This section was produced in collaboration with C P Panayiotopoulos, Department of Clinical Neurophysiology and Epilepsies, St Thomas’ Hospital, London, UK.
Epileptic foci in the occipital lobe may generate a multitude of visual phenomena. Examples of patients' drawings can be found in the literature
[1,
2]
but static representations cannot reflect the dynamic aspects that are crucial for a confident diagnosis. The sheer variety of phenomena make an exhaustive simulation impossible. Instead, the display aims to capture a common sequence of events, using the most commonly reported elements, namely, semi-transparent multi-colored circles. Typically, the elements are initially moving around in the far periphery on the left or right side. The elements may gradually increase in number and move towards towards the visual field center. En route, the elements often gradually fade from view.
Click on the display to run a right-sided simulation, click again to stop. The cross-hair represents the line of sight.
Common variations on the theme include:
Primary contents:
other elementary shapes, e g, squares or stars
large numbers of dots, spots, or lights
Transitions:
apparent deformation or displacement of objects in the environment
persisting percepts of objects
colorful imaginary scenery
localized or complete loss of vision
Locations: hemifield or entire field
Durations: up to 3 minutes
Recurrences: several times a day
There is a vast number of possible permutations and sequences but the individual patient typically perceives one and the same, stereotypical scenario, often tightly clustered in time.
Visual symptoms may or may not be followed by non-visual symptoms and signs. These include
retro-orbital pain or headache
a sensation of forced eye movements
contraversion of the eyes
palpebral jerks or forced closure
impaired or lost conciousness
convulsions
Among the non-visual symptoms, headache is by far the most common one, occurring in approximately two-thirds of the patients.
Careful evaluation of the patient's history commonly suffices for a confident clinical diagnosis. It is important to use a neutral terminology. Uncritical application of descriptive terms like fortifications, scintillations, or teichopsias, may misdirect attention to migraine auras. Paying close attention to the evolution over time (duration, recurrence pattern) and any associated symptoms or signs is usually most helpful. Yet, differentiation sometimes may be difficult. There are close associations between occipital seizures and classical
migraine. Neither condition confers immunity against the other and the one may trigger the other. Even the most experienced clinicians sometimes must resort to a diagnosis of migralepsy.
New 2020: a refined version of the above display has been included with a host of other symptomimetic displays in a new dynamic visual library. The library has the format of an iPhone/iPad app named
Visual Disorder Atlas.
Epileptic foci in the occipital lobe may generate a multitude of visual phenomena. Examples of patients' drawings can be found in the literature
[1,
2]
but static representations cannot reflect the dynamic aspects that are crucial for a confident diagnosis. The sheer variety of phenomena make an exhaustive simulation impossible. Instead, the display aims to capture a common sequence of events, using the most commonly reported elements, namely, semi-transparent multi-colored circles. Typically, the elements are initially moving around in the far periphery on the left or right side. The elements may gradually increase in number and move towards towards the visual field center. En route, the elements often gradually fade from view.