CT and MRI are indispensable for routine medical examination of neurovascular disorders. This article describes the imaging findings in acute infarction and carotid plaques, knowledge of which is essential for clinics of equilibrium disorders. Diffusion-weighted images are indispensable for detecting acute infarction, and perfusion MRI also yields important information about the ischemic status. Carotid bifurcation is one of the frequent sites of involvement in atheromatous diseases. A variety of imaging modalities are available for the evaluation of carotid plaques, including conventional contrast angiography, CT, ultrasound, and MRI. MRI is a non-invasive imaging method that reflects the chemical composition, concentration, water content or physical status of the tissues examined.
The cerebellar hemispheres, which constitute the major portion of the primate cerebellum, are considered to be involved in voluntary movement control and cognitive functions. Unlike those of the flocculus-paraflocculus complex and vermal lobule VI/VII, the oculomotor functions of the hemispheres are not yet well known. We recently found a new eye movement area in the hemispheric lobule VI/VII (H-VI/VII) in macaque monkeys. Unilateral lesions of H-VI/VII decreased the velocities of smooth pursuit, and delayed the onset of smooth pursuit and saccades. No hypo- or hypermetria was observed in the saccade amplitudes. A 50% impairment of the adaptations of smooth pursuit velocities, examined by brief acceleration of the target velocity during smooth pursuit, was observed. These lesion effects were prominent in the eye movements directed to the lesioned side. No spontaneous or gaze nystagmic eye movements were observed in association with the H-VI/VII lesions. Based on the results of comparison of the mossy and climbing fiber input organizations among the flocculus-paraflocculus, vermal lobule VI/VII and H-VI/VII, we suggest that the H-VI/VII is a new member of the oculomotor cerebellum that mediates a different function from that of the flocculus, paraflocculus and vermis.
We report on two cases of cerebellar infarction in the territory of the medial branch of the posterior inferior cerebellar artery (mPICA) mimicking acute peripheral vertigo. Case 1 was a 54-year-old man with WPW syndrome presenting with sudden vertigo. When he was admitted to our hospital, he had direction fixed horizontal nystagmus towards the left. His symptom disappeared in several days, however, MRI revealed a haemorrhagic infarct in the territory of the right mPICA. Case 2 was a 47-year-old man who was admitted with sudden rotatory vertigo. Direction fixed horizontal nystagmus towards the right was noted and head CT was normal. The nystagmus disappeared on the 5th day of the illness and caloric testing did not show canal paresis. Because of prolonged gate ataxia, a CT scan was performed again. It showed a cerebellar infarction and MRI revealed a cerebellar infarction of the left medial hemisphere and vermis. Infarcts of mPICA sometimes cause acute vertigo presenting horizontal direction fixed nystagmus mimicking peripheral vertigo. In a patient presenting with acute vertigo, head MRI should be performed when he or she has history of risk factor for cerebellar infarction such as diabetes mellitus, ischemic heart disease, and so on. The patients with prolonged ataxia and headache should also undergo MRI.
Ocular counter rolling (OCR) is the approximately conjugate rotational movement of the eyes about their visual axes, rotating opposite to the direction of head tilt. OCR may be induced by either angular acceleration acting on the semicircular canals, or by linear acceleration influencing otolith receptors. In the latter instance, the utricles are the main receptors. However, it has been suggested that an extralabyrinthine stimulus i.e., somatosensory input, can evoke OCR. We recorded OCR in six young, healthy volunteers and used eye analysis. We also recorded OCR when the subject sat down on a hard chair with and without a cushion in order to know if there was any effect of somatosensory input to the OCR. We used the Mann-Whitney U-test for the statistical analysis and P<0.05 was considered significant. There was no significant difference between the two groups. We considered there was not enough stimulation to the somatosensory input to affect the otolith-ocular reflex.
The superior semicircular canal dehiscence (SSCD) syndrome was first reported by Minor et al. in 1998. They reported that patients with SSCD typically exhibit symptoms of oscillopsia and pressure-/sound-induced vertigo due to the absence of the bony layer covering the superior semicircular canal. Although many cases of SSCD have been reported from America and Europe, only fourteen cases have been reported in Japan since 2003. We report a case of SSCD. The patient was a 30-year-old man who presented with the complaint of unsteadiness. He had been administered streptomycin for the treatment of pulmonary tuberculosis when he was 12 years old. Pure-tone audiometry showed a sloping pattern of sensorineural hearing loss bilaterally, with detection of 40 to 55 dB at high frequencies. Rightward-beating nystagmus was observed when the patient lay down, but not when he was sitting. Caloric responses were normal, ruling out the effect of streptomycin. Coronal computed tomography with 1.0-mm collimation revealed dehiscence of the left superior semicircular canal. Fistula symptoms were observed when positive pressure was applied to the external auditory canal. Tullio's phenomenon was also observed with sound stimulation (100 dB, 5Hz, click sound) to the left ear. These findings were compatible with the features of SSCD. The body-position dependency of the rightward-beating nystagmus could be attributable to changes in the intracranial pressure or intralabyrinthine pressure with the body posture, or to the nystagmus being of the pulse-synchronous type. A sloping pattern of the sensorineural hearing loss may be one of the characteristics of SSCD.
The author shows examples of lesion site detection in vestibular disorders using vestibular evoked myogenic potentials (VEMP). First, studies in vestibular neuritis are shown. When VEMP testing was performed in patients with vestibular neuritis, half of the patients showed abnormal VEMP results on the affected side, while the remaining half showed normal responses. These results imply that patients with vestibular neuritis can be subdivided into 2 categories based on combined use of caloric testing and VEMP testing; those with superior vestibular neuritis and those with total (superior and inferior) vestibular neuritis. Furthermore, combined use of electrical stimulation and acoustic stimulation allowed us to differentiate between labyrinthine lesions and retro-labyrinthine lesions. Then, the majority of patients with so-called vestibular neuritis had nerve lesions, while some patients could have had only labyrinthine lesions. VEMP testing was also useful for assessment of the recovery of the peripheral vestibular function after vestibular neuritis. Then, studies in central nervous system disorders are shown. Prolongation of the VEMP latencies was often observed in patients with multiple sclerosis and spinocerebellar degeneration, especially Machado-Joseph disease. Finally, future perspectives for ocular VEMP (oVEMP) and VEMP in the extremities are discussed.
Gravic body sway is used in daily medical practice as stabilometry. How is a test result understood and are interpretation and evaluation carried out? Stabilometry is a eguilibrium test with many analysis indices for evaluation of the body balance function. As for the analysis parameters, each shows the state of body balance control. Normal postural control depends on normal functioning of each organ involved in postural control . Each organ is a sense organ (vestibular system, vision, somatosensory), including the vestibular nerve, the brainstem, cerebellum, cerebrum, spine, muscles, etc., and malfunctioning of any of these components can be expected to result in unstable postural control. The function in which it holds a standing position posture at the time of a balanced obstacle is a function, which is going to rectify instability. The method of postural control changes a lot by how righting reflex is maintained at the time of an obstacle. It can guess us that control of recovery changes greatly with the parts and the obstacle grades of having received the obstacle. Various phenomena can be evaluated by carrying out analysis of these abnormalities by stabilometry. It was shown that the main analysis parameters are of great value in analyzing the various components of postural control.
Integration of the normal equilibrium function, space orientation and cognitive functions is needed to complete straight-line walking. Also, visual and vestibular inputs play important roles in a constantly varying 3-dimensional environment to ensure smooth locomotion. However, in vestibular disorders, patients suffer problems of gait instability. The characteristics of the instability might reflect the site and severity of the lesion. How can these abnormalities be delineated objectively? To gain an understanding from the physiological viewpoint, gait analysis under eyes-opened and blindfolded conditions was conducted using tactile sensors (F-scan system) in patients with various types of vestibular lesions. All of the data were reviewed and summarized to evaluate the usefulness and limitations of this analysis method. The coefficients of variation of gait phase-related parameters were evaluated, such as stance, swing and double support, integrated foot pressure, stability, movement and average length of the trajectories of the center of force (TCOF), and the pattern of foot pressure progression during stance which can be divided into three phases: body weight acceptance, body weight translation, and body weight thrust. Comparison of the mean values was conducted using the two-tailed t-test, with p<0.05 set as the criterion for statistical significance. The patients enrolled were those with vestibular neuritis (VN; 14 cases), acoustic tumors (AT; 61 cases: 27cases of small AT and 34 cases of large AT), and spinocerebellar degeneration (SCD; 12 cases). Healthy adults (23 subjects) served as controls. Gait instability is depicted by increment of the coefficient of variation of each gait phase. Visual cue plays an important role in providing feed-forward information for steady locomotion. Unilateral vestibular lesions could shift the body center of gravity towards the lesion side, which leads to greater foot pressure on the lesion-side foot with greater horizontal sway of the TCOF during gait, especially during gait with eyes closed. An irregular pattern of foot pressure progression could also reflect gait instability, and was most prominently found in the patients with SCD. As for the average length of TCOF, significantly longer trajectories were found in SCD patients, especially as compared with the findings in vestibular neuritis. In conclusion, gait analysis with the use of a foot pressure sensor can provide useful information for understanding gait abnormalities caused by vestibular disorders. It would be clinically useful to perform gait testing for the evaluation of gait abnormalities in vertigo patients.
Neurophysiological studies on quadruped animals have indicated the importance of the basal ganglia-brainstem system for the neural control of gait. However, recent advances in neuroimaging techniques have also begun to shed light on the role of the cortical motor areas, which project to the brainstem, the spinal cord and the basal ganglia, in the control of bipedal gait in primates. Hemodynamic measurements by single photon emission computed tomography or near-infrared spectroscopy are currently available for studying neural activity during human gait. Neuroimaging studies in healthy human subjects have shown increases in the brain activity during bipedal gait in the brainstem locomotor centers, cerebellum, basal ganglia, and multiple motor cortices, especially the supplementary motor area. Neuroimaging techniques have also been used to elucidate the pathophysiology of gait disturbances in neurological diseases. Decreases in gait-related activation of the supplementary motor area and cerebellar hemispheres, combined with overactivity of the vermis, were previously shown during gait in patients with Parkinson's disease. By contrast, enhanced activation of the lateral premotor cortex was observed during paradoxical improvement of Parkinsonian gait under visual guidance. These studies support the hypothesis that the basal ganglia-motor cortical system plays an important role in regulating human bipedal gait. Neuroimaging techniques are theoretically applicable to examining the influence of the vestibular system on gait and balance and vice versa, but no such studies have thus far been published. Future studies of vestibular-postural interactions using neuroimaging techniques may open a new era in the field of equilibrium research.