Peak velocities of voluntary saccades and fast phases of different qualities of nystagmus were studied in 20 normal subjects, 5 patients with pontine lesions and 5 patients with lesions in the frontal cortex. The peak velocity of saccades was related to the amplitude of the eye movement, the alertness of the subject and whether the subject could see the target or not. The effect of the age was not significant. The quick phases of caloric, optokinetic and angular acceleration induced nystagmus were equally rapid but somewhat slower than that of vestibular nystagmus recorded in standardized visual surrounding. In the same visual condition saccades were always faster than quick phases of nystagmus. Patients with cortical lesions had normal velocities in saccades and quick phases of nystagmus. Patients with pontine disorders had significantly reduced saccadic and quick phase velocity, and some of the patients exhibited dissociations between velocity mechanisms while the somewhat higher velocity in quick phase of vestibular nystagmus recorded in light is probably related to higher attention evoked by vestibular-visual interaction.

Adolescent↗

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Eye movements as a function of active headturnings.

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Adult↗

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Quantification of vestibular dysrhythmia.

Quantification of dysrhythmia in a nystagmus response has hitherto not been seriously attempted, possibly because the nystagmus response does not easily lend itself to description in mathematical or physical terms. Ideally the nystagmus response consists of a sequence of triangles. Each such triangle is determined by four qualities, i.e. the velocities and the durations of the fast and slow components. Thus, without serious loss of information it is possible to represent a nystagmus reaction by four sequences of values, one for each of the four above mentioned qualities. From each such sequence we have extracted relevant information and presented it in graphical form. It may be assumed that each of the four nystagmus qualitiees reflects the activity within separate 'neuronal systems'. Each of these four systems is then informed upon by three parameters for each nystagmus quality, i.e. by its mean, by its variation coefficient and by its sequential variation coefficient. It is claimed that these three diagrams contain nystagmus information not earlier considered.

Adult↗

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Vertigo as reflected by the nystagmogram. A clinical analysis.

Efforts to evaluate findings in the nystagmogram were made in a material of 338 vertiginous and dizzy patients. A spontaneous nystagmus, a positional nystagmus as well as a difference in caloric reactivity are as solitary findings of lettle value for revealing peripheral disorders. On the other hand, central disturbances are frequently revealed by inability to track a moving optic target, resulting in an irregular or a saccadic pattern, by persistence of vestibular nystagmus in light, by persistence of such nystagmus at eye-closure, by an increase in spontaneous nystgmus on eye-closure or by dysrhythmic nystagmus in caloric tests. Cases of functional vertigo seem to differ from cases of vertigo from other sources by their increase of spontaneous nystagmus (when present) or by persistence of caloric nystagmus on eye-closure.

Caloric Tests↗

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Dyspraxia of speech and of eye motility.

Five patients with a disturbance of their preprogramming of speech (dyspraxia of speech) were exposed to a comprehensive eye-motor test-battery. The saccades were found hypometric and inaccurate with irregular intervening pauses. The finding was interpreted as due to an extension of lesions from frontal cortical speech areas into visual motor cortex disturbing the normal preprogramming of voluntary saccades. The results were interpreted as supporting the assumption that voluntary saccades are initiated in the frontal cortex. An increase of vestibular nystagmus in these cases was related to a release of vestibular nystagmus due to the disappearance of cortical inhibition on brain stem acitivty.

Adult↗

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Velocity patterns of rapid eye movements.

The peak velocities of saccades and fast phases of nystagmus were examined and compared in 20 healthy subjects. The peak velocities of both types of eye movements increased with increase of amplitudes. The saccades were found to be fastest in light, slower in darkness and slowest behind closed eyelids. The peak velocities of the quick phases of optokinetic and of vestibular nystagmus were found to be the same. Fast phases of optovestibular (optic as well as vestibular stimulation) nystagmus produced significantly higher peak velocities than the two others. At the same amplitude and during the same visual conditions the saccades were significantly faster than any type of fast components of nystagmus. The difference in velocity between voluntary and reflexive eye movements is possibly related to differences in antagonistic activity during these eye movements, but also to specific synaptic events during the voluntary action.

Adult↗

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The dysrhythmia and the exponential constants of the postrotatory nystagmus qualities.

In 5 healthy individuals the postrotatory, exponential constants were estimated for each of the four nystagmus qualities, viz. the velocities and durations of fast and slow components. The residual spread (Sr) of each quality in a semilogarithmic plot was also determined. The value of the constant for postrotatory decay indicated a decrease of the velocity and an increase for the duration of the slow component, both with a significant difference between individuals, while for the corresponding values of the fast components no systematic change in the postrotatory reactions was indicated, nor any difference between individuals. The constant that corresponds to the value at maximum stimulus showed differences between individuals for each of the four nystagmus qualities, while Sr presented differences between individuals only for the two slow phase qualities. This technique to describe postrotatory nystagmus reactions by the two exponential constants for each of the four nystagmus qualities together with the residual spread for each of the qualities is intended for future 'on-line' nystagmus analysis.

Eye Movements↗

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Quantification of tracking eye movements in patients with neurological disorders.

Tracking eye movements were studied in 20 healthy subjects and in 24 patients with vestibular neuronitis, disorders within the frontal cortex, the cerebellum or the brain stem. The tracking tests were performed at six different target velocities between 10-60 degrees s-1 and different parameters were evaluated. The maximum velocity gain of smooth pursuit as normal in the group with vestibular neuronitis but reduced in the groups with disorders within the frontal cortex, cerebellum and the brain stem. The total amplitude of tracking and amplitude of smooth pursuit were normal in the groups with vestibular neuronitis and frontal cortical disorders, while in the groups with cerebellar and brain stem disorders it was reduced. The frequency of superimposed saccades with amplitude range of 3-10 degrees was significantly increased in all groups; however, in the group with vestibular neuronitis the increase was significant only during tracking in the direction of spontaneous nystagmus. The number of superimposed saccades with amplitude range of 11-20 degrees was significantly increased only in the group with cerebellar disorders. The frequency of square waves was not significantly increased in any group. Quantitative analysis of tracking eye movements seems to be a valuable aid for evaluation of site of lesions in the central nervus system.

Adolescent↗

PubMedDate not supplied

Clinical evaluation of dysrhythmia of postrotatory nystagmus.

Postrotatory responses of nystagmus were analysed in an exponential model by utilizing linear regression analysis. Four nystagmus qualities (velocity and duration of slow and fast phases) were studied in 10 patients with vestibular peripheral lesions, 10 patients with frontal lobe lesions and 10 patients with brain-stem lesions, together with 10 control subjects. In addition, pauses during the responses were quantified. Patients with frontal lobe lesions differed from other groups by scoring higher values of slow phase velocity and by exhibiting more pauses. The time constant was significantly shorter in patients with brain-stem lesion than in any other group. As regards other qualities, e.g. slow phase duration and fast phase velocity, or duration, no differences were observed. The pathological dysrhythmia may therefore be presented as changes in the gain and time constant of slow phase velocity as well as in pauses during nystagmus. Since all these changes may be encountered in normal subjects, one should be cautious in interpreting these changes as being pathological in each individual case.

Adult↗