A comparison of electroneuronography with facial nerve latency testing for prognostic accuracy in patients with Bell's palsy

The purpose of this study was to evaluate the ability of electroneuronography (ENOG), also called evoked electromyography (EEMG), and facial nerve latency testing (FNLT) to assess the prognosis of facial nerve palsy, using the House-Brackmann facial nerve grading system as criterion. From 1988 to 1994 these tests were employed at the ORL Clinic of the University of Ioannina in 250 patients with idiopathic facial nerve palsy. The ENOG test results indicated that when the amplitude of the compound muscle action potentials ranged from 51% to 95% of the normal value, 97% of the patients achieved complete functional recovery (grade 1) within at least 2 months. When the muscle action potential decreased to a value below 51% of normal values, prognosis for recovery was considerably worse. FNLT test results indicated that as the latency time extended, the recovery grade of the facial nerve worsened. When latency time was within the normal range (group A patients), about 92% of patients had complete functional recovery. In contrast all patients having either a very extended latency time or unable to be monitored (groups C and D) demonstrated incomplete functional recoveries that ranged from grade 11 to grade VI. Comparing each test with the House-Brackmann facial nerve grading system, we ascertained that the percent accuracy for ENOG was 97.6%, and that for FNLT was 94.4%.     

Integration of human herpesvirus 6 in a Burkitt's lymphoma cell line

Human herpesvirus 6 (HHV-6) genome has been found in several human lymphoid malignancies, but configuration of the HHV-6 genome has not been well delineated. We established the HHV-6-positive, Epstein-Barr virus-negative Burkitt's lymphoma cell line Katata. In this study we investigated the status of the HHV-6 genome in Katata cells. Neither linear nor circular HHV-6 DNA was detected by Gardella gel analysis. The fluorescence in situ hybridization technique enabled us to directly visualize the integrated HHV-6 DNA at the single-cell level. Only one integrated site of viral DNA was detected in metaphase chromosomes and it was preferentially located at the long arm of chromosome 22 (22q13). Treatment of the cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or with calcium ionophore A23187 led to induction of the HHV-6 immediate-early gene as well as the late gene. Sodium n-butyrate also gave rise to expression of the HHV-6 genes. The TPA inducibility was synergistically enhanced when combined with A23187 or n-butyrate. Our study provides, for the first time, an in vitro model system of latent HHV-6 infection whose genome is integrated into host DNA of lymphoma cells.     

Auditory-evoked potentials in general anesthesia monitoring: baseline study of availability in relation to hearing function in awake status

Background:  It has been confirmed that middle latency auditory-evoked potentials are good indicators of the hypnotic level in patients undergoing general anesthesia. The focal point for the evocation of auditory-evoked potentials is the presence of a serviceable hearing function. The aim of the study was to evaluate the limit of hearing loss above which the test could not be applied.
Methods:  To determine the limit of applicability of the technique, 100 subjects were studied. Twenty of them were normally hearing and 80 were affected by sensorineural hearing loss of various degrees. Each subject was submitted to pure tone audiometry, to determine hearing threshold, and then, in awake status, to auditory-evoked potentials recording using acoustic stimuli of 85 dB HL.
Results:  All the 20 normally hearing subjects showed a reliable auditory-evoked potentials. Among the 80 subjects affected by hearing loss, only five had no potentials. These five subjects presented a pure tone audiometry threshold greater than 85 dB HL.
Conclusion:  The study demonstrated that middle latency auditory-evoked potentials recorded using an A-Line^® (software version 1.4) AEP monitor (Danmeter, Odense, Denmark) can be carried out even in presence of hearing loss if the pure tone threshold is less than 85 dB HL.     

Method for the deconvolution of auditory steady-state responses

The potential evoked by a ‘train’ of N equally spaced auditory clicks, with an inter-click period shorter than the duration of the response to an isolated click, is said to be a steady-state response (SSR). Extracting the individual responses evoked by the clicks of the train during steady state can be key to understanding of the neurophysiological mechanisms underlying SSR generation. In the literature, this task has been dealt with only under the (unwarranted) assumption that the response of the system does not vary during the presentation of the clicks, i.e. no neurophysiological adaptation is present. In this work, a new, non-parametric algorithm is proposed that, relaxing the time-invariance hypothesis, allows the extraction from the SSR of the N waveforms individually evoked by the N clicks of the train. The performance of the approach is evaluated on simulated SSRs and on real data recorded from the temporal cortex of awake rats. Results show that the method is able to detect and assess possible adaptation of the neurophysiological system in the generation of SSRs.     

Latent Human Papillomavirus infection is comparable in the larynx and trachea

Recurrent respiratory papillomas are benign airway tumors caused by Human Papillomaviruses (HPVs) types 6 and 11. The disease is characterized by multiple recurrences of papillomas following surgical removal, caused by activation of latent HPV DNA. Most patients have laryngeal disease, while only a small subset has tracheal involvement. We have asked whether the lower frequency of tracheal papillomas was due to reduced prevalence of latent/subclinical tracheal HPV infection or reduced likelihood of activation to clinically apparent disease. A total of 121 biopsies of clinically normal laryngeal and tracheal tissues from 61 patients with laryngeal papillomas were analyzed for HPV DNA by polymerase chain reaction, confirmed by Southern blot hybridization. Patients were followed for 3-18 years (mean = 5.5 +/- 4.4), with only one developing subsequent tracheal disease. There was no significant difference in prevalence of latent HPV DNA between larynx and trachea, analyzing either those patients with a single biopsy or those with more than one biopsy of larynx, trachea, or both. There was also no significant difference between tracheal latency with HPV 6 and HPV 11. We conclude that HPV infects tracheal mucosa and is maintained as a latent infection in the trachea as efficiently as in the larynx. Therefore, we propose that the low frequency of tracheal disease reflects a lower frequency of HPV activation, and postulate that cellular factors that differ between the stratified squamous epithelium of the larynx and the ciliated pseudo-stratified columnar epithelium of the trachea contribute to this difference.     

Studying long-term effect of phenytoin either alone or combined with ascorbic acid on the anesthetic effect of urethane in rats

Phenytoin is an anticonvulsant drug known to interact with many other drugs. Previous data suggest that chronic administration of phenytoin delays urethane-induced loss of righting reflex (LRR) and this phenomenon being potentiated by concomitant administration of ascorbic acid (ASC). Therefore, we examined how phenytoin at two different doses combined or not with ASC (fixed dose) interact with both the latency to, and the duration for urethane-induced LRR in experimental rats. The results showed that lower dose of phenytoin (60 mg/kg rat b.i.d.) has significantly shortened the duration of LRR while higher dose of the drug (120 mg/kg b.i.d.) has delayed the latency to LRR (cut-off period of 15 min). Furthermore, addition of ASC to any of the two doses of phenytoin gave results similar to that observed for latency to and duration of LRR when phenytoin was given alone at the higher dose (120 mg/kg b.i.d.). Our data suggest a resistant effect of chronic administration of phenytoin on latency to and/or duration of loss righting reflex induced by urethane in experimental animals. A dose-response relationship of phenytoin in this regard is expected and needs further investigations. The resistant effect of phenytoin on righting reflex has been augmented when ASC was chronically given in combination. This result supports a possible interaction between the two drugs and needs further investigations at both experimental and clinical levels.     

Fos expression after mating in noradrenergic cells of the A1 and A2 areas of the medulla is altered by adrenalectomy

In the female rat, the integrity of the ventral noradrenergic bundle (VNAB) is necessary to carry stimuli from the uterine cervix and vagina to brain areas involved in mating-induced pseudopregnancy. Because adrenal hormones are known to alter noradrenergic function, we examined whether adrenalectomy altered mating-induced Fos expression in the A1 and A2 noradrenergic cell groups that project through the VNAB. Ovariectomized females were adrenalectomized (ADX) or sham-operated (Sham) and, 2 weeks after surgery, were given oestrogen and progesterone and mated. They received 15 intromissions, five intromissions or 15 mounts-without-intromission (mounts-only) from a male. Two hours after mating, rats were perfused and brains were collected; controls were perfused after being taken directly from their home cage. After immunocytochemical staining, Fos-immunoreactive (Fos-IR) and dopamine-beta-hydroxylase-immunoreactive (DBH-IR) cells and the percentage of DBH cells that were labelled with Fos (% DBH/Fos) were counted. In the A1 area, Fos-IR and percentage DBH/Fos were not affected by adrenalectomy. Although an overall effect of mating treatment was found for both measures, no specific mating treatment increased labelled cells above home cage levels. In the caudal, middle and rostral A2, 15 intromissions induced a significant increase in Fos-IR in Sham females above all other groups and a higher percentage of DBH/Fos in the middle and rostral A2 areas. ADX females showed no rise in either Fos-IR or percentage DBH/Fos after 15 intromissions. However, in the middle and rostral A2, ADX females showed significantly increased Fos-IR and percentage DBH/Fos after mounts-only treatment above Sham mounts-only females and all other ADX groups. These results demonstrate that adrenal hormones suppress activation of A2 cells to mounts-only stimuli but contribute to A2 activation in response to intromissions from males. The latter effect may result from stress associated with receipt of vaginocervical stimulation during mating.     

Determining abnormal latencies of multifocal visual evoked potentials: a monocular analysis

Purpose: To describe a methodology for measuring abnormal timing of monocular multifocal visual evoked potentials (mfVEP). Methods: The mfVEPs from 100 individuals with normal visual fields and normal fundus exams were analyzed. The stimulus was a 60 sector, pattern-reversing dartboard display. For each of the 60 locations of the dartboard and each channel and each eye, a template was derived based upon the average of the responses from the 100 normal individuals. In deriving this template, care was taken to exclude those responses reversed in polarity as compared to the average response. The best array of responses for each individual was compared to these templates. The relative latency of each response was measured as the temporal shift producing the best cross-correlation value. Results: The 95% confidence interval (CI) decreased as the signal-to-noise ratio (SNR) of the mfVEP responses increased. For example, the 95% CI decreased from over 17ms to under 9 ms as the SNR increased. Grouping and summing the responses also lead to an increase in SNR and a decrease in CI. Because the number of points exceeding the CI is not randomly distributed among normal individuals, a cluster criterion (e.g. two or more contiguous points within a hemisphere exceeding a given confidence interval) can be helpful. For example, while 18% of the eyes had 5 or more points exceeding the 5% confidence interval, only 6.5% of the eyes had a cluster of 5 of these points. The correlation between relative latency and age was relatively low (r=0.46). Conclusion: For detecting abnormalities in the timing of monocular, mfVEP responses, a template method provides a reasonable approach. In devising a particular test for abnormal timing, the CI should be based upon the SNR of the response. In addition, grouping and summing responses to increase SNR or employing a cluster test may also prove useful.