Thalamic metbolism and corticospinal tract integrity determine motor recovery in stroke

We studied the role of remote metabolic depressions and pyramidal tract involvement regarding motor recovery following a first hemiparetic ischemic stroke. In 23 patients the regional cerebral glucose metabolism (rCMRGlu) was measured with positron emission tomography and the location and spatial extent of the stroke lesions were assessed by magnetic resonance imaging. Motor impairment during the acute and chronic stages (4 weeks after stroke) was determined by a motor score and recordings of magnetic evoked motor potentials. Twelve patients recovered significantly, whereas 11 patients retained a disabling hemiparesis. In contrast to patients with good motor recovery, rCMRGlu was severely depressed in the thalamus on the lesion side in patients with poor motor recovery. This patient group also showed more severe damage to the pyramidal tract on magnetic resonance images and a more pronounced reduction of the magnetic evoked motor potential amplitude. Neither the size of the stroke lesions nor the spatial extent of the lesional and remote rCMRGlu depressions outside the thalamus correlated with the thalamic hypometabolism and the improvement of the motor score. We conclude that preservation both of parts of the pyramidal tract and of the thalamic circuitry is a major determinant for the quality of hand motor recovery following acute brain ischemia in the adult.

[MRI tomographic blood volume measurements in the diagnosis of a stroke: the results of a clinical pilot study]

PURPOSE

In this study the sensitivity of proving a stroke using regional cerebral blood volume (rCBV) maps were investigated. Another aim was to evaluate the strength of the ischaemia.

METHODS

Seven patients were examined during the acute phase of a stroke, eight during the subacute or chronically stage. To calculate rCBV-maps of one slice low dosed Gd-DTPA was injected as a bolus. Using the relaxation-effect the obtained signal intensity-time curves were converted pixel-wise to rCBV images. For the region of the infarction rCBV ratios were calculated relative to the corresponding area in the contralateral hemisphere.

RESULTS

Only 63% of the investigations carried out during the acute phase were utilizable. In all those cases a decrease of rCBV was found. The infarct area could only visually recognized if the rCBV ratio was lower than 0.7. The ratios of completely and partial necrotic areas of the infarctions were 0.481 and 1.028 respectively. With a p = 0.0015 these values are even statistically different.

CONCLUSIONS

During the acute stage the sensitivity of the rCBV measurement was not as high as that of morphological MR imaging. However, rCBV maps make it possible to estimate the strength of the ischaemia even during the first hours.

A gene for autosomal dominant paroxysmal choreoathetosis/spasticity (CSE) maps to the vicinity of a potassium channel gene cluster on chromosome 1p, probably within 2 cM between D1S443 and D1S197

Paroxysmal choreoathetosis/episodic ataxia is a heterogeneous neurological syndrome usually inherited in an autosomal dominant manner. Recently, the association of one form of episodic ataxia (defined by the presence of additional myokymia) with point mutations in the potassium channel gene KCNA1 was described. This gene locus on chromosome 12p (HGMW-approved symbol CSE) was excluded in a large pedigree with paroxysmal choreoathetosis and additional spasticity. Linkage to chromosome 1p where a cluster of related potassium channel genes is located, was demonstrated. Genotyping of 18 affected and 11 unaffected family members with 28 microsatellites over a region of 45 cM proved linkage with a lod score of 7.2 at a recombination fraction theta = 0 to D1S451/421/447/GGAT4C11. Crossing-over events in 9 patients and 4 unaffected offspring suggested a probable assignment of the gene to a region of 2 cM between D1S443 and D1S197.

Subcortical origin of visuomotor apraxia

Visuomotor apraxia (VMA) is a clinical syndrome characterized by a failure to make use of visual information when performing a target-directed movement. Visuomotor apraxia has traditionally been assumed to result from a disconnection of cortico-cortical fibres between visual and motor areas following occipito-parietal lesions. We describe a patient who developed a permanent contralesional and a temporary ipsilesional visuomotor apraxia as part of a complex neurological syndrome after a right [corrected] thalamic haemorrhage. MRI showed that the suprathalamic white matter was not involved but the most caudal fibres of the internal capsule appeared to be interrupted. To our knowledge this is the first case of a VMA with a lesion restricted to a deep subcortical area indicating that VMA can result from damage to subcortical projections rather than interruption of cortico-cortical fibres.

The pattern of motor deficits in relation to the site of stroke lesions

Thirty-two patients with hemispheric stroke lesions of distinct cortical functional zones (premotor, precentral, parietal) or of striatocapsular or striatothalamic subcortical territories were scored at the acute and chronic stage for the following sensorimotor arm-hand functions: force, praxis, motor attention, sensation and dexterity. The selection criterion was that in spite of the wide variation of lesion sites all patients had hemiparesis as the presenting clinical sign. Analysis of the scores showed that most patients showed apraxia, motor neglect or disturbed sensation in addition to hemiparesis. The distribution and severity of these deficits varied, so that different lesion groups showed different patterns. The actual functional impairment of arm-hand function was determined by the combined effect of these different sensorimotor dysfunctions.

Residual sensorimotor functions in a patient after right-sided hemispherectomy

Sensorimotor functions were examined in a patient with left-sided infantile hemiparesis who underwent hemispherectomy (HS) on the right side at age 18 for intractable epilepsy. Pathological examination of the removed hemisphere showed a porencephalic cyst of the temporal lobe and of the frontoparietal operculum. On examination, the patient had hemianopia to the left and sensorimotor deficits only of the distal limbs contralateral to the HS. She walked with a barely perceptible limp. Axial and proximal movements were quasi normal, so that the patient could fully elevate both arms, flex and extend the forearm with nearly normal power and execute small, isolated precision movements of the arm around the shoulder joint. This astonishing proximal motor repertoire was mimicked on the somatosensory side where cutaneous sensation and kinesthesia were normal above the elbow and knee and contrasted the pronounced distal sensorimotor dysfunctions. Movement analysis by means of an optoelectronic two-camera position analysis system (Selspot II) showed normal flexion-extension synergies during gait, but abnormal synergic coupling between the shoulder and elbow joint during reaching and prehension. Distal movements were still possible but could only be performed as rigidly coupled movement synergies, such as closing and opening of the fist along with arm adduction/flexion or abduction/extension. She could engage these synergies for grasping and holding large objects. The performance of individual, fractionated finger movements was impossible. Involuntary mirror movements were elicited in both the affected and the normal arm, but with distinctly different phase relationships, indicating that different circuitries contribute to their generation. The case study reveals the existence of a bilaterally organized sensorimotor system that has the potential to provide quasi normal performance of the axial-proximal body parts on both sides. This raises the question why this potential cannot be better used in cases with only partial unilateral brain damage and persistent hemiplegia.

Invariant temporal characteristics of manipulative hand movements

The measurement of eight manipulative serial hand movements showed a clear distribution of their temporal characteristics into two distinct groups. When the hand was used as a sense organ during active touch the finger movements across objects were restricted to a slow performance range below 2 Hz. Recordings from single mechanoreceptive afferents and calculations of their receptor densities indicated that these movements have to be slow to match the temporal requirements of the sequential sampling process from the mechanoreceptor populations. In contrast, manual skills not associated with the collection of sensory information like handwriting, typing or pencil shading, were performed rapidly. Their frequencies were close to those of fastest possible tapping. Evidence is provided that the different frequency groups are associated with distinct sensory control processes. The low frequency group represents movements involving focal sensory control (Julesz 1984). The high frequency group is not performed open-loop but monitored by preattentive sensory processes. The results indicate a dual sensory control mode operating in separate frequency domains of movement.

Sensorimotor disturbances in patients with lesions of the parietal cortex

Somatosensory and motor disturbances of hand function were examined in 9 patients with parietal lobe lesions. A quantitative score was used for the elaboration of sensorimotor profiles displaying the relative degree of functional impairment. In patients with anterior parietal lobe lesions somaesthesis was clearly more disturbed than motor function. Simple aspects of somaesthesis (surface sensibility, two-point discrimination, position sense) were disturbed to about the same degree as complex somatosensory (tactile recognition) tasks. On the other hand, patients with lesions of the posterior parietal lobe showed preferential impairment of complex somatosensory and motor functions (exploratory and manipulative finger movements). In 4 patients, analysis of motor behaviour by means of an optoelectronic system showed that reaching, formation of hand aperture and target acquisition were less disturbed than manipulative behaviour. Finger movement trajectories during dynamic digital palpation of objects were grossly deranged in the patients with posterior parietal damage. The temporal characteristics of the finger movements during active touch were completely destroyed. This leads to a breakdown of the finely tuned digital scanning process required for the sequential sampling of mechanoreceptive information. Remarkably, these patients could produce the exploratory finger movements imitatively. The motor disability of the parietal hand does not lie in the loss of the kinetic memory to perform these movements, but in the loss of their evocation by appropriate sensory stimuli. This deficit is not due to a lack of somatosensory information because that may be relatively well preserved. It is concluded that the motor disturbance in posterior parietal lobe disease lies essentially in the conception and execution of the spatiotemporal movement patterns necessary to bring those receptors into action which would normally provide the information about tactile objects. This illustrates the intricate mutual dependence of the spatiotemporal organization of receptor activation by movement and of the formation of movement trajectories on the basis of adequate sensory processing.