Objectives‐ To evaluate the following points about carpal tunnel syndrome (CTS): 1) characterization of a wide population; 2) sensitivity of electrodiagnostic tests, and particularly the contribution of disto‐proximal ratio test; 3) validity of a neurophysiological classification developed by us. Material and methods ‐ Prospective study in 500 hands with CTS symptoms. Neurophysiological “standard” tests were always performed: sensory nerve conduction velocity (SNCV) first‐ and third digit‐wrist and distal motor latency (DML). In “standard negative” hands disto‐proximal ratio technique (R) was performed. Neurophysiological classification: Extreme CTS (absence of median motor, sensory responses), Severe (absence of sensory response, abnormal DML), Moderate (abnormal SNCV, abnormal DML), Mild (abnormal SNCV, normal DML), Minimal (abnormal R or other segmental/comparative test, normal standard tests). Results‐ Sensibility of standard tests: 77%. R increased the diagnostic yield by 20%. CTS classification appeared reliable with significant differences between groups. Conclusion ‐ R is a useful test, the classification may be useful in clinical/therapeutical decisions.

Transcranial direct current stimulation (tDCS) at low intensity induces changes in cortical excitability that persist after polarization ends. The effects of anodal and cathodal polarization remain controversial. We studied changes in visual evoked potentials (VEPs) during and after anodal and cathodal tDCS by applying, in healthy volunteers, 1 mA polarization through surface electrodes placed over the occipital scalp (polarizing) and over the anterior or posterior neck-base (reference). We compared tDCS applied at two durations, 3 and 10 min and both polarities. We assessed VEP-P100 latencies and amplitudes in response to pattern-reversal checkerboard stimuli before, during, and after polarization. Anodal polarization reduced VEP-P100 amplitude whereas cathodal polarization significantly increased amplitude but both polarities left latency statistically unchanged. These changes persisted for some minutes after polarization ended depending on the duration of tDCS and on the contrast level of visual stimuli. tDCS-induced changes in VEPs seem to depend on the duration of polarization and type of visual stimuli used. The effects induced on visual cortical neurones during polarization are more consistent than the aftereffects. Studying these changes during polarization may therefore improve our understanding of these phenomena.

Blinking, a motor act consisting of a closing and an opening eyelid movement, can be performed voluntarily, spontaneously, and reflexly. In this study we investigated the kinematic features of voluntary, spontaneous, and reflex blinking in patients with Parkinson's disease (PD), OFF and ON dopaminergic treatment. Patients were asked to blink voluntarily as fast as possible. Spontaneous blinking was recorded for a minute during which the subjects just relaxed. Reflex blinking was evoked by electrical stimulation on the supraorbital nerve. Eyelid movements were recorded with the SMART analyzer motion system. Patients OFF therapy paused longer than controls during voluntary blinking but not during spontaneous and reflex blinking. The blink rate tended to be lower in patients OFF therapy than in controls and the spontaneous blinking had abnormally low amplitude and peak velocity. Finally, in patients OFF therapy the excitability of the neural circuit mediating the closing phase of the reflex blinking was enhanced. Dopaminergic treatment shortened the pause during voluntary blinking and increased the blink rate. In PD patients the longer pauses between the closing and opening phase in comparison to normal subjects, suggest bradykinesia of voluntary blinking. PD patients also display kinematic abnormalities of spontaneous blinking and changes in the excitability of the closing phase of reflex blinking.

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Patients with progressive supranuclear palsy (PSP) often have blinking abnormalities. In this study we examined the kinematic features of voluntary, spontaneous and reflex blinking in 11 patients with PSP and healthy control subjects. Patients were asked to blink voluntarily as fast as possible; spontaneous blinking was recorded during two 60 s rest periods; reflex blinking was evoked by electrical stimulation of the supraorbital nerve. Eyelid movements were recorded with the SMART analyzer motion system. During voluntary blinking the closing and opening phases lasted longer in patients than in healthy subjects. Furthermore, the peak velocity of the closing phase of voluntary blinking was lower in patients than healthy subjects. During spontaneous blinking the blink rate was markedly lower in patients than in control subjects. Patient's recordings also showed kinematic abnormalities of spontaneous (reduced peak velocity of both closing and opening phases) and reflex (reduced peak velocity and increased duration of the opening phase) blinking. Recordings during reflex blinking disclosed an enhanced excitability of the interneuronal pool mediating the closing and opening blink phases. Finally, the pause, a neurophysiological marker of the switching processes between the closing and opening phases, was prolonged in all the three types of blinking. The abnormal kinematic variables correlated with patients' clinical and kinematic features. Abnormal voluntary, spontaneous and reflex blinking in patients with PSP reflects the widespread cortical, subcortical and brainstem degeneration related to this disease.

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Following the AAEM electrodiagnostic guidelines, we developed a neurophysiological classification of carpal tunnel syndrome (CTS). Six hundred hands with clinical CTS (mean age 51.4 yr., female/male ratio 5.5/1, right/left ratio 1.8/1) were prospectively evaluated and divided into six classes of severity only on the basis of median nerve electrodiagnostic findings: extreme CTS (EXT-absence of thenar motor responses), severe CTS (SEV-absence of sensory response and abnormal distal motor latency-DML), moderate CTS (MOD-abnormal digit-wrist conduction and abnormal DML), mild CTS (MILD-abnormal digit wrist conduction and normal DML), minimal CTS (MIN-exclusive abnormal segmental and/or comparative study), and negative CTS (NEG-normal findings at all tests). Using this neurophysiological classification, the CTS groups appeared normally distributed (EXT 3% of cases, SEV 14%, MOD 36%, MILD 24%, MIN 21%, NEG 3%), and the age of patients and clinical findings appeared to be related to neurophysiological abnormalities. Significant differences in median neurophysiological parameters not included in the classification (such as palm-wrist sensory conduction velocity) were observed in the different CTS groups. The analysis of the groups showed that: 1) the majority of advanced cases (SEV and EXT) occurred in older patients (60-80 years), 2) most of the milder cases (MIN and MILD) occurred in young female patients. The aim of this study was to standardise the neurophysiological evaluation of CTS.

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