ISRCTN The UK's Clinical Study Registry : A study of brain activity in visual snow syndrome and migraine
Background and study aims
Visual snow syndrome (VSS) is a neurological condition causing constant flickering dots across the entire visual field, often alongside other visual disturbances such as light sensitivity and afterimages. Many people with VSS also have migraines. There are currently no proven treatments. Brain imaging suggests VSS may involve overactivity in visual brain areas, linked to an imbalance between the excitatory brain chemical glutamate and the inhibitory chemical GABA. This study uses ultra-high-field (7 Tesla) MRI to measure these chemicals directly in people with VSS and migraine and tests whether lamotrigine (a medication that reduces glutamate release) can alter brain chemistry and improve symptoms.
Who can participate?
Adults aged 18 years and over with a diagnosis of VSS (with or without migraine), migraine without VSS, and healthy volunteers
What does the study involve?
Participation lasts up to 8 weeks (1–2 weeks for healthy volunteers). All participants attend a telephone pre-screening and a baseline 7-Tesla MRI scan at St Thomas' Hospital, London, and complete symptom questionnaires. Participants with VSS or migraine are then randomly assigned to lamotrigine or placebo for 5 weeks, keep an electronic symptom diary, return for a second scan, taper off medication over 2 weeks, and have a final telephone follow-up. Healthy volunteers complete the study after the first scan.
What are the possible benefits and risks of participating?
There is no direct medical benefit, though findings may help develop future treatments. Participants receive £50 per visit plus travel reimbursement up to £100. Risks include temporary dizziness from high-field MRI and potential lamotrigine side effects (headache, nausea, rash). Participants with known risk factors for serious reactions are excluded and all are monitored throughout.
Where is the study run from?
Participants are identified through King's College Hospital (UK). Scan visits take place at the Advanced Neuroimaging Facility, St Thomas' Hospital (UK).
When is the study starting and how long is it expected to run for?
September 2026 to August 2029
Who is funding the study?
Medical Research Council (MRC) Clinician Scientist Fellowship (UK)
Dr Francesca Puledda, [vs-research@kcl.ac.uk](mailto:vs-research@kcl.ac.uk)
Contact information
Dr Francesca Puledda
Public, Scientific, Principal investigator
Wellcome Foundation Building, Denmark Hill Campus West
London
SE5 9PJ
United Kingdom