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In patients complaining of dizziness attributable neither to vestibular disorders nor to any neurological cause, static posturographic recordings can reveal signs consistent with the symptoms. These posturographic abnormalities are a sign, not of impairment of some other input of the fine-postural system, but of faulty integration of the multimodal sensory information that contributes to the control of orthostatic posture.
A thorough study of vestibular function cannot be limited to the evaluation of VOR alone; it must also include the study of VSR which serves to control erect stance under both static and dynamic conditions. In unilateral peripheral vestibular lesions (UVL) computerized stabilometry makes it possible to perform a more accurate evaluation of the VSR complex through the quantification of "postural sway". Furthermore, the diagnostic potential of stabilometry can be further fine-tuned by introducing a sensitization test, in particular the head retroflexion (OCR) and head shaking (OC-HST) tests. In the present study 61 patients with UVL of various etiology (viral, toxic, vascular, idiopathic) were studied. Besides electrooculography, stabilometry was performed under base conditions (eyes open and closed) and with sensitizing tests (OCR, OC-HST). L and S were used as statokinesigram parameters while frequency and oscillation amplitude on the sagittal and transverse planes were used as stabilogram parameters. Of the 61 UVL patients, 47.5% showed VOR compensation while static postural alterations were found in 31.1%; this raised to 50.8% when the sensitization test was introduced. Apparently the compensation phenomena became manifest more quickly for VOR than for VSR. The introduction of the sensitization test, however, markedly reduced this variance. The two sensitization, maneuvers used provided quantitatively equivalent results although in the absence of reciprocal agreement. Agreement was not even recorded between stabilometric HST and the head shaking test. This confirms the presence of two different routes for VOR and VSR. Nonetheless, the introduction of the sensitization test made it possible to identify those "false negative" VSR cases which were really pathological, thus making it possible to properly identify the patients' condition and arrange for adequate treatment.
The authors used a vertical force platform fitted with 4 pressure gauges (Societe Toennies). The static regime provides the statokinesigram, the lateral and sagittal stabilograms and their Fourier transformations. Information is collected with the eyes open and closed, thereby allowing the Romberg quotient to be determined. In the dynamic regime, the platform unexpectedly tilts to a toes-up position (4 degrees at a rate of 50 degrees/s). The activity of the tibialis anterior and soleus muscles is recorded by integrated electromyography. The early soleal response, provoked by the myostatic reflex, is followed by later responses due to the vestibulo-spinal reflex. These various parameters were recorded in young athletes and the obtained tracings are commented on.
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Posturographic recording with the patient's head in retroflexion has been proposed as a reliable test for diagnosing cervical vertigo. The clinical experience suggests that a positive result in this test-condition could be accepted as suggestive for cervical involvement, when other data corroborate it, but that it is not per se pathognomonic. In fact, this test is negative in most cases with other cervical indications, whereas it has been found positive, in cases with no cervical indications. A positive test, however, is significantly more frequent in "cervical" cases. On the other hand, otolithic influence upon the test-performance has also to be taken into account.
To perform postural measurements routinely a new device was developed which differs from existing equipment by its simple technique, high accuracy and low price. This device also allows to introduce this important examination technique to the daily ENT-practice.
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A force platform technology using bonded strain gauges was developed to analyse postural sway as a function of time. Physiologically, the human body is in a state of balance--independent of the position of head, neck, hip, arms or legs and despite permanent oscillations, as long as the centre of gravity projected onto the base of support falls within a limited area. Some examples demonstrate the principles and interpretation of measurements. The method is clinically appropriate to discover ataxias and to manifest Romberg's sign. The diagnostic scope is extended by including a tilting platform in a short test battery of various degrees of difficulty. In contrast to 20 healthy persons, 20 patients with Menière's disease showed an obviously reduced ability to remain standing during the attack-free interval.
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Vestibular Coriolis- and Purkinje-effect, which are known to induce vertigo, were investigated with respect to body posture. One aim of this investigation was to provide information concerning clinical vertigo symptoms. Standing on a rotatable stabilometer, 25 healthy subjects had to execute lateral head tilts during (Coriolis), or after (Purkinje), rotation varied with different constant velocities. The conditions were varied with respect to eyes open vs. eyes closed, head upright vs. head tilt to the right and left, direction of rotation clockwise vs. counterclockwise, active vs. passive head tilt, and active vs. passive body rotation. The results supported the expectation that destabilization was less severe with open than with closed eyes and that sway amplitudes were increased after head tilt as well as with a higher velocity of rotation. The direction of the induced body shift was, as expected, opposite to the initial vestibular stimulus. A forward shift after stop without head tilt was frequently found, being independent of the previous direction of rotation. Reported perceptions coincided mostly not with the initial vestibular signal but rather with the actual movement of compensation. Active instead of passive movements did not produce clearly different effects. The Purkinje experiment appeared to be equivalent to the situation when a patient with an acute lesion of a horizontal vestibular canal bends his head. The stabilogram under this condition may allow a prediction of the side of the lesion.
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