Investigating associations between biting time in the malaria vector Anopheles arabiensis Patton and single nucleotide polymorphisms in circadian clock genes: support for sub-structure among An. arabiensis in the Kilombero valley of Tanzania.

BACKGROUND: There is growing evidence that the widespread use of Long-Lasting Insecticidal Nets (LLINs) is prompting malaria vectors to shift their biting towards times and places where people are not protected, such as earlier in the evening and/or outdoors. It is uncertain whether these behavioural shifts are due to phenotypic plasticity and/or ecological changes within vector communities that favour more exophilic species, or involve genetic factors within vector species to limit their contact with LLINs. Possibly variation in the time and location of mosquito biting has a genetic basis, but as yet this phenomenon has received little investigation. Here we used a candidate gene approach to investigate whether polymorphisms in selected circadian clock genes could explain variation in the time and location of feeding (indoors versus outside) within a natural population of the major African malaria vector Anopheles arabiensis. METHODS: Host-seeking An. arabiensis were collected from two villages (Lupiro and Sagamaganga) in Tanzania by Human Landing Catch (HLC) technique. Mosquitoes were classified into phenotypes of "early" (7 pm-10 pm) or "late" biting (4 am -7 am), and host-seeking indoors or outdoors. In these samples we genotyped 34 coding SNPs in 8 clock genes (PER, TIM, CLK, CYC, PDP1, VRI, CRY1, and CRY2), and tested for associations between these SNPs and biting phenotypes. SNPs in 8 mitochondrial genes (ATP6, ATP8, COX1, COX2, COX3, ND3, ND5 and CYTB) were also genotyped to test population subdivision within An. arabiensis. RESULTS: The candidate clock genes exhibited polymorphism within An. arabiensis, but it was unrelated to variation in the timing and location of their biting activity. However, there was evidence of strong genetic structure within An. arabiensis populations in association with the TIM, which was unrelated to geographic distance. Substructure within An. arabiensis was also detected using mitochondrial markers. CONCLUSIONS: The variable timing and location of biting in An. arabiensis could not be linked to candidate clock genes that are known to influence behaviour in other Diptera. This finding does not rule out the possibility of a genetic basis to biting behaviour in this malaria vector, but suggests these are complex phenotypes that require more intensive ecological, neuronal and genomic analyses to understand.

Levodopa reversible loss of the Piper frequency oscillation component in Parkinson's disease.

OBJECTIVES: Although Parkinson's disease is typically characterised by bradykinesia, rigidity, and rest tremor, the possibility that two additional motor deficits are manifest during small hand muscle activity was explored-namely, weakness and abnormal physiological tremor. METHODS: A paradigm previously used in normal subjects reliably records the strength, tremor and surface EMG of index finger abducting contractions against a compliant (elastic) resistance. In addition to the well known physiological tremor at around 10 Hz, there are other co existing peak tremor frequencies at around 20 and 40 Hz; the last of these frequencies corresponds to the range of EMG Piper rhythm. The same technique was used to study parkinsonian patients while on and off dopaminergic medication. RESULTS: The maximum strength of finger abduction produced by first dorsal interosseous contraction was considerably lower when patients were off medication (mean (SD) 6.27 (1.49) N when off v 12.33 (3.64) N when on). There was also a marked reduction in the power of Piper frequency finger tremor (p<0.0005) and EMG (p<0.0005) oscillations that did not simply result from weaker contraction. CONCLUSION: As the components of physiological tremor at higher frequencies are thought to derive from CNS oscillations important in motor control, their loss in parkinsonism in association with severe off symptoms may represent an important pathophysiological link between dopaminergic depletion and parkinsonian motor deficits.

Unilateral lesions of the globus pallidus: report of four patients presenting with focal or segmental dystonia.

OBJECTIVES: To interpret clinical features after unilateral lesions of the globus pallidus on the basis of physiology of the basal ganglia. METHODS: Four patients with unilateral lesions in the globus pallidus (GP) were clinically examined and the literature on patients with pallidal lesions was reviewed. RESULTS: Three patients presented with contralateral dystonia largely confined to one arm in one case and one leg in two cases. One patient had predominant contralateral hemiparkinsonism manifested mainly as micrographia and mild dystonia in one arm. The cause of the lesions was unknown in two patients. In the other two symptoms had developed after head trauma and after anoxia. All lesions involved the internal segment of the GP. Two patients, including the patient with hemiparkinsonism, had additional involvement of the external segment of the GP. In the literature reports on 26 patients with bilateral lesions restricted to the GP only two with unilateral lesions were found. The patients with bilateral pallidal lesions manifested with dystonia, parkinsonism, or abulia. One of the patients with unilateral GP lesions had contralateral hemidystonia, the other contralateral arm tremor. CONCLUSION: These cases emphasise the importance of the GP, particularly its internal segment, in the pathophysiology of dystonia.

Botulinum toxin antibody testing: comparison between the mouse protection assay and the mouse lethality assay.

Conventionally, the standard test for detection of antibodies against botulinum toxin (BT-A) has been the mouse lethality assay (MLA). Because this test has a number of disadvantages, a novel mouse protection assay (MPA) was recently introduced. We sought to compare the results of both tests. Forty-three samples from 38 patients with cervical dystonia and complete or partial subjective BT-A therapy failure underwent simultaneous MPA and MLA testing. Twenty-seven samples showed concordant results in both tests. Eleven of them were MPA- and MLA-positive and 16 MPA- and MLA-negative, resulting in a significant association of the dichotomous test results (Fisher exact test, p <0.01). Sixteen samples showed discordant results. All of those were MPA-positive and MLA-negative. This excess of MPA-positive results was also significant (Wilcoxon signed-rank test, p <0.001). Of the patients with MPA-positive samples, 62% had complete and 38% had partial therapy failure. Of the patients with MLA-positive samples, 90% had complete and 10% had partial therapy failure. MPA and MLA results show significant association. Statistical analysis and predominance of partial therapy failure in MPA-positive patients demonstrate higher sensitivity of MPA. With its methodologic advantages, its test parameter being more relevant to BT-A therapy, and its higher sensitivity, the MPA appears to be superior to the MLA.

Disruption of spatial organization and interjoint coordination in Parkinson's disease, progressive supranuclear palsy, and multiple system atrophy.

Patients with basal ganglia diseases may exhibit ideomotor apraxia. To define the nature of the impairment of the action production system, we studied a repetitive gesture of slicing bread by three-dimensional computergraphic analysis in eight nondemented patients with Parkinson's disease in the "on" state, five with progressive supranuclear palsy and four with multiple system atrophy. Two patients with Parkinson's disease and two with progressive supranuclear palsy showed ideomotor apraxia for transitive movements on standard testing. A Selspott II system was used for kinematic analysis of wrist trajectories and angular motions of the shoulder and elbow joints. Patients with Parkinson's disease, progressive supranuclear palsy, and even some with multiple system atrophy exhibited kinematic deficits in the spatial precision of movement and velocity-curvature relationships; in addition, they failed to maintain proper angle/angle relationships and to apportion their relative joint amplitudes normally. Spatial disruption of wrist trajectories was more severe in patients with ideomotor apraxia. We posit that the basal ganglia are part of the parallel parieto-frontal circuits devoted to sensorimotor integration for object-oriented behavior. The severity and characteristics of spatial abnormalities of a transitive movement would therefore depend on the location and distribution of the pathologic process within these circuits.

Paroxysmal dystonic choreoathetosis: clinical features and investigation of pathophysiology in a large family.

Paroxysmal dystonic choreoathetosis (PDC) is an unusual hyperkinetic movement disorder characterized by attacks of chorea, dystonia, and ballism with onset in childhood. We report a large British family with dominantly inherited PDC linked to chromosome 2q and describe the clinical features in 20 affected family members. Attacks were precipitated by a variety of factors, including caffeine, alcohol, or emotion, and could be relieved by short periods of sleep in most subjects. The clinical features in the family are compared with those of 11 other PDC families in the literature and a core phenotype for PDC suggested. CSF monoamine metabolites measured at baseline and during an attack in one subject were found to increase during the attack. Magnetic resonance spectroscopy of brain and basal ganglia performed both during and between attacks was normal. Positron emission tomography using the D2 receptor ligand, 11C-raclopride, showed no abnormalities.

Physiological and pathological tremors and rhythmic central motor control.

In recent years there has been increasing interest in oscillatory neural activity in the CNS and in the role that such activity may have in motor control. It is thought that physiological tremor may be a manifestation in the periphery of such central oscillatory activity and that some pathological tremors are the result of derangement of these oscillators. This review re-evaluates both early and recent studies on physiological and pathological tremors and other peripheral oscillations in order to gain a new perspective on the nature and function of their central progenitors. This approach, namely using tremor as a 'window' into the function of central oscillations, is particularly suited to human investigations because of the obvious limitations of direct central recording. It is argued that physiological tremor is likely to be multifactorial in origin, with contributions not only from CNS 10-Hz range oscillatory activity, but also from motor unit firing properties, mechanical resonances and reflex loop resonances. Different origins are likely to dominate under different conditions. While some pathological tremors appear to arise as a distortion of central or peripheral components of physiological tremor, others arise de novo, such as the pathological oscillation of 3- to 6-Hz parkinsonian tremor. CNS oscillations outside the 10-Hz range are also found to modulate limb activity in normal individuals, and oscillatory activity exists in other motor systems such as eye movements. Finally, it is shown how studies of peripheral oscillations may help develop hypotheses on the role of CNS oscillations in motor control, including the proposed 'binding' function of synchronized oscillations and the possibility that motor signals could be coded by frequency of modulating oscillation as well as by synaptic connectivity.

Bilateral caudate and putamen grafts of embryonic mesencephalic tissue treated with lazaroids in Parkinson's disease.

Five parkinsonian patients were transplanted bilaterally into the putamen and caudate nucleus with human embryonic mesencephalic tissue from between seven and nine donors. To increase graft survival, the lipid peroxidation inhibitor tirilazad mesylate was administered to the tissue before implantation and intravenously to the patients for 3 days thereafter. During the second postoperative year, the mean daily L-dopa dose was reduced by 54% and the UPDRS (Unified Parkinson's Disease Rating Scale) motor score in 'off' phase was reduced by a mean of 40%. At 10-23 months after grafting, PET showed a mean 61% increase of 6-L-[(18)F]fluorodopa uptake in the putamen, and 24% increase in the caudate nucleus, compared with preoperative values. No obvious differences in the pattern of motor recovery were observed between these and other previously studied cases with putamen grafts alone. The amount of mesencephalic tissue implanted in each putamen and caudate nucleus was 42 and 50% lower, respectively, compared with previously transplanted patients from our centre. Despite this reduction in grafted tissue, the magnitudes of symptomatic relief and graft survival were very similar. These findings suggest that tirilazad mesylate may improve survival of grafted dopamine neurons in patients, which is in agreement with observations in experimental animals.

The pedunculopontine nucleus: its role in the genesis of movement disorders.

The pedunculopontine nucleus (PPN) is located in the dorso-lateral part of the ponto-mesencephalic tegmentum. The PPN is composed of two groups of neurons: one containing acetylcholine, and the other containing non-cholinergic neurotransmitters (GABA, glutamate). The PPN is connected reciprocally with the limbic system, the basal ganglia nuclei (globus pallidus, substantia nigra, subthalamic nucleus), and the brainstem reticular formation. The caudally directed corticolimbic-ventral striatal-ventral pallidal-PPN-pontomedullary reticular nuclei-spinal cord pathway seems to be involved in the initiation, acceleration, deceleration, and termination of locomotion. This pathway is under the control of the deep cerebellar and basal ganglia nuclei at the level of the PPN, particularly via potent inputs from the medial globus pallidus, substantia nigra pars reticulata and subthalamic nucleus. The PPN sends profuse ascending cholinergic efferent fibers to almost all the thalamic nuclei, to mediate phasic events in rapid-eye-movement sleep. Experimental evidence suggests that the PPN, along with other brain stem nuclei, is also involved in anti-nociception and startle reactions. In idiopathic Parkinson's disease (IPD) and parkinson plus syndrome, overactive pallidal and nigral inhibitory inputs to the PPN may cause sequential occurrences of PPN hypofunction, decreased excitatory PPN input to the substantia nigra, and aggravation of striatal dopamine deficiency. In addition, neuronal loss in the PPN itself may cause dopamine-resistant parkinsonian deficits, including gait disorders, postural instability and sleep disturbances. In patients with IPD, such deficits may improve after posteroventral pallidotomy, but not after thalamotomy. One of the possible explanations for such differences is that dopamine-resistant parkinsonian deficits are mediated to the PPN by the descending pallido-PPN inhibitory fibers, which leave the pallido-thalamic pathways before they reach the thalamic targets.

Benign hereditary chorea--entity or syndrome?

The existence of "benign hereditary chorea" (BHC), a rare disorder of childhood-onset familial chorea without other neurologic features or progression, has increasingly been questioned, because many patients with this disorder were subsequently diagnosed with different conditions. We therefore analyzed all published reports of families with BHC and contacted their authors to obtain follow-up information. In addition, we reviewed all patients in whom at least one of the authors had at some stage considered a possible diagnosis of BHC. Of 42 families reported to have BHC in the literature, we obtained follow-up information on 11 families, three of which had been seen by us. An additional seven new, unreported families and four sporadic cases, in which this diagnosis was suspected by at least one of us at one point, were reviewed and videotaped. On reviewing the videotapes of the 11 families in the literature, the diagnosis of BHC was changed in nine. In the remaining two families, atypical features suggesting different diagnoses were present in the original reports. In none of our own previously unreported patients (seven familial and four sporadic) was BHC diagnosed unequivocally by all evaluators after review of their video recordings. In three of these families and all four sporadic patients the diagnosis was changed; in one family multifocal myoclonus could not be differentiated from chorea by any author, and in the remaining three families no consensus between the raters was found. Apart from the 11 families in whom we obtained follow-up information, analysis of the remaining 31 reports on families with BHC also revealed atypical features in the majority. We conclude that BHC is not a diagnosis, but a syndrome that requires further investigation. Whether there is a distinct entity "BHC" with a single gene abnormality remains to be proven.

Limb apraxias: higher-order disorders of sensorimotor integration.

Limb apraxia comprises a wide spectrum of higher-order motor disorders that result from acquired brain disease affecting the performance of skilled, learned movements. At present, limb apraxia is primarily classified by the nature of the errors made by the patient and the pathways through which these errors are elicited, based on a two-system model for the organization of action: a conceptual system and a production system. Dysfunction of the former would cause ideational (or conceptual) apraxia, whereas impairment of the latter would induce ideomotor and limb-kinetic apraxia. Currently, it is possible to approach several types of limb apraxia within the framework of our knowledge of the modular organization of the brain. Multiple parallel parietofrontal circuits, devoted to specific sensorimotor transformations, have been described in monkeys: visual and somatosensory transformations for reaching; transformation of information about the location of body parts necessary for the control of movements; somatosensory transformation for posture; visual transformation for grasping; and internal representation of actions. Evidence from anatomical and functional brain imaging studies suggests that the organization of the cortical motor system in humans is based on the same principles. Imitation of postures and movements also seems to be subserved by dedicated neural systems, according to the content of the gesture (meaningful versus meaningless) to be imitated. Damage to these systems would produce different types of ideomotor and limb-kinetic praxic deficits depending on the context in which the movement is performed and the cognitive demands of the action. On the other hand, ideational (or conceptual) apraxia would reflect an inability to select and use objects due to the disruption of normal integration between systems subserving the functional knowledge of actions and those involved in object knowledge.

Detailed genotyping demonstrates association between the slow acetylator genotype for N-acetyltransferase 2 (NAT2) and familial Parkinson's disease.

In a preliminary report we demonstrated an association between the slow acetylator genotype of N-acetyltransferase 2 (NAT2) and familial cases of Parkinson's disease (FPD). Using a considerably more precise NAT2 typing method, which detects all mutant NAT2 alleles with a frequency of >1% in the white population, we have now retyped all the original patients and control subjects to investigate the reliability of our initial findings. The slow acetylator genotype remained considerably more common among FPD (73%) than normal control subjects (NPC, 43%) or the disease (Huntington's disease [HD]) control group (52%) with an odds ratio (OR) of 3.58 (95% confidence interval (CI): 1.96-6.56; p = 0.00003) for FPD versus NPC and an OR of 2.50 (95% CI: 1.37-4.56, p = 0.003) for FPD versus HD. Furthermore, the wild-type allele 4 conferred a protective effect with an OR of 0.39 (95% CI: 0.23-0.64; p = 0.0025) for FPD versus NPC and an OR of 0.50 (95% CI: 0.30-0.85, p = 0.01) for FPD versus HD. The results of this study support an association between the NAT2 slow acetylator genotype and FPD in our population.

The timing of primary orthostatic tremor bursts has a task-specific plasticity.

Primary orthostatic tremor is characterized by unsteadiness and shakiness of the legs while standing. It is due to a remarkably strong and regular EMG modulation at approximately 16 Hz that is thought to be of CNS origin. Previous studies have shown that the tremor frequency is the same in all involved muscles and that the time relation between bursts of activity in different muscles may be fixed (e.g. always co-contracting or always contracting in an alternating pattern). Here we have used frequency domain analysis of postural muscle EMG signals in five primary orthostatic tremor patients and in two normal controls to explore the nature of such fixed timing patterns. The timing is found not to relate simply to the relative conduction times for passage of rhythmic bursts from a central oscillation to different muscles. Indeed, although the timing pattern (expressed as phase) of the 16-Hz EMG bursts in different postural muscles remains constant while the subject adopts a certain steady posture, it is different for different subjects and also changes when the same subject adopts a different posture. It seems unlikely that such complex task-dependent timing relations of rhythmic postural muscle activity are due to the primary pathology of primary orthostatic tremor. Instead, we suggest that the abnormally strong peripheral manifestation of a 16-Hz CNS oscillation merely unmasks normal central processes so that the timing patterns may provide a clue to the nature of postural motor control.

Essential tremor: an overdiagnosed condition?

The diagnosis of essential tremor (ET) and its differentiation from other types of tremor is often difficult. In 1994 Bain et al. defined a classical phenotype by studying 20 patients with pure essential tremor and similarly affected family members in at least three generations. We assessed how many of the patients diagnosed by different neurologists at our institution as having ET conformed to this defined phenotype. We randomly selected 50 patients who were diagnosed with ET by any neurologist at the National Hospital for Neurology and Neurosurgery since the publication of the Bain et al. report, and determined the number of patients who had clinical features compatible with the phenotype that it had defined. Only 25 (50%) of these patients had ET so defined. Ten patients clearly had alternative diagnoses: four had clear additional dystonia, two neuropathic tremor, two had unilateral leg tremor, one drug-induced tremor, and one sudden onset after head trauma. The remaining 15 patients also had atypical features including myoclonus (one), onset in a body part other than the arms (six), sudden onset (two), rest tremor (seven), onset after the age of 65 years (four), a family member with an isolated head tremor (one), or reduced armswing (two). The diagnosis of ET is overused even among experienced neurologists, and other types of tremor should be considered in atypical patients before making this diagnosis.

Human anticipatory eye movements may reflect rhythmic central nervous activity.

To investigate the possibility that rhythmic activity originating in the central nervous system may modulate human eye movements, anticipatory eye movements were generated by tracking an intermittently obscured sinusoidally moving target. Eight subjects tracked intermittently obscured sinusoids of three different frequencies and of two different amplitudes. Eye movements were recorded by an infra-red reflection technique. The eye velocity records were analysed in the frequency domain by power spectral estimates. During periods where the target was obscured, eye movements consisted of a staggered series of anticipatory saccades with intervening smooth anticipatory eye movements or relatively stationary periods. In sections where the intervening smooth components of anticipatory tracking were of high velocity (above 15 deg/s), a superimposed smooth tremulous oscillation at around 10 Hz was sometimes present. Coherence analysis showed that this 10 Hz range oscillation of smooth anticipatory movement was not derived from head tremor and that the same oscillation was present in both eyes. This oscillation was not generally observed during smooth tracking of pseudorandom waveforms. Investigation of anticipatory eye movements has revealed a 10-Hz range oscillation or "tremor" superimposed upon smooth movements that might in other circumstances be inhibited by direct visual feedback. This smooth eye movement oscillation is thought to originate from the central nervous system and may reflect a widespread frequency modulation of motor commands.

Primary central nervous system lymphoma presenting with a parkinsonian syndrome of pure akinesia.

The incidence of primary central nervous system lymphoma (PCNSL), once a rare tumour, has risen significantly in both immunocompetent and immunosuppressed patients. Although infiltration of the basal ganglia is not uncommon in PCNSL, extrapyramidal movement disorders are generally not recognised as a mode of clinical presentation of this type of cerebral tumour. We present the unusual case of a 75-year-old man who developed a parkinsonian syndrome of "pure akinesia" due to autopsy-confirmed PCNSL primarily involving the globus pallidus bilaterally. Parkinsonism due to bilateral pallidal lesions is known but rare, and such cases help in the understanding of basal ganglia function with regard to akinesia and freezing.

Unilateral pallidotomy for Parkinson's disease: results after more than 1 year.

OBJECTIVE: To examine follow up results of unilateral ventral medial pallidotomy in 22 patients with advanced Parkinson's disease more than 1 year after the operation in comparison with their results (previously reported) at 3 months. METHODS: Twenty patients who had undergone unilateral pallidotomy were assessed with the core assessment programme for intracerebral transplantation (CAPIT) protocol preoperatively, at 3 months postoperatively, and again after a median postoperative follow up of 14 months. Two further patients had only one evaluation 3 months postoperatively. RESULTS: The reduction of contralateral dyskinesias (median 67%) at 3 months was slightly attenuated after 1 year to 55% (both p<0.001 compared with baseline). A less pronounced effect on ipsilateral and axial dyskinesias decreased from 39% to 33% (p<0.005 and p<0.01), and from 50% to 12.5% (p<0.001 and p<0.01), respectively. However, there was no significant change between the 3 month and the follow up assessment. The modest improvement of the contralateral unified Parkinson's disease rating scale (UPDRS) motor score in the "off" state remained improved compared with preoperative levels, but less significantly (26%, p<0.001, and 18%, p<0.01). The activities of daily living (ADL) subscore of the UPDRS in the off state remained improved with median changes of 23% and 22% at follow up (both p<0. 005). There was no significant improvement of "on" state or ipsilateral off state motor scores. Median modified Hoehn and Yahr scores in off and on state were unchanged, as was the time spent off. Speech in off had significantly deteriorated by 1 year after the operation. CONCLUSIONS: The beneficial effects of unilateral pallidotomy persist for at least 12 months and, dyskinesias are most responsive to this procedure.