Predictive role of evoked potential examinations in patients with clinically isolated optic neuritis in light of the revised McDonald criteria

VEP Score of a Left Eye Had Predictive Values for Achieving NEDA-3 over Ten Years in Patients with Multiple Sclerosis

BACKGROUND

The aim of this study was to determine the predictive value of visual evoked potentials (VEPs) in patients with relapsing-remitting multiple sclerosis (RRMS) in achieving no evidence of disease activity-3 (NEDA-3) during up to 10 years of first-line immunomodulatory therapy and to determine whether the lateralization of optic nerve damage may have prognostic significance concerning clinical disability and response to therapy.

METHODS

In a retrospective study, a total of 83 patients (53 female and 30 male) with RRMS participated. The average age of patients was 38.31 ± 9.01. Patients were followed for 2, 5 or 10 years. VEPs were measured at the beginning of the follow-up and after many years of monitoring. Data on optical neuritis (ON) were obtained from medical history. The degree of disability was estimated by the neurologist (independent rater), and magnetic resonance (MR) imaging of the endocranium was performed with gadolinium contrasts. Achieving NEDA-3 is considered a favorable outcome of treatments.

RESULTS

Among those treated, 19 (22.9%) reached NEDA-3, while 64 (77.1%) did not reach NEDA-3. The values of the evoked potential (EP) score for the left eye (r = 0.008, odds ratio (OR) = 0.344 (0.156-0.757)) and latency for the left eye (r = 0.042, OR = 0.966 (0.934-0.999)) at the onset of disease were predictive factors for achieving NEDA-3.

CONCLUSIONS

A normal VEP at the beginning of RRMS increases the chance of reaching NEDA-3 by about six times.

Multimodal Evoked Potentials as Potential Biomarkers of Disease Activity in Patients With Clinically Isolated Syndrome

Objective

There is an ongoing search for markers useful in monitoring and predicting disease activity at the early stage of multiple sclerosis (MS). The goals of this study were to prospectively evaluate the changes in parameters of multimodal evoked potentials (EP) and cognition within a 3-year follow-up period in patients with clinically isolated syndrome (CIS), and to assess the prognostic value of baseline findings with regard to the disease outcomes.

Methods

In 29 patients (20 women, nine men, mean age 31.1) multimodal (visual, brainstem auditory, somatosensory, event-related) EP and neuropsychological tests (NT) were performed at baseline (T0) and after 1 (T1) and 3 (T3) years. Their results were compared longitudinally between baseline, T1, and T3. Baseline results confirmed conversion of CIS into multiple sclerosis (MS) and disability level at T1 and T3 using multiple comparisons and a logistic regression model.

Results

Apart from mean N13/P16 SEP (somatosensory evoked potentials) amplitude (lower at T1 and T3 than at baseline (T0 1.02 ± 0.37 μV, T1 0.90 ± 0.26 μV, T3 0.74 ± 0.32 μV, p < 0.05 for both comparisons), no significant changes of EP or NT parameters were found in longitudinal assessment. Baseline P300 Pz latency was longer for the patients with MS than for those with CIS at T1 (352.69 vs. 325.56 ms). No predictive value was shown for any of the analyzed baseline variables with regard to conversion from CIS into MS.

Significance

Baseline ERP abnormalities were associated with their short-term conversion into MS. ERP are worth considering in multimodal EP evaluation at the early stage of MS.

Optical coherence tomography and electrophysiology of retinal and visual pathways in Wilson's disease

We evaluated correlations between positive findings of changes on brain magnetic resonance imaging (MRI) and selected morphological and electrophysiological parameters of the retinal and visual systems in Wilson's disease. Fifty-eight Wilson's disease symptomatic patients were divided according to whether they displayed brain changes on MRI (positive, n = 39; negative, n = 19). All participants and healthy control group (n = 30), underwent retinal optical coherence tomography to assess the thickness of macula and the total retinal nerve fiber layer. Visual evoked potentials were measured and electroretinography was performed. Macular and retinal nerve fibers were thinner in participants with changes on MRI than in participants without changes. Electrophysiological parameters were markedly different in the MRI positive group compared with the negative group and 30 healthy controls; however, some abnormalities were evident in cases without visible brain pathology. Morphological and electrophysiological changes of retinal and visual pathways are associated with MRI visualized brain injury in Wilson's disease and may be useful for detecting the degree of neurodegeneration.

Update on clinically isolated syndrome

Optic neuritis, myelitis and brainstem syndrome accompanied by a symptomatic MRI T2 or FLAIR hyperintensity and T1 hypointensity are highly suggestive of multiple sclerosis (MS) in young adults. They are called "clinically isolated syndrome" (CIS) and correspond to the typical first multiple sclerosis (MS) episode, especially when associated with other asymptomatic demyelinating lesions, without clinical, radiological and immunological sign of differential diagnosis. After a CIS, the delay of apparition of a relapse, which corresponds to the conversion to clinically definite MS (CDMS), varies from several months to more than 10 years (10-15% of cases, generally called benign RRMS). This delay is generally associated with the number and location of demyelinating lesions of the brain and spinal cord and the results of CSF analysis. Several studies comparing different MRI criteria for dissemination in space and dissemination in time of demyelinating lesions, two hallmarks of MS, provided enough substantial data to update diagnostic criteria for MS after a CIS. In the last revision of the McDonald's criteria in 2010, diagnostic criteria were simplified and now the diagnosis can be made by a single initial scan that proves the presence of active asymptomatic lesions (with gadolinium enhancement) and of unenhanced lesions. However, time to conversion remains highly unpredictable for a given patient and CIS can remain isolated, especially for idiopathic unilateral optic neuritis or myelitis. Univariate analyses of clinical, radiological, biological or electrophysiological characteristics of CIS patients in small series identified numerous risk factors of rapid conversion to MS. However, large series of CIS patients analyzing several characteristics of CIS patients and the influence of disease modifying therapies brought important information about the risk of CDMS or RRMS over up to 20 years of follow-up. They confirmed the importance of the initial MRI pattern of demyelinating lesions and of CSF oligoclonal bands. Available treatments of MS (immunomodulators or immunosuppressants) have also shown unequivocal efficacy to slow the conversion to RRMS after a CIS, but they could be unnecessary for patients with benign RRMS. Beyond diagnostic criteria, knowledge of established and potential risk factors of conversion to MS and of disability progression is essential for CIS patients' follow-up and initiation of disease modifying therapies.

Clinical neurophysiology of multiple sclerosis

The availability of new treatments able to modify the natural course of multiple sclerosis (MS) has generated interest in paraclinical measures to monitor disease evolution. Among these, neurophysiologic measures, mainly evoked potentials (EPs), are used in the functional assessment of central sensorimotor and cognitive networks affected by MS. EP abnormalities may reveal subclinical lesions, objectivate the involvement of sensory and motor pathways in the presence of vague disturbances, and provide indications of the demyelinating nature of the disease process. However, their diagnostic value is much lower than that of magnetic resonance imaging, and is more sensitive to brain and cervical spinal cord lesions. The application of EPs in assessing disease severity and monitoring the evolution of nervous damage is more promising, thanks to their good correlation with disability in cross-sectional and longitudinal studies, and potential use as paraclinical endpoints in clinical trials. Recent evidence indicates that EPs performed early in the disease may help to predict a worse future progression in the long term. If confirmed, these data suggest the possible usefulness of EPs in the early identification of patients who are more likely to develop future disability, thus requiring more frequent monitoring or being potential candidates for more aggressive disease-modifying treatments.

The neuro-ophthalmology of multiple sclerosis

Multiple sclerosis (MS) is a disease marked by focal demyelinating inflammatory plaques throughout the CNS. Neuro-ophthalmologic sequelae are common in MS and may arise from the disease itself or from treatment of the disease. Both afferent and efferent functions may be affected. Despite much progress, our understanding of the pathophysiology of MS, and the efficacy of our available treatments, remain inadequate. Here, we review the chief neuro-ophthalmologic abnormalities associated with MS and discuss the emerging diagnostic and therapeutic advances that are likely to further our understanding of MS and its treatment.

Predictive value of motor evoked potentials in clinically isolated syndrome

OBJECTIVES

To assess the predictive role of several measures obtained by transcranial magnetic stimulation (TMS) in patients with clinically isolated syndrome (CIS) for the risk of conversion to multiple sclerosis (MS) during the first 2 years.

MATERIALS AND METHODS

We investigated 34 patients with CIS. After 2 years of follow-up and classification into two groups according to MS diagnosis, initial TMS measures were compared to determine their predictive values for conversion to MS.

RESULTS

Sixteen patients developed MS. We observed a significant difference between the two groups for contralateral silent period and no significant difference for the central motor conduction time, amplitude ratio, motor threshold, ipsilateral silent period, and the transcallosal conduction time.

CONCLUSIONS

Contralateral silent period (SP) seems to be a valuable parameter to early distinguish patients who will develop MS or not. This result about SP during CIS has never been described until now. An increased contralateral silent period would predict a conversion to MS with a positive predictive value of 75%, but this result needs to be confirmed in larger groups.

Sudomotor dysfunction in patients with optic neuritis

OBJECTIVES

Optic neuritis (ON) is a frequent initial manifestation of multiple sclerosis (MS). Autonomic failure affecting the pupillary function is known to exist in ON patients, and patients with MS are known to have more widespread autonomic dysfunction. For example, sudomotor dysfunction is well known in MS. We carried out a study investigating sudomotor abnormalities in ON patients, and later followed these patients at risk of developing MS.

METHODS

Firstly, sudomotor function was measured by sympathetic skin responses (SSRs) in 13 ON patients and in 22 healthy controls. Secondly, thermoregulatory sweating was measured by an evaporimeter after a heating stimulus in 13 ON patients and in 14 healthy control subjects.

RESULTS

The SSR latencies to electrical stimuli in the ON patients were significantly prolonged in the upper and lower extremities (p = 0.013-0.002), indicating sudomotor dysfunction. No statistically significant thermoregulatory sweating dysfunction could be found in the ON patients compared to the controls. All ON patients underwent a follow-up (mean duration 12.5 years) during which eight ON patients (62%) converted to clinically definite MS. It seemed that SSRs had no value for identifying patients who later developed MS.

INTERPRETATION

Our results enlarge the knowledge of autonomic disorders in ON patients, showing that sudomotor function may also be involved.

Neurophysiological markers

After the advent of immunomodulatory treatment in Multiple Sclerosis and after several options for early treatment have become available, the early identification of patients non responder has become a very important issue. Therefore, methods are needed for the detection of disease activity and, particularly in more advanced phases of the disease, of disease progression. Neurophysiological methods, mainly evoked potentials (EPs), are widely used in the functional assessment of sensory and motor pathways. Their usefulness in the assessment of disease activity is limited by the fact that, although they can also reveal clinically silent lesions, EPs abnormalities are present only if their corresponding pathway is involved. With this respect, EPs have been extensively replaced by magnetic resonance imaging (MRI), with the exception of optic nerve in which the sensitivity of EPs and MRI is similar. Nevertheless, EPs can be useful for the assessment of disease progression, since their abnormalities have been demonstrated to be more strictly related to disability than MRI lesion burden. With this perspective, EPs can still be useful in the identification of non responder by providing the clinician with objective functional assessment of eloquent pathways in patients with ambiguous new symptoms, for the confirmation of a dubious relapse, and by providing a method for detecting worsening of nervous conduction for the confirmation of disease progression.