Sporadic rapid-onset dystonia-parkinsonism syndrome: failure of bilateral pallidal stimulation

We report on a woman who had a severe sporadic nonprogressive dystonia-parkinsonism syndrome with rapid onset of symptoms at age 21. Secondary causes for dystonia were ruled out. No response to levodopa/carbidopa was seen. The patient fulfilled all diagnostic criteria of rapid-onset dystonia-parkinsonism, except for autosomal-dominant inheritance. Bilateral deep brain stimulation of the globus pallidus failed to alleviate her symptoms.

[Parkinson's disease--new horizons]

New information about the pathology and genetics of Parkinson's disease opens up new possibilities for treatment. A key role is played by a pathologically folded protein, the distribution of which in the brain permits new conclusions about the stage of the disease. Gene mutations in affected families provide further clues as to the pathological process. In addition to symptom control, future treatment strategies will be aimed in particular at slowing down the underlying pathological process, and will therefore go in the direction of neuroprotection and neurorestoration. Dopamine agonists that can slow cell degeneration are already the first-line treatment in patients under 70 years of age.

Effects of deep brain stimulation on prehensile movements in PD patients are less pronounced when external timing cues are provided

It has been repeatedly demonstrated that the movements of patients with Parkinson's disease (PD) are less impaired when external timing cues are provided. This suggests that the basal ganglia, which are impaired in PD, are less involved in the control of externally timed movements. In the present study, we tested this hypothesis by contrasting the effect of deep brain stimulation (DBS) in the basal ganglia (more precisely, the internal globus pallidum) on internally versus externally timed movements. Our first movement task was a standard prehensile task involving a reach-to-grasp movement. In the externally-timed condition, the target object was moving rapidly away from the subject; in the internally-timed condition, the target object was stationary. We found, that for most aspects of the prehensile movement the effect of DBS was less pronounced in the externally than in the internally timed condition. A similar reduction of the DBS effects in the externally-timed condition was also found for a second movement task, which required an isolated grasping movement. We conclude that the basal ganglia are significantly less involved in the control of externally timed movements.

Chronic high-frequency globus pallidus internus stimulation in different types of dystonia: a clinical, video, and MRI report of six patients presenting with segmental, cervical, and generalized dystonia

The results of deep brain stimulation (DBS) of the globus pallidus internus (Gpi) in six patients with generalized, focal, and segmental dystonia are presented. Pre- and postoperative assessments are given for one patient with generalized inherited dystonia and for five patients with idiopathic segmental or cervical dystonia. Clinical symptoms were evaluated before and 3-12 months after surgery using the Burke-Fahn-Marsden (BFM) dystonia rating scale for primary torsion dystonia and the Tsui scale for cervical dystonia. The Short-Form Health Survey (SF-36) was completed by each patient to document preoperative and postoperative health status. Also, neurological status was documented by video before and during chronic stimulation. Magnetic resonance imaging studies were performed to show the anatomical localization of the electrode leads. Five patients showed a progressive improvement within 7 days. One patient with cervical dystonia and Meige's syndrome showed no improvement for 3 months, but beneficial effects were observed after 12 months. On average, the BFM movement scale scores decreased by 72.5% and Tsui scale scores by 63%. SF-36 showed an improvement in health status by an average of 36% according to eight different health categories. We conclude that chronic high-frequency Gpi stimulation in different types of dystonia is a very effective and safe treatment.

Contraversive eye deviation during deep brain stimulation of the globus pallidus internus

Clinical signs help determine correct electrode positioning during stereotactic implantation for chronic high-frequency pallidal stimulation in Parkinson's diease (PD). The authors describe a patient who had marked, sustained, contraversive eye deviation caused by stimulation during pallidal surgery. The underlying mechanism is probably an excitation of fibers in the internal capsule by volume-conducted current spread. Such conjugate eye deviation is thus not necessarily an indication of incorrect electrode placement.

Postural reflexes evoked by tapping forehead and chest

We investigated whether a tap with a reflex hammer to the forehead can elicit responses in the leg muscles and whether vestibular stimulation is the crucial prerequisite for eliciting these responses. We also measured the postural changes caused by the tap and by the compensatory, presumably reflex-like reactions of the subject. Tap-evoked activity of leg muscles was easily elicited during upright stance in normal subjects and was also seen in two subjects without vestibular function. The pattern of muscle activation clearly showed a counteraction to the tap-evoked perturbation of stance. Taps applied to the chest elicited similar reflexes. Since these two conditions imply a different activation of the vestibular apparatus, the vestibular input alone cannot account for the observed leg muscle reflexes. We suggest that multisensory reflex pathways that integrate vestibular and proprioceptive inputs account for these reflexes.

[Gliomatosis cerebri: two case reports with atypical clinical and neuroradiologic findings]

The diagnosis of the rare disease Gliomatosis cerebri requires the correlation of clinical, radiological, and pathological findings. We report on two patients with intravitally diagnosed gliomatosis cerebri. Due to the unusually high malignancy of the tumor cells, diagnosis was complicated by atypical findings such as gadolinium enhancement in MRI and raised intracranial pressure. The clinical course, differential diagnosis, and literature are summarized briefly.

Dipole source analysis in persistent mirror movements

To elucidate the pathomechanism underlying persistent mirror movements (MM), we modelled the origin of electric brain activity associated with these movements. Movement-related cortical potentials (MRCP) in a group of subjects affected by persistent mirror movements were compared with those of a control group. The data of the normal subjects were best explained with two bilaterally active electric sources in the sensorimotor cortices with a clear preponderance of the hemisphere contralateral to the movement. In contrast, the MM subjects presented a fairly symmetric source activity in both hemispheres during unilateral intended movements. In the control group, the source representing the activity of the motor cortex ipsilateral to the moving finger reduced activity before the beginning of the movement; this was interpreted as an inhibition of the ipsilateral motor cortex during unilateral movement. In the MM group, however, this inhibition was not seen. Furthermore, while normal subjects demonstrated no relevant activity of an additional source placed near midline motor structures (supplementary motor area; SMA), subjects with MM showed considerable activity of this dipole source. These findings suggest that subjects with persistent MM have abnormal bilateral activation of the primary motor areas, probably together with an additional activation of mesial motor structures. This assumption fits well with the observation of an incomplete decussation of the pyramidal tract. The bilateral activation is then explained as a compensatory strategy in order to achieve sufficient force in the innervated target muscles.

Can short-latency vestibulospinal reflexes in lower leg muscles be elicited by tapping the head?

A gentle tap on the forehead evoked short-latency motor responses in the sternocleidomastoid muscle, which may be vestibulocollic reflexes with characteristics similar to those elicited by clicks. We tested this paradigm in subjects standing upright, in order to determine the differential effects of taps on the forehead on the patterns and latencies of spinal stretch and vestibulospinal reflexes, which are important for postural control. Taps on the forehead elicited short-latency inhibitory electromyographic responses in both gastrocnemius muscles with a mean latency of 48.3 +/- 3.1 ms (onset) to 98.3 +/- 6.3 ms (end). Taps on the sternum elicited similar responses from the gastrocnemius muscles, indicating that vestibular stimulation is not essential for eliciting these responses. Both responses may play a role in predetermining the strategy for correcting body perturbations. The actual reflex is probably elicited by somatosensory input from the neck, which converges with vestibular input for the multisensory control of posture.

Topography and dipole analysis of reafferent electrical brain activity following the Bereitschaftspotential

The cerebral events related to limb movements can be studied noninvasively with the method of evoked potentials. In this study, a brain potential is analysed that follows the onset of a simple finger movement. Because this potential occurred after active as well as after passive movements, its previously alleged reafferent somatosensory nature is confirmed in this study. Detailed topographic analysis revealed that this potential has the same polarity and merges with the preceeding Bereitschaftspotential (BP; in the active movement) at central electrodes, whereas at parietal electrodes polarity is opposite to the BP. In individual subjects, the maximum of the BP and the peak of the reafferent potential are separated by a small gap, previously described as pre-motion positivity. A comparison with the N20 potential of the electrically evoked somatosensory potential showed similar potential topography, albeit opposite polarity. The dipole analysis supported the view that the reafferent and the electrically evoked potentials are likely to arise from the same cortical area, namely the primary somatosensory cortex.

[Functional eye muscle changes in endocrine orbitopathy]

BACKGROUND

To determine the functional changes in the extraocular muscles in patients with thyroid-associated ophthalmopathy (TAO).

PATIENTS AND METHODS

Horizontal saccades with an amplitude of 20 degrees were carried out over a period of 2 min. Eight patients with acute TAO and five patients with chronic TAO were compared with ten age-matched healthy individuals. Ocular movements were recorded using the "Ober 2" system based on infrared technology. For evaluation of fatigue effects, the parameters of the first five and the last five saccades were analysed.

RESULTS

A significant difference of four and five, respectively, out of nine tested saccadic variables including maximum velocity (Vmax) was found both before and after fatigue. In comparison to normal subjects, patients with chronic TAO revealed mildly increased reduction of Vmax after fatigue. Results in patients with acute TAO were related to the action of the most severely affected muscle. On active contraction of the medial rectus muscle (adducting saccades), Vmax was not significantly decreased after fatigue. On passive elongation of the medial rectus muscle (abducting saccades), however, Vmax was initially markedly decreased and increased significantly after fatigue.

CONCLUSIONS

Functional changes of extraocular muscles in patients with TAO can be demonstrated by saccadic analysis. The inverse change in velocity after fatigue in acute disease indicates an improvement of muscle elasticity during exertion and strongly supports the concept that early impairment of bulbar motility in active TAO results from contracture of myofilaments. Thus, analysis of the fatigue effect may help to differentiate between acute and chronic disease.

[Measuring saccades in endocrine orbitopathy]

Thyroid-associated ophthalmopathy (TAO) is evaluated mainly by orthoptic examination and morphometric parameters such as ultrasound, CT scanning or magnetic resonance imaging. Inflammatory changes of the extraocular muscles lead to an impairment of eye movement. Recent evidence suggests that saccades are altered by changes to the extraocular muscles. Although of potential interest, this phenomenon has so far received little attention. To determine the role of saccades as a potential diagnostic tool for assessing the function of the affected muscles, we have begun to analyze saccadic parameters in patients with TAO. Preliminary results of this study are reported in the present paper. For registration of both horizontal and vertical eye movements, we used the "Ober-2-Apparatus," which uses the infrared technique. Horizontal and vertical saccades with an amplitude of 10 degrees were analyzed in 20 healthy persons and 30 patients suffering from TAO. Patients showed changes in the quality of saccades, such as the appearance of glissades and additional correctional saccades as well as quantitative changes, such as an increase in the maximum speed and latency. Our current data suggest the presence of saccadic alterations in TAO. Our ongoing studies are designed to evaluate whether characteristic changes can be assigned to certain stages of the disease and whether assessment of saccadic changes in a promising tool for early detection and functional follow-up in patients with TAO.

Movement-related cortical potentials in persistent mirror movements

Mirror movements (MMs) are involuntary movements executed on one side of the body during voluntary movements of the contralateral homologous body parts which may abnormally persist into adulthood. In 6 subjects affected by persistent MM with autosomal dominant inheritance, movement-related cortical potentials (MRCPs) during self-paced, voluntary extensions of either the left or right middle finger were recorded from 30 EEG electrodes simultaneously with the electromyogram (EMG) of both extensor digitorum communis muscles. The negative potentials before and during EMG onset were evaluated statistically for the two electrodes next to the cortical hand areas. A comparison with 7 normal subjects revealed no marked differences for the Bereitschaftspotential (BP) and the negative slope (NS'). Only in the periods around EMG onset (from -50 to +50 msec) a significant difference between both groups was found. The MM subjects showed fairly symmetric potentials over the right and left hemispheres, whereas the potentials of the control subjects were lateralized to the hemisphere contralateral to the intended movement. No difference was found for the amplitude of the maximum negative peak of MRCP following EMG onset. Our data showed no evidence for a different type of movement preparation in MM subjects as compared to normals. We propose that the additional ipsilateral cortical activation around movement onset may be the cortical mechanism, which compensates for abnormal ipsilateral corticospinal pathways in subjects with persistent MM.

Scalp topography and analysis of intracranial sources of face-evoked potentials

Several reports have described that a positive vertex peak of an evoked potential varied in amplitude and latency specifically when images of faces were the eliciting stimulus. The scalp topography and the possible underlying dipole sources of this peak are the subject of this report. We presented black-and-white photographs of human faces, flowers and leaves to 16 healthy subjects and recorded the evoked brain potentials from 31 scalp electrodes. We found the previously described higher amplitude of the positive vertex peak when faces were the crucial stimulus, but the latency of this peak was the same (180 ms) for all three categories of stimulus. At the posterior temporal electrodes, the face waveforms showed a negative peak at 175 ms, which was only rudimentary in the waveforms elicited by the other stimuli. Since in most previous reports a mastoid reference was used, it is most likely that the previously described latency shift of the positive vertex peak associated with face stimuli was due to the interaction with this posterior temporal peak. The dipole analysis of the possible generators of the recorded potentials suggested the sequential activation of occipital, lateral temporal and mesio-temporal brain structures during the perception of a human face.

Rotational vertigo in embolic stroke of the vestibular and auditory cortices

We describe the unique case of a woman with embolic infarction within the right middle cerebral artery territory who had nonepileptic rotational vertigo, nausea, and unsteady gait that gradually resolved within a week. A well-demarcated lesion of the posterior insula (homologous to parieto-insular vestibular cortex in monkeys) was probably the cause. This is supported by a contraversive tilt of perceived vertical and by involvement of the adjacent auditory (Heschl's) cortex. Dipole source analysis of late auditory evoked potentials revealed a decreased amplitude of a dipole source in the right insular cortex, whereas two other dipoles situated in the temporal lobe showed symmetric activity.

Frontal and parietal premovement slow brain potentials in Parkinson's disease and aging

During the anticipation of a stimulus that induces a predetermined pattern of behavior, a slowly increasing negative electric potential can be recorded from the human scalp at central and parietal electrodes and has been named contingent negative variation (CNV). We used a simple and a choice reaction time paradigm to investigate premovement potentials in patients with Parkinson's disease (PD) and in normal controls. There was a clear CNV in young subjects whereas it was negligible in the elderly control subjects and absent in the patients. In addition, we found a slowly increasing positive frontal potential. In normals the steepness of this potential decreased with the complexity of the task (simple vs. choice) and with age. This difference was abolished in the patients: If a slowly increasing positivity was observed at all, it was, on average, larger in the choice task. Reaction times of the patients were disproportionally prolonged in the simple compared to the complex task. These findings support the hypothesis that storing or initiating a simple preprogrammed motor response is more impaired in PD than selecting and initiating a motor response of a more complex task. The electrophysiological recordings suggest that impaired activation of the frontal lobes may be responsible for this deficit.

Noninvasive assessment of cerebral hemodynamics and tissue oxygenation during activation of brain cell function in human adults using near infrared spectroscopy

Near Infrared Spectroscopy (NIRS) was employed to noninvasively and continuously (temporal resolution 0.5 s) assess changes in cerebral hemodynamics and oxygenation during various functional states of the adult human brain. During cognitive stimulation (performing calculations) a frontal increase in local cerebral blood volume and oxygenated hemoglobin concentration was observed in most (10 of 12) subjects. During visual stimulation (observing a picture) this was demonstrated in the occipital region in all three subjects. Deoxygenated hemoglobin either decreased, remained unchanged or slightly increased during these procedures. Epileptic patients were examined during spontaneously occurring complex-partial seizures. During these seizures extremely large increases in blood volume and oxygenated hemoglobin concentration were measured. In conclusion, this feasibility study indicates that NIRS might become a useful and simple bedside tool to assess brain function.

Bereitschaftspotential: is there a contribution of the supplementary motor area?

Bereitschaftspotentials (BPs) preceding simple repetitive finger movements were recorded in 11 normal volunteers. By modeling the recorded data with multiple equivalent dipoles we found that bilateral sources in the motor cortex were the best fitting hypothesis for the early BP. The activity of the source contralateral to the moving finger was increased during the steep slope of the late BP before and during the motor potential. Around and after electromyogram (EMG) onset, separate sources were detected for the motor potential close to the anterior wall of the central sulcus, and for the reafferent somatosensory potential in the postcentral gyrus. Their source wave forms showed short transient deflections peaking about 10 msec and 100 msec, respectively, after EMG onset. No evidence was found for significant source currents in the supplementary motor area (SMA), which has been suggested as the main generator of the BP. Placing probe dipoles arbitrarily into the region of the SMA did not result in the detection of a large source activity. Therefore, we conclude that the SMA does not provide a major contribution to the scalp BP during simple repetitive finger movements.

Transcranial cortical stimulation in syringomyelia: correlation with disability?

Central motor conduction times were studied using transcranial magnetic stimulation in 17 patients with syringomyelia. Central motor conduction time (lower-limb pathway) was prolonged or responses were absent in 44% of stimulations. When results were compared with clinical findings and magnetic resonance tomography, only a weak correlation was found. Transcranial magnetic stimulation is thus of limited value for diagnosing and monitoring the course of syringomyelia.

[Tuberculous radiculomyelitis--good response to therapy only in early detection]

This is a report of a case of radioculomyelitis secondary to tuberculous meningitis. The importance of an early diagnosis is stressed in the light of reports on good outcome after prompt commencement of therapy. Polymerase chain reaction is now available for quick confirmation of the suspected diagnosis.

Normal and pathological saccadic dysmetria

Initial saccades to visual targets are generally not precise in either normal subjects or patients with saccadic dysmetria. Quantitative criteria have to be applied to clearly distinguish between normal and pathological saccadic dysmetria, which is often found in patients with cerebellar lesions. To establish these criteria, the accuracy of visually guided horizontal saccades (10 degrees and 20 degrees target steps) was studied in a group of 24 patients with lesions affecting the cerebellum or its connections, and compared with data from 17 normal subjects. Eye movements were recorded with infrared oculography. Saccades of normal subjects had an average gain of 0.92-0.95 depending on the stimulus condition. Centripetal saccades were significantly larger than centrifugal saccades, for 20 degrees target steps. Most patients (n = 15) had significantly larger saccadic amplitudes than normal subjects (hypermetria), at least in one direction. Saccades in the opposite direction could be either hypometric, hypermetric or normal. Two patients had hypometric saccades in both directions. For one of the patients with hypermetria, in addition, the amplitude difference between centrifugal and centripetal saccades was significantly larger than in the normal subjects. Five patients had no significant pathology of the initial (primary) saccade, but a pathological pattern of corrective saccades. Two patients had normal saccades under all conditions. The quantitative comparison with normal subjects allows the detection even of mild pathology. According to our results, a pathology can be assumed when the average gain of saccades in at least one direction is 1.0 or more, or when more than two out of 20 saccades are followed by two corrective saccades of which the last is in the direction opposite to the initial saccade (pathological pattern of corrective saccades). Target steps of 20 degrees reveal a pathological condition more often than 10 degrees target steps. The application of quantitative criteria might be useful to establish a diagnosis of pathologic saccadic dysmetria even in instances in which it is clinically not obvious.

The time course and location of cerebral evoked activity associated with the processing of colour stimuli in man

Area V4 has been located in man in the region of the fusiform gyrus on the inferior surface of the occipital lobe. Using multiple dipole source analysis on multichannel EEG recordings of visual evoked potentials to coloured 'Mondrian' stimuli in man, we have confirmed that activity is consistently seen in this area regardless of the retinal area stimulated and have obtained new information concerning its time course. Three different localized centres of activity follow the visual stimulus, with peak latencies of 90, 110 and 160 ms, and arising respectively in the region of visual areas V1, V2/V3 and V4. The time course and character of the V4 dipole activity to a colourless black-and-white Mondrian is indistinguishable from that to the coloured Mondrian, supporting the evidence that the cells of V4 are not exclusively concerned with colour processing.

Electric brain potentials evoked by pictures of faces and non-faces: a search for "face-specific" EEG-potentials

In three different experimental series, electroencephalographic responses evoked by changes in pictorial patterns were recorded in 29 adult human subjects (19 females, 10 males). Quantitative data evaluation for the evoked responses from electrodes T5, T6, Cz, Pz (10-20 system) was performed. The stimuli were projected to a 4 x 6 degree binocularly viewed field. The patterns changed within 6 ms every 2.5-4.5 s according to a random program. Paradigm (1): Identical line drawings of a face, a tree and a chair were used, either black on white (P-stimuli) or white on black (N-stimuli); in each set altogether 160 slides appeared in semi-random order. At Cz and Pz a prototypical EEG-response evoked by face stimuli was found exhibiting 3 prominent peaks, very similar for P-stimuli and N-stimuli. A P150 maximum was especially pronounced in the responses to face stimuli but absent in the evoked potentials aroused by chair or tree stimuli. The difference curves (face-chair, face-tree, chair-tree) supported the hypothesis of "face-responsive" components in these responses. Paradigm (2): 4 x 6 degree slides (black and white photographs) of 54 different human faces, 53 different vases and 53 different pairs of shoes were projected as in paradigm (1), but instruction to the subjects on a supposed post-test memory task raised their attention during the recordings. "Face-responsive" components (an early N 140-160, P 210-240, N 300) were more marked in female than in male subjects, and again most pronounced at electrode Cz. Paradigm (3): When a recognition task was included in paradigm (2)--9 out of 192 items were memorized 20 minutes before the recording session--essentially the same evoked potentials were obtained as in (2), but an additional late positive wave (450-600 ms) appeared in the responses to all stimuli. We assume that the "face-specific" components--a designation which is used cautiously considering the limited number of non-face stimuli--do not originate in the temporo-occipital cortical face region, but in limbic structures (amygdala, hippocampus) deep in the temporal lobe or in the gyrus cinguli. In the present study no significant hemispheric differences (T5, T6) in the evoked responses were found (all stimulus categories), but such differences are known to appear with highly schematic face stimuli.