Illusory Splitting as Visual Aura Symptom in Migraine

Abstract

Illusory splitting was illustrated as a visual migraine aura symptom in six of 562 Migraine Art pictures. In this type of illusion, objects or persons appear to be split, along fracture lines of varying form and orientation, into two or more parts that may be displaced and separated from each other. The illusion is strongly associated with the presence of elementary geometric hallucinations. Phenomenological similarities and differences of illusory splitting to the visual perceptual disturbances of fragmentation and mosaic illusion are discussed.

Illusory splitting, whereby an object or a person appears fractured, with the parts being displaced or separated from each other (1), has been reported as a rare visual aura symptom in migraine. Wilson (2) described a distorted vision with objects appearing as if ‘broken’. Rose & Gawel (3) published, in a set of illustrations of the visual symptoms of the migrainous visual aura, a picture that presented, under the name of ‘fragmentation of the visual image’, definite examples of illusory splitting along horizontal and oblique axes with lateral displacement of the parts. A case report of an adolescent girl with recurrent episodes of unconsciousness, probably due to basilar migraine, included the note that once she experienced ‘split vision’, followed by a severe pounding bilateral headache and vomiting (4). In an account of his personal migraine attacks, Creditor (5) noted that scintillating scotomas were frequently preceded by a ‘visual distortion in which the halves of people’s faces were vertically displaced in the midline in such a way that one eye appeared to be a centimetre or two lower than the other' (p. 1030). Splitting of a person's image along a vertical axis, with vertical displacement of the parts, was also recorded in one of Bruyn's (6) patients, who, some hours before her attack, ‘saw people as longitudinally cut into two (right and left) halves but subsequently joined after the left half had been caudally displaced over a distance of about 6 inches, so that the left half of the face was opposite to the right half of the neck, the left half of the neck opposite to the right half of the chest, etc.’ (p. 163). Queiroz et al. (7) also mentioned ‘fractured vision’ as a visual migraine aura symptom.

It is likely that the small number of communications about this symptom does not reflect its true prevalence in migraine. In this study, an assessment was made of the paintings and drawings produced by migraine sufferers as entries to the four national Migraine Art competitions (8, 9). This collection includes a sample of illustrations of illusory splitting which provides the material for a study of the phenomenological characteristics of the said illusion.

Methods

Four Migraine Art competitions, jointly sponsored by the Migraine Action Association (formerly the British Migraine Association) and Boehringer Ingelheim UK Ltd, produced approximately 900 pictures by artists, amateur and professional, who suffered from migraine (8, 9). A number of artists requested the return of their artworks after the appropriate judging had taken place, leaving 562 pictures for analysis.

Pictorial representations of illusory splitting were studied with respect to their relationship with visual field defects and visual hallucinations. Visual field defects were assessed with respect to uni- or bilaterality, form and extent. Visual hallucinations were scored according to the form dimensions described for the analysis of drug-induced visual imagery (10). These include the categories random, line, curve, web, lattice, tunnel, spiral, kaleidoscope and complex hallucinations.

All 562 Migraine Art pictures were examined by both authors and six (1.1%) were identified as illustrating illusory splitting. Of the six artists, three were female and three male, and all were over 16 years of age. Attempts were made to contact the six patients by letter in which they were asked to give a description of the migraine experiences represented in their picture, submitted to the Migraine Art competition some 10–17 years before. In all four patients who were traced, a diagnosis of migraine with aura could be made on the basis of their responses to a questionnaire (11) assessing the diagnostic criteria of the International Headache Society (IHS) for migraine (12).

Results

In three Migraine Art pictures, illusory splitting is represented as a visual illusion that occurs in isolated fashion, i.e. without being accompanied by other types of visual illusion. Figure 1 illustrates a dining room with the table set for a meal. Splitting occurs along multiple linear and arc-like fracture lines which pass through the ceiling, walls, window frame, floor covering and other diverse objects such as the electric light shade, the dining table, place settings and chairs. These fracture lines are bordered by fortification spectra and areas with some loss of colour perception. The artist writes: ‘When the visual disturbance first begins, there is a bright zigzag pattern which jumps with the movements of my eye. As my eyes travel around the room, different areas are lit up by the zigzag and appear fractured from the rest of the room, so that the overall impression of the room is a jumble of detached areas. While all this is happening, I am becoming aware of an increasing revolving catherine wheel just to the right of my head and nearly out of sight.’ In Fig. 2, the artist's mirror image is distorted by arc-like white lines that result in the displacement of the sufferer's spectacle frames. According to the artist, his visual disturbance ‘always started with fractured vision in the upper part of my sight. The visual disturbance was always round the top of my vision in brilliant pulsating zigzags.’Fig. 3 illustrates splitting of a human face, representing the mirror image of the artist's face, with displacement of the two halves along the vertical axis. The artist writes: ‘The picture is meant to show what I see, but the eyes are how I feel … The onset of an attack is always marked by zigzag lines that are very fluorescent. During an attack things seem distorted, people’s faces seem to be split, they are also blurred.' In three further Migraine Art pieces, splitting is depicted together with other visual illusions, including tilted vision, inverted vision and optic allesthesia, diplopia, and metamorphopsia (not illustrated).

Figure 1 Figure 2 Figure 3

In two of the six pictures, illusory splitting is allied with an incomplete loss of vision distributed over the total visual field (Figs 2 and 3). Two of the six pictures indicate a colour perception disturbance with some loss of colour vision (Fig. 1) or metachromatopsia (Fig. 3). In five of the six pictures, illusory splitting is associated with different types of visual hallucinations. According to the taxonomy of Siegel & Jarvik (10), these visual hallucinations can be assigned to the form dimensions random (two pictures), line (four pictures) and curve (three pictures). In two pictures, these elementary geometric hallucinations apparently constitute the fracture lines along which illusory splitting occurs (for an example see Fig. 2).

All four patients who had responded to the follow-up enquiry stated that they had experienced illusory splitting repeatedly, with a duration of a few minutes (range 2–10 min), and always followed by an attack of migraine headache.

Discussion

Since there exists only a limited number of case reports of illusory splitting both in migraine patients and in patients suffering from other neurological disorders, few attempts have been made to achieve a comprehensive description of the phenomenological features of this illusion. The most thorough study previously available was published by Hécaen & Albert (1), who recorded that the ‘illusion of splitting of an object into two parts may occur along a horizontal or vertical axis and may be accompanied by separation of the parts, such that they do not touch’ (p. 147). The present series of Migraine Art pictures expands this description. In illusory splitting, an object or a person appears to be split into two or more parts along one or more fracture lines of varying forms. The form of the fracture line may be linear (with a horizontal, vertical or oblique orientation) or curved. Illusory splitting may be accompanied by displacement, with shifts of the split parts along a linear fracture line, or by separation, which can occur with all forms of fracture lines. Illusory splitting is strongly associated with elementary visual hallucinations of varying form dimensions. These visual hallucinations seem to act, in some cases, as the fracture lines along which illusory splitting occurs. In some cases, illusory splitting is encountered together with other visual illusions, loss of vision or disturbances of colour perception.

Except for illusory splitting along the vertical meridian, the pathomechanisms of illusory splitting are unknown and may be heterogeneous for different varieties of the said illusion. Splitting of images along the vertical meridian can result, together with a bitemporal hemianopia, from a disturbance of the optic chiasm (13–15). Illusory splitting occurring along vertical or other axes has also been described in patients with lesions in the parietal lobe and neighbouring temporal and occipital regions. A patient with a left-sided parieto-temporo-occipital glioblastoma had the visual illusion of persons being cut vertically with displacement of the two halves (16). A patient with a right parietal glioma recorded that her son's head appeared split between the eyes and nose with the two parts separated horizontally (17). However, more observations providing clinico-anatomic correlations are needed to establish a clearer association between the said illusion and lesion localization.

Illusory splitting can be differentiated from the fragmentation of visual images (18) and from the geometrizating illusion (19) or mosaic illusion (20). Fragmentation was first described for eidetic images (18), but the same features can also be present in visual illusions and hallucinations (21). In the said forms of visual imagery, fragments of perceptual objects may occur that seem to be devoid of all connections, organization and meaning (21). The outlines of these isolated fragments may be similar to those of the split parts in illusory splitting, although they frequently are more irregularly delineated. In contrast to fragmentation, in illusory splitting all split parts or fragments remain visible, although displaced and separated. Rose & Gawel (3) have applied the term ‘fragmentation of the visual image’ to account for typical examples of illusory splitting occurring as a migraine aura symptom, but this use of terminology cannot be recommended. Geometrizating illusion (19) or mosaic illusion (20) denotes the fragmentation of the visual image into multiple geometric patterns of varying form dimensions, interlaced as in a mosaic. The forms of the mosaic pieces featuring in the mosaic illusion can be similar to those observed in fragmentation of images and the bordering lines of the mosaic pieces can be similar to those that occur in illusory splitting. Unlike fragmentation of images, in mosaic illusion the whole image of the perceptual object remains recognizable, being produced by the piecemeal gathering of the multiple fragments. In contrast to illusory splitting, mosaic illusion results in a much more complex fragmentation of the visual image, governed by the tendency towards geometrization of the fragments.