Autosomal dominant cerebellar ataxias encompass a broad spectrum of clinical features with high prevalence of non-ataxia symptoms. Certain features distinguish different genetic subtypes. A new algorithm for ADCA classification at disease onset is proposed.
Current concepts regarding the organisation of the motor system indicate the existence of a frontoparietal circuit involved in prehension and manipulation, whose damage may result in a motor behavioural disorder strongly resembling the one originally described as limb-kinetic apraxia. To determine the specific clinical and kinematic features of this distinctive praxic disorder, 5 patients with corticobasal degeneration (apraxic group), 5 with Parkinson's disease (nonapraxic group), and 10 control subjects were studied by a comprehensive apraxic battery, three-dimensional motion analysis of manipulative movements and motor evoked potentials. A mathematical model [quality of movement coefficient (QMC)] was applied to quantify differential kinematic characteristics between elementary motor deficits and the praxic disorder. Transcranial magnetic stimulation was used to evaluate corticomotoneural projections and cortical inhibition. All five patients in the apraxic group exhibited a unilateral praxic deficit characterised by derangement of fractionated and segmental finger movements. QMC was significantly greater in apraxic than in nonapraxic patients (P < 0.02), revealing a chaotic movement with marked interfinger uncoordination. Conventional transcranial magnetic stimulation parameters were within normal limits in both groups of patients; however, the silent period was significantly shorter in the apraxic limb when compared with control subjects (P < 0.001). Limb-kinetic apraxia is a distinctive disorder affecting the performance of finger and hand postures and movements over and above a corticospinal or basal ganglion deficit. Disruption of the frontoparietal circuit devoted to grasping and manipulation, together with defective cortical inhibition, which would also interfere with the selection and control of hand muscle activity, are the most likely underlying physiopathological mechanisms of limb-kinetic apraxia in patients with corticobasal degeneration.
OBJECTIVE
To determine the effect of a single dose of apomorphine on internal globus pallidus (GPi) neuronal discharge in patients with Parkinson's disease (PD).
PATIENTS AND METHODS
Nine PD patients who underwent microelectrode‐guided posteroventral pallidotomy (PVP) were studied. After identification of a single GPi unit discharge with sufficient spike S/N ratio to allow reliable thresholding, basal recording was followed by a single 3‐mg subcutaneous injection. One‐minute samples were recorded 10′, 30′, and 60′ after apomorphine.
RESULTS
In four patients, recording was lost after 5–10 minutes. In two, changes were observed at peak‐of‐dose but recording was then lost, whereas three completed recording and returned to baseline, all five showing significant reduction in GPi firing rate (mean ± standard deviation for basal and post‐apomorphine were 143 ± 55.6 and 52 ± 19.2, respectively; p <0.002).
CONCLUSION
In patients with PD, apomorphine induces changes in GPi spontaneous discharge and modifies firing rates resembling recordings in normal primates. These findings show that clinical improvement as well as induction of dyskinesias following DA administration could be mediated by reduction of GPi outflow.
OBJECTIVE: To determine the effect of a single dose of apomorphine on internal globus pallidus (GPi) neuronal discharge in patients with Parkinson's disease (PD).PATIENTS AND METHODS: Nine PD patients who underwent microelectrode-guided posteroventral pallidotomy (PVP) were studied. After identification of a single GPi unit discharge with sufficient spike S/N ratio to allow reliable thresholding, basal recording was followed by a single 3-mg subcutaneous injection. One-minute samples were recorded 10Ј, 30Ј, and 60Ј after apomorphine.RESULTS: In four patients, recording was lost after 5-10 minutes. In two, changes were observed at peak-of-dose but recording was then lost, whereas three completed recording and returned to baseline, all five showing significant reduction in GPi firing rate (mean ± standard deviation for basal and postapomorphine were 143 ± 55.6 and 52 ± 19.2, respectively; p <0.002).CONCLUSION: In patients with PD, apomorphine induces changes in GPi spontaneous discharge and modifies firing rates resembling recordings in normal primates. These findings show that clinical improvement as well as induction of dyskinesias following DA administration could be mediated by reduction of GPi outflow.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.