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Daith ear piercing, vagus nerve stimulation
and the
treatment of migraine headaches
Christopher Blatchley
London Migraine Clinic
April 2022
Keywords: migraine, vagus nerve stimulation, Daith ear piercing, visual stress,
pattern glare.
© Copyright C Blatchley
Address for correspondence
Dr Chris Blatchley MB BChir
London Migraine Clinic
chrisblatchley@doctors.org.uk
Abstract
Following widespread reports on social media in 2015 of improvement in
migraine after Daith ear piercing (DP), many thousands of migraine sufferers
have visited lay piercing studios for migraine treatment in the hope of gaining
improvement in their migraines. Despite this, no medical research by others has
been performed. We report audits of two series of patients attending the
London Migraine Clinic for DP.
In Series 1, 30 of 42 consecutive patients reported an improvement in headache
1-4 months after piercing, with a three-fold increase in average symptom-free
days/month from 6.4 to 19.7. The improvement was retained in 9 of the 11
patients we were able to reach at 12 month follow-up. A reduction in headache
and visual discomfort often occurred immediately following the DP, so we
investigated the change in visual discomfort, before and after piercing, when
viewing a series of gratings made up of parallel lines known to produce
discomfort in migraineurs. The reduction in discomfort after piercing was
significantly greater in the patients who subsequently reported improvement in
migraines.
In Series 2, prior to piercing, as part of pre-treatment assessment,115 patients
received temporary stimulation with fine needles in the cartilage of the ear. Two
points of stimulations were compared. The first was at the antitragus (innervated
by the great auricular nerve, which is without vagal connections) and the second
at the inferior surface of the crus helis at the inferior Daith point (an area
innervated by the vagus nerve). Stimulation of the antitragus produced no
effect, whereas stimulation of the Daith point measurably reduced visual
discomfort and other symptoms, such as headache, within one minute. In about
three-quarters of patients the symptoms returned over the same time scale
when the needle was removed. There was a further significant reduction in both
visual discomfort and other symptoms following therapeutic piercing.
The changes are strongly suggestive of vagal stimulation, though this requires
confirmation. We conclude that DP is potentially a simple, inexpensive and
effective treatment for a proportion of patients with severe migraine, and can be
rapidly introduced through existing channels.
Glossary
ABVN Auricular branch of the vagus nerve
ATN Auriculo-temporal nerve (a branch of the trigeminal nerve)
CNxx xxth Cranial nerve
DP Daith ear piercing
GAN Great auricular nerve
LON Lesser occipital nerve
MEG Magnetoencepalography
VNS Vagus nerve stimulation
tVNS transcutaneous electrical VNS
sVNS sustained percutaneous VNS
Introduction
Soon after it came into vogue as a cosmetic ear decoration in 1992, Daith ear
piercing (DP) patients began to report a serendipitous reduction in migraines.
The reports of migraine improvement increased slowly at first, but in 2015 the
practice of DP spread virally on social media after Dr Thomas Cohn, a pain
physician in the USA, reported the reduction in headaches on his website. Since
then many thousands of migraineurs have had a DP for migraines. In late 2016,
when we first heard of the reports, any evidence of efficacy was limited to some
amateur surveys. We analysed one of these surveys in detail and found that the
relationship within the data suggested further professional surveys were
justified. Since May 2017, we have conducted four in-depth web-based surveys
of over 4500 migraineurs with a DP (over 850 with migraines >10 years and
piercing >12 months) and all four have corroborated the reports of migraine
reduction from the initial amateur survey (Blatchley et al. 2017)
To date, the only published work on Daith piercing is one case report of a single
patient, advocating further research (Rizzo et al., 2017). Nevertheless, there is a
physiological rationale for supposing that DP might affect migraines. The DP
passes through the crus helis, a fold of cartilage on the superior margin of the
auditory meatus innervated by the auricular branch of the vagus nerve (ABVN)
(see Figure 1b and 1c). Invasive vagus nerve stimulation (iVNS) is an established
treatment for both migraines and epilepsy, and there has been considerable
research in non-invasive transcutaneous electrical stimulation of the ABVN
(tVNS) as an alternative (Gu et al., 2018; Tassorelli et al., 2018) . Unlike the
transcutaneous electrical devices, which are used intermittently, the piercing
remains in situ permanently, so that any potential effect on the ABVN is likely to
be sustained (sVNS), perhaps through irritation of terminations of the ABVN. This
possibility, along with our own survey data, supported the need for a detailed
audit of the effects of a DP on migraines.
We therefore started to offer DP to migraine patients who had sought treatment
from searches on the internet. To our great surprise, it soon became apparent
that most patients were reporting a marked and immediate improvement in
symptoms such as “brain fog”, neck ache, jaw pain and visual comfort, and not
just headache. Many reported complete disappearance of headache and
symptoms, and this could often be witnessed in the patient’s reactions
immediately after the piercing was performed.
It is well established that high contrast patterns of parallel lines (gratings) reliably
cause visual discomfort in migraineurs, and that this discomfort is critically
dependent on the characteristics of the pattern (Wilkins et al., 1984; Marcus and
Soso, 1989). From March 2018 we started to audit the changes in visual
discomfort caused by gratings before and immediately after DP. The reduction in
visual discomfort after piercing was often clear to observe during the treatment
(described in Series 1 below) but we were concerned that this might simply be a
placebo response potentially related to the distraction from the pain produced
by the piercing process, though, it is worth noting that the pain response to
piercing is very variable. We therefore audited the effects of temporary
diagnostic stimulation with a fine needle that gave little or no pain. In many
patients we found that needle stimulation of the Daith piercing point
immediately reduced discomfort from gratings as well as symptoms (headache
and “brain fog” etc) which returned when the needle was removed. As a check,
we then added similar temporary stimulation to an area of the ear not
innervated by the ABVN, which we hypothesised would be inactive (described in
Series 2 below).
We report the results of the two series of patients who attended the London
Migraine Clinic seeking a DP for their migraines and who underwent the above
examinations.
Series 1
Methods
In March 2018 we commenced collecting data from a series of 40 consecutive
patients (39 women) with longstanding headache. Our patients had been seeking
a DP as a result of their social media and internet searches. They completed a
comprehensive headache questionnaire. After detailed explanation of the
procedure they gave their signed consent.
Piercing
The DP passes through the cartilage of the crus helis, from the superior surface
adjacent to the cymba conchae to the inferior surface adjacent to the roof of the
auditory meatus, see Figure 1a and 1b.
Figure 1 a. A Daith piercing with associated jewellery; b. Anatomy of the pinna. c. Innervation of the
pinna (schematic). ABVN – auricular branch of the vagus nerve (CN10); ATN –auriculo-temporal
nerve (from CN5);; GAN – great auricular nerve (from cervical nerves) ; LON – lesser occipital nerve
(from cervical nerves). d. Acupuncture needle positions in Series 2.
The skin was first cleaned with 70% alcohol. A sharp 18-gauge disposable needle
(a “blade”) was used to puncture the epidermis on the superior surface of the
crus helis. It then passed through the cartilage to emerge through the inferior
surface. The needle was used to guide the jewellery that then remained in situ in
the ear. Designs of jewellery included a closed ring, or a curved bar with metal
retaining balls screwed top and bottom. We avoided surgical stainless steel
because of its nickel content, and 100% titanium was used instead (this could be
coated with 100% gold according to patient preference). All equipment and
jewellery were vacuum autoclaved and the needle and guides were disposable
single-use.
There is considerable technique in performing a Daith piercing well, and we
worked with a piercer of many years’ experience. Surprisingly, the piercing was
often painless. In patients who experienced pain, it was short-lasting.
Assessment of visual discomfort when viewing visual gratings.
Visual discomfort from gratings was assessed before and immediately after DP
using a series of three gratings with different line spacing, followed by a series of
10 gratings with increasing contrast, each with the same line spacing. The line
spacing in each grating is expressed as the spatial frequency, measured as cycles
per degree (cpd). One cycle is one pair of black and white lines of equal width. It
has previously been shown that a spatial frequency of approximately 3 cpd
elicits the most discomfort (Wilkins et al., 1984). The initial of three gratings had
line widths that gave spatial frequencies of 0.5, 3 and 9 cpd at the viewing
distance of 0.6m, as used in the Pattern Glare Test (Wilkins and Evans, 2001). The
subsequent 10 gratings all had the same spatial frequency of 3 cpd, with
increasing contrast from 2.7% to 94%. All the patterns were circular in outline,
and at 0.6m subtended 9 degrees at the eye. The room illuminance was 150 lux.
Patients viewed each pattern for 1-2 seconds and reported any discomfort on a
6-point scale: “none”, “aware”, “slight”, “moderate”, “severe”, “intolerable”.
A comparison group of 130 patients without a medical history of headaches and
not attending for a piercing (89 male, 41 female) was separately assessed for
visual discomfort with the same gratings during a routine sight test under
matched lighting conditions.
Follow Up Details
We followed up patients by email with a link to an online survey tool which
included questions on frequency, severity, associated symptoms, medication use
etc. The follow up was conducted from 31 May 18, 1-4 months after DP, and
from 20 May 19, 12 or more months after DP.
Assessment of headaches
Headaches and other symptoms associated with migraine were assessed in
detail. Patients were asked about the frequency of migraines/severe headaches,
other non-migraine headaches and completely symptom-free days, both initially
and at follow-up. At follow-up they were also asked: “Overall, how has your Daith
Piercing altered your migraines/severe headaches?”, with the options of “a lot
worse”, “a little worse”, ”no obvious change”, ”a little improved”, “greatly
improved” and “I no longer have them”.
Results of Series 1
At 1-4 months we were able to follow up 42/57 patients (73%). We report on
these 42 patients, who had received a DP between March and May 2018. They
had longstanding headaches for an average of 16 years (minimum 1 year,
maximum more than 20 years). Their headaches were frequent (with an average
of less than seven symptom-free days per month) and they were severe
(preventing work in 80% of cases). 36% patients experienced aura.
Immediate response to gratings
Figure 2 shows the average rating of the 42 migraine patients before and
immediately after DP for the three gratings that varied in spatial frequency (left
panel), and subsequently for the ten gratings that increased in contrast (right
panel). The average rated discomfort from all patterns was significantly greater
before the DP than it was immediately afterwards (t(41)=10.1, p<.0001).
Figure 2. The ratings of visual discomfort from the gratings before and after DP. Left panel: high
contrast gratings with spatial frequencies 0.5, 3 and 9 cpd. Right panel: variable contrast gratings
with spatial frequency 3 cpd. Separate curves show the ratings before and after DP.
In the comparison group of 130 patients (89 male 41 female) without a medical
history of migraines, 125/130 reported no discomfort from the gratings. The
discomfort was “slight” in 4 patients (3 female) and “moderate” in only one male.
Clinical changes in symptoms at 1-4m follow-up
For the group as a whole, there was a highly significant reduction in migraine
days and increase in symptom-free days (Wilcoxon tests, z>4.19, p<.0001, two-
tail, both measures). There was also an associated and highly significant
reduction in migraine severity (t(36)=7.05,p<.0001).
This improvement was further illustrated when the entire group was sub-divided
according to the response to the question at follow-up: “Overall, how has your
Daith Piercing altered your migraines/severe headaches?”. The choice of
answers is shown in the first column of Table 1, and tabulated against the mean
number of migraine days and symptom-free days per month, at consultation
before DP and at follow-up. Patients’ subjective assessment of the change in
their migraines is consistent with the change in their reported migraine and
symptom-free days.
Table 1. Average migraine days and symptom-free days in the month before DP and at follow-up,
grouped according to reported overall improvement at follow-up.
Reported Improvement
at 1-4m follow-up
Migraine days
Symptom-free days
N
Before
DP
At
follow-up
Before
DP
At
follow-up
A lot worse
0
A little worse
2
3.5
7.3
14.0
3.5
No obvious change
10
12.5
17.4
7.4
9.2
A little improved
14
9.9
7.9
5.1
11.6
Greatly improved
13
9.4
1.5
7.5
26.3
No longer have them
3
2.2
1.5
8.5
29.0
As can be seen from Table 1, individuals who reported their headaches were
“greatly improved” showed a substantial reduction in migraine days and a
substantial increase in symptom-free days. The corresponding figures were less
pronounced in those who reported “little improvement”, and those who reported
“No obvious change” showed little difference between before DP and follow-up.
Relationship between immediate response to gratings at DP and later clinical
outcome
For the group as a whole there was also a correlation between the reduction in
rated visual discomfort from gratings at DP and the subsequent change at 1-4m
in migraine days (rho=0.31, p<.05) and symptom-free days (rho=0.32, p<.05). This
improvement is similarly illustrated by subdividing the entire group according to
reported overall improvement at 1-4 months, see Table 2.
Table 2. Mean rated discomfort before and after DP, grouped according to overall improvement
Reported Improvement at
1-4m follow-up
N
Mean Before
DP
Mean After
DP
Mean
difference
A lot worse
0
A little worse
2
4.00
3.00
1.00
No obvious change
10
2.08
1.00
0.92
A little improved
14
2.73
0.55
2.09
Greatly improved
13
2.77
0.46
2.31
No longer have them
3
2.00
0.33
1.67
Long-term effects of DP
At 12 months post DP we were able to reach only 11 of the 30 patients who had
reported overall improvement at 1-4 months (we did not follow up the 12
patients who had reported no improvement). 5 of the 11 also reported that the
effect “had not begun to wear off”. See Figure 3 for the averaged data.
Figure 3. Data from the 11/30 patients previously reporting improvement when followed up at 1-4
months (8/11 had reported little improvement and 3/11 great improvement). At 12 months 1
reported migraine stopped, 9 great improvement, 1 little improvement and 1 no obvious change.
Note that the reported migraine days did not include mild “other headache” days.
Interim Discussion: Series 1
Patients in Series 1 had headaches that were frequent and debilitating. At first
follow-up more than half the patients reported an improvement, and the
improvement was marked in 38% patients. In the small sample we were able to
follow up at one year, 9/11 continued to report great improvement. Visual
discomfort from patterns occurred in most patients with migraine, and the
average reduction from DP predicted the improvement in headache not only at
1-4m follow-up, but also at 12month.
0
5
10
15
20
25
30
0 5 10 15
Days per month
Months since DP
Migraine days
Symptom-free
days
Series 2
To explore the contribution from placebo response in the results observed in
Series 1, we added temporary diagnostic stimulation with fine needles prior to
piercing, for a consecutive series of 115 patients (treated between March and
December 2019). We were then able to compare the immediate effects of DP
with stimulation of both the Daith point and an inactive point.
Methods
The general procedures for initial questionnaire, consent and method of piercing
remained the same as in Series 1. For Series 2 we added temporary stimulation
with fine 31G solid needles 0.25mm in diameter, consecutively at the two points
shown in Figure 1d, Needle 1 into the antitragus, an area not innervated by the
ABVN, and Needle 2 in the future lower Daith piercing point on lower surface of
the crus helis, an area that is innervated by the ABVN. We explained that we
would be inserting two diagnostic needles in sequence in separate places to
measure the response, and obtained consent. We were careful not to explain the
specific significance of each needle. In all cases the fine needles were inserted
through the epidermis into the cartilage. In all patients, insertion of the needle
produced little or no discomfort. Prior to insertion we cleaned the area with 70%
alcohol.
Patients were asked to observe the patterns and rate discomfort four times: at
the outset, whilst each needle was inserted, and again after the DP. They were
also asked to report any change in symptoms after insertion of each needle and
again after its withdrawal.
Results of Series 2
At initial assessment the patients reported an average of 8.2 migraine days per
month and 7.5 symptom-free days. The migraine headaches were severe
enough to interfere with work in 75% of cases. 59 (51%) patients reported aura.
Changes in Visual Discomfort
The visual discomfort ratings before, during Needle 1, during Needle 2 and after
the DP are shown as separate curves in Figure 4. Needle 1 (in the antitragus, see
Figures 1b and 1d) had no effect on ratings. The overall mean ratings before and
after Needle 1 were 1.34 and 1.35, respectively; t(114)=1.06, p=.29. By contrast,
Needle 2 in the Daith point significantly reduced ratings of discomfort (mean
rating 1.00, t(112)=8.04, p<.0001). A further significant reduction resulted from
the DP (mean rating 0.54, t(113)=11.61, p<.0001).
Figure 4. The ratings of visual discomfort from the gratings. Left panel: high contrast gratings with
spatial frequencies 0.5, 3 and 9 cpd. Right panel: variable contrast gratings with spatial frequency 3
cpd. For all points the standard error was less than 0.23. Separate curves show the ratings before
needle stimulation, during stimulation with Needle 1 (N1), during stimulation with Needle 2 (N2)
and after DP. (The curves “before” and “N1” are nearly superimposed.)
For all points the standard error was less than 0.17
Changes in Symptoms
Patients were questioned concerning the effects of the needle stimulation on
symptoms, and whether the symptoms returned when the needle was removed.
Table 3 shows the symptoms reported and the number of patients reporting
them before DP. It also shows the change in symptoms when the needles were
removed.
Table 3. Symptoms reported prior to DP, and the effect on these symptoms after insertion and
removal of Needle 1 (antitragus) and Needle 2 (lower Daith point) , and after DP.
Symptoms
Number with
symptom
Symptom
reduction
with Needle 1
Return of
symptoms on
withdrawal of
Needle 1
Symptom
reduction
with Needle 2
Return of
symptoms on
withdrawal of
Needle 2
Symptom
reduction with
DP
Headache
61
(53%)
2
(3%)
2
(3%)
47
(77%)
37
(61%)
58
(95%)
Photophobia
19
(17%)
1
(5%)
0
(0%)
14
(74%)
14
(74%)
18
(95%)
Neck/shoulder
tension
78
(68%)
3
(4%)
1
(1%)
63
(81%)
50
(64%)
73
(94%)
Jaw tension
29
(25%)
0
(0%)
0
(0%)
24
(83%)
18
(62%)
29
(100%)
Brain fog
52
(45%)
1
(2%)
1
(2%)
34
(65%)
26
(50%)
42
(81%)
Vision clarity
31
(27%)
2
(6%)
1
(3%)
24
(77%)
18
(58%)
30
(97%)
Vision comfort
34
(30%)
2
(6%)
1
(3%)
22
(65%)
15
(44%)
30
(88%)
As can be seen from Table 3, Needle 1 had little effect on any symptom, whereas
Needle 2 reduced most symptoms and did so usually only whilst it was in place.
The DP reduced nearly all symptoms.
Discussion
Currently, published medical research on Daith Piercing (DP) for migraines is
limited to one case report, even though many thousands of migraineurs have
visited lay piercing studios for 20 years to self-treat their migraines. Two initial
questions need addressing:- 1. Is there a central effect of DP beyond that of
placebo? 2. If there is, then how effective is it in reducing migraines and how long
does the effect last?
Our research is an audit of treatment with a DP, and not a placebo-controlled
trial. A DP is a visible procedure in a group of patients who are both
knowledgeable and motivated, and it would be clear to them whether they had
an active or placebo treatment. Effective trial design requires initial data.
Presently there are none, so we decided on an incremental research path to
discover whether the reported responses were likely to be entirely placebo, and
whether further research was justified.
Our research supports the hypothesis that there is a marked and long-lasting
central effect on migraine in some patients, possibly mediated via stimulation of
the vagus nerve. While it does not exclude placebo, it is difficult to explain the
findings as entirely placebo for the following consecutive reasons:-
1. Migraineurs are known to find visual patterns of black and white parallel
lines uncomfortable. Prior to a DP, patients’ responses were entirely as
expected when both the spatial frequency and the contrast of the
patterns were varied. After DP the rated discomfort consistently followed
a similar but reduced pattern of response. Other subjective symptoms
were also reduced, and the patients’ experience was obvious to witness in
the treatment room. The consistency of the change after DP was
remarkable and statistically highly significant. While these changes might
be explained by the pain/distraction of piercing, it is more difficult to
explain them in terms of patients’ expectations. Patients might possibly
have expected the discomfort to increase with increasing pattern
contrast, but they would not have known of the effects of changes in
spatial frequency.
2. An acupuncture needle (Needle 2) inserted into the point later to be
pierced with the DP produced an equally consistent (though less marked)
reduction in rated discomfort and other symptoms, even though the
needle produced minimal or no discomfort when inserted. These changes
support at least an element of non-placebo response, but the distraction
of piercing or patient expectations have not been excluded as possible
explanations.
3. After removal of Needle 2, the symptoms returned in many patients. The
increase and decrease in effect occurred within 60s of insertion/removal.
4. An acupuncture needle (Needle 1) inserted into the cartilage of the
antitragus, a structure not innervated by the ABVN, produced no change
whatever in symptoms or ratings of discomfort. The difference between
the effects of the two needles was profound. One would reasonably
anticipate some effect of the antitragus needle if distraction were to affect
discomfort when viewing the gratings. The dissociation is similar to that
already seen in studies with auricular transcutaneous electrical
stimulation (Gu et al., 2018) which have used the same inert area as a
comparison point.
5. Further knowledge is still required before design of a placebo-controlled
study can be attempted. fMRI and MEG imaging studies may be useful in
assessing immediate central response.
In summary, patients rated visual discomfort from the series of visual gratings.
Plots of the rated discomfort were consistent with those expected from the
literature for each of the stimulation methods (piercing or needles). At every
stage we have sought to explore any effect of DP as placebo. With each element
of our research it has become progressively more difficult to explain the effects
as entirely placebo.
Popularity of Daith piercing
DP is generally only available in non-medical piercing studios, so it is difficult to
assess the numbers performed. It was a rare piercing until news that it had an
effect on migraines started spreading virally on the internet from March 2015.
Blue Banana piercing studios have informed us (personal communication) that
they have performed more than 32,000 DPs since May 2015, an average of 10
per week per clinic in each of their 13 UK clinics. Informal discussions with other
clinics suggest that this is not atypical. Evidently large numbers of patients are
seeking a DP from non-medical clinics.
Patients with migraine appear to be seeking a DP because routine medical
treatments have not succeeded. Our online surveys of those with a DP record
that 90% had previously seen their family doctor and 50% a neurologist before
seeking a DP. Patients with a positive response are unlikely to seek the further
advice of a neurologist, which may explain why neurologists rarely report
successful outcomes, despite the large numbers of DPs being performed without
medical supervision.
Placebo response.
Randomised placebo-controlled studies are the gold standard for assessing the
effects of treatment, but are difficult to apply to an obviously visible intervention
such as a DP, so other evidence must also be sought.
Quantifying a placebo response can be a challenge, especially in headache. In a
2002 meta-analysis (Van Der Kuy and Lohman, 2002) of 22 placebo controlled
studies of 19 different prophylactic treatments for migraine it was concluded
that no placebo response ever resulted in a reduction in mean attack frequency
>40%, at least in the studies reviewed.
The decay of the placebo effect over time has also been explored (Sun et al.,
2013). The DP is given as a single procedure. If the response to DP were entirely
placebo, we would suggest it reasonable to expect a decay in efficacy within a
few months, and that there would be little or no placebo response from a single
intervention remaining after a year.
Researchers of transcutaneous electrical stimulation of the ear have compared
stimulation of the cymba conchae (innervated by the ABVN) with a control area
(innervated by the non-vagal GAN). fMRI imaging showed that stimulation of the
cymba conchae activated known vagal projections (including the solitary tract and
the spinal trigeminal nucleus), but this did not occur with stimulation of the
control area (Frangos, Ellrich and Komisaruk, 2015). Although there are no
imaging studies of the effects of a DP, this study supports our choice of the
antitragus as an inactive comparison (with Needle 1).
Our clinic patients attended with the specific intention of obtaining a piercing,
having researched the topic on the internet. It is prudent to assume that their
hopes of success were influenced by positive reports. However, online chat
forums express mixed views - from great success, through temporary or no
effect, to a priori statements that “it can’t possibly work”. Our patients generally
saw it as “worth a try” because no other treatments had worked adequately, but
did not generally expect success. During the consultation we made it clear that
the DP is not effective for everybody, and patients were given the chance to
either refuse treatment or delay it pending further thought.
Migraines and visual discomfort from gratings
The relationship between migraines and visual symptoms (including discomfort
from patterns and flicker, as well as photophobia) is well established. The
immediate reduction in discomfort from visual gratings following DP was
unexpected and is difficult to attribute simply to the distraction/discomfort of
piercing. Stimulation with fine needles causes minimal pain and yet has a
marked effect on visual discomfort, while needle stimulation of a non-vagal area
had no effect at all. The modulation of visual discomfort is unlikely to be by
direct action on the visual pathways, and instead points to other more general
central mechanisms that are also associated with migraine.
The visual gratings used in this study were “strong” patterns in the following
respects:-
1. They elicit visual distortions and discomfort, particularly in individuals
with migraine (Marcus and Soso, 1989) or photosensitive epilepsy
(Kasteleijn-Nolst Trenité and Parisi, 2012)
2. They are epileptogenic in patients with photosensitive epilepsy (Wilkins,
Darby and Binnie, 1979)
3. They have the spatial frequency (2-4 cycles/degree) that produces the
greatest cortical excitation in normal controls (Wilkins et al., 1984).
4. They elicit high-amplitude evoked potentials and gamma activity in EEG
and MEG studies (Adjamian et al., 2004) and strong cortical
haemodynamic responses in BOLD fMRI studies (Huang et al., 2003)
5. Sleep deprivation (a recognised pro-convulsant) produces increased
distortions in and discomfort from visual gratings (Wilkins et al., 1984).
All the above observations are consistent with other evidence that the visual
cortex is hyper-excitable in migraine (Aurora and Wilkinson, 2007). The
reduction in pattern-induced discomfort by Daith piercing is consistent with a
reduction in the hyper-excitability of the cortex, as occurs when vagal stimulation
is used to treat epilepsy (Uthman, 2000).
Anatomy, embryology and neurophysiology of the innervation of the external
ear, including the CNS connections
The sensory innervation of the external ear is supplied by four separate nerves,
see Figure 1c and Figure 5a. The ABVN is particularly relevant because it
innervates the superior and inferior surfaces of the crus helis, a fold of cartilage
that the Daith piercing passes through. The origins and distribution of the ABVN
and auriculo-temporal nerve (ATN), a branch of the trigeminal nerve (TGN), are
both relevant and complicated.
Figure 5a. Schematic innervation of external auricle the auricular branch of the vagus nerve
showing the ABVN in green (CN X), the auriculotemporal nerve (ATN) in red (CN V3), the lesser
occipital nerve (LON) in blue (C2), and the great auricular nerve (GAN) in yellow (C2-3). b From
Gray’s Anatomy Adapted from reference (He et al., 2012).
Embryology of peripheral innervation of the external ear
The detailed sensory innervation of the external ear has been described by
several authors (Peuker and Filler, 2002; He et al., 2012; Bermejo et al., 2017)
each with small differences. Embryologically, both the sensory neurons and the
auricular cartilage originate from neural crest cells. The upper antero-superior
parts of the auricular cartilage (including the tragus, crus helis and cymba
conchae) originate from the neural crest cells that migrated into the 1st arch,
whereas the lower postero-inferior parts below the crus helis (including the
cavum conchae and antitragus) arise from the 2nd arch neural crest cells (Anthwal
and Thompson, 2016). The auditory meatus originates from the ectodermal 1st
cleft between the two arches, and the eustachian tube/middle ear from the
endodermal 1st pouch.
The name ABVN suggests vagus root origins but it is a complex mixture of fibres
related to the facial nerve (CN 7) - 2nd arch, the glossopharyngeal nerve (CN 9) -
3rd arch, and the vagus nerve - 3rd & 4th arches. The complexity is illustrated
schematically in Figure 5b. The TGN (CN 5) develops entirely from the 1st arch.
The ABVN has fibres originating from both the glossopharyngeal nerve (CN 9)
and the vagus nerve (CN 10). It then passes around or through the mastoid
process, where a small branch joins from the facial nerve (CN 7). After reaching
the posterior surface of the external ear (which it innervates), it passes through
the auricular cartilage in line with the division between embryological origins of
the upper and lower parts to reach the anterior surface in the cavum conchae.
Fibres which are applied closely to the cartilage then spread out to innervate the
cymba conchae above the crus helis, and the cavum conchae below. Fibres also
extend to innervate the posterior wall of the auditory canal, and some reach the
posterior surface of the tragus. The boundaries of the areas supplied by the
ABVN and ATN are particularly indistinct, with extended overlapping in poorly
defined watershed areas. There is considerable individual variation between the
boundaries of the areas innervated by these nerves.
The distinction is clearer for the area innervated by cervical root nerves
(supplying the LON and GAN) in the lower ear (see Figure 5a). We chose the
antitragus as an inert reference comparison point because it is both cartilaginous
and innervated solely by the GAN originating from spinal roots C2-3 (Peuker and
Filler, 2002). The ear lobe itself has no cartilage.
Central neuronal connections to the brainstem - The ABVN and ATN both contain a
mixture of large diameter myelinated and small diameter minimally myelinated
or un-myelinated fibres, with the ABVN fibres passing the brainstem. Nomura
has confirmed histologically that the ABVN projects to both the solitary and
trigeminocervical tracts and other areas in the brainstem (Nomura and Mizuno,
1984). Henssen has written an extensive review of the these dense
interconnections (Henssen et al., 2019). Using fMRI, Frangos confirmed in
humans that transcutaneous electrical stimulation of the area of the ear
innervated by the ABVN produced changes in activity in mid-brain and
brainstem, whereas similar stimulation of the antitragus/earlobe (innervated
from C2-3) had no such effect (Frangos, Ellrich and Komisaruk, 2015). Bermejo
discusses the evidence that the effects of electrical stimulation are via the large
myelinated and not the unmyelinated fibres (Bermejo et al., 2017). It is possible
but as yet unconfirmed that unmyelinated fibres are directly stimulated by
irritation from a DP.
Potential mechanism of action
Invasive electrical stimulation of the vagus nerve reduces cortical excitability in
epilepsy and is used to treat both epilepsy (Uthman, 2000) and intractable
migraine. Transcutaneous electrical stimulation of the auricular branch of the
vagus nerve is used to treat migraines (Gu et al., 2018) and has also been shown
to have an effect on epilepsy (Yuan and Silberstein, 2016). Visual discomfort
from grating patterns is thought to reflect cortical excitability in migraine (Huang
et al., 2003). The location of the piercing is important. No other ear piercing
(including tragus piercing) has been associated with migraine reduction, in line
with the reduced or absent innervation by the ABVN.
The immediate reduction in symptoms and visual discomfort after needle
stimulation or DP is therefore consistent with vagus nerve stimulation from
sensory nerve irritation, and an associated reduction in cortical excitability.
Cosmetic ear piercings through cartilage (of which DP is only one), are routinely
performed in piercing studios. It is uniformly recognised that they are slow to
heal because blood supply to cartilage is low and epithelialisation along the track
of the piercing is slow. Low-grade inflammation can continue for several months
and is routinely managed by piercing studios.
Problems/side effects/infection rate
A DP is not easy to perform and requires experience and technical expertise.
Piercing studios have been piercing ear cartilage for many years and are
generally well versed in offering aftercare regimes:-
1. Immediate effects – Unlike cervical VNS (invasive or transcutaneous) the DP
stimulates afferent fibres only, so no direct effect on the heart from
stimulation of vagal efferents would be expected, and none are reported.
Perhaps surprisingly, most report little or no pain during piercing.
2. Short term effects - primarily related to discomfort and care with sleeping.
3. Longer term effects – It is common to experience irritation and crusting
around the piercing for 1-3 months and occasionally longer. Nevertheless
infection requiring medical intervention is largely avoidable by cleanliness
regimes. Infection necessitating piercing removal is uncommon, but the
risk of potentially serious infection requiring antibiotics must not be
ignored, and must be taken into account in aftercare.
Conclusion
DP is potentially an inexpensive, safe and effective migraine treatment that can
be rapidly introduced. Further research on a larger cohort of migraine patients is
required.
We are currently collaborating on a 12 month observational follow-up of
customers who have chosen to have a Daith piercing for their migraines, with
Blue Banana, a national chain of piercing studios in the UK who perform up to
200 Daith piercings a week, many of them in migraine sufferers.
Acknowledgements
We would particularly like to thank Professor Arnold Wilkins, Emeritus Professor
at Essex University, for the idea of using pattern gratings to measure visual
discomfort and for assisting in the statistical analysis and write-up. Professor
Wilkins has been researching pattern and colour processing in visual pathways
for many years, and without his advice this research would not have been
possible. We would also like to thank Dr Clare Baker and Dr Winifred Neuhuber
for advice concerning the embryology of the ear.
Funding
There was no external funding.
References
Adjamian, P. et al. (2004) ‘Induced visual illusions and gamma oscillations in
human primary visual cortex’, European Journal of Neuroscience. doi:
10.1111/j.1460-9568.2004.03495.x.
Anthwal, N. and Thompson, H. (2016) ‘The development of the mammalian outer
and middle ear’, Journal of Anatomy. doi: 10.1111/joa.12344.
Aurora, S. K. and Wilkinson, F. (2007) ‘The brain is hyperexcitable in migraine’,
Cephalalgia. doi: 10.1111/j.1468-2982.2007.01502.x.
Bermejo, P. et al. (2017) ‘Innervation of the Human Cavum Conchae and Auditory
Canal: Anatomical Basis for Transcutaneous Auricular Nerve Stimulation’,
BioMed Research International. doi: 10.1155/2017/7830919.
Blatchley, C. and Wilkins, A. (2017) ‘Report on the first survey into the effects of
Daith Piercing on migraines’,
https://www.researchgate.net/profile/Chris-Blatchley
Frangos, E., Ellrich, J. and Komisaruk, B. R. (2015) ‘Non-invasive access to the
vagus nerve central projections via electrical stimulation of the external ear:
FMRI evidence in humans’, Brain Stimulation. doi: 10.1016/j.brs.2014.11.018.
Gu, Q. et al. (2018) ‘Non-invasive vagus nerve stimulation for acute treatment of
high-frequency and chronic migraine: an open-label study’, J Headache Pain. doi:
10.1186/s10194-018-0900-0.
He, W. et al. (2012) ‘Auricular acupuncture and vagal regulation’, Evidence-based
Complementary and Alternative Medicine. doi: 10.1155/2012/786839.
Henssen, D. J. H. A. et al. (2019) ‘Vagus nerve stimulation for primary headache
disorders: An anatomical review to explain a clinical phenomenon’, Cephalalgia.
doi: 10.1177/0333102419833076.
Huang, J. et al. (2003) ‘Visual distortion provoked by a stimulus in migraine
associated with hyperneuronal activity’, Headache. doi: 10.1046/j.1526-
4610.2003.03110.x.
Kasteleijn-Nolst Trenité, D. and Parisi, P. (2012) ‘Migraine in the borderland of
epilepsy: “Migralepsy” an overlapping syndrome of children and adults?’,
Epilepsia. doi: 10.1111/j.1528-1167.2012.03711.x.
Van Der Kuy, P. H. M. and Lohman, J. J. H. M. (2002) ‘A quantification of the
placebo response in migraine prophylaxis’, Cephalalgia. doi: 10.1046/j.1468-
2982.2002.00363.x.
Marcus, D. A. and Soso, M. J. (1989) ‘Migraine and stripe-induced visual
discomfort’, Archives of Neurology, 46(10), pp. 1129–1132. doi:
10.1001/archneur.1989.00520460125024.
Nomura, S. and Mizuno, N. (1984) ‘Central distribution of primary afferent fibers
in the Arnold’s nerve (the auricular branch of the vagus nerve): A transganglionic
HRP study in the cat’, Brain Research. doi: 10.1016/0006-8993(84)90756-X.
Peuker, E. T. and Filler, T. J. (2002) ‘The nerve supply of the human auricle’,
Clinical Anatomy. doi: 10.1002/ca.1089.
Rizzo, A. C. et al. (2017) ‘Daith piercing in a case of chronic migraine: A possible
vagal modulation’, Frontiers in Neurology. doi: 10.3389/fneur.2017.00624.
Sun, W. et al. (2013) ‘Development of a placebo effect model combined with a
dropout model for bipolar disorder’, Journal of Pharmacokinetics and
Pharmacodynamics. doi: 10.1007/s10928-013-9305-5.
Tassorelli, C. et al. (2018) ‘Noninvasive vagus nerve stimulation as acute therapy
for migraine’, Neurology. doi: 10.1212/WNL.0000000000005857.
Uthman, B. M. (2000) ‘Vagus nerve stimulation for seizures’, in Archives of
Medical Research. doi: 10.1016/S0188-4409(00)00060-6.
Wilkins, A. et al. (1984) ‘A neurological basis for visual discomfort’, Brain. doi:
10.1093/brain/107.4.989.
Wilkins, A. and Evans, B. J. W. (2001) Pattern Glare Test. ioo sales, London.
Wilkins, A. J., Darby, C. E. and Binnie, C. D. (1979) ‘Neurophysiological aspects of
pattern-sensitive epilepsy’, Brain. doi: 10.1093/brain/102.1.1.
Yuan, H. and Silberstein, S. D. (2016) ‘Vagus Nerve and Vagus Nerve Stimulation,
a Comprehensive Review: Part II’, Headache. doi: 10.1111/head.12650.
