Chronic central nervous system involvement in Lyme borreliosis.

We describe four patients with marked chronic meningoencephalomyelitis caused by tick-transmitted Borrelia burgdorferi infection. Imaging techniques showed either MS-like lesions or evidence of vascular involvement, as in other spirochetal infections, especially in meningovascular syphilis.

Downbeat nystagmus indicates cerebellar or brain-stem lesions in vitamin B12 deficiency.

Two cases of vitamin B12 deficiency caused by gastric atrophy are described. Together with the neuropsychiatric features usually associated with this condition, a downbeat nystagmus syndrome was observed. It is concluded that vitamin B12 deficiency may also result in lesions to those cerebellar or brain-stem structures that are generally assumed to cause downbeat nystagmus.

Influence of transcutaneous nerve stimulation (TNS) on acute pain.

Using transcutaneous nerve stimulation (TNS) simple surgical procedures such as tooth extractions and nerve biopsies can be performed without the usual anesthetics. Estimation of threshold and suprathreshold intensities of painful electrical stimuli show no significant change during TNS. Only the threshold for non-painful electrical stimuli is slightly increased. Cortical potentials evoked by electrical peripheral nerve stimulation are not significantly modulated by TNS. Latencies of the early components 0, I--III are unchanged, the amplitudes only slightly reduced. These observations are in contradiction to the 'gate-control' theory of pain.

Pain perception in man after long term spinal cord stimulation.

Thresholds of non-painful and painful perception for electrical stimuli are not altered significantly during dorsal column stimulation either in the area of induced paresthesia or outside it. After long term stimulation of the dorsal column the thresholds for stimuli are significantly higher within the area of induced paresthesia but not outside it. Median nerve evoked somatosensory cortical potentials are not altered by conditioning or simultaneous DC stimulation. During DCS in three of eight patients only the vibration evoked cortical potentials were attenuated in the early three components of the potential.

Pain reduction in amputees by long-term spinal cord stimulation. Long-term follow-up study over 5 years.

This follow-up study analyzes the results of dorsal column stimulation instituted between 1972 and 1974 for the relief of pain in 84 patients, including 64 amputees. Good results decreased from 52.4% after 2 years of stimulation to 39% after 5 years. Special therapeutic problems in amputees are discussed.

Huntington's disease: alterations of visual and somatosensory cortical evoked potentials in patients and offspring.

In 13 patients suffering form Huntington's chorea (H.Ch.), VEPs and SEPs were investigated in comparison to 9 clinically inconspicuous offspring and normal adults. 1. The mean amplitude of VEP was reduced in choreatic patients and in four out of nine offspring. 2. Latencies of P100 in VEP were normal in all subjects. 3. The late components were reduced in amplitude and rather irregular in shape. 4. The latencies of SEPs were slightly prolonged, less marked in the early peaks and more pronounced in the later ones. 5. The late components after 70 to 100 msec were often attenuated or even absent. 6. The mean amplitude of the first two peaks was reduced. 7. Interhemispheric asymmetries were pronounced in three out of nine offspring.

Visual evoked potentials by central foveal and checkerboard reversal stimulation in multiple sclerosis.

In 200 patients with suspected MS, the diagnostic value of VEP elicited by checkerboard reversal and central foveal stimulation was compared. No significant difference was evident, but both methods overlap. The more stable checkerboard reversal stimulation should be preferred as a diagnostic method. Only in suspected MS with normal checkerboard responses, additional foveal responses may give supplementary information. Normal VEPs cannot exclude a prior retrobulbar neuritis.

Experience with dorsal column stimulation (DCS) in the operative treatment of chronic intractable pain.

The results of DCS in 50 patients are altogether favourable; they are better for the group of amputation and phantom pain than for the group of peripheral nerve lesions. For patients with malignoma pain no valid comment can be given. The influence of DCS is mostly immediate in bouts of acute pain, slower in chronic permanent pain, where a longer period of stimulation is needed. The observation of such longer stimulation periods together with the experience that during DCS there is a shift in the pain threshold, even in segments above the stimulus including also the face, seems to indicate a participation of higher neuronal centers in the assumed gate control.

Spinal cord stimulation in post-amputation pain.

One of the pre-operative screening tests for dorsal column stimulation involves direct acute precutaneous stimulation of the dorsal column. The test simulates the postoperative therapeutic situation, shows the patient's reactions to electrically induced paresthesias and enables physician and patient to evaluate beforehand the degree of pain relief to be obtained with the implant.

Motion perception of head or trunk modulates cervico-ocular reflex (COR).

In 15 sitting volunteers with eyes covered the vestibulo- and cervico-ocular reflexes were tested with sinusoidal movements around the vertical axis of the body, at frequencies of 0.05, 0.1 and 0.2 s-1 and a total amplitude of 40 degrees. When the trunk was moved against the fixed head, the subjects described mainly an illusionary head movement at 0.05 s-1, while, at 0.2 s-1 only the trunk movement was perceived. Subjects asked to imagine head motion during COR showed increased eye shifts and total saccadic amplitudes. With concentration on trunk movement perception these values decreased.

Modulation of vestibulo-ocular reflex (VOR) by active stabilization of head to trunk.

Horizontal vestibulo-ocular reflex (VOR) with covered eyes was tested in 15 healthy subjects sitting on a rotation chair (40 degrees, 0.05, 0.1, 0.2, 0.33 Hz) under two conditions: (a) head fixed to chair by a neck support; (b) with instruction to turn the head together with the passively moved trunk. In situation (b), saccadic amplitudes/sec, nystagmus frequency, gain of nystagmus slow phase velocity and amplitudes of maximum eye shift were enhanced significantly. The phase of maximum eye shift changed from 180 degrees up to 270 degrees with respect to stimulus position. The distribution of nystagmus saccades over the stimulus period showed enhanced peak values and a slight phase shift.

Eye movements during active head turning with different vestibular and cervical input.

Eye movements were measured in 15 volunteers during vestibulo-ocular reflex (VOR), cervico-ocular reflex with the head fixed from the ceiling (passive COR), during voluntary stabilization of the head in space while the trunk was moved sinusoidally (active COR) and active head movements with and without additional vestibular or cervical stimuli. The subjects were sitting with eyes covered on a rotating chair swinging sinusoidally at 40 degrees peak to peak amplitude at 0.05, 0.1 and 0.2 Hz. The saccadic activity during passive COR is below the VOR and increases slightly during active COR. During voluntary head movements it shows a marked increase and is further activated if cervical or vestibular stimuli are added. The amplitudes of eye shifts of passive and active COR are not different. During active head movements and more with additional cervical or vestibular input, they increase significantly. The phase of the maximum eye shifts to head position is anticompensatory during passive COR and compensatory during VOR. The phase lead of about 45 degrees during active head movements is less during active COR but is larger with additional cervical and vestibular stimuli reaching 90 degrees.

The vestibulo-ocular response during transient arousal shifts in man.

Horizontal vestibulo-ocular response (VOR) evoked by continuous sinusoidal rotation (0.1 Hz, +/- 90 degrees) was recorded in 20 young and healthy volunteers by DC oculography (EOG). Arousal was assessed by EEG and by reaction time measurement. While alert subject showed the characteristic VOR with vestibular nystagmus, the quick repositioning flicks disappeared during light sleep and changed to largely compensatory smooth eye deviations. This state of reduced arousal was also characterized by EEG attenuation and slow reaction times. Furthermore, we observed brief states with complete extinction of the vestibular response but without significant EEG change. The results demonstrate the high variability of VOR with shifting arousal. The polysynaptic system in the reticular formation which generates the fast phase of the nystagmus beat is far more modifiable than the three-neuronal reflex arc of the slow nystagmus component.

Tonic cervical stimulation: does it influence eye position and eye movements in man?

In healthy subjects eye movements were analysed during body rotation, during trunk torsion either with the head passively held stationary in space or with the head voluntarily stabilized in space, and during voluntary head movements. Trapezoidal movements around the vertical axis were performed (+/- 40 degrees, plateau 10 s, duration of ramp 1 or 4 s). Moreover the influence of a tonic head deviation up to 40 degrees on optokinetic nystagmus and on vestibulo-ocular reflex during sinusoidal turning was examined. Eye movements were recorded by DC-electrooculography. Saccadic and slow components of eye movements and the shift of eye position during the plateau of the trapezoidal stimulus were analysed. For all modes of stimulation during the plateau no nystagmus occurred. At the end of the dynamic phase of the stimulus relatively frequent eye deviations--mostly in the direction of the head deviation--were observed, not only after turning the trunk with the head stabilized in space (cervical stimulation) but also after turning head and trunk together. The fact that such eye deviations are thus observed even in the absence of any tonic, especially cervical stimulus, supports the assumption that they cannot be attributed to a tonic stimulus but merely to an effect of the preceding phasic stimulus which outlasts them. Also amplitude and direction of eye shifts during the plateau do not depend on a tonic stimulus, but merely on the eye deviation reached at the end of the dynamic phase of stimulation. Optokinetic nystagmus and vestibulo-ocular reflex are not influenced by an additional tonic cervical stimulus.