Brain nervous mechanisms involved in the so-called extra pyramidal motor and psychomotor disturbances

Bilateral contemporaneous posteroventral pallidotomy for the treatment of Parkinson's disease: neuropsychological and neurological side effects. Report of four cases and review of the literature

The authors report the underestimated cognitive, mood, and behavioral complications in patients who have undergone bilateral contemporaneous pallidotomy, as seen in their early experience with functional neurosurgery for Parkinson's disease (PD) that is accompanied by severe motor fluctuations before pallidal stimulation. Four patients, not suffering from dementia, with advanced (Hoehn and Yahr Stages III-IV), medically untreatable PD featuring severe "on-off" fluctuations underwent bilateral contemporaneous posteroventral pallidotomy (PVP). All patients were evaluated according to the Core Assessment Program for Intracerebral Transplantations (CAPIT) protocol without positron emission tomography scans but with additional neuropsychological cognitive, mood, and behavior testing. For the first 3 to 6 months postoperatively, all patients showed a mean improvement of motor scores on the Unified Parkinson's Disease Rating Scale (UPDRS), in the best "on" (21%) and worst "off" (40%) UPDRS III motor subscale, a mean 30% improvement in the UPDRS II activities of daily living (ADL) subscore, and 60% on the UPDRS IV complications of treatment subscale. Dyskinesia disappeared almost completely, and the mean daily duration of the off time was reduced by an average of 60%. Despite these good results in the CAPIT scores, one patient experienced a partially regressive corticobulbar syndrome with dysphagia, dysarthria, and increased drooling. No emotional lability was found in this patient, but he did demonstrate severe bilateral postoperative pretarsal blepharospasm (apraxia of eyelid opening), which interfered with walking and which required treatment with high-dose subcutaneous injections of botulinum toxin. No patient showed visual field defects or hemiparesis, but postoperative depression, changes in personality, behavior, and executive functions were seen in two individuals. Postoperative abulia was reported by the family of one patient, who lost his preoperative aggressiveness and drive in terms of ADL, speech, business, family life, and hobbies, and became more sleepy and fatigued. One patient reported postoperative mental automatisms, such as compulsive mental counting, and circular thoughts and reasoning during off phases; postoperative depression was found in two patients. However, none of the patients demonstrated these symptoms during intraoperative microelectrode stimulation. These findings are compatible with previous reports on bilateral pallidal lesions. A progressive lowering of UPDRS subscores was seen after 12 months, consistent with the progression of the disease. Bilateral simultaneous pallidotomy may be followed by emotional, behavioral, and cognitive deficits such as depression, obsessive-compulsive disorders, and loss of psychic autoactivation-abulia, as well as disabling corticobulbar dysfunction and apraxia of eyelid opening, in addition to previously described motor and visual field deficits, which make this surgery undesirable even though significant improvement in motor deficits can be achieved.

Long-term ongoing reorganizations of the processes of analysis of kinesthetic afferentation at the level of cat motor cortex neurons after damage to the ventrolateral nucleus of the thalamus

The changes in the functional characteristics of neurons of field 4 of the motor cortex (MC) of cats before and at various times (from a week up to five months) following an ipsilateral lesion of the ventrolateral nucleus of the thalamus were investigated in semichronic experiments. The reactions of the cells to tactile stimulation of the forelimb and its passive movement at the wrist at an average speed of 170 degrees/sec were studied. It was demonstrated that a correlation between the impulse activity at speed maxima and the acceleration of monoarticular movement is characteristic for a number of cells of the MC of the intact brain. Experimental confirmation was obtained of the hypothesis, formulated on the basis of the results of preceding investigations, regarding a disturbance of the mechanism of detection by MC neurons of the kinematic indicators of movement following damage to the thalamus. It was established that compensation of this disturbance is associated with the facilitation of conduction to MC neurons of somatosensory afferentation. It is concluded that a morphofunctional reorganization of particular intracortical components of sensorimotor coupling underlies the mechanisms of the compensatory plasticity of the MC.

Leksell's posteroventral pallidotomy in the treatment of Parkinson's disease

Between 1985 and 1990, the authors performed stereotactic posteroventral pallidotomies on 38 patients with Parkinson's disease whose main complaint was hypokinesia. Upon re-examination 2 to 71 months after surgery (mean 28 months), complete or almost complete relief of rigidity and hypokinesia was observed in 92% of the patients. Of the 32 patients who before surgery also suffered from tremor, 26 (81%) had complete or almost complete relief of tremor. The L-dopa-induced dyskinesias and muscle pain had greatly improved or disappeared in most patients, and gait and speech volume also showed remarkable improvement. Complications were observed in seven patients: six had a permanent partial homonymous hemianopsia (one also had transient dysphasia and facial weakness) and one developed transitory hemiparesis 1 week after pallidotomy. The results presented here confirm the 1960 findings of Svennilson, et al., that parkinsonian tremor, rigidity, and hypokinesia can be effectively abolished by posteroventral pallidotomy, an approach developed in 1956 and 1957 by Lars Leksell. The positive effect of posteroventral pallidotomy is believed to be based on the interruption of some striopallidal or subthalamopallidal pathways, which results in disinhibition of medial pallidal activity necessary for movement control.

The metabolic anatomy of Parkinson's disease: complementary [18F]fluorodeoxyglucose and [18F]fluorodopa positron emission tomographic studies

We studied the metabolic anatomy of typical Parkinson's disease (PD) using [18F]fluorodeoxyglucose (FDG) and [18F]fluorodopa (FDOPA) and positron emission tomography (PET). Fourteen PD patients (mean age 49 years) had FDG/PET scans, of which 11 were scanned with both FDOPA and FDG. After the injection of FDOPA, brain uptake and arterial plasma radioactivity were monitored for 2 h. Striatal FDOPA uptake was analyzed with regard to a two-compartment model, and target-to-background ratios (TBRs) and TBR-versus-time slopes were also calculated. Regional patterns of metabolic covariation were extracted from FDG/PET data using the Scaled Subprofile Model (SSM). SSM pattern weights, FDOPA uptake constants (Ki), TBRs, and TBR slopes were correlated with clinical measures for bradykinesia, rigidity, tremor, gait disturbance, left-right asymmetry, dementia, and overall disease severity. In PD patients, rate constants for FDOPA uptake correlated with individual measures of bradykinesia (p = 0.001) and gait disability (p less than 0.05). SSM analysis revealed a distinct pattern of regional metabolic asymmetries, which correlated with motor asymmetries (p less than 0.001) and left-right differences in Ki (p less than 0.01). Our data suggest that in PD patients, FDG/PET and FDOPA/PET may provide unique and complementary information about underlying disease processes.

RU 24722, a new eburnamine derivative, induces selective alterations in cerebral glucose utilization in freely moving rat

The effect of a new eburnamine derivative, RU 24722, a putative phasic activator of catecholaminergic systems on local cerebral glucose utilization was studied in freely moving rats 15 min, 90 min and 6 h after the intraperitoneal administration of the drug (25 mg/kg). Of the 53 brain regions examined, 9 exhibited significant time-dependent increases of glucose utilization (up to 45-55%). Some changes were early and transient, as in the substantia nigra reticulata and the paraventricular nuclei. Other areas showed sustained (median septal nucleus) or delayed increases of glucose utilization (lateral septum, dorsal subiculum, hippocampal fimbria, fronto-parietal motor cortex and ventral cochlear nucleus). No significant alterations of glucose utilization could be elicited in the locus coeruleus and raphe nuclei, and none of the brain regions showed a decrease in glucose consumption. Our findings suggest that RU 24722 preferentially stimulates the activity in some brain areas involved in cognitive, vegetative and locomotor functions.

Motor impairment after unilateral electrolytic lesions of the substantia nigra in baboons: behavioral data with quantitative and kinematic analysis of a pointing movement

Unilateral electrolytic lesions of the substantia nigra (SN) were carried out stereotaxically on 4 baboons which had been previously trained to perform a visually guided pointing movement. For a few days after operation, all animals exhibited a behavioral impairment affecting the contralateral body half and consisting of dystonic flexed posture and akinesia. The animals were thus unable to perform the pointing task with the contralateral hand. After a delay which depended on the extent of the SN lesion, the animals began to make the pointing movement again. Postoperative changes were then observed only on the side opposite the SN lesion. These consisted of an increase in the latency and particularly the duration of the movement without any change in the accuracy. The kinematic analysis of the hand trajectory showed that the contralateral increase in the movement duration corresponded to a regular decrease in the velocities. Study of the recovery over 120 days after SN lesion showed a progressive improvement which was faster with regard to movement duration than to movement latency. These data clearly point to the functional role of the SN in the initiation and particularly in the execution of movement. Quantitative and kinematic analysis of this pointing movement makes it possible to detect and quantify very closely the changes in movement program and execution induced by a SN lesion. This experimental model will be useful for pharmacological in vivo studies allowing a more specific assessment of the functional role of the neurotransmitters involved in SN dysfunction.

The functional neuroanatomy of infantile autism

Infantile autism is a behavioral syndrome consisting of specific disturbances of social relating and communication, language, response to objects, sensory sensitivity and motility. The uniqueness of this syndrome suggests one underlying pathophysiologic mechanism, although multiple etiologies, which could activate or replicate such a mechanism, have been demonstrated. Review of considerable experimental evidence and clinical observation suggests that the symptomatology of autism, including the disturbances of social relating and communication, can best be explained as a disorder of sensory modulation. This in turn suggests a neurophysiologic mechanism consisting of dysfunction of a cascading series of neurophysiologic levels or interacting neuronal loops in the brainstem and diencephalon which subserve modulation of sensory input. Some of those same systems modulate motor output in response to sensory input, and their dysfunction may release the abnormal perseverative motility of infantile autism. Other experimental evidence and clinical observations stress the language deficits of autism and implicate dysfunction of cortical structures. Brainstem and diencephalic centers project rostrally to telencephalic structures and these, in turn, modify brainstem and diencephalic function. Theories of rostrally and caudally directed sequences of pathoneurophysiologic contributions to the system dysfunction in autism are compared. It is concluded that the symptoms of autism can best be explained in terms of dysfunction of brainstem and related diencephalic behavioral systems and their elaboration and refinement by selected higher neural structures.

Glutamate decarboxylase distribution in discrete motor nuclei in the cat brain

The distribution of activity of glutamate decarboxylase (GAD), the enzyme synthesising gamma-aminobutyric acid (GABA), was measured in the cat brain by means of microdissection of the structures from frozen slices and a radioisotopic assay for the enzyme. About 20 cerebral regions were chosen for study because of their role in sensorimotor integration. GAD presented an uneven distribution among these areas. Highest activities were found in the basal ganglia, particularly in the substantia nigra and in the globus pallidus, and to a lesser extent in the cerebellum. Relatively low levels of the enzyme were found in the thalamus and in the cerebral motor cortex. Special detailed studies were made in the caudate nucleus, the substantia nigra, and in the red nucleus for the purpose of defining the intranuclear distribution of their GABAergic innervation. There were only small differences in the rostro-caudal distribution of the enzyme in the head of the caudate nucleus but GAD activity was higher in the ventral than in the dorsal part of the structure. In the substantia nigra, GAD activity was high in both the medial and intermediate thirds of the structure. The GAD activity decreased from the caudal to the rostral part of the nucleus. GAD levels were lower in the caudal part of the red nucleus than in the rostral part. These results indicate that GABA would be present as a putative neurotransmitter in many motor nuclei of the cat brain. In view of the general inhibitory action of this amino acid, this could be related to the presence of inhibitory responses widely distributed in these nuclei as identified by mean of electrophysiological studies. The origin of these GABAergic innervations in many cases remains to be determined.

Bradykinesia following unilateral lesions restricted to the substantia nigra in the baboon

Unilateral lesions were made in the substantia nigra of baboons which had been previously trained to carry out a visually guided pointing movement. During the early post-operative period, the animals were unable to perform the task with the contralateral forelimb because of the severity of the akinesia affecting it. After one or two weeks, the animals began to make the movement; at this time, there was a purely contralateral increase in the latency and particularly the duration of the movement, while its accuracy remained unchanged.

Morphometric studies of rat glial cell ultrastructure after urease-induced hyperammonaemia

The ultrastructure of astrocytes and oligodendrocytes was investigated in hyperammonaemic rats injected daily with urease for 4 days. Glial cells were randomly photographed and magnified x28 000. Cell and nuclear sizes were estimated by planimetry and mitochondrial size and density were measured by image analysis. After 4 days of hyperammonaemia the astrocyte cytoplasmic area was increased by 46%. Mitochondrial area was increased by 20%, but after correction for cytoplasmic oedema the number and size of mitochondria were not significantly increased. The nuclear and cytoplasmic areas of oligodendrocytes were unchanged. The mitochondria of oligodendrocytes were small in the hyperammonaemic group and so was their percentage area to cytoplasmic area, but their numbers were unchanged. It was concluded that hyperammonaemia induces astrocyte oedema and increases the astrocyte mitochondrial content. These findings support the assumption that the astrocytes are the active cells in the brain metabolism of ammonia. The decrease in oligodendrocyte mitochondrial content could be considered a point against an active function of oligodendrocyte mitochondria in ammonia metabolism in hyperammonaemia.

Effects of 1694 and other dopaminergic agents on circling behavior

One hour after the administration of 40 mg/kg of amineptine chlorydrate (1694) the HVA concentration in the striatum was increased but the concentrations of DA, NA, 5HT and 5-HIAA in the striatum, cortex, thalamus-hypothalamus and pons-midbrain of rats were not significantly altered. Unilateral lesioning at the level of the entopeduncular nucleus in cats and rats resulted in spontaneously occurring ipsiversive circling behavior in the two species. However circling was more sustained in cats than in rats. Apomorphine, d-amphetamine, methamphetamine, L-dopa and piribedil (ET-495) exaggerated the ipsiversive circling. 1694 (amineptine chlorydrate), a new agent, was comparatively more active than L-dopa and ET-495 and less active than apomorphine, d-amphetamine and methamphetamine. Although in higher doses (30--40 mg/kg), 1694 caused increased exploratory activity it was not associated with any stereotypy. Its biochemical and pharmacological effects are comparable to those of d-amphetamine and methamphetamine. Removal of the contralateral (with respect to the side of the entopeduncular lesion) motor cortex in the lesioned cat abolished spontaneous and drug-induced circling movements. The results of this and of previous studies support the idea that these dopaminergic agents act on the striopallidal system of the intact side which is no longer properly counterbalanced by the corresponding system of the lesioned side. Although this experimental model is useful to determine the degree of dopaminergic activity of various chemical agents it does not duplicate the motor disorders encountered in parkinsonism which are associated with a decreased concentration of dopamine.

Parkinsonian akinesia, rigidity and tremor in the monkey. Histopathological and neuropharmacological study

Parkinsonian postural tremor and rigidity most likely involve the disruption of the dopaminergic (DA) nigrostriatal mechanisms and the corresponding rubro-olivo-cerebello-rubral loop without excluding the involvement of related dentato-rubral and dentato-thalamic nervous fascicles. The integrity of the magnocellular division of the red nucleus and of the rubrotegmentospinal pathway, however, is apparently essential for the expression of rigidity. Akinesia most likely results from the bilateral involvement of brain stem catecholaminergic (CA) mechanisms including the DA nigrostriatal pathways. Finally the integrity of the pallidothalamic fibers seems to represent an essential feature for the improvement of these motor disorders by DA agonists, suggesting that certain of these agents, such as apomorphine, exert their main effects through the neostriatal DA receptors.

Physiopathology of experimental Parkinsonism in the monkey

Postural or Parkinson-like tremor, which results from the impairment of mechanisms which are predominantly lateralized in the brain, is most likely related to the combined impairment of the dopaminergic nigrostriatal pathway and the corresponding rubro-olivo-cerebello-rubral loop (without excluding the possiblity that other nervous mechanisms interconnected with these structures may represent an alternative disturbance). The integrity of the internal division of the pallidum and the ventrolateral area of the thalamus and their efferent fibers as well as the motor cortex and certain of its cortico-subcortico-spinal pathways (Figures 1 and 2) is apparently an essential feature for the elaboration of the rhythmic bursts associated with the appearance of postural tremor. The integrity of the spinal sensory roots and the rubro-tegmentospinal tract is not a prerequisite for the expression of postural tremor, a condition which seems essential for the production of rigidity. The latter facts suggest that the disturbances which subserve these two types of motor impairment, often concomitantly present in Parkinsonism, partially involve the impairment of different mechanisms although the loss of the DA fibers originating in the substantia nigra and ending in the neostriatum (Figure 1) appears to represent a disturbance common to both types of disorders. Bradykinesia which may be associated with an impairment of catecholamine metabolism (and more especially the neostriatal DA mechanisms) on both sides of the brain may also result from bilateral lesions of the pallidum or of its outflow corresponding, in the main, to the pallidothalamic fibers ending in the ventrolateral thalamus. The latter types of lesion most likely exclude the influence of the monoaminergic, cholinergic and gabaminergic activities normally originating in the striopallidal system and influencing the activity transmitted to other CNS mechanisms. Severe akinesia, however, apparently depends on more profound and generalized disturbances of brain monoamine metabolism with or without the involvement of other ill-defined mechanisms. At any rate the impairment of the brain DA mechanisms (and especially those of the neostriatum) seems to represent a major feature in the production of the Parkinsonian type of akinesia. Further work is needed to establish the relative importance of the loss of catecholaminergic mechanisms other than those of the neostriatum in the production of akinesia.