Temporal discrimination thresholds (TDT) for recognition of paired sensory (tactile, auditory and visual) stimuli given over a wide range of time intervals were assessed in 44 patients with Parkinson's disease (PD) and 20 age-matched normal subjects. A significant increment in TDT for all three sensory modalities was found in PD patients compared with controls. This abnormality was greatly attenuated for about 2 h by a single levodopa/carbidopa (250/25 mg) tablet. A significant correlation was found between disease severity as assessed clinically and TDT. Patients with more severe PD had higher TDT values. The study of the peripheral median nerve and cortical somatosensory evoked potential recovery curves following double electrical stimulation of the index finger showed no differences between patients and control subjects, nor changes from 'off' to 'on' motor state which could explain the findings. These results indicate the existence of an abnormality of timing mechanisms in PD.
Somaesthetic temporal discrimination (STD) is the ability to perceive as separate two successive somaesthetic stimuli applied to the same or different parts of the body. Paired electrical stimuli were applied to the index finger, using different time-intervals, to study the STD threshold (STDT) in 84 normal subjects and 51 patients with focal cerebral lesions. Abnormal STDT values were found on the affected side ofpatients with a lesion of the primary somatosensory cortex, and internal capsulethalamus. Lesions which did not produce sensory impairment but caused abnormal STDT were located in the posterior parietal cortex, the head of the caudate nucleus, the putamen, the medial thalamus and the lenticular nucleus. somatosensory cortex (PSC). A "time-organising system" which Lies in the infericr parietal lobe and the bank of the superior temporal sulcus has also been implicated in the anatomical basis of STD.9We have applied a simple test, using electrical stimulation of the index finger, to assess STD in a large number of untrained normal subjects of all ages and in patients with focal cerebral lesions.Subjects and method Fifty one neurologically stable patients with focal cerebral lesions demonstrated by CT and MRI brain scan, with no evidence of any other disturbance of the peripheral or CNS, were studied and compared with 84 normal untrained subjects. The mean (SD) age was 54-2 (18) (range 24-87) for patients and 44 75 (19-7) (range 12-83) for controls. All subjects were in good general condition, with a normal level of consciousness and had no language difficulty at the time of the study. Patients with a gnostic defect, right-left confusion or dyscalculia were not included in the study.Patients were divided according to the distribution of the lesions demonstrated by CT brain scan and the presence or absence of a sensory defect in the hands. The latter was defined as normal when patients had no error in any somaesthetic test applied to the limb; mild defect when minimal errors were detected in fine sensory tasks, that is, recognising different fabrics; severe defect when clear exteroceptive and propioceptive abnormalities were present but patients could still feel electrical stimulation with high stimulus intensity. The primary complex of the SEP was defined as normal when the three typical waves (N-20/P-25/N-33) were recorded on parietal electrodes with normal latency and amplitude; mild abnormality when the N-20 or P-25 waves were delayed by no longer than 5 ms but had normal amplitude, and severe abnormality when no SEP potentials were recorded or were barely distinguishable. To be considered without sensory defect patients had to have normal sensation clinically and show no abnormality of the SEPs. The stimulus consisted of a rectangular electrical pulse of 02 ms with an intensity of three times the sensory threshold generated by a Grass S-88 stimulator and was applied through ring electrodes attached to the index finger. In the same session, median nerve sensory potentials and cortical SEPs (from...
We investigated the prevalence of dementing disorders in the city of Pamplona, Spain, using a door-to-door two-phase approach. We first administered the Cambridge Examination of Mental Disorders of the Elderly (CAMDEX) to all survivors, as of March 1, 1991, of a probability sample of the total population identified in 1989 (n = 1,127). Using specified diagnostic criteria, the study neurologists extensively investigated those subjects who screened positive on CAMDEX. We found 194 subjects affected by dementia, 119 had Alzheimer''s disease; 51 vascular or mixed dementia, and 16 secondary dementia. The prevalence of both dementia and Alzheimer''s disease increased steeply with advancing age and was consistently higher in women. The prevalence of combined vascular and mixed dementia increased less rapidly with age, and was generally higher in men. Alzheimer''s disease was the most common type of dementia. Our prevalence figures for dementia and Alzheimer''s disease are similar to those previously reported in Europe.
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