Pattern and motion-related visual-evoked potentials in neuroborreliosis: follow-up study

Optic nerve involvement in patients with Lyme neuroborreliosis: an electrophysiological study

PURPOSE

The aim of this neurophysiological study was to retrospectively analyze visual evoked potentials (VEPs) acquired during an examination for diagnosing optic nerve involvement in patients with Lyme neuroborreliosis (LNB). Attention was focused on LNB patients with peripheral facial palsy (PFP) and optic nerve involvement.

METHODS

A total of 241 Czech patients were classified as having probable/definite LNB (193/48); of these, 57 were younger than 40 years, with a median age of 26.3 years, and 184 were older than 40 years, with a median age of 58.8 years. All patients underwent pattern-reversal (PVEP) and motion-onset (MVEP) VEP examinations.

RESULTS

Abnormal VEP results were observed in 150/241 patients and were noted more often in patients over 40 years (p = 0.008). Muscle/joint problems and paresthesia were observed to be significantly more common in patients older than 40 years (p = 0.002, p = 0.030), in contrast to headache and decreased visual acuity, which were seen more often in patients younger than 40 years (p = 0.001, p = 0.033). Peripheral facial palsy was diagnosed in 26/241 LNB patients. Among patients with PFP, VEP peak times above the laboratory limit was observed in 22 (84.6%) individuals. Monitoring of patients with PFP and pathological VEP showed that the adjustment of visual system function occurred in half of the patients in one to more years, in contrast to faster recovery from peripheral facial palsy within months in most patients.

CONCLUSION

In LNB patients, VEP helps to increase sensitivity of an early diagnostic process.

Effect of Dioptric Blur on Pattern-Reversal and Motion-Onset VEPs as Used in Clinical Research

Purpose

To describe the effect of dioptric blur on visual evoked potentials (VEPs) induced by motion onset (MO-VEPs).

Methods

The effect of dioptric blur up to 4 D on MO-VEPs was tested on 12 subjects using central, peripheral, and full-field stimulation with a low-contrast structure of concentric circles with spatial frequency <1 c/°. The results were compared to VEPs evoked by 15' and 60' checkerboard pattern-reversal (PR-VEPs). The relationship between peak time and interpeak amplitude of the dominant components was related to the level of dioptric blur using linear regression.

Results

The MO-VEPs did not show a significant peak prolongation (P > 0.28) or amplitude attenuation (P > 0.14) with the blur, whereas for the PR-VEPs we observed a significant decrease in amplitude (P < 0.001) and increase in peak time (P < 0.001) for both checkerboard sizes.

Conclusions

For MO-VEPs induced by radial motion of low contrast and low spatial frequency pattern, the change in retinal blur does not affect the peak time or the interpeak amplitude of the dominant N2 component.

Translational Relevance

The resistance to retinal blur that we demonstrated for MO-VEP provides a diagnostic opportunity to test the integrity of the visual system and reveal a retrobulbar impairment even in uncorrected refractive errors.

Pattern- and motion-related visual evoked potentials in HIV-infected adults

PURPOSE

The goal of the current study was to explore visual function in virally suppressed HIV patients undergoing combined antiretroviral therapy (cART) by using pattern-reversal and motion-onset visual evoked potentials (VEPs).

METHODS

The pattern-reversal and motion-onset VEPs were recorded in 20 adult HIV+ patients with a mean age of 38 years and CD4 cell counts ≥230 × 10⁶ cells/L of blood.

RESULTS

Nine out of 20 patients displayed VEP abnormalities. Pattern-reversal VEPs pathology was observed in 20% of subjects, and 45% HIV patients had impaired motion-onset VEPs. Five out of 16 neurologically asymptomatic HIV patients had prolonged motion-onset VEP latencies in both eyes. Four neurologically symptomatic patients displayed simultaneously abnormal motion-onset and pattern-reversal VEP latencies: monocular involvement was observed in two patients with Lyme and cytomegalovirus unilateral optic neuritis. Binocular involvement was noted in two patients with cognitive deficits. Correlation analysis between disease duration, CD4 cell count, HIV copies in plasma, MoCA and electrophysiological parameters did not show any significant relationships.

CONCLUSIONS

The functional changes of the visual system in neurologically asymptomatic virally suppressed HIV patients displayed higher motion-onset VEP sensitivity than in standard pattern-reversal VEP examinations. This promising marker, however, has no significant association with clinical conditions. Further exploration is warranted.

Visual electrophysiology in the clinical evaluation of optic neuritis, chiasmal tumours, achiasmia, and ocular albinism: an overview

BACKGROUND AND METHODS

In routine clinical evaluation of optic neuritis and chiasmal tumours, pattern electroretinography and visual evoked potentials (VEPs) to pattern-reversal stimulation are useful examinations. Similarly, in achiasmia and ocular albinism, VEPs to flash and pattern-onset stimulation provide relevant information.

RESULTS

The role of visual electrophysiology in these diseases is to assess potential dysfunction of the visual pathway: (a) at the acute stage of optic neuritis, to determine the magnitude of conduction block of the optic nerve fibres; (b) at the clinical recovery stage of optic neuritis, to determine optic nerve conduction delay due to demyelination, and to follow possible remyelination; (c) at the recovery of optic neuritis when visual acuity does not normalise, to define loss of optic nerve fibres and retrograde degeneration of retinal ganglion cells; (d) in tumours at the chiasm, to detect abnormal conduction along the crossed and/or uncrossed fibres; and (e) in achiasmia or albinism, which are both congenital disorders associated with nystagmus, to detect achiasmia and absence of or reduced optic nerve fibre decussation at the chiasm, or to detect ocular albinism and excess of optic nerve fibre decussation at the chiasm. In optic neuritis, two recent examinations have been used to detect retrograde axonal degeneration: photopic negative response of the electroretinogram, to assess dysfunction of ganglion cell axons; and optic coherence tomography, to measure thinning of the retinal nerve fibre layer. In optic neuritis, multifocal VEPs provide a promising clinical examination, because this can show areas that are associated with normal or abnormal optic nerve fibre function.

CONCLUSIONS

Visual electrophysiology defines function of the visual pathway and is relevant: (1) in optic neuritis, when visual acuity does not recover well; (2) in tumours of the chiasm with normal visual fields, as in paediatric patients who cannot adequately perform perimetry; and (3) in children with congenital nystagmus and suspected achiasmia or ocular albinism.

Visual mismatch negativity in the dorsal stream is independent of concurrent visual task difficulty

The manipulation of attention can produce mismatch negativity-like components that are not necessarily connected to the unintentional sensory registration of the violation of probability-based regularity. For clinical purposes, attentional bias should be quantified because it can vary substantially among subjects and can decrease the specificity of the examination. This experiment targets the role of attention in the generation of visual mismatch negativity (vMMN). The visual regularity was generated by a sequence of two radial motions while subjects focused on visual tasks in the central part of the display. Attentional load was systematically varied and had three levels, no-load, easy, and difficult. Rare, deviant, and frequent standard motions were presented with a 10/60 ratio in oddball sequences. Data from 12 subjects was recorded from 64 channels and processed. vMMN was identified within the interval of 142-198 ms. The mean amplitude was evaluated during the aforementioned interval in the parietal and fronto-central regions. A general linear model for repeated measures was applied to the mean amplitude with a three-factor design and showed a significant difference [F (1, 11) = 17.40, p = 0.002] between standard and deviant stimuli and between regions [F (1, 11) = 8.40, p = 0.01]; however, no significant effect of the task [F (2, 22) = 1.26, p = 0.30] was observed. The unintentional detection of irregularity during the processing of the visual motion was independent of the attentional load associated with handling the central visual task. The experiment did not demonstrate an effect of attentional load manipulation on mismatch negativity (MMN) induced by the motion-sequence, which supports the clinical utility of this examination. However, used stimulation paradigm should be further optimized to generate mismatch negativity that is stable enough to be usable not only for group comparisons but also for a single subject assessment.