We have performed a proteomic analysis of the inner ear proteins using 2D-GE. In the process of analysis, we have found very unique properties of the LOCH gene product. The COCH gene mutated in DFNA9, an autosomal dominant hereditary sensorineural hearing loss and vestibular disorder, encodes cochlin. DFNA9 patients show symptoms such as episodes of vertigo, tinnitus, aural fullness and hearing loss. Clinically, these symptoms are consistent with the criteria for Meniere's disease. LOCH is the only gene identified so far whose mutation leads to the symptoms of Meniere's disease in a significant portion of the carriers. We showed that Cochlin constitutes 70% of inner ear proteins, and identified three cochlin isoforms in the inner ear tissue, p63s, p44s and p40s, which exhibit significant molecular heterogeneity. Structure analysis of Cochlin isoforms showed that the mutations influence only the full-length isoform of Cochlin (p63s), and not the processed Cochlin isoforms (p44s and p40s), which do not contain the LCCL domain. What happens to the LCCL domain once it is cleaved from full-length Cochlin was an open issue. We further characterized the expression and structure of Cochlin isoforms by iso-form-specific antibodies that recognize three distinct domains. Inner ear, as well as perilymph proteins were analyzed by western blot analysis. We have detected Cochlin isoforms in the inner ear tissue and we have identified a novel short 16 kDa isoform in the perilymph, named Cochlin-tomoprotein (CTP), corresponding to the N-terminus of full-length Cochlin (p63s) and the LCCL domain. Notably, CTP contains all of the known mutation sites associated with DFNA9. Our results on the formation and processing of these isoforms in the inner ear will be central to a better understanding of Cochlin function and its role in the pathophysiology of DFNA9. Furthermore, using above mentioned results, we are now performing a translational research to improve diagnosis and prognosis in patients with sensorineural hear-ing loss and vestibular disorders.
We studied the properties of horizontal semicircular canal (HC) nerve-activated vestibulospinal neurons, which include vestibulo-spinal (VS) and vestibulo-oculo-spinal (VOS) neurons. Axonal pathways, projection levels, and locations of HC nerveactivated vestibulospinal neurons were studied. The HC nerve was selectively stimulated. HC nerve-activated vestibulospinal neurons were mainly located in the ventral portion of the medial and lateral vestibular nuclei, and the middle portion of the descending nucleus. The majority of HC nerve-activated VS and VOS neurons sent descending axons through the medial vestibulospinal tract (MVST); the remaining neurons sent descending axons through the ipsilateral (i-) lateral vestibulospinal tract (LVST). Most neurons that had descending projections through the i-MVST were VS neurons, while most that had descending projections through the contralateral MVST were VOS neurons. All neurons with descending projections through the i-LVST were VS neurons. Almost all the HC nerve-activated vestibulospinal neurons were activated antidromically only from the cervical segment. No neurons were activated from the L3 segment. On the other hand, 14% of the utricular and 7% of the saccular nerve-activated vestibulospinal neurons were activated from the lumbar segment. The projection of HC nerveactivated vestibulospinal neurons to regions below the thoracic spinal cord appears to be minor, which is in marked contrast with the projection of otolith-activated neurons. It is likely that the majority of HC nerve-activated vestibulospinal neurons terminate in the cervical cord and have strong connections with neck motoneurons.
We encountered a patient who developed dizziness due to the vasovagal reflex (VVR) during the Schellong test (ST). A 32-year-old woman had a chief complaint of dizziness. Present Illness: She had repeatedly since childhood experienced dizziness attacks associated with darkness in front of her eyes immediately after standing up. She easily developed motion sickness. Dizziness continued to occur when she was standing in a bus or train, when she was in the bath, or when she got excited. She was admitted to a hospital in the district and ECG and a blood test were conducted, but no abnormal findings were revealed. Past History: She had bronchial asthma in childhood. She had a gastric ulcer and received drug treatment in january 1997. Family history was unremarkable. She had a positive Schellong test. Immediately after standing up, her pulse rate sharply increased from 94 to 123/min., and 5 min. after standing up, the pulse rate became 127/min. She complained of dizziness immediately before the end of the testing, and the pulse rate and blood pressure measured at the time were 75/min., showing a sharp decline, and 90/55, showing a slight decrease, respectively. Thereafter, she had decreased consciousness and was immediately laid in a supine position. She soon became alert. Blood pressure recovered to 106/62 and the pulse rate to 94. Neural symptoms were absent. Treatment and Clinical Course: Although she developed WR during ST, her condition could be diagnosed as orthostatic dysregulation (OD) because it met the criteria for diagnosis of OD. However, a diagnosis of postural tachycardia syndrome (POTS) was made according to the theory that WR and OD are special types of POTS. She is under medication with an α-receptor agonist agent. Patients are always at risk, although not high, of developing VVR and falling during ST, which may be associated with injury. Therefore, after the experience of the present case in our hospital, we reevaluated the procedures of ST and decided on crite-ria for the discontinuation of the testing to prevent accidents.
Acute cerebellar infarction and/or hemorrhage may present with vertigo, vomiting, and inability of standing or walking. Therefore, these symptoms might be taken for an acute peripheral vestibular lesion. To study a key differential point of cerebellar infarction and/or hemorrhage, we reviewed clinical records of 14 patients clinically and neuro-radiologically diagnosed as cerebellar infarction or hemorrhage, ten men and four women, mean age 60.1 years old, at the Tokyo Metropolitan Neurological Hospital. In 11 patients, some abnormal eye movements such as lateral gaze-evoked nystagmus, impaired smooth eye movement, saccade eye movement and optokinetic nystagmus, and poor vestibulo-ocular reflex suppression were observed. Two of the 14 patients did not have any abnormal eye movement but developed slight ataxia at the onset. All three patients that had an affected flocculonodule lobe showed poor vestibu-lo-ocular reflex suppression. Two patients who had involvement of the posterior vermis showed saccadic or ataxic pursuit but normal saccades. Our results were in agreement with the reports on monkeys that showed the posterior vermis controls both saccade accuracy and smooth pursuit velocity, but the lesion was not exactly the same. We should suspect cerebellar infarction and/or hemorrhage when we see elderly patients who complain of vertigo, vomiting, and headache, and who have the high risk factors for stroke. In addition to those characteristics, we should be careful of findings of ataxia and abnormal eye movement such as lateral gaze nystagmus, impaired pursuit, ocular dysmetria, and impaired optokinetic nystagmus.
We have used three-dimensional (3-D) motion analysis to measure equilibrium function in patients with vertigo or dizziness. The reliability of the analysis depends on the accuracy of the values of reflective markers on 3-D coordinates. In this paper, we studied the reliability of the 3-D motion analysis method described above using two kinds of experiments. In our routine examinations, 2 CCD video cameras are used to record subjects. Thirty pictures were taken during a one-minute video recording. Experiment 1: A subject carried a board with 3 reflective markers attached and walked around while being video recorded for 8.3 seconds. Distances between each pair of three markers were 14.8 cm and 13.6 cm, and these values were analyzed. Similarly, an angle of 90.5 degrees formed by two lines connecting each pair of markers was analyzed. The mean differences between the real value and analyzed value were calculated for the entire 8.3 seconds. Those differences of the two distances were 0.08 cm and 0.14 cm, while the difference of the angle was 0.5 degree. Experiment 2: Analysis of the acceleration of a reflective marker in free falling was repeated twelve times. The analyzed values between 0.167 seconds and 0.267 seconds after the beginning of the falling were rather accurate. However, shapes of the marker were recorded as an ellipse 0.300 seconds after beginning the fall. Therefore, it became impossible to obtain accurate values of reflective markers in 3-D coordinates. One of the reasons for this phenomenon may be overexposure due to the slow shutter speed of CCD video cameras. Despite such a problems, our experiments indicated that 3-D motion analysis appeared to be sufficiently accurate to measure equilibrium function.