RESUMO
BACKGROUND AND PURPOSE: Traditionally dystonia has been considered a disorder of basal ganglia dysfunction. However, recent research has advocated a more complex neuroanatomical network. In particular, there is increasing interest in the pathophysiological role of the cerebellum. Patients with cervical and focal hand dystonia have impaired cerebellar associative learning using the paradigm eyeblink conditioning. This is perhaps the most direct evidence to date that the cerebellum is implicated in patients. METHODS: Eleven patients with DYT1 dystonia and five patients with DYT6 dystonia were examined and rates of eyeblink conditioning were compared with age-matched controls. A marker of brainstem excitability, the blink reflex recovery, was also studied in the same groups. RESULTS: Patients with DYT1 and DYT6 dystonia have a normal ability to acquire conditioned responses. Blink reflex recovery was enhanced in DYT1 but this effect was not seen in DYT6. CONCLUSIONS: If the cerebellum is an important driver in DYT1 and DYT6 dystonia our data suggest that there is specific cerebellar dysfunction such that the circuits essential for conditioning function normally. Our data are contrary to observations in focal dystonia and suggest that the cerebellum may have a distinct role in different subsets of dystonia. Evidence of enhanced blink reflex recovery in all patients with dystonia was not found and recent studies calling for the blink recovery reflex to be used as a diagnostic test for dystonic tremor may require further corroboration.
Assuntos
Piscadela/fisiologia , Doenças Cerebelares/fisiopatologia , Condicionamento Psicológico/fisiologia , Distonia Muscular Deformante/fisiopatologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Tronco Encefálico/fisiopatologia , Estimulação Elétrica , Eletromiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Previous studies of the cortical control of human facial muscles documented the distribution of corticobulbar projections and the presence of intracortical inhibitory and facilitatory mechanisms. Yet surprisingly, given the importance and precision in control of facial expression, there have been no studies of the afferent modulation of corticobulbar excitability or of the plasticity of synaptic connections in the facial primary motor cortex (face M1). In 25 healthy volunteers, we used standard single- and paired-pulse transcranial magnetic stimulation (TMS) methods to probe motor-evoked potentials (MEPs), short-intracortical inhibition, intracortical facilitation, short-afferent and long-afferent inhibition and paired associative stimulation in relaxed and active depressor anguli oris muscles. Single-pulse TMS evoked bilateral MEPs at rest and during activity that were larger in contralateral muscles, confirming that corticobulbar projection to lower facial muscles is bilateral and asymmetric, with contralateral predominance. Both short-intracortical inhibition and intracortical facilitation were present bilaterally in resting and active conditions. Electrical stimulation of the facial nerve paired with a TMS pulse 5-200 ms later showed no short-afferent inhibition, but long-afferent inhibition was present. Paired associative stimulation tested with an electrical stimulation-TMS interval of 20 ms significantly facilitated MEPs for up to 30 min. The long-term potentiation, evoked for the first time in face M1, demonstrates that excitability of the facial motor cortex is prone to plastic changes after paired associative stimulation. Evaluation of intracortical circuits in both relaxed and active lower facial muscles as well as of plasticity in the facial motor cortex may provide further physiological insight into pathologies affecting the facial motor system.
Assuntos
Músculos Faciais/fisiologia , Córtex Motor/fisiologia , Adulto , Estimulação Elétrica , Eletromiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Plasticidade Neuronal , Estimulação Magnética Transcraniana , Adulto JovemRESUMO
Adaptation of a rapid ballistic movement requires that commands for the next movement are updated on the basis of sensory error signals from the current movement. Previous experiments, mostly using visual feedback, have demonstrated that adaptation is highly sensitive to the timing of feedback and can be substantially impaired by delays of 100 ms or so. Here, we use the phenomenon of surround inhibition (SI) to explore the consequences of somatosensory feedback delay in a task requiring participants to flex the index finger without generating any electromyographical (EMG) activity in other fingers. Participants were requested to perform brief isolated flexion movements of the index finger. After a short period of practice, SI in the distant abductor digiti minimi (ADM) muscle was quantified by measuring the amplitude of EMG responses evoked by a standard pulse of transcranial magnetic stimulation to the contralateral motor cortex at the onset of flexion. SI indicates that the response during flexion was smaller than the response at rest. After this, two training blocks were performed in which the ADM muscle was vibrated (80 Hz, 100 ms) either at the onset (VIB(onset)) of finger flexion or with a delay of 100 ms (VIB(100)). SI was reassessed after training. SI measured after VIB(onset) training was transiently more effective than at baseline. In contrast, SI was unchanged compared to baseline after VIB(100). The present study demonstrates that SI can be modified by experience. The timing of the sensory stimulation was found to be critical for the modification of SI, suggesting that only sensory signals closely related to the movement onset can induce adaptive changes, presumably through a feed-forward process.
Assuntos
Adaptação Fisiológica/fisiologia , Biorretroalimentação Psicológica/fisiologia , Movimento/fisiologia , Inibição Neural/fisiologia , Análise de Variância , Eletromiografia , Potencial Evocado Motor/fisiologia , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Tempo de Reação , Fatores de Tempo , Estimulação Magnética Transcraniana , VibraçãoAssuntos
Movimento/fisiologia , Neostriado/citologia , Neostriado/fisiologia , Vias Neurais/fisiologia , Animais , Feminino , MasculinoRESUMO
BACKGROUND: Primary cervical dystonia is the most common form of adult-onset focal dystonia. Although most frequently sporadic, 15-20% of patients report a positive family history, suggesting a possible genetic cause. Head tremor is often present in patients with cervical dystonia and may be a prominent symptom. OBJECTIVE: To describe the clinical characteristics of patients with tremulous cervical dystonia. METHODS: Patients with primary cervical dystonia attending our botulinum toxin clinic were assessed with an interview and neurological examination and their notes reviewed. Patients were classified as having either tremulous or non-tremulous cervical dystonia, according to the presence or absence of head tremor on examination. Clinical and demographic data were compared between groups. RESULTS: From 273 patients included (190 females, 83 males), 125 (46%) were classified as tremulous and 148 (54%) as non-tremulous. Tremulous patients were more likely to have a segmental distribution (61% vs. 25%), often involving the arms (48%), and had more frequently associated arm tremor (55% vs. 10%). A positive family history of dystonia and/or tremor was more frequent in tremulous patients (50% vs. 18%). CONCLUSIONS: Patients with cervical dystonia with associated head tremor are more likely to have a segmental distribution (with frequent arm involvement), associated arm tremor and a positive family history, suggesting a genetic etiology in this subgroup of patients.
Assuntos
Saúde da Família , Torcicolo/complicações , Torcicolo/genética , Tremor/etiologia , Tremor/genética , Idoso , Antidiscinéticos/uso terapêutico , Toxinas Botulínicas/uso terapêutico , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Torcicolo/tratamento farmacológico , Tremor/tratamento farmacológicoRESUMO
Functional neurological disorders are common, disabling and often difficult to treat. There is little consensus on the best approach to management. Multidisciplinary inpatient approaches are employed in some centres for patients with severe refractory symptoms, but their efficacy and, in particular, long-term outcomes are uncertain. We conducted a study using questionnaires completed retrospectively by patients treated at a specialised multidisciplinary inpatient programme at the National Hospital for Neurology and Neurosurgery. Consecutive patients with functional motor symptoms admitted to this centre between 2006 and 2008 were invited to participate. Questionnaires were sent at least 2 years after discharge. We contacted 32 patients, and 26 responded. The majority had symptoms for at least 3 years prior to admission; 58 % of patients reported benefit from the programme on discharge. This self-reported benefit to symptoms and function was after a 2-year follow-up period in the majority of patients, but return to work or cessation of health-related financial benefits was uncommon even in those who improved. Seventy-four percent of those questioned stated they would recommend the programme to others with similar symptoms. Attribution of symptoms to stress or emotional state was correlated with favourable outcome. Our data suggest that multidisciplinary inpatient treatment for patients with refractory functional motor symptoms provides self-reported benefit in the long-term. Prospective analysis of such interventions and the determinants of benefit need assessment in order to improve the service and target treatment to patients most likely to benefit.