Visual snow syndrome, the spectrum of perceptual disorders, and migraine as a common risk factor: A narrative review

Visual Snow Syndrome is unstable: A longitudinal investigation of VSS symptoms in a Naïve population

OBJECTIVE

This study aimed to investigate the nature of subclinical Visual Snow Syndrome (VSS). We sought to develop a means of recruiting naïve participants with subclinical VSS symptoms to participate in research; and to understand whether subclinical VSS symptoms are stable across time. VSS is a recently characterised neurological condition, whose primary symptom is visual snow (dynamic noise in the visual field). There is evidence that VSS may be common in the general population and that it is unnoticed by many who experience it. To fully characterise VSS, it is important to understand whether (and how) subclinical VSS progresses to a clinical form.

METHODS

Here, we present two related studies: Study 1 develops and validates the Melbourne Visual Snow Questionnaire (MVSQ), a tool for screening the general population for VSS symptoms; and Study 2 investigates the stability of subclinical VSS. We developed the MVSQ based on the results of other recent work investigating undiagnosed cases of VSS, and a validated questionnaire designed to identify people with tinnitus for research participation. We then tested the MVSQ in a population with clinical VSS, including assessing face validity (i.e., the extent to which people with clinical VSS believed the questionnaire accurately captured their symptoms). In Study 2, we deployed the MVSQ in a naïve sample of 155 participants, who completed the MVSQ twice, 6 weeks apart.

RESULTS

The results of Study 1 indicated that the MVSQ was a viable method of recruiting people who experience VSS symptoms for research participation. It was deemed to have appropriate face validity and to pose little burden to those who completed it. In Study 2, VSS symptoms changed substantially across a 6-week period. Cohen's weighted kappa for diagnosis was 0.56, 95% CI [0.43, 0.69]. However, the impact of perceptual experiences was low and did not change over time, rank ICC = 0.71, 95% CI [0.59, 0.82].

INTERPRETATION

The MVSQ is appropriate for assessing perceptual experiences in the general population. Determining the exact time scale across which symptoms fluctuate is important for understanding both clinical and subclinical cases of VSS.

Migraine is a risk factor for pseudophakic positive dysphotopsia following monofocal lens implantation

OBJECTIVE

To identify neuroadaptation-related risk factors for persistent positive dysphotopsia (>6 months) following monofocal lens implantation.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients of an academic institution and a private practice in Saint Louis, Missouri. Inclusion criteria were adults with cataract extraction between January 2010 and April 2021 with monofocal intraocular lens implantation. Exclusion criteria included dementia, <20/40 acuity, visual pathway damage, visual field loss, and significant pathology causing photopsia.

METHODS

Participants were surveyed via telephone.

RESULTS

There were 385 participants (385 eyes), of whom 66 had persistent dysphotopsia (58 positive), 298 had none, and 21 had nonpersistent dysphotopsia. Among the 58 who had positive persistent dysphotopsia, mean Pseudophakic Dysphotopsia Questionnaire 6 (PDQ-6) score was 14.11 (SD, 8.46). There were no significant differences in sex or race. Migraine prevalence was greater among those with dysphotopsia (21.2%) than among those without (11.4%; p = 0.054). History of migraine was associated with an increase in PDQ-6 score of 2.76 points (p = 0.006). Six people in each group had Visual Aura Rating Scale (VARS) scores greater than zero. Mean VARS score was 0.48 for those with dysphotopsia and 0.14 for those without (p = 0.03). History of migraine or increased VARS score, younger age, and female sex were associated with lower satisfaction.

CONCLUSION

History of migraine was associated with increased dysphotopsia severity and decreased patient satisfaction. Although further study with a larger sample size is warranted, these preliminary results highlight the potential of simple questions to individualize lens choice, reduce the risk of dysphotopsia, and improve patient satisfaction.

Visual snow syndrome in patients with migraine: widening the clinical spectrum of the syndrome with permanent and episodic manifestations

PURPOSE

Migraine is the comorbidity most frequently associated with visual snow syndrome (VSS), but the prevalence of VSS in patients with migraine (PWM) has not been studied. Our objective was to evaluate the frequency of VSS in PWM and to analyze if symptoms of VSS happened in a permanent or episodic manner (eVSS) in this population.

METHODS

We conducted a multicenter observational cross-sectional study. PWM was recruited from headache units, and a survey about the presence of visual snow symptoms was administered. The frequency and characteristics of patients that met current VSS criteria were analyzed. Demographic and clinical features of patients with VSS, eVSS, and PWM with no visual snow were compared.

RESULTS

A total of 217 PWM were included. Seventeen patients (7.8%) met the VSS criteria. VSS patients had visual aura more frequently (58.8% vs. 31%; p = 0.019) and a higher MIDAS score (96.6 vs. 47.7; p = 0.014). Fifty-eight PWM (26.7%) showed visual snow and associated features in an episodic way and were classified as eVSS. Patients with VSS showed a tendency towards a higher frequency of visual symptoms than patients with eVSS (p > 0.05). No statistically significant differences in sociodemographic characteristics and comorbid conditions were found between VSS and eVSS.

CONCLUSION

The prevalence of VSS in PWM may be higher than that described for the general population. Some PWM may present similar visual symptoms to patients with VSS but in an episodic manner. Our study reinforces the observation that the clinical spectrum of visual snow is likely to be broader than previously described.

[Migraine and psychosomatic comorbidity]

As a common neurological disorder (10-15% of the population), migraine is associated with numerous comorbidities, particularly other pain syndromes, mental illnesses and functional disorders. These 'psychosomatic' comorbidities increase with migraine severity. Severely affected, comorbid patients also often have a poorer response to specific migraine therapy. Interestingly, migraine and the comorbidities mentioned have a number of common aetiological or facilitating factors, e.g. genetic factors, and show a higher incidence in women and in people with previous traumatic experiences, as well as (in the case of pain syndromes) signs of central sensitization. Another common feature is the association with current or chronic stress. We propose an extended diathesis-stress model that takes into account interrelated but individually different vulnerabilities and, depending on the stress experience, can depict both the occurrence of individual disorders (e.g. an isolated migraine) and the joint occurrence of migraine with other pain syndromes and other psychosomatic comorbidities. In summary, psychosomatic comorbidities should always be kept in mind in migraine therapy and, if necessary, treated early and multimodally.

Visual snow syndrome: recent advances in understanding the pathophysiology and potential treatment approaches

PURPOSE OF REVIEW

Visual snow syndrome (VSS) is a disorder characterized by persistent visual disturbances, including the visual snow phenomenon, palinopsia, heightened perception of entoptic phenomena, impaired night vision, and photophobia. The purpose of this review is to provide an update on recent findings over the past 18 months in VSS research and to summarize the current state of treatment approaches.

RECENT FINDINGS

Electrophysiological studies have revealed cortical hyperresponsivity in visual brain areas, imaging studies demonstrated microstructural and functional connectivity alterations in multiple cortical and thalamic regions and investigated glutamatergic and serotoninergic neurotransmission. These findings suggest that VSS might be a network disorder.Only few treatment studies are currently available demonstrating limited response to medication and even worsening or triggering of visual symptoms by certain antidepressants. Promising nonpharmacological treatments include mindfulness-based cognitive therapy, the use of chromatic filters, and research on visual noise adaption and neuro-optometric visual rehabilitation therapy (NORT). However, the level of evidence is still low and further research is needed including larger trials and involving objective measures of individual dysfunction.

SUMMARY

Although there has been recent progress, we still have not fully understood the nature of VSS. Further research is needed on a clinical and pathophysiological level to successfully treat the condition.

Subjective and objective responses to caloric stimulation help separate vestibular migraine from other vestibular disorders

BACKGROUND

Nystagmus generated during bithermal caloric test assesses the horizontal vestibulo-ocular-reflex. Any induced symptoms are considered unwanted side effects rather than diagnostic information.

AIM

We hypothesized that nystagmus slow-phase-velocity (SPV) and subjective symptoms during caloric testing would be higher in vestibular migraine (VM) patients compared with peripheral disorders such as Meniere's disease (MD) and non-vestibular dizziness (NVD).

METHODS

Consecutive patients (n = 1373, 60% female) referred for caloric testing were recruited. During caloric irrigations, patients scored their subjective sensations. We assessed objective-measures, subjective vertigo (SVS), subjective nausea (SNS), and test completion status.

RESULTS

Nystagmus SPV for VM, MD (unaffected side), and NVD were 29 ± 12.8, 30 ± 15.4, and 28 ± 14.2 for warm irrigation and 24 ± 8.9, 22 ± 10.0, and 25 ± 12.8 for cold-irrigation. The mean SVS were 2.5 ± 1.1, 1.5 ± 1.33, and 1.5 ± 1.42 for warm irrigation and 2.2 ± 1.1, 1.1 ± 1.19, and 1.1 ± 1.16 for cold-irrigation. Age was significantly correlated with SVS and SNS, (p < 0.001) for both. The SVS and SNS were significantly higher in VM compared with non-VM groups (p < 0.001), and there was no difference in nystagmus SPV. VM patients SVS was significantly different to the SVS of migraineurs in the other diagnostic groups (p < 0.001). Testing was incomplete for 34.4% of VM and 3.2% of MD patients. To separate VM from MD, we computed a composite value representing the caloric data, with 83% sensitivity and 71% specificity. Application of machine learning to these metrics plus patient demographics yielded better separation (96% sensitivity and 85% specificity).

CONCLUSION

Perceptual differences between VM and non-VM patients during caloric stimulation indicate that subjective ratings during caloric testing are meaningful measures. Combining objective and subjective measures could provide optimal separation of VM from MD.

Elucidating the Visual Snow Spectrum: A Latent Class Analysis Study

Objective

People with visual snow syndrome (VSS) experience a range of perceptual phenomena, in addition to visual snow (VS; flickering pinpricks of light throughout the visual field). We investigated the patterns of perceptual phenomena associated with VSS in a large sample of people without prior knowledge of VSS or its associated symptoms. Methods and Measures. Two thousand participants completed a screening questionnaire assessing the frequency and severity of perceptual phenomena associated with VSS. We used latent class analysis (LCA), a clustering technique which identifies qualitatively different subgroups within a given population, to investigate whether the presence (or absence) of VS impacted class structure.

Results

Of 1,846 participants included for analysis, 41.92% experienced VS some of the time, including 4.49% who had VSS without prior knowledge. The mean number of perceptual phenomena experienced was 2.03. Optimal four-class LCA solutions did not substantially differ whether VS was included in the model; instead, classes differed in the frequency and total number of symptoms experienced. Discussion. Our results suggest that the perceptual phenomena associated with VSS are likely to be common in the general population and do not necessarily indicate an underlying pathology. We also showed that visual snow itself does not explain the presence of other perceptual phenomena.

The World Health Organization Intersectoral Global Action Plan on Epilepsy and Other Neurological Disorders and the headache revolution: from headache burden to a global action plan for headache disorders

The World Health Organization (WHO) Intersectoral Global Action Plan on Epilepsy and Other Neurological Disorders was developed by WHO to address the worldwide challenges and gaps in provision of care and services for people with epilepsy and other neurological disorders and to ensure a comprehensive, coordinated response across sectors to the burden of neurologic diseases and to promote brain health across life-course. Headache disorders constitute the second most burdensome of all neurological diseases after stroke, but the first if young and midlife adults are taken into account. Despite the availability of a range of treatments, disability associated with headache disorders, and with migraine, remains very high. In addition, there are inequalities between high-income and low and middle income countries in access to medical care. In line with several brain health initiatives following the WHOiGAP resolution, herein we tailor the main pillars of the action plan to headache disorders: (1) raising policy prioritization and strengthen governance; (2) providing effective, timely and responsive diagnosis, treatment and care; (3) implementing strategies for promotion and prevention; (4) fostering research and innovation and strengthen information systems. Specific targets for future policy actions are proposed. The Global Action Plan triggered a revolution in neurology, not only by increasing public awareness of brain disorders and brain health but also by boosting the number of neurologists in training, raising research funding and making neurology a public health priority for policy makers. Reducing the burden of headache disorders will not only improve the quality of life and wellbeing of people with headache but also reduce the burden of neurological disorders increasing global brain health and, thus, global population health.

Visual snow syndrome and migraine: a review

Visual snow syndrome is a neurological condition characterized by ongoing prominent phenomena described consistently as tiny dots moving across the entire visual field, often associated with complex visual symptoms. These can take the form of afterimages, entoptic phenomena, nyctalopia and light sensitivity. Although some of these symptoms can be benign, they can nonetheless become significantly impactful for many who experience them, particularly in cases that have a sudden and abrupt start. As visual snow syndrome becomes increasingly recognized in clinical practice we begin to learn about its typical presentation and underlying pathophysiology. Treatment of visual snow, however, still proves quite challenging, and efforts need to be focused on unravelling the biological mechanisms of the syndrome. This endeavour has characterized the most recent research on visual snow, mostly involving neuroimaging, neurophysiological and neurobehavioral studies aimed at understanding its underlying neural signature. Another important aspect of the syndrome, which will likely prove critical in deepening our understanding of visual snow, is represented by the intricate biological and historical connexion with migraine. This narrative review focused on visual snow syndrome will explore its clinical, pathophysiological and treatment aspects in detail.

Effectiveness of Vestibular Rehabilitation in Improving Health Status and Balance in Patients with Fibromyalgia Syndrome: A Single-Blind Randomized Controlled Trial

BACKGROUND

Fibromyalgia Syndrome (FMS) is a highly prevalent health problem whose main symptom is widespread pain, although it presents as other manifestations, such as loss of balance, that seem to mainly affect visuo-vestibular information.

OBJECTIVE

to compare the effects of a Vestibular Rehabilitation (VR) program versus those of a Conventional Physical Exercise (CPE) program on the health status of patients with FMS.

METHODS

A single-blind randomized controlled trial was performed. Patients with FMS were randomly assigned to VR or CPE programs. The protocols were performed in 40 min group sessions, twice weekly, for 16 sessions. Perceived health status, static and dynamic balance, verticality perception, confidence in balance, sensitization and kinesiophobia were measured at baseline, post-treatment and at the three-month follow-up and analyzed using an intention-to-treat approach.

RESULTS

Forty-eight subjects were randomly assigned, of whom thirty-five completed the planned VR (n = 19) or CPE (n = 16) program. At the three-month follow-up, there were differences in physical health status measured with the SF-12 (mean = -4.36, SE = 1.88, p = 0.027), balance during walking (mean = 1.90, SE = 0.57, p = 0.002), the perception of verticality in degrees (mean = 3.61, SE = 1.51, p = 0.024) and the anteroposterior position of the center of pressure (mean = -7.88, SE = 2.80, p = 0.009), as well as a decrease in the number of falls (mean = 0.98, SE = 0.44, p = 0.033), favoring the VR group.

CONCLUSIONS

Vestibular Rehabilitation can be as beneficial as conventional exercise in improving the state of health in patients with Fibromyalgia Syndrome, providing additional improvements in physical health status, body balance, the perception of verticality and the number of falls.

Visual Disturbances Spectrum in Pediatric Migraine

Migraine is a complex neurological disorder with partially unknown pathophysiological mechanisms. The prevalence in childhood ranges from 7.7% to 17.8%, thus representing the most frequent primary headache. In half of the cases, migraine is accompanied or preceded by various neurological disturbances, among which the visual aura is the best known. In literature, other conditions, such as Alice in Wonderland Syndrome and Visual Snow syndrome, are characterized by visual manifestations and are often associated with migraine. The aim of this narrative review is to describe the spectrum of visual disturbances in pediatric migraine and their pathophysiological mechanisms.

Differential Diagnosis of Visual Phenomena Associated with Migraine: Spotlight on Aura and Visual Snow Syndrome

Migraine is a severe and common primary headache disorder, characterized by pain as well as a plethora of non-painful symptoms. Among these, visual phenomena have long been known to be associated with migraine, to the point where they can constitute a hallmark of the disease itself. In this review we focus on two key visual disorders that are directly or indirectly connected to migraine: visual aura and visual snow syndrome (VSS). Visual aura is characterized by the transient presence of positive and negative visual symptoms, before, during or outside of a migraine attack. VSS is a novel stand-alone phenomenon which has been shown to be comorbid with migraine. We discuss key clinical features of the two disorders, including pathophysiological mechanisms, their differential diagnoses and best treatment practices. Our aim is to provide an aid for clinicians and researchers in recognizing these common visual phenomena, which can even appear simultaneously in patients with an underlying migraine biology.

Migraine in the context of chronic primary pain, chronic overlapping pain disorders, and functional somatic disorders: A narrative review

OBJECTIVE

To contextualize migraine as the most common primary headache disorder in relation to other chronic primary pain and non-pain functional somatic and mental conditions.

BACKGROUND

Migraine is increasingly understood as a sensory processing disorder within a broader spectrum of symptom disorders. This has implications for diagnosis and treatment.

METHOD

Narrative review based on a search of the literature of the last 15 years on the overlap of migraine with other symptom disorders.

RESULTS

Migraine as the prototypical primary headache disorder not only comprises many non-headache symptoms in itself, it also shows high comorbidity with other chronic pain and non-pain conditions (e.g., fibromyalgia syndrome, irritable bowel syndrome, functional non-epileptic seizures, depression, anxiety, and posttraumatic stress disorder). Such "symptom disorders" share several etiological factors (e.g., female preponderance, psychological vulnerability) and psychophysiological mechanisms (e.g., altered sensory processing, pain expectancy). These facts are acknowledged by several recent integrative conceptualizations such as chronic primary pain, chronic overlapping pain conditions, or functional somatic disorders. Accordingly, migraine management increasingly addresses the total symptom burden and individual contributors to symptom experience, and thus incorporates centrally acting pharmacological and non-pharmacological, that is, psychological and behavioral, treatment approaches.

CONCLUSIONS

Migraine and also other primary headache disorders should be seen as particular phenotypes within a broader spectrum of symptom perception and processing disorders that require integrative diagnostics and treatment. A harmonization of classifications and better interdisciplinary collaboration are desirable.

Prevalence and risk factors of migraine headache among university students: A cross-sectional study in Lebanon

Background Migraine constitutes a major public health concern since it negatively affects both the quality of life and the productivity of patients. Migraine among students can cause impaired academic performance and limit their daily activities. Objective This study aims to assess the prevalence of migraine among university students using the ID Migraine screening tool and to evaluate risk factors associated with migraine. Methods A cross-sectional study was performed over a period of six months targeting 1144 university students recruited from the different faculties. Results Migraine was suggested in 35.8% of subjects based on ID-Migraine. Migraine prevalence was significantly higher among women (42% versus 23.3% of men). After adjusting for covariates, women, daily coffee consumption, having unorganized meals, eating fast food and fasting were the main predictors of migraine.  Almost 41% of migraine students had a family history of migraine and only 26.7% sought medical help. Interestingly, most of the migraine students (84.8%) took headache medications without referring them to their doctor. Conclusion Recognizing headache risk factors among migraine students and adopting lifestyle changes accordingly can be an effective strategy to prevent the chronification of the attacks, decrease headache frequency and improve patients’ quality of life.

Natural course of visual snow syndrome: a long-term follow-up study

Visual snow syndrome is characterized by a continuous visual disturbance resembling a badly tuned analogue television and additional visual and non-visual symptoms causing significant disability. The natural course of visual snow syndrome has not hitherto been studied. In this prospective longitudinal study, 78 patients with the diagnosis of visual snow syndrome made in 2011 were re-contacted in 2019 to assess symptom evolution using a semi-structured questionnaire. Forty patients (51% of 78) were interviewed after 84 ± 5 months (mean ± SD). In all patients, symptoms had persisted. Visual snow itself was less frequently rated as the most disturbing symptom (72 versus 42%, P = 0.007), whereas a higher proportion of patients suffered primarily from entopic phenomena (2 versus 17%, P = 0.024). New treatment was commenced in 14 (35%) patients, of whom in seven, visual snow syndrome was ameliorated somewhat. Three (7%) experienced new visual migraine aura without headache, and one (2%) had new migraine headache. There were no differences in the levels of anxiety and depression measured by the Patient Health Questionnaire 8 and the Generalized Anxiety Disorder Scale 7. Thirty-eight patients (49%) were lost to follow-up. In visual snow syndrome, symptoms can persist over 8 years without spontaneous resolution, although visual snow itself might become less bothersome.

Vestibular Disability/Handicap in Fibromyalgia: A Questionnaire Study

Fibromyalgia (FM) is a poorly understood, central pain processing disorder characterized by a broad range of symptoms, such as chronic pain, sleep disruption, chronic fatigue, and psychosomatic symptoms. In addition, recent studies have shown that FM patients also experience dizziness. We aimed to establish a prevalence rate of vestibular symptoms in a population of FM patients through a battery of questionnaires investigating socio-demographic, clinical and psychological characteristics, combined with the Dizziness Handicap Inventory (DHI) and the Situational Vertigo Questionnaire (SVQ). A total of 277 respondents, officially diagnosed with FM, completed the full study, while 80 controls were also included for DHI and SVQ questionnaires. We found that FM participants were significantly affected by vestibular symptoms, which correlated with FM-associated pain and non-pain symptoms. The dizziness reported by FM participants showed peculiar features suggesting an FM-intrinsic mechanism of vestibular dysfunction, possibly linked to migraine and dysautonomia conditions. Correlations between dizziness and depressive mood (or neuroticism), revealed an impact of dizziness on psychological status, leading to depressive reactions and interpersonal difficulties, and possibly involving a noxious, self-sustained stress condition. In conclusion, data showed a manifesting dizziness condition in FM patients that warrants careful clinical attention due to its possible inherent role in the syndrome.

Persistent Postural-Perceptual Dizziness: Precipitating Conditions, Co-morbidities and Treatment With Cognitive Behavioral Therapy

Persistent postural perceptual dizziness (PPPD) is a common chronic vestibular disorder characterized by persistent vestibular symptoms, including postural instability and non-spinning vertigo, which is aggravated by motion, upright posture and moving or complex visual stimuli. In our review of 198 cases seen over a 5 year period, we have confirmed a number of common precipitating conditions for PPPD, including anxiety disorders and vestibular migraine. Vestibular abnormalities, including a unilateral loss of vestibular hypofunction and isolated otolith abnormalities, were found on investigation in just under half the cases. The use of cognitive behavioral therapy (CBT) as a treatment for PPPD resulted in impressive reductions in anxiety and measures of dizziness over follow up periods of up to 6 months.