Quantification of clinical scores through physiological recordings in low-responsive patients: a feasibility study.

Clinical scores represent the gold standard in characterizing the clinical condition of patients in vegetative or minimally conscious state. However, they suffer from problems of sensitivity, specificity, subjectivity and inter-rater reliability.In this feasibility study, objective measures including physiological and neurophysiological signals are used to quantify the clinical state of 13 low-responsive patients. A linear regression method was applied in nine patients to obtain fixed regression coefficients for the description of the clinical state. The statistical model was extended and evaluated with four patients of another hospital. A linear mixed models approach was introduced to handle the challenges of data sets obtained from different locations.Using linear backward regression 12 variables were sufficient to explain 74.4% of the variability in the change of the clinical scores. Variables based on event-related potentials and electrocardiogram account for most of the variability.These preliminary results are promising considering that this is the first attempt to describe the clinical state of low-responsive patients in such a global and quantitative way. This new model could complement the clinical scores based on objective measurements in order to increase diagnostic reliability. Nevertheless, more patients are necessary to prove the conclusions of a statistical model with 12 variables.

Blink reflex prepulse inhibition and excitability recovery: influence of age and sex.

OBJECTIVE: Age and sex affect various reflexes in healthy humans. Their respective influence on prepulse inhibition (PPI) of the trigeminofacial blink reflex (BR) and BR excitability recovery has not as yet been investigated in detail. METHODS: We studied the trigeminofacial BR bilaterally in 62 healthy volunteers (31 males, age 41.0 ± 13.2 years, mean ± SD, 31 females, 39.2 ± 11.7 years) following right supraorbital nerve stimulation. Single sweeps were recorded either alone (n = 8) or conditioned by a prepulse applied 100 ms earlier to the dominant index finger though ring electrodes (n = 8). Latency and amplitude of the ipsilateral R1 component, as well as latency and area-under-the-curve of the ipsilateral R2 and contralateral R2c components were measured in single traces and then averaged per subject. BR excitability recovery was established bilaterally following right supraorbital nerve stimulation with paired pulses. Six responses were averaged on-line per interstimulus interval (ISI 160, 300, and 500 ms). RESULTS: Unconditioned BR did not differ significantly between males and females, but R2 and R2c latencies increased with age. Prepulse stimulation caused significant facilitation of R1 (latency and amplitude), and inhibition of R2 and R2c (latency and area), irrespective of age. PPI of R2 and R2c area was significantly more pronounced in men. BR excitability recovery was significantly influenced by age, but not by sex. Multiple regression showed inverse correlation of age with conditioned R2 and R2c area at ISI 300 ms and 500 ms (P < 0.01 each), indicating reduced excitability recovery. No parameter showed significant interaction of age × sex. CONCLUSION: These data indicate less pronounced PPI of the trigeminofacial BR in females, concurring with previous reports of sex differences in protective reflexes, but also suggesting less rigorous filtering of information flow to the brain in females. Reduced BR excitability to paired-pulse stimulation may counteract age-related disinhibition of brainstem interneuronal circuitry. SIGNIFICANCE: The present findings allow new insight into human brainstem physiology.