential (AP) and after-hyperpolarization (AHP). Type A exhibits a broad AP followed by a single, deep AHP, and shows transient rectification ascribed to A-like currents. Type B exhibits a narrow AP followed by a double (an early fast and a delayed slow) AHP. In some type B MVNn, a prolonged plateau potential or a low-threshold calcium spike (LTS) can be evoked. Firing responses of MVNn to step, ramp, or sinusoidal current modulation indicated that type B neurons have more kinetic characters than type A showing tonic responses. In electrophysiological studies using slice preparations, since most of the afferents and efferents were terminated, the property of each individual neuron was difficult to link to the role in the entire network. However, recent studies using in vitro whole brain preparation that preserves the root of cranial nerves and the neural circuits in the brain, a combination of whole-cell patch clamp and RT-PCR techniques that can identify the neuronal transmitter, or molecular techniques like fluorescent promoter gene transfer into specific areas leading to the identification of the afferent origin of the recorded neuron, are revealing the function of intrinsic membrane properties of neurons in the network. Realistic neuron models based on physiological results have also been developed, which provides an other way to understand single neuron properties in relation to the whole network.
Recently, the method for diagnosis of benign proximal positional vertigo (BPPV) improved by the spread of infrared charge-coupled device (CCD) cameras. However, central positional vertigo may be involved in cases of positional vertigo and it is necessary to perform the diagnosis carefully. Since we experienced a case of brainstem malignant lymphoma with rotatory nystagmus in the positioning nystagmus test on the first medical examination, we reported the case. Although the chief complains were a floating sensation, nausea, and vomiting, along with medical treatment progress, the condition has improved gradually and rotatory nystagmus has also disappeared.
Recently, vertigo or dizziness has been linked to abnormal serotonin regulation in the hippocampus. According to the DSM-VI and ICD-10, vertigo or dizziness is a common symptom of anxiety disorder, somatoform disorder, and depression. In today's stressful society, we are now observing record increases in the number of patients with depression. Because of this increase, otolaryngologists are now encountering an increasing number of patients with depression-related dizziness or vertigo. We treated 41 patients with depression-related vertigo or dizziness with a selective serotonin reuptake inhibitor (SSRI: paroxetine or fluvoxamine) or a selective norepinephrine reuptake inhibitor (SNRI: milnacipran). We graded the effects of treatment according to three levels: outstanding, effective, or not effective. Besides dizziness, the chief complaints of patients we treated were problems with sleep, headache, heavy headedness, shoulder stiffness, and loss of motivation. Drug effectiveness or the overall recovery rate was defined as the ratio of the number of patients showing outstanding and effective improvements to the total number of patients treated with a particular drug. The overall recovery rate for patients treated with paroxetine was 82% (14/17), for patients treated with fluvoxamine it was 90% (10/11), and for patients treated with milnacipran it was 62% (8/13). Side effects were observed in 22% (9/41) of the patients. Symptoms disappeared in about 2 weeks after drug treatment began. SSRIs and SNRIs are now the drugs-of-choice for treating anxiety- or depressionrelated vertigo because they are associated with fewer adverse effects than traditional antidepressants. Moreover, when compared to tranquilizers, SSRIs and SNRIs tend to be less habit-forming. As an adjunct to psychological counseling, dizziness associated with psychiatric disorders can also be treated in otolaryngological outpatient clinics with relevant drugs.To effectively treat these dizzy patients, collaboration between the patients' otolaryngologists and psychiatrists or psychological counselors is also important.
Japanese traditional medical diagnosis using Ki-Ketsu-Sui in vertiginous patients was examined. Among all parameters, the highest positive rate was demonstrated for Suitai. Kiutsu and Kikyo also showed high positive rates, suggesting that psychogenic factors play important roles in the occurrence of vertigo. Multiple parameters were shown to be positive in young and elderly patients, suggesting that multiple factors may contribute to the occurrence of vertigo. A high positive rate was present for Suitai but not for Oketsu with peripheral vestibular disorder. On the other hand, vertebrobasilar insufficiency and idiopathic vertigo demonstrated a high positivity rate for Suitai, Oketsu, and Ketsukyo, suggesting the contribution of vascular disorders to the occurrence of vertigo.
We studied psychological conditions in patients with balance problems using the POMS (profile of mood states) questionnaire. One hundred and eighty seven patients with balance problems were enrolled in this study. At the time of their first visit to our clinic, they were asked to fill in POMS questionnaires. Their responses were analyzed, and given scores for 6 emotional scales. Patients showed a tendency towards high scores. In comparison of the scores of patients diagnosed as having somatic diseases with other patients, patients who were not diagnosed with somatic diseases had significantly higher scores (or lower V-factor) than those with somatic diseases. From the viewpoints of POMS testing, patients with Meniere's disease seemed to be subdivided into two subgroups. POMS questionnaire testing seemed to be useful at the vertigo/dizziness clinic.
A characteristic feature of Ménière's disease is the spontaneous occurrence of vertigo attacks, most often without warning. The unpredictability of vertiginous spells is a major threat for uncontrolled or cluster type patients. Nevertheless, it is difficult to predict spells in spite of advances in vestibular research because vestibular tests are not sensitive enough to detect the fine vestibular abnormalities associated with Ménière's disease. In this paper, we show that nonlinear analysis of stabilometry signals can detect a pre-ictal phase preceding the vertiginous spell by means of the dynamical similarity between a reference state and pre-ictal state. Our results confirmed that nonlinear changes in the multi-link network of the postural control system allowed the prediction of 12 out of 17 spells within 3 days (sensitivity: 70.6%). In contrast, the conventional measure showed a lower sensitivity and specificity. Our results are very encouraging to gain a new insight into the mechanism responsible for pre-ictal to ictal transition in inner ear pathophysiology and the corresponding therapeutic implications.
There are many patients with vertigo or dizziness, and the causes are diverse. Although a patient with central vestibular disorder including cerebral infarction must be treated urgently by a neurologist, the patient often consults an otolaryngologist with-out a full examination by an internist because they often lack specific symptoms of neurological dysfunction except vertigo. We used a questionnaire to clarify the role of otolaryngologists in the treatment of acute vertigo. Replies were obtained from 29 internists and 35 otolaryngologists. Seventy percent of the otolaryngologists answered that internists should initially examine the patient with acute vertigo. On the other hand, half of the internists answered that the otolaryngologists should perform the initial exam. Most otolaryngologists think that central vestibular disorder, just like a stroke or systemic disease, should be excluded by internists at first. Otolaryngologists see many central vestibular disorder patients who were initially diagnosed as peripheral vestibular disorder with normal brain computed tomographies (CTs) and no neurological abnormalities except for nystagmus at the onset. CT can not always uncover central nervous system disorder including small infarctions or brain stem lesions, especially at onset. Although it is not always easy to establish the diagnosis of central vestibular disorder, neuro-otological examinations, especially nystagmus tests and eye movement tests, are useful to achieve this. Otolaryngologists play an important role in the differential diagnosis between peripheral and central vestibular disorders at the onset of the clinical course. The most important point in the treatment of an acute vertigo patient is cooperation between doctors of different departments.