Hair cell regeneration has been gradually shown to occur in the inner ears of mammals as well as birds; this has been particularly demonstrated in the vestibular system rather than the organ of Corti. Several new strategies including mitosis, self repair, transdifferentiation, and cell transplantation are being pursued to brimg about hair cell regeneration. This review discusses the field of inner ear hair cell regeneration in birds and mammals, and the relationship of inner ear regeneration to functional recovery.
High intensity signals on T2-weighted magnetic resonance imaging (MRI) of cerebral white matter are common in aged people. A recent study suggests that these lesions increase with risk factors for stroke from arteriolosclerosis. Some investigators have identified a relationship between these white matter lesions and dementia or motor deficits. The clinical significance of these white matter lesions remains unclear. To investigate the relationship between these white matter lesions identified on magnetic resonance imaging and dizziness in elderly patients, we evaluated findings on brain MRI of patients with dizziness (n=108) and patients without dizziness (n=28) aged over 60 years old. Deep white matter hyperintense signals (DWMH) and periventricular hyperintensity (PVH) were graded using a qualitative rating scale (Fazekas et al.). Patients with dizziness, especially originating in the central nervous system, showed significantly more severe white matter lesions (grade 2-3). We suggest that older patients with severe white matter high intensity signals experience dizziness due to vascular insufficiency from arteriolosclerosis.
White matter high intensity lesions on T2-weighted magnetic resonance imaging (MRI) are often detected in aged people. Arteriosclerosis appears to be the most important causative factor in the development of such high intensity signals, and the extent of white matter lesions is thought to reflect the extent of brain arteriosclerosis. We reported that elderly patients with dizziness, especially of central origin, showed significantly more severe white matter lesions. To investigate the relationship between these white matter lesions identified on magnetic resonance imaging and balance dysfunction in elderly patients, we evaluated findings on brain MRI and body sway examined by a stabilometer in patients with dizziness (n=79) aged over 60 years old. Deep white matter hyperintense signals (DWMH) and periventricular hyperintensity (PVH) on MRI was graded usig a qualitative rating scale (Fazekas et al.). Sway of the body's center of gravity was recorded with eyes open and closed for 60 seconds using a stabilometer. Sway area, locus length, and right-left (X position) and forward-backward (Y position) deviations of the center of sway were measured. The measurement values of these parameters were compared with standard values in healthy subjects. Patients with normal values in all 8 items were regarded as stable, and patients with values beyond the normal range were regarded as unstable. In patients with dizziness aged 60-79 years old, those with severe white matter lesions (grade 2-3) on MRI were signifi-cantly unstable. We suggested that elderly patients with severe white matter lesions tended to have postural abnormalities and show dysfunction of the central nervous system due to brain arteriolosclerosis.
Galvanic nystagmus (GN) has been studied with regard to equilibrium. However, the nystagums-provoking mechanism has not been clarified. In this study, we considered Meniere's disease (MD) to be a unilateral vestibular disorder model, and analyzed GN recorded in MD by video-oculography. The subjects were 10 patients with MD (38-60 years). The patients were divided into an acute group of 5 patients who had the last insult within 2 weeks and a chronic group of 5 patients who had the last insult more than 4 weeks before. Stimulation of the cathode using direct current at 1, 2, or 3 mA for 30 sec was alternately performed on the affected and healthy sides in the acute and healthy subjects as controls using the mean frequency of nystagums and slow phase velocity. The mean frequency of nystagmus caused by stimulation at 2 MA on the affected side was significantly lower in the acute group (0.453±0.354 Hz) than in the control group (1.088±0.437 Hz) (P<0.05). The mean slow phase velocity was also lower in the acute group (1.494±1.223 deg/sec) than in the control group (5.053±5.236 deg/sec)(P<0.1). There were no significant differences in the mean frequency of nystagmus and slow phase velocity caused by stimulation between the healthy side in the acute group and the control group. The mean frequency of nystagmus and slow phase velocity caused by stimulation on the affected and healthy sides were not significantly different between the chronic and control groups. The reduction of responses on the affected side in the acute MD stage suggested the involvement of the vestibule and semicircular canal as the stimulation receptors of GN examination. In the chronic stage, since the condition was considered to be the steady state without vertigo, the results were considered to be due to central and peripheral compensation.
In recent years, some case reports have inidicated the presence of intracranial hypotension accompanied with headache, neck pain, and vertigo after whiplash injury, but there are many questions about the pathophysiology. The aim of the present study was the verification of clinical manifestations and MRI findings in 7 cases of abnormal RI cisternogram after whiplash injury. RI cisternogram showed the early appearance of radioactivity in the kidneys and urinary bladder, suggesting CSF leakage in the 7 cases. The site of CSF leakage was at the cervicothoracic level in 1, spinal level in 5, and uncertain in the remaining case. Cervical MRI showed no abnormality related to spinal cord compression or CSF leakage. MRI of the head showed subdural fluid collection in 2 cases and brain sinking accompanied with descent of the cerebellar tonsils in 1 case. Clinical features included orthostatic headache, neck pain or stiffness, visual disturbance, dizziness and early fatigue in all 7 cases. Lower back pain was reported in 6, slight fever in 5, vertigo in 4, tinnitus in 4, and dyshidrosis in 1. Our results suggest that intracranial hypotension may be caused by whiplash injury. The causal relationship with whiplash injury, action mechanism, and treatment are important future considerations.
Periodic alternating nystagmus (PAN) may be related to vestibulocerebellar system disease, occur with a loss of vision, and be congenital in origin. Acquired PAN has been reported in association with a variety of conditions, many of which involve the cerebellum. However, our case with PAN was a patient with an acoustic tumor localized in the internal auditory canal. This case was a 28-year-old female. She underwent an initial medical examination in June 2004. Her chief complaint was hearing impairment. However, in all test, we could not identify any audiogram abnormality. In September of the same year, she became dizzy, and had a vertigo attack on the 15th November. We thus admitted to hospital. During this hospitalization, we identified PAN in the equilibrium test. Waespe et al. have reported that experimental ablation of the nodulus and uvula of the cerebellum in monkeys causes PAN; baclofen abolishes this nystagmus. Pharmacological evidence suggests that the nodulus and uvula maintain inhibitory control vestibular responses using GABA. Thus, the GABA agonist baclofen is able to abolish PAN due to experimental or clinical lesions of the nodulus and uvula. Leigh et al. have presented a hypothetical explanation for PAN based on instability in central vestibular-optokinetic pathways. They have suggested that normal vestibular adaptation mechanisms act to reverse the direction of PAN. In this case, the characteristic pattern of peripheral nystagmus was indicated, PAN was abolished without baclofen, and MRI imaging showed that the acoustic tumor was localized in the internal auditory canal. Furthermore, findings of cerebellar disorder were not seen. So, our case's PAN seems to support the latter opinion.