Michele Tinazzi

ATP13A2 missense mutations in juvenile parkinsonism and young onset Parkinson disease

Objective: To assess the prevalence, nature, and associated phenotypes of ATP13A2 gene mutations among patients with juvenile parkinsonism (onset <21 years) or young onset (between 21 and 40 years) Parkinson disease (YOPD). Methods: We studied 46 patients, mostly from Italy or Brazil, including 11 with juvenile parkinsonism and 35 with YOPD. Thirty-three cases were sporadic and 13 had positive family history compatible with autosomal recessive inheritance. Forty-two had only parkinsonian signs, while four (all juvenile-onset) had multisystemic involvement. The whole ATP13A2 coding region (29 exons) and exon-intron boundaries were sequenced from genomic DNA. Results: A novel homozygous missense mutation (Gly504Arg) was identified in one sporadic case from Brazil with juvenile parkinsonism. This patient had symptoms onset at age 12, levodopa-responsive severe akinetic-rigid parkinsonism, levodopa-induced motor fluctuations and dyskinesias, severe visual hallucinations, and supranuclear vertical gaze paresis, but no pyramidal deficit nor dementia. Brain CT scan showed moderate diffuse atrophy. Furthermore, two Italian cases with YOPD without atypical features carried a novel missense mutation (Thr12Met, Gly533Arg) in single heterozygous state. Conclusions: We confirm that ATP13A2 homozygous mutations are associated with human parkinsonism, and expand the associated genotypic and clinical spectrum, by describing a homozygous missense mutation in this gene in a patient with a phenotype milder than that initially associated with ATP13A2 mutations (Kufor-Rakeb syndrome). Our data also suggest that ATP13A2 single heterozygous mutations might be etiologically relevant for patients with YOPD and further studies of this gene in Parkinson disease are warranted.

Pain and motor complications in Parkinson's disease

Aims: To study the association of pain with motor complications in 117 patients with Parkinson’s disease. Methods: Patients were asked to refer any pain they experienced at the time of study and lasting since at least 2 months. Basic parkinsonian signs and motor complications (including motor fluctuations and dyskinesia) were assessed and Unified Parkinson’s Disease Rating Scale (UPDRS) motor score part III (during on) and part IV were calculated. Information on age, sex, duration of disease, use of dopamine agonists and levodopa, years of levodopa treatment and current levodopa dosage, medical conditions possibly associated with pain, and depression were collected. Single and multiple explanatory variable logistic regression models were used to check the association of pain with the investigated variables. Results: Pain was described by 47 patients (40%) and could be classified into dystonic (n.19) and non dystonic pain (n.16); in 12 patients both types coexisted. Multiple explanatory variable logistic regression models indicated a significant association of pain with motor complications (adjusted OR, 5.7; 95% CI, 2 to 16.5; p = 0.001). No association was found between pain, dystonic or non dystonic, and the other investigated variables including medical conditions known to be associated to pain in the general population. There was a significant correlation (r = 0.31, p<0.05) between severity of pain (measured on a Visual Analogue Scale) and severity of motor complications (UPDRS part IV). Conclusions: Pain may be a representative feature of Parkinson’s disease frequently associated with motor complications. The association is independent of a number of potentially relevant demographic and clinical variables.

Role of the somatosensory system in primary dystonia

The pathophysiology of dystonia is still not fully understood, but it is widely held that a dysfunction of the corticostriatal–thalamocortical motor circuits plays a major role in the pathophysiology of this syndrome. Although the most dramatic symptoms in dystonia seem to be motor in nature, marked somatosensory perceptual deficits are also present in this disease. In addition, several lines of evidence, including neurophysiological, neuroimaging and experimental findings, suggest that both motor and somatosensory functions may be defective in dystonia. Consequently, abnormal processing of the somatosensory input in the central nervous system may lead to inefficient sensorimotor integration, thus contributing substantially to the generation of dystonic movements. Whether somatosensory abnormalities are capable of triggering dystonia is an issue warranting further study. Although it seems unlikely that abnormal somatosensory input is the only drive to dystonia, it might be more correlated to the development of focal hand than generalized dystonia because local somesthetic factors are more selectively involved in the former than in the latter where, instead it seems to be a widespread deficit in processing sensory stimuli of different modality. Because basal ganglia and motor areas are heavily connected not only with somatosensory areas, but also with visual and acoustic areas, it is possible that abnormalities of other sensory modalities, such as visual and acoustic, may also be implicated in the pathophysiology of more severe forms of primary dystonia. Further studies have to be addressed to the assessment of the role of sensory modalities and their interaction on the pathophysiology of different forms of primary dystonia.

Effect of Balance Training on Postural Instability in Patients With Idiopathic Parkinson’s Disease

Background. Postural instability (PI) is a disabling sign of Parkinson’s disease (PD) not easily amenable to treatment with medication. Objective. To evaluate the effects of balance training on PI in patients with PD. Methods. A total of 64 patients with PI were randomly assigned to the experimental group (n = 33) for balance training or to the control group (n = 31) for general physical exercises. Each patient received 21 treatment sessions of 50 minutes each. Patients were evaluated by a blinded rater before and after treatment as well as 1 month posttreatment using the Berg Balance Scale (BBS), Activities-Specific Balance Confidence Scale (ABC), postural transfer test, self-destabilization of the center of foot pressure test, number of falls, Unified Parkinson’s Disease Rating Scale (UPDRS), modified Hoehn and Yahr (H&Y) Staging Scale, and Geriatric Depression Scale (GDS). Results .At the end of treatment, the experimental group showed significant improvements in all outcome measures, except for the UPDRS and the H&Y scale. Improvement was maintained at the 1-month follow-up in all outcome measures except for the GDS. No significant changes in performance were observed in the control group. Conclusions. A program of balance training can improve PI in patients with PD.

Comprehensive analysis of the LRRK2 gene in sixty families with Parkinson's disease

Mutations in the gene leucine-rich repeat kinase 2 (LRRK2) have been recently identified in families with Parkinsons disease (PD). However, the prevalence and nature of LRRK2 mutations, the polymorphism content of the gene, and the associated phenotypes remain poorly understood. We performed a comprehensive study of this gene in a large sample of families with Parkinsons disease compatible with autosomal dominant inheritance (ADPD). The full-length open reading frame and splice sites of the LRRK2 gene (51 exons) were studied by genomic sequencing in 60 probands with ADPD (83% Italian). Pathogenic mutations were identified in six probands (10%): the heterozygous p.G2019S mutation in four (6.6%), and the heterozygous p.R1441C mutation in two (3.4%) probands. A further proband carried the heterozygous p.I1371 V mutation, for which a pathogenic role could not be established with certainty. In total, 13 novel disease-unrelated variants and three intronic changes of uncertain significance were also characterized. The phenotype associated with LRRK2 pathogenic mutations is the one of typical PD, but with a broad range of onset ages (mean 55.2, range 38–68 years) and, in some cases, slow disease progression. On the basis of the comprehensive study in a large sample, we conclude that pathogenic LRRK2 mutations are frequent in ADPD, and they cluster in the C-terminal half of the encoded protein. These data have implications both for understanding the molecular mechanisms of PD, and for directing the genetic screening in clinical practice.

Learning potentiates neurophysiological and behavioral placebo analgesic responses.

Abstract Expectation and conditioning are supposed to be the two main psychological mechanisms for inducing a placebo response. Here, we further investigate the effects of both expectation, which was induced by verbal suggestion alone, and conditioning at the level of N1 and N2–P2 components of CO2 laser‐evoked potentials (LEPs) and subjective pain reports. Forty‐four healthy volunteers were pseudorandomly assigned to one of three experimental groups: Group 1 was tested with verbal suggestion alone, Group 2 was tested with a conditioning procedure, whereby the intensity of painful stimulation was reduced surreptitiously, so as to make the volunteers believe that the treatment was effective, Group 3 was a control group that allowed us to rule out phenomena of sensitization and/or habituation. Pain perception was assessed according to a Numerical Rating Scale (NRS) ranging from 0 = no pain sensation to 10 = maximum imaginable pain. Both verbal suggestions (Group 1) and conditioning (Group 2) modified the N2–P2 complex, but not the N1 component of LEPs. However, the suggestion‐induced LEP changes occurred without subjective perception of pain decrease. Conversely, the N2–P2 amplitude changes that were induced by the conditioning procedure were associated with the subjective perception of pain reduction. Compared to natural history, conditioning produced more robust reductions of LEP amplitudes than verbal suggestions alone. Overall, these findings indicate that prior positive experience plays a key role in maximizing both behavioral and neurophysiological placebo responses, emphasizing that the placebo effect is a learning phenomenon which affects the early central nociceptive processing.

Temporal processing of visuotactile and tactile stimuli in writer's cramp

Neurophysiological studies in animals show that basal ganglia are involved not only in motor and nonmotor timing functions but also in integrating tactile and visual signals delivered in the peripersonal space. We tested temporal discrimination of cross‐modal and unimodal stimuli in 13 controls and 14 patients with writers cramp, a disorder supposedly linked to dysfunction of basal ganglia. Subjects were asked to discriminate whether pairs of visual, tactile, or visuotactile stimuli were simultaneous or sequential (temporal discrimination threshold) and which stimulus preceded the other (temporal order judgment). Patients were impaired in temporal processing of tactile and cross‐modal stimuli. A significant positive correlation between temporal deficits and the severity of disability was detected for both affected and unaffected sides. Findings suggest that multimodal and not only modality‐specific temporal processing is defective in focal hand dystonia. Deficits of temporal processing of stimuli delivered to the unaffected side may represent a behavioral index of the susceptibility to develop dystonia and thus have remarkable practical and theoretical implications. Ann Neurol 2003

Reversible changes of motor cortical outputs following immobilization of the upper limb

We mapped the cortical representations of the abductor pollicis brevis, flexor carpi radialis, biceps and deltoid muscles in six subjects with unilateral wrist fractures, immediately after the removal of the splint. This was repeated 1 month later in three out of the six subjects. Duration of immobilization was 1 month. Muscle maps were obtained by delivering four focal magnetic pulses for each scalp position (1 cm apart with reference to Cz) over the contralateral hemisphere. Motor evoked potentials (MEPs) were averaged off-line and expressed as a percentage of the motor action potential evoked by supramaximal peripheral nerve stimulation. Volume, area and threshold of the motor maps showed no significant hemispheric differences within each muscle in 10 control subjects. In the first recording session the volume of each immobilized muscle was distinctly higher when compared to that of controls in terms of absolute value and side-to-side ratio. This finding disappeared 1 month later. Moreover, MEP amplitude difference recorded from hand muscle could be reversed during a small tonic voluntary contraction. Immobilization had no significant effect on the threshold for activation of the target muscles and on the area of the motor map. The increase in MEP amplitudes occurred without changes in spinal excitability as tested by the F wave. These findings suggest that immobilization of the upper limb induces a reversible enhancement of the excitability of structures along the corticomotoneuronal pathway. Sustained restriction of volitional movements and reduction in somatic sensory inputs might promote this functional modulation of the motor system.

Inhibitory action of forearm flexor muscle afferents on corticospinal outputs to antagonist muscles in humans

1 To find out whether muscle afferents influence the excitability of corticospinal projections to antagonist muscles, we studied sixteen healthy subjects and one patient with a focal brain lesion. 2 Using transcranial magnetic and electrical brain stimulation we tested the excitability of corticomotoneuronal connections to right forearm muscles at rest after conditioning stimulation of the median nerve at the elbow. Somatosensory potentials evoked by median nerve stimulation were also recorded in each subject. 3 Test stimuli delivered at 13–19 ms after median nerve stimulation significantly inhibited EMG responses elicited in forearm extensor muscles by transcranial magnetic stimulation, but did not inhibit responses to electrical stimulation. In contrast, magnetically and electrically elicited responses in forearm flexor muscles were suppressed to the same extent. 4 The higher the intensity of the test shocks, the smaller was the amount of median nerve‐elicited inhibition. Inhibition in extensor muscles was also smaller during tonic wrist extension, or if the induced electrical stimulating current in the brain flowed from posterior to anterior over the motor strip rather than vice versa. Test responses evoked by magnetic transcranial stimulation in the first dorsal interosseous and in brachioradialis muscles were not inhibited after median nerve stimulation at the elbow. Stimulation of digital nerves failed to inhibit motor potentials in extensor muscles. 5 Test stimuli delivered at 15 and 17 ms after radial nerve stimulation significantly inhibited EMG responses elicited in forearm flexor muscles by magnetic transcranial stimulation. 6 In the patient with a focal thalamic lesion, who had dystonic postures and an absent N20 component of the somatosensory‐evoked potentials but normal strength, median nerve stimulation failed to inhibit magnetically evoked responses in forearm extensor muscles. 7 We propose that activation of median nerve muscle afferents can suppress the excitability of cortical areas controlling the antagonist forearm extensor muscles acting on the hand. The inhibitory effect occurs at short latency and might assist spinal pathways mediating reciprocal inhibition by contrasting the co‐activation of antagonistic pools of corticospinal cells.

Long-lasting depression of motor-evoked potentials to transcranial magnetic stimulation following exercise

We used transcranial magnetic stimulation to study the modulation of motor cortex excitability after rapid repetitive movements. Eleven healthy subjects aged 24–32 years were evaluated. Serial motor-evoked potential (MEP) recordings were performed from the right thenar eminence every 5 min for a period of 20 min at rest and for a period of 35 min after repetitive abduction-adduction of the thumb at maximal frequency for 1 min. All subjects presented distinct changes in MEP amplitude after exercise with an approximately 55% mean maximal decrease compared with basal conditions and complete recovery 35 min after the end of the exercise. The time course of MEP amplitude changes presented the following trend: (1) a rapid decrease phase within the first 5 min; (2) a maximal depression phase of 10 min duration (from the 5th to the 15th min); and (3) a slow recovery phase. No significant modifications in post-exercise MEP amplitude were found in ipsilateral non-exercised muscles. In order to determine the level where these changes take place, we recorded the M and F waves induced by median nerve stimulation at the wrist (all subjects) and MEPs in response to transcranial electrical stimulation (five subjects) at rest and during the decrease and maximal depression phases. None of these tests were significantly affected by exercise, indicating that the motor cortex was the site of change. Evaluation of maps of cortical outputs to the target muscle, performed in four subjects, showed an approximately 40% spatial reduction in stimulation sites evoking a motor response during the maximal depression phase. These data prove that exercise induces a reversible, long-standing depression of cortical excitability, probably related to intracortical presynaptic modulation, which transitorily reduces the motor representation area.