Gluteal compartment syndrome due to rhabdomyolysis after heroin abuse

We report a 30-year-old man who developed painful swelling of his right leg and complete sciatic nerve palsy after an i.v. injection of heroin. Excessive elevation of serum creatine phosphokinase indicated the presence of rhabdomyolysis. Fasciotomy of the gluteus maximus led to rapid and complete recovery from sciatic nerve palsy. Nontraumatic rhabdomyolysis may cause a gluteal compartment syndrome that requires immediate fasciotomy.

Comparison of psychophysical and evoked potential methods in the detection of visual deficits in multiple sclerosis

We compared the diagnostic sensitivity of traditional visual tests such as the Snellen-test and pattern reversal VEPs with psychophysical and electrophysiological tests involving motion processing and psychophysical tests of contrast processing in detecting visual deficits in a group of MS patients. A total of 30 patients with a definite diagnosis of MS and 22 age-matched controls selected from a pool of healthy volunteers participated in this study. Visual evoked potentials elicited by reversing checkerboards and moving random dot patterns (motion-onset VEPs) were recorded. The recognition of motion-defined forms (motion-defined letter test, MDL-test) and of contrast reduced optotypes was measured psychophysically. Of 30 patients, 29 showed deficits in at least one of the tests applied. The highest detection rate was obtained for a simple psychophysical test, the MDL-test, which revealed abnormalities in 80% of the patients. This is about 12% more than pattern VEPs could detect. Conversely, abnormalities in motion-onset VEPs were found in only 16% of the patients. Our results show that by adding a simple psychophysical test of form-from-motion analysis our capability to demonstrate an involvement of the visual system in MS patients may be promoted considerably.

Developmental and genetic regulation of programmed neuronal death

Apoptotic neuronal death is a key mechanism that regulates the elimination of neuronal precursor cells during the development of the mammalian brain. The principal action of neurotrophins such as nerve growth factor is probably the suppression of the preexistent machinery of programmed cell death that is readily activated in neurons deprived of neurotrophins. Potassium-mediated neuronal depolarization prolongs neuronal survival in vitro and has become a major model of examining neuronal apoptosis. Apoptosis induced by potassium deprivation triggers a lethal cascade of events that includes specific RNA and protein synthesis, induction of interleukin 1-converting enzyme-like protease activity, and generation of free radicals. Neuronal susceptibility to apoptosis is also regulated by the expression of bcl-2 family proteins. Current research focuses on the significance of these findings for the premature death of adult neurons in human neurodegenerative diseases.

[Neurologic side-effects of pharmacologic corticoid therapy]

Many side effects of steroid treatment have been reported. Even experienced neurologists may not know all important side effects to the nervous system. Autonomic nervous system dysfunction, psychosis and myopathy are more frequently encountered than dependency, reversible dementia, brain atrophy and benign intracranial hypertension. This review describes symptomatology, pathogenesis and treatment of these steroid-induced side effects.

Voluntary facial palsy with a pontine lesion

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Autosomal dominant cerebellar ataxia type I clinical features and MRI in families with SCA1, SCA2 and SCA3

Sixty-five patients suffering from autosomal dominant cerebellar ataxia-I(ADCA-1) were subjected genotype phenotype correlation analysis using molecular genetic assignment to the spinocerebellar ataxia type 1, 2 or 3 (SCA1, -2 or -3) locus, clinical examination, eye movement recording and morphometric analysis of MRIs. Pyramidal tract signs, pale discs and dysphagia were more frequent in SCA1 compared SCA2 and SCA3 patients. Saccade velocity was reduced in 56% of SCA1 and all SCA2, but only in 30% of SCA3 patients. MRIs of SCA2 patients showed atrophy changes typical of severe olivopontocerebellar atrophy (OPCA). The morphological changes in SCA1 were similar but less pronounced. In contrast, SCA3 patients had only mild cerebellar and brain stem atrophy distinct from typical OPCA. The principal finding of this study is that mutations of the SCA2 and SCA3 gene cause phenotypes which can be distinguished in vivo by recording of eye movements and morphometric MRI analysis. Correlative plotting of saccade velocity and diameter of the middle cerebellar peduncle yields a clear separation of SCA2 and SCA3. Spinocerebellar ataxia type I falls into an intermediate range that overlaps with both SCA2 and SCA3. However, the clinical syndrome observed in SCA1 patients is different from that in SCA2 and SCA3.

Wrist tremor: investigation of agonist-antagonist interaction by means of long-term EMG recording and cross-spectral analysis

We have developed a method to observe and quantify the phasic relationship between the burst patterns of antagonistic muscles in any roughly periodic movement, such as tremor, for up to 24 h. This paper describes our approach, in which long-term EMG recordings are evaluated by a procedure based on cross-spectral analysis. The method is then illustrated by data from 6 patients with essential tremor. Our data confirm earlier observations that a particular patient may show different burst patterns at different times. However, as opposed to tremor analysis based on short-term recording, our method allows quantitative statements on the relative frequency of the burst patterns, as they occur under everyday conditions. In addition, our data suggest that in ET (a) alternating tremor activity in one hand may occur simultaneously with synchronous activity in the other hand; (b) along with the classical alternating and co-contracting patterns there may be significant 'non-classical' activity, that cannot be called alternating or synchronous.

[Influence of genetic factors on multiple sclerosis]

Epidemiological studies have provided evidence for a genetic contribution to the susceptibility of multiple sclerosis (MS). One in six patients has at least one affected family member. The concordance rate is approximately 25% in monozygotic twins, and 3% in siblings, however the prevalence in adopted siblings is similar to the general population (0.1%) MS is thought to be a T cell-mediated autoimmune disease and therefore genes controlling the immune response have been studied intensively as potential susceptibility factors. The best documented association was found for genes of the human-leukocyte antigen complex. Other possible susceptibility genes may reside in the regions of the T cell receptors and the tumour necrosis factors. So far it is clear, that MS is a multifactorial disease in which several genes must be involved. Population genetics and molecular biology will help to characterise further these susceptibility factors.

P3 and contingent negative variation in Parkinson's disease

Patients with idiopathic Parkinson's syndrome, most of them in early stages of the disease, and matched healthy controls participated in a continuous performance task while their EEGs were recorded from 15 electrodes. During preparation of movements, a contingent negative variation (CNV) maximal at central and posterior sites was visible. This CNV was reduced in the patient population. A large P3-like positive deflection occurred after go and no-go stimuli that called for execution (go) or suppression (no-go) of a button press. Compared to healthy controls, the positive wave in Parkinson patients was significantly reduced after go stimuli and maximally attenuated when no-go stimuli had indicated to suppress the motor response. In contrast, P3 amplitudes after irrelevant "ignore' stimuli was not significantly reduced in the patients. These results are interpreted in the framework of a model of striatal function postulating (i) that populations of cortical and striatal neurons form distributed functional units (Hebbian cell assemblies), and (ii) that mutual inhibition between such cortico-striatal cell assemblies is mediated by the neostriatum, the forebrain structure primarily affected in Parkinson's disease.

Vestibular neuritis spares the inferior division of the vestibular nerve

Acute unilateral vestibulopathy, or vestibular neuritis, is the second most common cause of vertigo. To quantify the involvement of the different semicircular canal (SCC) afferents in this disease, we studied the three-dimensional (3D) properties of the vestibuloocular reflex (VOR) in 16 patients 3-10 days after onset of symptoms. Using 3D magnetic search coil eye movement recordings, we measured the speed and axis of eye rotation during spontaneous nystagmus and during rotation in the planes of the different SCCs. In all patients, spontaneous nystagmus axes clustered between the direction expected with involvement of just one horizontal SCC and the direction expected with combined involvement of the horizontal and anterior SCC on one side. Likewise, dynamic asymmetries were found only during rotations about axes which stimulated the ipsilesional horizontal or ipsilesional anterior SCCs. No asymmetry was found when the ipsilesional posterior SCC was stimulated. Thus, both measurements suggest that vestibular neuritis is a partial and not a complete unilateral vestibular lesion and that this partial lesion affects the superior division of the vestibular nerve which includes the afferents from the horizontal and anterior SCCs.

Interaction of smooth pursuit and the vestibuloocular reflex in three dimensions

1. What is the neural mechanism of vestibuloocular reflex (VOR) cancellation when a subject fixates a target moving with the head? One theory is that the moving target evokes pursuit eye movements that add to and cancel the VOR. A recent finding with implications for this theory is that eye velocity vectors of both pursuit and the VOR vary with eye position, but in different ways, because pursuit follows Listing's law whereas the VOR obeys a "half-Listing" strategy. As a result, pursuit cannot exactly cancel the VOR in most eye positions, and so the pursuit superposition theory predicts an eye-position-dependent pattern of residual eye velocities during cancellation. To test these predictions, we measured eye velocity vectors in humans during VOR, pursuit, and cancellation in response to torsional, vertical, and horizontal stimuli with the eyes in different positions. 2. For example, if a subject is rolling clockwise (CW, frequency 0.3 Hz, maximum speed 37.5 deg/s) while looking 20 deg up, the VOR generates an eye velocity that is mainly counterclockwise (CCW), but also leftward. If we then turn on a small target light, located 20 deg up and moving with the subject, then pursuit superposition predicts that the CCW component of eye velocity will shrink and the horizontal component will reverse, from leftward to rightward. This pattern was seen in all subjects. 3. Velocities depended on eye position in the predicted way; e.g., when subjects looked 20 deg down, instead of 20 deg up, during CW roll, the reversal of horizontal eye velocity went the other way, from rightward to leftward. And when gaze was 20 deg right or left, analogous reversals occurred in the vertical eye velocity, again as predicted. 4. Analogous predictions for horizontal and vertical stimulation were also borne out by the data. For example, when subjects rotated rightward while looking 20 deg up, the VOR response was leftward and CCW. When the target light switched on, the torsional component of the response reversed, becoming CW. And analogous predictions for other eye positions and for vertical stimulation also held. 5. For all axes of stimulation and all eye positions, eye velocity during cancellation was roughly parallel with the gaze line. This alignment is predicted by pursuit superposition and has the effect of reducing retinal image slip over the fovea. 6. The fact that the complex dependence of eye velocity on the stimulation axis and eye position predicted by pursuit superposition was seen in all subjects and conditions suggests strongly that the VOR indeed is canceled additively by pursuit. However, eye velocities during cancellation were consistently smaller than predicted. This shrinkage indicates that a second mechanism, besides pursuit superposition, attenuates eye velocities during cancellation. The results can be explained if VOR gain is reduced by approximately 30%, and if, in addition, pursuit is driven by retinal slip rather than reconstructed target velocity in space.

Ocular exploration of space as a function of neck proprioceptive and vestibular input--observations in normal subjects and patients with spatial neglect after parietal lesions

We recently argued that the specific compensation of spatial neglect by manipulating neck proprioceptive and vestibular input is due to a central "correction" of the disturbed neural transformation process converting the afferent input coordinates from the peripheral sensory organs into a central representation of egocentric space. Both types of stimulation were proposed to induce a reorientation of the deviated or distorted egocentric spatial reference frame. The aim of the present study was to observe this process of reorientation under a condition in which no visual stimulus can attract the subject's attention and thus influence exploration behaviour from outside. We recorded eye movements of normal subjects and of three patients with spatial neglect after right parietal lesions while searching for a non-existent target in complete darkness. It was assumed that the area of the outer space that subjects spontaneously explore under this condition is a direct function of the subject's representation of egocentric space. Ocular space exploration was biased and confined almost entirely to the right side of the midsagittal plane in patients with neglect. This spatial distribution of exploratory eye movements changed remarkably with left-sided neck muscle vibration as well as with left-sided vestibular stimulation using ice water calorics. The spatial area of exploration was significantly enlarged to the contralesional side and the exploration maximum shifted in the same direction. Whereas with both types of stimulation space exploration of patients with neglect was similar to that of normal subjects when not being stimulated, neck proprioceptive and vestibular stimulation in normal subjects induced a quasi neglect-like exploration pattern, i.e. a bias to one side of the objective midsagittal plane. If ocular space exploration was, however, related to the subjectively perceived position of the midsagittal plane in space, eye movements were symmetrically distributed and carried out to both sides of subjective "straight ahead" in all experimental conditions, in normal subjects as well as in patients with neglect. The present results support the above hypothesis and indicate that neck proprioceptive as well as vestibular input directly contribute to the computation of the subject's central representation of egocentric space used for localizing body orientation and for guiding motor behaviour in space.

Acceleration deficit in patients with cerebellar lesions. A study of kinematic and EMG-parameters in fast wrist movements

Slowness of goal-directed movements is a frequent symptom following cerebellar lesions. So far it has not been demonstrated whether this slowness represents compensation for impaired braking which is a feature of cerebellar dysfunction with the consequence of hypermetria, or whether it is an independent part of cerebellar movement disorder. To resolve this question we tested 18 cerebellar patients in a paradigm where they not only had to perform fast goal-directed wrist flexion movements (amplitudes 5 degrees and 30 degrees) but also wrist flexion movements as fast and large as possible without particular target. In normals antagonist activity is minimal in large movements without target. Although subjects were clinically only mildly affected they regularly showed a 'slowness of movement' resulting from a reduction of peak acceleration. This in turn was due to the reduced generation of agonist activity. Peak velocity was not significantly decreased because the acceleration phase was adequately prolonged. Since these changes were most pronounced in the 'fast' movements without target the compensation hypothesis should be discarded. The reduction of acceleration must at least partially be due to a genuine cerebellar deficiency in the fast generation of agonist activity.

Otolith-semicircular canal interaction during postrotatory nystagmus in humans

The otolith-semicircular canal interaction during postrotatory nystagmus was studied in ten normal human subjects by applying fast, short-lasting, passive head and body tilts (15, 30, 45, or 90 degrees in the roll or pitch plane) 2 s after sudden stop from a constant-velocity rotation (100 degrees/s) about the earth-vertical axis in yaw. Eye movements were measured with three-dimensional magnetic search coils. Following the head tilt, activity in the semicircular canal primary afferents continues to reflect the postrotatory angular velocity vector in head-centered coordinates, whereas otolith primary afferents signal a different orientation of the head relative to gravity. Despite the change in head orientation relative to gravity, postrotatory eye velocity decayed closely along the axis of semicircular canal stimulation (horizontal in head coordinates) for large head tilts (90 degrees) and also for small head tilts (15-45 degrees) for reorientations in the pitch plane. Only for small head tilts (15-45 degrees) in the roll plane was there a reorientation of the eye rotation axis toward the gravitational vector. This reorientation was approximately compensatory for 15 degrees head tilts. For 30 degrees and 45 degrees head tilts the eye rotation axis tilted toward the gravitational vector by about the same amount as for 15 degrees head tilts. These results suggest that, with the exception of small head tilts in the roll plane, there was no compelling data showing a relationship between the eye rotation axis and head tilt and that postrotatory nystagmus is largely organized in head-centered rather than gravity-centered coordinates in humans. This indicates a rudimentary, nonlinear, and direction-specific interaction of semicircular canal and otolith signals in the central vestibular system in humans.

[Gene therapy of neurologic diseases. Experimental approaches and clinical perspectives]

So far, it has not been possible to treat many neurological conditions causally. However, in the past few years underlying genetic defects have been characterized for a substantial number of neurodegenerative disorders. Experimental methods have been developed that allow for efficient gene transfer into defined regions of the mammalian CNS. Such techniques can be applied to deliver genes into target cells of a recipient organism or to transfer genetically modified cells into defined regions of the CNS. Candidate genes for gene therapy are those encoding for neurotrophins and neurotransmitters for symptomatic therapy and, in the case of neurodegenerative disorders with localized gene defects, the wild-type allele as a causal treatment approach. In this review article, we describe some of the most widely used strategies for gene transfer to the CNS. We also report on the results obtained with animal models for human disease, and discuss both the chances and problems of gene therapy approaches in clinical medicine.

Disintegration and reorganization of cortical motor processing in two patients with cerebellar stroke

Cerebello-cerebral interaction plays a fundamental role in movement processing. Extensively studied in monkeys, cerebello-thalamo-cerebral information processing is less clear in humans. Taking advantage of the tight linkage between cerebellum and cerebral motor cortex, the objective of this experiment was to gain information on cerebellar function, dysfunction and recovery by analyzing movement-related cortical potentials (MRCPs). MRCPs were recorded prior to voluntary repetitive finger movements from two cerebellar stroke patients, in the acute phase of cerebellar stroke and after clinical recovery. Ten normal subjects served as controls. The main result was a significant depression of late MRCP components over the contralateral motor cortex when patients performed index finger movements of the affected side in the acute phase, and improvement of depressed components after clinical recovery, 8-10 months later. Topographic maps of late MRCP components showed diffusely enlarged potential fields with ataxic movements in the acute phase, and re-focused fields on follow-up. We conclude that (1) late MRCP components are particularly sensitive to cerebellar input in humans and can reflect different functional states of the cerebellum, (2) disturbance of motor cortex function after cerebellar stroke (diaschisis) can occur as a temporary phenomenon that reverses with good clinical recovery.

Friedreich's ataxia with retained tendon reflexes: molecular genetics, clinical neurophysiology, and magnetic resonance imaging

Lower limb areflexia is generally regarded as an essential criterion for the diagnosis of Friedreich's ataxia (FRDA). We describe a family with a recessive form of early-onset ataxia in which one member had a phenotype typical of FRDA whereas another, with retained tendon reflexes in the lower limbs, did not have electrophysiologic evidence of the usual severe afferent axonal neuropathy of FRDA. In contrast, somatosensory evoked potentials, eye-movement recordings, and MRI of the head and cervical cord provided results highly suggestive of FRDA in both patients. We performed genetic linkage analysis in this family, using markers tightly linked to the FRDA locus on chromosome 9. Inheritance of identical paternal and maternal genotypes by the affected members, but not by their unaffected siblings, provided supporting evidence that this disorder may result from mutation within the FRDA gene or is tightly linked to the investigated loci on chromosome 9.

Reliability, specificity and sensitivity of long-term tremor recordings

We have developed a method of long-term EMG recording that has proven suitable for the quantification of pathological tremor. In the present paper we show that the principal parameters of the method (tremor occurrence, tremor intensity, tremor frequency) are highly reproducible and that the method is specific and sensitive for detection of pathological tremor. Twelve patients with essential tremor (ET) and 13 patients with Parkinson's disease (PD) were recorded repeatedly on 3 successive days. For each patient group and for each parameter the intersubject variability was much larger than the intersubject variability. The intraclass correlation coefficient "R" was in the order of 0.9 for each parameter and the mean of Pearson's correlation coefficient between successive days was also approximately 0.9. Recordings from normal controls demonstrated that the method's specificity for pathological tremor is 94.1% and its sensitivity is 96%.

The development of goal-directed reaching in infants: hand trajectory formation and joint torque control

Nine young infants were followed longitudinally from 4 to 15 months of age. We recorded early spontaneous movements and reaching movements to a stationary target. Time-position data of the hand (endpoint), shoulder, and elbow were collected using an optoelectronic measurement system (ELITE). We analyzed the endpoint kinematics and the intersegmental dynamics of the shoulder and elbow joint to investigate how changes in proximal torque control determined the development of hand trajectory formation. Two developmental phases of hand trajectory formation were identified: a first phase of rapid improvements between 16 and 24 weeks of age, the time of reaching onset for all infants. During that time period the number of movement units per reach and movement time decreased dramatically. In a second phase (28-64 weeks), a period of "fine-tuning" of the sensorimotor system, we saw slower, more gradual changes in the endpoint kinematics. The analysis of the underlying intersegmental joint torques revealed the following results: first, the range of muscular and motion-dependent torques (relative to body weight) did not change significantly with age. That is, early reaching was not confined by limitations in producing task-adequate levels of muscular torque. Second, improvements in the endpoint kinematics were not accomplished by minimizing amplitude of muscle and reactive torques. Third, the relative timing of muscular and motion-dependent torque peaks showed a systematic development toward an adult timing profile with increasing age. In conclusion, the development toward invariant characteristics of the hand trajectory is mirrored by concurrent changes in the control of joint forces. The acquisition of stable patterns of intersegmental coordination is not achieved by simply regulating force amplitude, but more so by modulating the correct timing of joint force production and by the system's use of reactive forces. Our findings support the view that development of reaching is a process of unsupervised learning with no external or innate teacher prescribing the desired kinematics or kinetics of the movement.

Fixation instability and oculomotor abnormalities in Friedreich's ataxia

Eye movements were studied in 13 patients with Friedreich's ataxia and correlated with MRI findings to investigate whether oculomotor abnormalities can be traced to cerebellar disturbances in this disease. One of the most prominent eye signs was fixation instability (square-wave jerks, SWJ.). Besides SWJ the patients showed various combinations of cerebellar, vestibular and brain-stem oculomotor signs. Our patients did not comprise a homogeneous group with regard to their oculomotor findings. There was no correlation between the severity of any of the so-called cerebellar oculomotor disturbances and the number of SWJ. We tried to correlate the extent of oculomotor disturbances with floccular atrophy and atrophy of the dorsal vermis on MRI in seven of the patients. None of the oculomotor features (including SWJ) correlated with flocculus or dorsal vermis size. Furthermore, floccular and vermal measurements on MRI were normal. Accordingly, we think it unlikely that the oculomotor disturbances, including SWJ, are attributable to cerebellar pathology per se.