Pattern electroretinography response in amblyopic adults

INTRODUCTION

Amblyopia is generally a unilateral disorder, defined by at least a difference of two lines of visual acuity between both eyes with the best-corrected visual acuity, a decrease in contrast sensitivity, and a decrease in stereopsis. Pattern electroretinogram (PERG) is a noninvasive technique that provides a retinal biopotential and is a highly sensitive indicator of changes in the macular area. Our aim was to evaluate if there are differences in the retinal response of an amblyopic eye compared with a normal eye (NE).

METHODS

We evaluated twenty-four adult volunteers, twelve amblyopes (mean 43.42 ± 12.72 years old), and twelve subjects with NE (mean 35.58 ± 12.85 years old). None of the subjects in the two groups had comorbidities. A complete optometric examination was performed including parameters such as visual acuity (VA) by far and near with ETDRS chart, eye alignment with cover test, and evaluation of retinal cells response with PERG.

RESULTS

The refractive error found in the NE group of subjects had a mean of - 0.95 ± 1.65D, while the amblyopic group showed a mean of - 2.03 ± 4.29D. The VA in amblyopic eyes had a mean of 0.38 ± 0.20 logMAR. Analyzing PERG data, we observed significant differences in the P50-N95 amplitudes of the amblyopic group compared with the NE group (p < 0.0001-amblyopic eye vs. NE; p = 0.039-fellow eye vs. NE).

DISCUSSION

These findings suggest that amblyopic patients may also present other impairments beyond the visual cortex. PERGs seem to be an important complementary examination in the diagnosis of other impairments in amblyopia.

Contribution of glial cells to the neuroprotective effects triggered by repetitive magnetic stimulation: a systematic review

Repetitive transcranial magnetic stimulation has been increasingly studied in different neurological diseases, and although most studies focus on its effects on neuronal cells, the contribution of non-neuronal cells to the improvement triggered by repetitive transcranial magnetic stimulation in these diseases has been increasingly suggested. To systematically review the effects of repetitive magnetic stimulation on non-neuronal cells two online databases, Web of Science and PubMed were searched for the effects of high-frequency-repetitive transcranial magnetic stimulation, low-frequency-repetitive transcranial magnetic stimulation, intermittent theta-burst stimulation, continuous theta-burst stimulation, or repetitive magnetic stimulation on non-neuronal cells in models of disease and in unlesioned animals or cells. A total of 52 studies were included. The protocol more frequently used was high-frequency-repetitive magnetic stimulation, and in models of disease, most studies report that high-frequency-repetitive magnetic stimulation led to a decrease in astrocyte and microglial reactivity, a decrease in the release of pro-inflammatory cytokines, and an increase of oligodendrocyte proliferation. The trend towards decreased microglial and astrocyte reactivity as well as increased oligodendrocyte proliferation occurred with intermittent theta-burst stimulation and continuous theta-burst stimulation. Few papers analyzed the low-frequency-repetitive transcranial magnetic stimulation protocol, and the parameters evaluated were restricted to the study of astrocyte reactivity and release of pro-inflammatory cytokines, reporting the absence of effects on these parameters. In what concerns the use of magnetic stimulation in unlesioned animals or cells, most articles on all four types of stimulation reported a lack of effects. It is also important to point out that the studies were developed mostly in male rodents, not evaluating possible differential effects of repetitive transcranial magnetic stimulation between sexes. This systematic review supports that through modulation of glial cells repetitive magnetic stimulation contributes to the neuroprotection or repair in various neurological disease models. However, it should be noted that there are still few articles focusing on the impact of repetitive magnetic stimulation on non-neuronal cells and most studies did not perform in-depth analyses of the effects, emphasizing the need for more studies in this field.

Longstanding effects of continuous theta burst stimulation in adult amblyopes

CLINICAL RELEVANCE

Continuous theta burst stimulation may be an important tool in the therapeutic management of amblyopia, when trying to correct the established neuronal imbalance. It is important to understand whether two sessions of continuous theta burst stimulation produce greater and longstanding changes in visual acuity and suppressive imbalance than one session of continuous theta burst stimulation.

BACKGROUND

We hypothesise that through the usage of continuous theta burst stimulation (cTBS) it is possible to change cortical excitability in a situation where visual impairment is present.

METHODS

We selected 22 adult amblyopes, 18 females and 4 males, with an age range of 20-59 years. They were randomised into two groups: group A with 10 amblyopes was submitted to one session of cTBS and group B with 12 amblyopes submitted to two sessions of cTBS. Visual acuity (VA) and suppressive imbalance (SI) were evaluated immediately before and after stimulation in both groups A and B. A follow-up was done in both groups.

RESULTS

For both group A and B, the VA improvements were significant after cTBS (p = 0.005 and p = 0.003, respectively). Regarding SI, both group A and B had significant improvements after cTBS (p = 0.03 and p = 0.005, respectively). Comparing groups, A and B no significant differences were found with regard to the results obtained both for VA (p = 0.72) and SI (p = 0.24). However, significant differences were found between group A and B with regard to the duration of stimulation effect for VA (p = 0.049) and SI (p = 0.03).

CONCLUSION

We conclude that two sessions of cTBS do not produce better results than one session of stimulation. However, it seems that two sessions of cTBS produce longstanding effects in VA and SI.

Can pattern electroretinography be a relevant diagnostic aid in amblyopia? - A systematic review

INTRODUCTION

Pattern Electroretinography (PERG) is a highly sensitive electrophysiological technique used as an indicator of changes in retinal macular area. Amblyopia seems to result from a cortical visual imbalance but changes at the retinal level may also be present. The purpose of this systematic review was to evaluate if there are any consistent changes described in the scientific literature in PERG responses of amblyopic eyes.

MATERIALS AND METHODS

Searches were conducted in PubMed and Embase databases, using the keywords "Electroretinography" and "Amblyopia", combined with MeSH or Emtree terms "Pattern Electroretinography", "amblyopia", "PERG" and "amblyopia". PERG P50-N95 amplitude and P50 latency were analysed as well as the methodology used.

RESULTS

A total of 234 articles were found and 6 articles were included for review. One of the articles reported results in adults and five of them in children. One of the articles in children reported no changes in either P50-N95 amplitude or P50 latency. All articles that described differences between the amblyopic eye and the normal eye found a decrease in P50-N95 amplitude and/or a delay in P50 latency.

CONCLUSIONS

This review shows promising findings for the use of PERG in amblyopia as an aid in the diagnostic protocol, since this technique may be able to detect an apparent functional impairment of the amblyopic eye.

Theta burst stimulation in adults with symmetric and asymmetric visual acuity

PURPOSE

Theta Burst Stimulation can influence adult neuro-visual response in imbalanced visual pathways, possibly by influencing cortical excitability. Our objective was to compare suppressive imbalance (SI) and visual acuity (VA) after applying repetitive Transcranial Magnetic Stimulation between groups of subjects with normal binocular vision, visual asymmetry, and amblyopia.

METHODS

Thirty-five volunteers between 19 and 51 years of age were split into three groups: 6 volunteers with asymmetric VA (group A); 19 amblyopes (group B); and 10 subjects with normal binocular vision (group C). VA and SI of all groups were evaluated before and after a single session of continuous Theta Burst Stimulation (cTBS) or placebo stimulation over the right occipital cortex.

RESULTS

In both groups A and B, we found a significant VA improvement in the non-dominant eye after cTBS (p = 0.04 and p = 0.01, respectively). In SI evaluation, group A and group B also revealed a significant improvement after the cTBS session (p = 0.03 and p = 0.01, respectively). Finally, in the group of volunteers with normal binocular vision and for placebo groups A and B, there were no significant differences in VA and SI after cTBS.

CONCLUSIONS

Amblyopic and visually asymmetric individuals improved VA and SI of the non-dominant eye after cTBS when compared to baseline and to placebo stimulation. These enhancements were not found in the group of volunteers with normal binocular vision. We can therefore reasonably assume that cTBS may interfere with the visual system of subjects that present some kind of asymmetry, possibly by improving neuronal imbalances.

Theta-Burst Stimulation Is Able to Impact Cognitive Processing: A P300 and Neuropsychological Test Study

INTRODUCTION

Theta-burst stimulation (TBS) is a safe non-invasive neurostimulation technique used to improve cognitive and neuropsychiatric impairments. Combined outcome evaluation using event-related potentials (ERPs) and neuropsychological tests may allow a more thorough assessment of TBS treatment efficacy; however, some mixed results have been found, and their use remains scarce. Our main objective was to evaluate whether a session of TBS to the left dorsolateral prefrontal cortex (DLPFC) can impact upon the performance of both neuropsychological and neurophysiological tests.

METHODS

This double-blind sham-controlled study involved 28 healthy adults, between 18 and 30 years. Volunteers were randomly allocated to receive excitatory (intermittent [iTBS]), inhibitory (continuous TBS [cTBS]) or sham stimulation on the left DLPFC. Subjects were evaluated using ERPs (auditory oddball paradigm P300) and neuropsychological tests (Trail making test [TMT] and Stroop test of words and colours [STWC]), using a pre-post stimulation protocol.

RESULTS

Inhibitory stimulation led to significantly delayed P300 peak latencies (p < 0.001), with no consistent change in N2P3 amplitudes. cTBS also significantly influenced the expected group performance in Stroop C and Stroop interference (p = 0.025) compared to the iTBS and sham groups. No significant results were found in TMT tests after TBS.

CONCLUSION

Our results suggest that P300 and specific Stroop colour and words test parameters can be similarly influenced by the same TBS protocol. This emphasizes the importance of mixed evaluation using neuropsychological and neurophysiological resources in research associated with the use of transcranial magnetic stimulation and cognition.

Theta burst stimulation over the prefrontal cortex: Effects on cerebral oximetry and cardiovascular measures in healthy humans

Theta Burst Stimulation (TBS) is a non-invasive neurophysiological technique, able to induce changes in synaptic activity. Research suggests that TBS may induce changes in cerebral oxygenation, cerebral blood flow, blood pressure and heart rate but there are conflicting results across studies. Thus, the objective of our sham-controlled study is to evaluate if TBS applied to the dorsolateral prefrontal cortex (DLPFC) of healthy volunteers produces changes in cerebral oximetry, heart rate and blood pressure. Forty-nine volunteers of both sexes were randomly allocated to one of five stimulation groups. Before and after real TBS or sham stimulation, blood pressure, heart rate, and cerebral oxygenation of the volunteers were measured. Cerebral oxygenation values were obtained with a near infra-red spectroscopy system. We found a significant reduction in left cortex oximetry after continuous TBS (cTBS) over the left DLPFC (p = 0.039) and a non-significant reduction in right cortex oximetry (p = 0.052). Right hemisphere inhibition (using cTBS) seemed to originate a significant reduction of 8 mmHg in systolic arterial pressure. No other changes were seen in oximetry, cardiac frequency and diastolic arterial pressure. In our group of normal subjects, cTBS applied to the left DLPFC was able to reduce oxygenation in the left cortex. Right hemisphere inhibition was associated with a significant reduction in systolic pressure.

Can theta burst stimulation safely influence auditory hearing thresholds in healthy young adults?

OBJECTIVE

This TBS sham-controlled study aimed to evaluate the effects of intermittent TBS (iTBS) and continuous TBS (cTBS) upon ipsilateral hearing thresholds after stimulation on the left auditory cortex.

METHODS

Sixty healthy adults, aged between 19 and 32 years (median of 23 years), were randomly distributed into three groups and underwent iTBS, cTBS or sham stimulation. Each double-blind experimental session comprised two pure tone audiometric evaluations per subject, before and after stimulation. To assess volunteer safety, a follow-up of at least 48 hours was implemented.

RESULTS

The iTBS group mean thresholds displayed a tendency to decrease after stimulation, predominantly in the 500 Hz-6000 Hz interval and group comparisons revealed significant differences between the iTBS and sham groups for 500 Hz (p = 0.041) and between the iTBS and cTBS groups for 4000 Hz (p = 0.038). Neither relevant side effects nor any significant hearing threshold impairment after active or sham stimulation were found.

CONCLUSIONS

A single stimulation session led to an effective neuromodulation of the auditory cortex, reflected in lower thresholds when using iTBS.

SIGNIFICANCE

These encouraging results with this safe noninvasive tool suggest that iTBS may have the potential to positively influence hearing thresholds.

Bilateral theta-burst magnetic stimulation influence on event-related brain potentials

Theta-burst stimulation (TBS) can be a non-invasive technique to modulate cognitive functions, with promising therapeutic potential, but with some contradictory results. Event related potentials are used as a marker of brain deterioration and can be used to evaluate TBS-related cognitive performance, but its use remains scant. This study aimed to study bilateral inhibitory and excitatory TBS effects upon neurocognitive performance of young healthy volunteers, using the auditory P300' results. Using a double-blind sham-controlled study, 51 healthy volunteers were randomly assigned to five different groups, two submitted to either excitatory (iTBS) or inhibitory (cTBS) stimulation over the left dorsolateral pre-frontal cortex (DLPFC), two other actively stimulated the right DLPFC and finally a sham stimulation group. An oddball based auditory P300 was performed just before a single session of iTBS, cTBS or sham stimulation and repeated immediately after. P300 mean latency comparison between the pre- and post-TBS stimulation stages revealed significantly faster post stimulation latencies only when iTBS was performed on the left hemisphere (p = 0.003). Right and left hemisphere cTBS significantly delayed P300 latency (right p = 0.026; left p = 0.000). Multiple comparisons for N200 showed slower latencies after iTBS over the right hemisphere. No significant difference was found in amplitude variation. TBS appears to effectively influence neural networking involved in P300 formation, but effects seem distinct for iTBS vs cTBS and for the right or the left hemisphere. P300 evoked potentials can be an effective and practical tool to evaluate transcranial magnetic stimulation related outcomes.

Translation and validation of Convergence Insufficiency Symptom Survey (CISS) to Portuguese - psychometric results

PURPOSE

Translate and adapt the Convergence Insuficiency Symptom Survey (CISS) questionnaire to the Portuguese language and culture and assess the psychometric properties of the translated questionnaire (CISSvp).

METHODS

The CISS questionnaire was adapted according to the methodology recommended by some authors. The process involved two translations and back-translations performed by independent evaluators, evaluation of these versions, preparation of a synthesis version and its pre-test. The final version (CISSvp) was applied in 70 patients (21.79 ± 2.42 years) students in higher education, and at two different times, by two observers, to assess its reliability.

RESULTS

The results showed good internal consistency of the CISSvp (Cronbach's alpha - α=0.893). The test re-test revealed an average of the differences between the first and second evaluation of 0.75 points (SD ± 3.53), which indicates a minimum bias between the two administrations. The interrater reliability assessed by intraclass correlation coefficient ranged from 0.880 to 0.952, revealing that the CISSvp represents an appropriate tool for measuring the visual discomfort associated with near vision tasks with a high level of reproducibility.

CONCLUSIONS

The CISS Portuguese version, showed good psychometric properties and has been sown to be applicable to the Portuguese population, to quantify the visual discomfort associated with near vision, in higher education students.

PLEKHG5 deficiency leads to an intermediate form of autosomal-recessive Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) comprises a clinically and genetically heterogeneous group of peripheral neuropathies characterized by progressive distal muscle weakness and atrophy, foot deformities and distal sensory loss. Following the analysis of two consanguineous families affected by a medium to late-onset recessive form of intermediate CMT, we identified overlapping regions of homozygosity on chromosome 1p36 with a combined maximum LOD score of 5.4. Molecular investigation of the genes from this region allowed identification of two homozygous mutations in PLEKHG5 that produce premature stop codons and are predicted to result in functional null alleles. Analysis of Plekhg5 in the mouse revealed that this gene is expressed in neurons and glial cells of the peripheral nervous system, and that knockout mice display reduced nerve conduction velocities that are comparable with those of affected individuals from both families. Interestingly, a homozygous PLEKHG5 missense mutation was previously reported in a recessive form of severe childhood onset lower motor neuron disease (LMND) leading to loss of the ability to walk and need for respiratory assistance. Together, these observations indicate that different mutations in PLEKHG5 lead to clinically diverse outcomes (intermediate CMT or LMND) affecting the function of neurons and glial cells.

Antibiotic susceptibility of Streptococcus pneumoniae isolates in Portugal. A multicenter study between 1989 and 1993

A total of 1,104 strains of Streptococcus pneumoniae were isolated from hospitalized patients (75.5%) and from colonization sites at the Public Health Institute (24.5%) during the last 4 years (1989-1993). Penicillin resistance (defined as MIC > or = 0.1 microgram/liter) was found to increase in time: 4.6% in 1989, 4.9% in 1990, 6.4% in 1991, 11.3% in 1992, and 17% in 1993. In 1992, 0.8% of the strains had penicillin MIC = 2 mg/liter. Increase in penicillin resistance was also evident among invasive strains [blood, cerebrospinal fluid (CSF), pleura]: 2/92 isolates from 1989-1992 (2.3%) were penicillin resistant as compared to 7/101 isolates from 1992 (6.9%). Multiresistance (resistance to three or more antibiotics) was 4.4% with penicillin, tetracycline, chloramphenicol being the predominant resistant phenotype at the end of 1992. In 1993, strains with resistance to penicillin plus chloramphenicol plus tetracycline increased further. Erythromycin resistance was usually associated with clindamycin resistance, but the majority of such strains remained susceptible to penicillin. Drift in the direction of increasing MIC values was also noted during this 3-year period among "susceptible" isolates: bacteria with MIC of 6-10 ng/ml representing the majority of isolates in 1990-1991 decreased and were replaced by cells with MIC of 20 ng/ml. The most frequent pneumococcal serotypes were 23, 19, 3, 6, 14, 9, and 8, with the frequency of type 9 increasing from 2.9% (in 1989) through 3.2% (1990) to 6.4% (1992). Among all antibiotic resistant strains, the prevalent serotypes were 23, 9, 14, and 6. The chromosomal backgrounds of resistant isolates tested by pulsed-field gel electrophoresis showed close resemblance to the background of the serotype 23F multiresistant clone first identified in Spain. The data suggest that the recent large increase in the frequency of penicillin-resistant pneumococci represents the import of this clone into Portugal during the early 1990s. The increased frequency of drug-resistant pneumococci highlights the importance of continued surveillance of these dangerous pathogens.

High-level tetracycline resistant Neisseria gonorrhoeae isolated in Portugal

The first high-level tetracycline resistance (MIC > or = 16 mg/l) isolates of Neisseria gonorrhoeae (TRNG) were reported in 1990 from patients attending a Sexual Transmitted Disease (STD) Center in Lisbon. The TRNG prevalence was 4% in 1991, 5.3% in 1992 and 10,8% in 1994, exploding to 52.2% in 1995. The tet M determinant was evaluated by PCR. The digests of PCRP using HpaII produced the restriction pattern 2 for all the strains, except one (pattern 3). 78.3% of the TRNG strains were beta-lactamase producers and the 4.5 MDa penicillinase plasmid was the dominant (83%), 90% and 93.3% of the TRNG strains belonged to the auxotype NR and to the serogroup IA, respectively. The IA-8/NR class represented 58.3% of the TRNG isolates, suggesting a clonal spreading.

["Salmonella typhi" resistant to chloramphenicol isolated north of Lisbon (author's transl)]

Thirteen strains of Salmonella typhi phage type A/Tan isolated in a typhoid endemic zone north to Lisbon (November 1977-June 1979) showed a low chloramphenicol resistance (MIC = 32 microgram/ml). None of these strains could transfer chloramphenicol resistance at 28 or 37 degrees C. Production of chloramphenicol-acetyl-transferase by these strains could not be demonstrated. No extrachromosomal DNA was detected by agarose-gel electrophoresis. A chromosomal resistance mechanism is postulated which could act on the permeation system.