Michael A. Gresty

Migraine and Ménière's disease: is there a link?

Background: A possible link between Ménière’s disease (MD) and migraine was originally suggested by Prosper Ménière. Subsequent studies of the prevalence of migraine in MD produced conflicting results. Objective: To determine the lifetime prevalence of migraine in patients with MD compared to sex- and age-matched controls. Methods: The authors studied 78 patients (40 women, 38 men; age range 29 to 81 years) with idiopathic unilateral or bilateral MD according to the criteria of the American Academy of Otolaryngology. Diagnosis of migraine with and without aura was made via telephone interviews according to the criteria of the International Headache Society. Additional information was obtained concerning the concurrence of vertigo and migrainous symptoms during Ménière attacks. The authors interviewed sex- and age-matched orthopedic patients (n = 78) as controls. Results: The lifetime prevalence of migraine with and without aura was higher in the MD group (56%) compared to controls (25%; p < 0.001). Forty-five percent of the patients with MD always experienced at least one migrainous symptom (migrainous headache, photophobia, aura symptoms) with Ménière attacks. Conclusions: The lifetime prevalence of migraine is increased in patients with MD when strict diagnostic criteria for both conditions are applied. The frequent occurrence of migrainous symptoms during Ménière attacks suggests a pathophysiologic link between the two diseases. Alternatively, because migraine itself is a frequent cause of audio-vestibular symptoms, current diagnostic criteria may not differentiate between MD and migrainous vertigo.

Neural Correlates of Visual-Motion Perception as Object- or Self-motion

Both self-motion and objects moving in our visual field generate visual motion by displacing images on the retina. Resolving this ambiguity may seem effortless but large-field visual-motion stimuli can yield perceptual rivalry between the real percept of object-motion and the illusory percept of self-motion (vection). We used functional magnetic resonance imaging to record brain activity in human observers exposed to constant-velocity roll-motion. This stimulus induced responses in areas reaching from calcarine to parieto-occipital and to ventral and lateral temporo-occipital cortex and the anterior insula. During vection, early motion-sensitive visual areas and vestibular parieto-insular cortex deactivated, whereas higher-order parieto- and temporo-occipital areas known to respond to optical flow retained identical activity levels. Within this sustained response, these latter areas displayed transient activations in response to each perceptual switch as identified in event-related analyses. Our results thus show that these areas are responsive to the type of visual motion stimulus and highly sensitive to its perceptual bistability. The only region to be more active during perceived self-motion was in, or close to, the cerebellar nodulus. This activation may correspond to the gain increase of torsional optokinetic nystagmus during vection and/or to changes in sensory processing related to the rotational percept. In conclusion, we identified neural correlates of perceiving self-motion from vision alone, i.e., in the absence of confirmatory vestibular or proprioceptive input. These functional properties preserve the organisms ability to move accurately in its environment by relying on visual cues under conditions when the other spatial senses fail to provide such information.

Tremor, the cogwheel phenomenon and clonus in Parkinson's disease.

Resting and postural tremor, intention and action tremor, clonus and the cogwheel phenomenon in Parkinsons disease have been characterised in terms of frequency content using spectral analysis. Typical resting tremor ranged in peak frequency from 4 to 5.3 HZ with tremor in each individual varying only by 0.2 to 0.3 HZ. The peak frequency of postural tremor ranged between 6 and 6.2 HZ. Intention tremor appeared to be an exaggeration of postural tremor. Clonus evoked by active or passive stretch at the wrist had a frequency of 6 HZ and appeared to be a continuation of postural tremor. The cogwheel phenomenon was found at frequencies between 6 and 6.5 HZ and between 7.5 to 9 HZ. Action tremor was indistinguishable from the cogwheel phenomenon. Some patients had either a symptomatic resting tremor with a concurrent 6 HZ component of smaller amplitude or a symptomatic postural tremor with a 4-5 HZ component of smaller amplitude. These combinations would produce two peaks in the power spectrum. When this occurred EMG studies showed that individual muscles had two types of rhythmical activation suggesting that the tremors have separate mechanisms. Likewise some patients had a symptomatic 6 HZ tremor on posture with a second peak at 8-10 HZ in the physiological band. Therefore, the 6 HZ postural tremor is not an exaggeration of physiological tremor. On the basis of wave form and frequency similarities postural tremor, the low frequency type of active or passive cogwheeling, intention tremor and clonus possibly involve a common spinal mechanism. Higher frequency cogwheel phenomenon and action tremor may be an exaggeration of physiological tremor. More than 80% of patients with Parkinsons disease manifest tremors at both 4-5 HZ and 6 HZ. This combination would appear to be the strongest objective criterion for the diagnosis of basal ganglia disease.

Bilateral loss of vestibular function: clinical findings in 53 patients.

Abstract The clinical presentations and aetiologies of a series of 53 cases of bilateral vestibular failure (BVF) seen by the authors over a decade were evaluated by retrospective review of the medical records. Thirty-nine per cent of patients had associated neurological disease; 13% had a progressive cerebellar syndrome with disabling gait ataxia, abnormal eye movements and cerebellar atrophy on neuro-imaging. BVF was usually unsuspected. Nine per cent had cranial or peripheral neuropathies and in this group there was no abnormality of brain stem/cerebellar oculomotor function, but hearing loss was common. Eleven per cent revealed BVF and hearing loss secondary to meningitis, and 6% had other neurological disorders. Idiopathic BVF was found in 21% of cases, characterised by paroxysmal vertigo and/or oscillopsia, but no abnormal clinical signs. Gentamicin ototoxicity accounted for a further 17%, while autoimmune disease was present in 9% of patients. Otological or neoplastic disease was diagnosed in the remaining 13% of patients. It was concluded that neurological, audiological and ocular motor assessments allow the probable cause of BVF to be defined in approximately 80% of cases. A group of BVF related to autoimmune pathologies is reported for the first time, indicating the need for immunological screening. Idiopathic BVF may present with only minor visual or vestibular symptoms, while in patients with cerebellar degeneration, BVF may be unsuspected and, thus, underdiagnosed.

Simulator based rehabilitation in refractory dizziness

Abstract.Patients with chronic vestibular symptoms are common in neurological practice but the most effective treatment remains an open question. The purpose of our study was to conduct a controlled, between–group comparison of patients’ responses to a customised exercise regime (Group C, for customised) versus treatment additionally incorporating simulator based desensitisation exposure (Group S, for simulator) integrating whole–body or visual environment rotators. Forty chronic peripheral vestibular patients who had previously undergone conventional vestibular rehabilitation without notable improvement were randomly assigned into Group C or S. Individuals attended therapy sessions twice weekly for eight weeks and were provided with a customised home programme. Response to treatment was assessed at four–week intervals with dynamic posturography, vestibular time constants, and questionnaires concerning symptoms, symptom–triggers and emotional status. At final assessment posturography and subjective scores had significantly improved for both groups, although Group S showed greater improvement. A statistically significant improvement for visual vertigo symptom scores was noted only for Group S (p < 0.01; total improvement 53.5 %). Anxiety and depression levels significantly decreased for both groups; improvements were significantly correlated particularly to improvements in visual vertigo (SCQ) (p < 0.01; r = 0.53 and r = 0.57, respectively). Significant differences were noted between groups (p = 0.02) for posturography scores. Vestibular time constants showed no notable change in either group. Conclusions: Both groups improved but exposure to simulator motion gave overall better results. These effects were also observed in psychological symptoms and partly relate to simulator effects on visual vertigo symptoms. Visual motion and visuo–vestibular conflict situations should be incorporated in the rehabilitation of patients with refractory dizziness.

Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon

OBJECTIVES The frequency of pathologically reduced click thresholds for vestibular activation was explored in patients with the Tullio phenomenon (sound induced vestibular activation). METHODS Seven patients (eight affected ears) with symptoms of oscillopsia and unsteadiness in response to loud external sounds or to the patient’s own voice were examined. In all but one patient, vestibular hypersensitivity to sound was confirmed by the fact that eye movements could be produced by pure tones of 110 dB intensity or less. Conventional diagnostic imaging was normal in all cases and three of the patients had normal middle ears at surgical exploration. Thresholds for click evoked vestibulocollic reflexes were compared with those of a group of normal subjects. Galvanic stimulation was used as a complementary method of examining the excitability of vestibular reflexes. RESULTS All the patients showed a reduced threshold for click activation of vestibulocollic reflexes arising from the affected ear. Short latency EMG responses to clicks were also present in posterior neck and leg muscles, suggesting that these muscles receive vestibular projections. Galvanic stimulation produced a normal pattern of body sway in four of the five patients tested. CONCLUSIONS A pathologically reduced threshold to click activation (⩽70 dB NHL (average normal hearing level)) seems to be a consistent feature of the Tullio phenomenon and a useful diagnostic criterion. This in turn is most likely to be due to an increased effectiveness of the transmission of sound energy to saccular receptors. Activation of these receptors probably contributed to the vestibular symptoms experienced by the patients.

Motorist's vestibular disorientation syndrome.

Six patients are described who experienced difficulty in driving a motor car. Four had illusions that the car was turning, which occurred particularly on open, featureless roads or the brows of hills and caused the driver to stop. All patients had peripheral or central neurootological abnormalities, but the only finding consistent with the directionality of the symptoms was an unpleasantly increased sense of circularvection during optokinetic stimulation in the direction of the illusion. These problems occur because of a false sense of orientation arising either from inappropriate signals from disordered vestibular canal and otolith organs or from a disordered central interpretation of vestibular information, and become manifest in the absence of adequate visual stabilisation. The other two patients with lateralised vestibular disease made inappropriate steering adjustments in the direction of the imbalance of vestibular tone.

Assessing the impact of essential tremor on upper limb function

We compared the impact of essential tremor on the performance of three manual tasks: drawing spirals, holding a cup full of water and a joystick-controlled tracking test. Tremor amplitude and frequency were measured by accelerometry during the tracking test, when holding the cup and whilst a standard posture was maintained. The inter-relationships between tremor amplitude, frequency and task impairment were then examined. The results showed that the amplitude and frequency of essential tremor (measured from the principal spectral peak) changed with different activities, with the mildest postural tremors changing most in frequency (by up to 4–5 Hz). The amplitude of tremor decreased in almost every case during the tasks, relative to posture, and this decrement was greatest for the most severe tremors. We also demonstrate that for practical purposes, such as routine clinical situations and therapeutic trials, the effect of essential tremor upon upper limb function can be usefully assessed by two simple complementary techniques: rating spirals and measuring the volume of water split from a cup. The impairments in carrying out these tasks and the tracking test were highly correlated with one another and also with the amplitude and frequency of postural tremor. The concept of tremor “suppressability” is introduced: the relative percentage decrease in the amplitude of a particular tremor during the performance of a specific task compared to that recorded whilst holding a standard posture.

Eye movement responses to combined linear and angular head movement

SummaryLateral eye movements evoked by linear head motion were evaluated in human subjects by subtracting the eye movement responses to headcentred angular oscillation in the dark, about a vertical axis, from the responses evoked by similar oscillation with the head displaced 30 cm eccentrically from the axis. The centred oscillation gave a purely angular stimulus whereas the eccentric oscillation gave an additional tangential linear acceleration acting laterally to the head. The stimuli used were relatively unpredictable, enveloped sinewaves at 0.02 to 1.2 Hz, 60°/s peak angular velocity, 0.004 to 0.24 g peak tangential acceleration, and subjects were either given no instructions or were told to imagine fixating on targets at 60 cm or 5 m distance. Eye movements of significantly higher velocity were evoked in the eccentric position, particularly at the higher frequencies and when subjects imagined near targets. The increase in velocity of eye movement was attributed to the linear stimulus and probably derives from stimulation of the otolith organs. The frequency response of the gain (°/s/g) of these movements gave an approximate slope of −1, indicating that the eye velocity bears a constant proportionality to linear head velocity. The findings are in accord with the theoretical prediction that eye movements compensating for linear head motion should only be required for viewing near targets. These otolithic influences on eye movements could either the mediated by a direct “otolith-ocular reflex” which is subservient to viewing conditions or, alternatively, the otolith signals may modify the activity of other oculomotor mechanisms.

Cardiovascular responses elicited by linear acceleration in humans

Abstract Although activation of otolith receptors is known to elicit cardiovascular responses in animals, it is unclear whether vestibular stimulation can evoke changes in blood pressure and heart rate (which are independent of motion sickness) in humans. In the present study, ten normal subjects and three patients with profound bilateral reduction in vestibular function, who were seated upright with the torso aligned with the gravitation vector, were subjected to fore, aft, or lateral linear acceleration (≈0.2 g, attaining ≈2 m/s in 900 ms, and decelerating for 3 s at 0.07 g). The head was fixed in the upright position, pitched maximally downward (chin on chest) or maximally backward (≈40–50°) during the accelerations. In normal subjects, all directions of linear acceleration produced an average increase in systolic blood pressure of approximately 7–9 mmHg and a rapid decrease in the interval between R-waves of the electrocardiogram of 14–27 ms; these responses persisted for only a few seconds. In contrast, the cardiovascular responses in patients with vestibular dysfunction were much smaller (e.g., the maximal pressor response to forward linear acceleration was <4 mmHg). Head position during accelerations had little effect on the cardiovascular responses that were elicited in the population of normal subjects. However, although the population response was similar across directions of acceleration and head positions, many individuals exhibited larger cardiovascular changes during some stimulus conditions than during others. These data suggest that vestibular stimulation during linear accelerations can produce cardiovascular responses in humans and support the hypothesis that the vestibular system contributes to maintaining stable blood pressure during movement and changes in posture.