Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology
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Comparative Study Clinical Trial
Comparison of different modalities for detection of small fiber neuropathy.
In general, large fiber sensory function is easier to assess than small fiber function both clinically and electrophysiologically. Therefore, small fiber sensory neuropathies are more difficult to diagnose. The relative sensitivities of different electrodiagnostic tests for small fiber neuropathy are not known. We sought to determine and compare the sensitivities of quantitative thermal sensory testing (QST), quantitative sudomotor axon reflex testing (QSART), and cardiovascular autonomic testing for diagnosis in patients with clinically suspected small fiber neuropathy. ⋯ Of the modalities tested, QSART was most sensitive in confirming the clinical suspicion of a small fiber neuropathy. Autonomic cardiovascular abnormalities were also common in our patients. Clinical examination and QSART may be optimal for screening patients for small fiber neuropathy.
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The purpose of this study was to assess the patterns of mismatch negativity (MMN) and N100 component in comatose patients and to evaluate their prognostic value vis-à-vis return of consciousness. ⋯ MMN and auditory evoked potentials provide a reliable assessment of the functional status of comatose patients. When present, MMN and the N100 differ from those found in normal subjects in terms of latencies and amplitudes. As a predictor of return of consciousness MMN had high specificity and low sensitivity, whereas the N100 had high sensitivity and low specificity. This study demonstrates that the recording of MMN and the auditory N100 can be a very useful aid in the assessment of coma and in predicting whether or not a patient will regain consciousness.
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Spectral EEG analysis has been claimed to reduce subjective variability in EEG assessment of hepatic encephalopathy and to allow the detection of mild encephalopathy. ⋯ In conclusion, spectral EEG analysis may improve the assessment of mild hepatic encephalopathy by decreasing inter-operator variability and providing reliable parameters correlated with mental status.
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To study the event related potentials (ERPs) in coma and altered states of consciousness, their relationship with the clinical status and coma outcome. ⋯ ERPs can be recorded in some comatose patients and are likely to reflect implicit orienting processes rather than preserved consciousness. Their presence implies a good prognosis but no conclusion can be drawn from their absence.
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We recorded somatosensory evoked magnetic fields (SEFs) to median nerve stimulation from 15 patients in the acute stage (1-15 days from the onset of the symptoms) of their first-ever unilateral stroke involving sensorimotor cortical and/or subcortical structures in the territory of the middle cerebral artery (MCA). Neuronal activity corresponding to the peaks of the N20m, P35m and P60m SEF deflections from the contralateral primary somatosensory cortex (SI) was modelled with equivalent current dipoles (ECDs), the locations and strengths of which were compared with those of an age-matched normal population. Four patients with pure motor stroke had symmetric SEFs. ⋯ Three patients with pure sensory stroke and lesions in the opercular cortex had normal SEFs from SI. We conclude that the SEF deflections N20m, P35m and P60m from SI are related to cutaneous sensation, in particular discriminative to touch. The results also demonstrate that basic somatosensory perception can be affected by lesions in the opercular cortex in patients with functionally intact SI.