N. G. Henriksson

Electric analysis of the Romberg test.

Two electric scales, based on Straingauge technique, have been used for objective recording of postural reflexes. The deviations in lateral as well as the leanings in anterio-posterior direction with closed and open eyes have been studied. Normal subjects seem to deviate with averagely about 6–7% of their body weight in the lateral direction and about double as much in the anterio-posterior direction. With closed eyes normals seem to lean more forward than with open eyes. An integration of the deviation from the individual position of equilibrium is suggested as an adequate measure for postural adequacy.

Studies on Habituation of Vestibular Reflexes: VI. Habituation in darkness of calorically induced nystagmus, laterotorsion and vertigo in man

Fifteen normal subjects received 12 consecutive caloric irrigations, all in darkness, with water of 30°C in the right ear. For each calorization nystagmus and laterotorsion were recorded and maximum vertigo was indicated by the subject. Four qualities were compared; (1) eye-velocity, (2) duration of nystagmus, (3) laterotorsion, and (4) vertigo.There was a response decline of these four qualities. The order of habituation rate from the greatest to the slightest was: (1) vertigo, (2) eye-velocity, (3) duration of nystagmus equal to laterotorsion. At the end of the irrigations vertigo had usually disappeared with nystagmus and laterotorsion still present.The mode of response decline of each of the four qualities showed considerable individual differences.There was a growing dysrhythmia of nystagmus with increasing habituation.

Effect of Cigarette Smoking on the Vestibular Nystagmus Pattern

Cigarette smoking was shown to give rise to obvious changes of the vestibular nystagmus pattern and these changes were ascribed to central influences. It was demonstrated that the fast phase affected the nystagmus pattern by changing its velocity, but above all by changing the time for its interruption of the slow phase. Early interruptions thus increased the frequency and decreased the amplitude. The qualities initiated in the vestibular receptor, the speed of the slow component and the deviations of the eyes in the direction of the fast component, were not significantly changed. Heavy smokers were found to have less changes in the nystagmus pattern by smoking than moderate smokers.

Vestibular activity at experimental variation of labyrinthine pressure.

After proving elasticity within the walls of the membranous labyrinth in a previous paper, the same technique was now used for recording vestibular activity at different endolymphatic pressures. When the intralabyrinthine pressure was increased by instillation of fluid via the posterior vertical canal the activity in the horizontal ampullar nerve showed extensive variations lasting about as long as the saccule was changing its volume. After this change the activity resumed the level found at normal pressure. The rotatory responses at these positive pressures were largely the same as those found at the zero-levels. At pressures below the zero-level the rotatory response was nearly always abolished. Some membrane properties were discussed in relation to electrolyte ion concentrations in the perilymph. The findings were discussed in relation to the pathophysiology of Menieres disease.

Studies of cristospinal reflexes (laterotorsion). II. Caloric nystagmus and laterotorsion in normal individuals.

A previously reported method for simultaneously recording the cristo-ocular (nystagmus) and cristo-spinal (laterotorsion) reflexes is reviewed. Calorically induced turning of the head, neck and body produced changes in weight on two pneumatic systems introduced beneath the head of supine individuals, which was expressed as laterotorsion. This recording was made in addition to the usual nystagmus. Such records were collected, studied and subjected to statistical analysis.Spontaneous laterotorsions of normal individuals were always less than 269 g after two minutes. Caloric laterotorsion was always in the direction of the slow component and averaged 828 g.Maximum laterotorsion and nystagmus were fairly consistent for a given individual but varied between individuals.A statistical analysis revealed a significant correlation between vertigo and laterotorsion but not between vertigo and nystagmus.The lack of quantitative correlation between nystagmus and laterotorsion was evidenced by unequal patterns of behav...

Eye Movements as a Function of Active Headturnings

Eye movements caused by turnings of the head present a very stable pattern with the eyes directed in the same direction as the headturnings. The initial deviation, the maximum deviation and the resting deviation of the eyes have been calculated as a function of the velocity of the head. This study is meant to form a basis for a future analysis of pathological cases in which other patterns of eye movements are found.

DC-Determined Displacement of the Nystagmus Beat in Rotatory Tests

The deviation of the eyes induced by vestibular stimuli is defined as the distance in degrees from the mid-position of the eyes to the position to which the eyes return in the fast phase. At an intensive angular stimulus the eyes are found to lead the head and to such an extent that the whole nystagmus beat can be displaced in the direction of the fast phase. The deviation of the eyes in the fast direction seems to be closely related to the deflection of the cupula and subsides exponentially in the postacceleratory period in about the same way as does the speed of the slow component. The eyes, however, reach their mid-position before the nystagmus disappears, indicating that a certain degree of intensity in the stimulus is needed to make the eyes deviate in the direction of the fast phase.

Studies of Cristospinal Reflexes (Laterotorsion): III. Patterns of Cristoocular and Cristospinal Reflexes in Clinical Oto-neurology

A comparative study of caloric nystagmus, vertigo and laterotorsion was made in normal subjects and in patients with peripheral labyrinthine lesions, Menieres disease, meningo-encephalitis and brain tumors. Variations were found in the patterns of behaviour in the various lesions. As examples: in Menieres disease nystagmus and vertigo decreased in their responses to caloric stimulation but laterotorsion remained normal, while meningoencephalitis showed a normal response of nystagmus but a decrease in laterotorsion.This induced us to consider the hypothesis that cristo-ocular and cristospinal reflexes have different mechanisms modulating them despite the common origin of their stimulus. The possibility of different receptor cells and neurons for the cristo-ocular and the cristo-spinal reflexes was also discussed. A better resistance of the units involved in the vestibulo-spinal reflex would then also explain the normal caloric laterotorsion in Meniere cases.A pilot study of brain tumors indicated that di...