[Morphological study of brainstem auditory evoked potentials. The effect of the position of the reference electrode]

INTRODUCTION

In view of the discrepancy between the siting of electrodes and the effects on BAEP, we made a morphological study of 30 healthy volunteers, 15 men and 15 women.

DEVELOPMENT

In each person we obtained the BAEP with the active electrode on the ear lobe ipsilateral to the stimulated ear and the reference ear successively at four different sites: vertex (Cz), high frontal (Fz), earlobe contralateral to the stimulated ear and the spinous process of the seventh cervical vertebra (CV7). The I, III and V waves were present in all cases and tests, followed in frequency by II, IV and VII. In Cz and Fz the first five deflections were almost always seen, and these are the most useful for neurodiagnosis. The waves of greatest amplitude were 1 in both sexes in the ear lobe and CV7 for Fz and Cz in men and V for women. Regarding the complex morphological variants, the greatest incidence in the III IV V complex was observed in Fz in both sexes. In CV7 there was a greater range of variants, as found by other workers, but with greater morphological separation of waves IV and V. They were infrequent in waves I II and VI VII and least common in Fz and Cz.

CONCLUSION

We consider that the BAEP obtained with reference to Cz and Fz are ideal for interpretation, since there is greater constancy, global amplitude and morphological clarity of the first five deflections and less morphological complexity of the other waves.

[The influence of reference electrode position on auditory evoked potentials in the brainstem]

INTRODUCTION

In view of the discrepancy in the placement of electrodes and their effects on the auditory evoked potentials of the brainstem (PEAT), we made a statistical study of these potentials using four different sites for the reference electrode to determine the best position for it.

SUBJECTS AND METHODS

The study was done in 30 healthy volunteers aged between 17 and 22 years, 15 men and 15 women. In each person successive measurements were made of the PEAT, with the reference electrode on the vertex (Cz), high frontal (Fz), ear lobe of the opposite side to that of the ear being stimulated and the spinal apophysis of the 7th cervical vertebra (CV). In all cases the active electrode was placed on the ipsilateral ear lobe of the ear being stimulated. After obtaining tables of the normal values for the latency and wave amplitude of waves I to VII in each electrode montage used, we made a study of sex differences and results from the other ear using Student's t test for paired data.

RESULTS

No statistically significant differences were found between the latencies and amplitudes of the waves I to VII for the PEAT obtained with the montage used.

CONCLUSIONS

From our results, we may conclude that the position of the reference electrode does not seem to be a major factor when obtaining PEAT. However, in view of the recordings made, we prefer the reference electrode to be at Cz or Fz when obtaining PEAT, since a clearer recording is obtained when these positions are used. Influence of the reference electrode on PEAT.

[Somatosensory trigeminal evoked potentials after gingival stimulation of the mental nerve. Normal values]

OBJECTIVE

Somatosensory evoked potentials were recorded following unilateral stimulation of the mental nerve in the gum of 100 healthy volunteers aged between 17 and 22 years.

METHODS AND RESULTS

Responses were recorded until 100 ms with electrodes placed over the scalp (C5/C6) referenced to central frontal (Fz). In 10 subjects, simultaneous recordings were made in masticatory and facial muscles to detect possible muscle artefacts. Stimulation was effected using a specially-designed stimulator adaptable to each individual. Contralateral responses consisted of four very constant deflexions (N12, P19, N26 and P35) forming a W-shaped complex of mean duration 31.27 ms. Tables of normality were compiled for latencies and amplitudes with confidence intervals of 99.8% reliability. Constancy of deflexions, stability of response (by serial studies), and possible sexual differences were also studied. Muscle artefacts were ruled out, and the participation of the mental nerve in the genesis of the responses was confirmed.

CONCLUSION

We consider the proposed method a reliable alternative to other procedures used to obtain TEPs.

[Tables of normal values of average and long latency auditory potentials]

INTRODUCTION AND OBJECTIVE

In view of the disparity of data and methodology concerning medium (MAEP) and long latency (LAEP) acoustic evoked potentials, we have obtained tables of normal values using a reliable method and statistical study of these potentials in 30 healthy persons, in order to serve as a basis for clinical reference and for possible further studies.

MATERIAL AND METHODS

In the MAEP we used the two types of stimuli most commonly employed, first a click and then a rising-plateau-falling tone (2-6-2). We observed that this did not affect the latency or amplitude of the different waves, although the best defined waves are obtained with tones. In the LAEP we always used a tone with rise-plateau-fall of 10-50-10, as recommended by the American Electroneurophysiological Society. In all cases the intensity was of 70 db, with rarefaction and masking of the contralateral ear with an intensity of 50 db. Self-adhesive electrodes were used for captation; the active one was placed on the ipsilateral ear lobe and the reference electrode in Cz for the LAEP. For the LAEP the lower filter was of 1 Hz and the higher of 70 Hz. In view of the variety of filters recommended, 10 Hz at the lower level and 500, 1000 and 2000 at the higher level were used successively for the MAEP. We observed that these did not affect the latency or amplitude of the waves, so these three values may all be used equally well.

RESULTS AND CONCLUSIONS

In the inter-sexual study, no differences were seen between men and women. Nor were there significant differences between the acoustic evoked potentials on the right and left sides of the same person.

Outpatient group therapy for anorexia nervosa: a preliminary study

Group therapy is generally recognized as an important form of psychotherapy for anorexia nervosa patients, but there are few controlled studies of its effectiveness. The aim of the current study was to determine the effectiveness of cognitive-behavioural therapy (CBT) for the treatment of anorexia nervosa in outpatients. Twenty-six outpatients with anorexia nervosa, were assessed for depression (BDI, Beck Depression Inventory), eating psychopathology (EDI, Eating Disorders Inventory), eating attitudes (EAT, Eating Attitudes Test) and weight at the beginning and at the end of the treatment and at one year follow-up. Our results substantiate the effectiveness of the CBT approach as a treatment and also at one year follow-up. Good EAT scores were observed in 70% of our cases after the treatment and in 60% at follow-up. Further research should assess the effectiveness of therapeutic groups more intensively because of their economic advantages.

Skeletal maturation of wrist and hand ossification centers in normal Spanish boys and girls: a study using the Greulich-Pyle method

The skeletal maturation of the upper limb distal segment was studied in 239 Spanish boys and girls between birth and 14 years of age. The atlas of Greulich and Pyle, offering standards of skeletal development of white North American children, was used as reference. The results obtained show firstly that in absolute terms, the ossification process is earlier in girls than in boys. This difference is maximum between 5 and 11 years of age. The boys show a delay of around 3 months with respect to their North American opposites. The girls, in contrast, show a better fit to the corresponding (female) standard of the atlas. In general, the highest agreement between bone age and chronologic age is for the ossification centers of the distal epiphysis of the ulna and radius and for those of the metacarpal bones. At the level of the carpus, individual analysis of the ossification centers shows that the capitate and hamate bones in the girls evolve most in accord with chronologic age. At the other extreme, and in both sexes, the ossification centers of the trapezium and trapezoid bones are statistically furthest from chronologic age.