AIMS: To determine whether Parkinson's disease and multiple system atrophy each has a distinct pattern of micturition abnormalities and whether a urodynamic evaluation could be useful in the ...differential diagnosis between the two diseases. METHODS: Sixty two patients (30 with Parkinson's disease and 32 with multiple system atrophy) underwent a complete urodynamic evaluation and neurophysiological testing. RESULTS: Of the parkinsonian patients 36.6% had normal micturition findings with normal bladder sensitivity; 26.7% had delayed or incomplete pelvic floor relaxation; 26.7% had hyperreflexia with vesicosphincteric synergy; and 10% had hyperreflexia with vesicosphincteric synergy associated with incomplete pelvic floor relaxation. Parkinsonian patients with a normal urodynamic pattern had significantly less severe disease and a shorter duration of disease in years than those who had abnormal patterns. Patients with hyperreflexia had significantly higher severity of disease. All the patients with multiple system atrophy had hyperreflexia with synergy. Two urodynamic patterns were identified: hyperreflexia with vesicosphincteric synergy (90.6% of patients), and hyperreflexia with vesicosphincteric synergy and incomplete pelvic floor relaxation (in 9.4%). Hyperreflexia with synergy correlated neither with the severity nor with the duration of disease. Sphincter EMG analysis showed that all the parkinsonian patients had normal sphincter EMG whereas 24 of the 32 patients with multiple system atrophy had neurogenic signs. CONCLUSIONS: Urodynamic evaluation and sphincter EMG are both useful tests in the differential diagnosis between Parkinson's disease and multiple system atrophy. Urodynamic findings may be abnormal before patients with multiple system atrophy reach an advanced stage of the disease. Recordings of EMGs from perineal muscles become abnormal as the disease progresses in multiple system atrophy but not in Parkinson's disease.
The silent period after contralateral and ipsilateral transcranial magnetic brain stimulation was studied in patients with Parkinson's disease before and after dopaminergic and anticholinergic ...therapy; in normal subjects before and after L-dopa administration and in patients with drug-induced parkinsonism. In patients and normal subjects the silent period was also studied after peripheral nerve stimulation. The silent period after transcranial cortical stimulation was shorter in Parkinson's disease patients than in normal subjects. In patients with Parkinson's disease L-dopa prolonged the silent period after transcranial brain stimulation and after ipsilateral cortical stimulation. Biperiden prolonged the silent period after transcranial brain stimulation. In normal subjects, L-dopa produced similar but smaller changes. In the patients with drug-induced parkinsonism the silent period after transcranial magnetic stimulation was shorter than normal subjects. The peripheral silent period was similar in normal subjects and in patients and did not change after drug administration. In conclusion cortical silent period is abnormal in patients with Parkinson's disease and drug-induced parkinsonism. Dopaminergic drugs modulate the duration of the cortical silent periods in patients and in normal subjects, through mechanisms acting mainly at basal ganglia and possibly also directly at cortical level.
Repetitive transcranial magnetic stimulation (rTMS) delivered at various intensities and frequencies excites cortical motor areas. Trains of stimuli (at 5-Hz frequency, and suprathreshold intensity) ...progressively increase the size of motor evoked potentials (MEPs) and the duration of the cortical silent period (CSP) in normal subjects. Because antiepileptic drugs, acting mainly on sodium channels, depress MEP facilitation during rTMS, we suggested that rTMS trains facilitate the MEP size by inducing synaptic potentiation primarily involving voltage-gated sodium channels. The aim of this study was to evaluate the effect of lidocaine-a drug that acts selectively on sodium channels-on the rTMS-induced changes in cortical excitability. We tested the changes in motor threshold, MEP size, CSP duration evoked by focal rTMS and the M-wave amplitude in healthy subjects before and after lidocaine infusion. Lidocaine abolished the normal rTMS-induced facilitation of MEPs but left the other rTMS variables and the M-wave unchanged. Our results suggest that the MEP facilitation related to rTMS-induced synaptic potentiation results from an increase in cortical excitatory interneuron excitability that involves voltage-gated sodium channels.
Objective: To verify whether laser evoked potentials are useful in assessing the function of small afferent fibers and to compare dysfunction of large and small afferent fibers in patients with ...diabetic polyneuropathy.
Methods: The brain potentials evoked by CO
2 laser stimulation of the hand and foot were studied in diabetic patients (
n=45) with various degrees of peripheral nerve damage. Laser evoked potentials (which assess the function of small myelinated afferents) were also compared with ulnar and sural nerve sensory action potentials (which assess the function of large myelinated afferents) by scoring the abnormalities of the two neurophysiological tests with similar criteria.
Results: Laser evoked potentials were often absent; the mean latency was normal and mean amplitude decreased, as expected in axonopathies. Although clinical examination showed more frequent impairment of vibratory than pinprick sensation, laser evoked potentials and sensory action potentials yielded similar abnormality scores and showed a strong intra-individual correlation.
Conclusions: Laser evoked potentials, possibly better than standard clinical examination for assessing the abnormalities of small-diameter afferents, indicate that diabetic polyneuropathy induces large- and small-afferent dysfunction in parallel.
The physiological mechanisms underlying the lengthening of the silent period (SP) evoked in active upper limb muscles by repetitive transcranial magnetic stimulation (rTMS) of the motor areas were ...studied in normal subjects. rTMS was delivered at frequencies of 1 Hz, 2 Hz, 3 Hz, 5 Hz, 10 Hz and 15 Hz and at an intensity just above the motor threshold (Mth). Trains delivered at 2 Hz, 3 Hz, 5 Hz, 10 Hz and 15 Hz significantly prolonged the cortical SP, whereas stimuli at 1 Hz did not. The first few stimuli in the train already prolonged the duration of the cortical SP: the other stimuli did not prolong it further. Motor evoked potentials remained unchanged in amplitude regardless of the frequencies and number of stimuli in the train. The effect of intensity of stimulation was studied by delivering trains at suprathreshold intensity (110% and 140% of Mth) and 3-Hz frequency and with trains at subthreshold intensity and 5-Hz and 10-Hz frequencies. SPs had a longer duration at 140% than at 110% Mth intensity. SPs elicited by 3-Hz trains at 140% and 110% Mth intensity lengthened to a similar extent over the course of the train. rTMS delivered at an intensity below Mth did not evoke cortical SPs over the course of the trains. Repetitive stimulation of the cortical forearm motor areas prolonged the duration of the cortical SP in forearm flexor muscles but failed to evoke SPs in the biceps muscles. The maximal single stimulus intensity and less intense stimuli delivered in short trains evoked SPs of similar duration. We propose that rTMS delivered in trains at frequencies higher than 1 Hz and at suprathreshold intensity prolongs the cortical SP mainly through temporal summation of inhibitory interneurones.
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