J R Soc Med 2001;94:286-287
© 2001 Royal Society of Medicine
A diagnostic sign in migraine?
R N de Silva MD MRCP(UK)
Department of Neurology, Essex Centre for Neurology & Neurosurgery,
Oldchurch Hospital, Romford RM7 0BE, UK
 |
SUMMARY
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At the bedside it was noted that, after ocular fundoscopy, patients
with
migraine complained more often of an after-image than did
non-migraineurs.
This phenomenon was then investigated in consecutive
patients attending a
general neurology outpatient clinic.
The relative risk for the diagnosis of migraine in patients reporting an
after-image was 2.91 (95% confidence interval 1.96 to 4.34), and the
sensitivity, specificity and positive predictive value of this observation for
the diagnosis of migraine were 0.63, 0.75 and 0.55 respectively. After-images
were equally likely to be reported by migraineurs with and without aura, and
by patients with migraine equivalents.
The after-image phenomenon probably reflects the heightened sensitivity to
visual stimuli of patients with migraine. Although a diagnosis of migraine is
primarily established by the patient's history, the presence of an after-image
following ocular fundoscopy may support this diagnosis.
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INTRODUCTION
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Migraineurs frequently describe visual symptoms during the aura
phase or
while experiencing headache. These include photopsias,
scotomas, scintillating
scotomas, fortification spectra, blurred
vision and photophobia. Positive and
negative visual phenomena
can arise from migrainous disturbances of the retina
(producing
monocular symptoms), but are more commonly caused by occipital
lobe
dysfunction (producing bilateral abnormalities). Migraineurs
also seem
sensitive to various physical stimuli, including light,
noise, smell and
movement. Visual stimuli that trigger migraine
attacks include sunlight,
flickering or flashing lights and
striped patterns. During the routine
clinical examination of
neurological patients it was noted that patients who
had migraine
reported visual after-images following routine ocular fundoscopy
more
commonly than non-migraineurs. The current study was designed
to
determine the utility of this observation in establishing
a diagnosis of
migraine in an unselected clinic population.
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METHODS
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Consecutive new patients attending the general neurological
outpatient
clinic over six months completed a questionnaire
on visual symptoms after
fundoscopy. Patients were asked whether
fundoscopy had been performed, what if
anything had been noted
afterwards and how long any after-images had lasted.
The questionnaires
were issued and collected by clinic nurses, and the
contents
were not discussed during the consultation. Pupils were not
dilated
and the maculae were not examined specifically. Migraine
with and without aura
and migraine equivalents were diagnosed
by application of International
Headache Society
criteria
1.
Other
diagnoses were established on clinical grounds.
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RESULTS
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A total of 263 patients were seen. No patient reported insufficient
visual
acuity to perceive light, and the pupillary light responses
were normal in all
cases. Fundoscopy was not done in 41 patients,
and 2 were unable to complete
the questionnaire (severe dementia
and severe learning disability). The
results are in
Table 1.
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Table 1. Numbers of patients with and without migraine, reporting the presence
and absence of a visual after-image following fundoscopy
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The after-image was usually a bright spot, but black spots and dots were
also reported. The duration was usually between 30s and 2 min. The observation
was equally likely to be made by migraineurs with and without aura and
patients with migraine equivalents. All migraineurs were interictal at the
time the examination took place.
The relative risk for the diagnosis of migraine in individuals reporting an
after-image following ocular fundoscopy was 2.91 (95% confidence interval 1.96
to 4.34). The sensitivity, specificity and positive predictive value of the
observation for the diagnosis of migraine were 0.63, 0.75 and 0.55
respectively. As expected, migraine was diagnosed more commonly in women than
in men, the ratio of female to male being 2:1 when an after-image was reported
and 1.6:1 when it was not. There was no difference in median age between
individuals with migraine reporting and not reporting an after-image. In those
patients in whom migraine was not diagnosed clinically, the ratio of female to
male was slightly higher in the group reporting an after-image (1.3:1).
Patients without migraine and not reporting an after-image were older than
those reporting this phenomenon (P=0.0021).
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DISCUSSION
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Whilst the diagnosis of migraine will always be based on the
patient's
history, examination of the ocular fundus is usually
part of the physical
evaluation of a patient with headache and
an after-image following this
procedure may support such a diagnosis.
It is not known how the sensitivity
and specificity of this
observation will be influenced if applied to a
specialist ‘headache
clinic’ population, or for that matter a
general practice
population with a variety of complaints including
non-neurological
ones. Also, the study needs to be repeated with different
practitioners,
preferably without their knowledge, in case the current
investigator
has influenced the identification of after-images by altering
his
technique subconsciously. It is noteworthy that in the non-migraine
group of
the current study, those reporting an after-image were
younger than those not
reporting it. This may reflect a tendency
for this phenomenon to disappear
with ageing. In migraineurs
(where no similar age-related trend was seen) the
observation
was made almost three times as commonly, and this probably
reflects
the heightened sensitivity of such patients to visual stimuli.
Using
the term ‘flight of colours’, Feldman and
colleagues described the
reduced or abolished after-images after
stimulation of each eye by a bright
pocket-light in patients
with defective central
vision
2. The
observation of a heightened
response in patients with migraine seems to be
novel. Unlike
the critical flicker fusion
threshold
3, where
migraineurs without
aura are reported to have a lower threshold than those
with
aura, the current observation does not discriminate between
the two
subgroups.
How might the phenomenon arise? Presumably it is mediated at the cortical
level, since it is bilateral. Mechanisms such as those responsible for
‘spreading depression’ can be evoked to account for it, but await
more detailed evaluation by studies of cortical blood flow. It would also be
interesting to study susceptible subjects to see whether the presence of
after-images depends on different colours, strengths and durations of ocular
illumination. Electrophysiological studies with transcranial magnetic
stimulation confirm cortical hyperexcitability in migraineurs. 13 of 15
migraine patients (14 migraine with aura, 12 women, mean age 39.9 SD 8.2
years) developed phosphenes after standardized occipital cortex stimulation by
magnet, compared with only 2 of 8 normal controls (5 women, mean age 37.3 SD
6.0 years)4.
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Acknowledgments
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I thank Wan-Thai Weissman for help with data collection. The
questionnaires
were distributed and collected after completion
by Anne Humphrays, Helen
Burke, Kathy Denby and Norma Morgan.
Christopher Hawkes gave helpful advice on
data interpretation
and regarding the discussion.
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REFERENCES
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-
Headache Classification Committee of the International Headache
Society. Classification and diagnostic criteria for headache disorders,
cranial neuralgias and facial pain. Cephalagia1988; 8(suppl 7):1
-96
-
Feldman M, Todman L, Bender MB. "Flight of colours" in
lesions of the visual system. J Neurol Neurosurg
Psychiatry 1974;37:1265
-72[Abstract/Free Full Text]
-
Coleston DM, Kennard C. Responses to temporal visual stimuli in
migraine: the critical flicker fusion test.
Cephalalgia1995; 15:396
-8[Medline]
-
Aurora SK, Cao Y, Bowyer SM, Welch KMA. The occipital cortex is
hyperexcitable in migraine: experimental evidence.
Headache 1999;
39: 469-78[Medline]
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SUMMARY
INTRODUCTION
