Neurourology and Urodynamics 32:53–57 (2013)
Motor Cortex Stimulation in Refractory Pelvic and
Perineal Pain: Report of Two Successful Cases
Jean-Marie Louppe,1Jean-Paul Nguyen,1Roger Robert,2Kevin Buffenoir,2Edwige de Chauvigny,3
Thibault Riant,2Yann Pe ´re ´on,4Jean-Jacques Labat,2and Julien Nizard3*
1Service de Neurochirurgie, Centre Hospitalier Universitaire, Nantes, France
2Service de Neurotraumatologie, Centre fe ´de ´ratif des pathologies fonctionnelles pelvi-pe ´rine ´ales,
Centre Hospitalier Universitaire, Nantes, France
3Centre d’Evaluation et de Traitement de la Douleur, Centre Hospitalier Universitaire, Nantes, France
4Laboratoire d’Explorations Fonctionnelles, Centre de Re ´fe ´rence Maladies Neuromusculaires Nantes-Angers,
Centre Hospitalier Universitaire, Nantes, France
Aims: In some patients, with refractory chronic pelvic and perineal pain, pain and quality of life are barely alleviated
despite optimal medical treatment, infiltrations and surgical release of the pudendal nerve. The management of these
patients is complex, especially after failure of neuromodulation techniques (spinal cord stimulation. S3 nerve root
stimulation and direct stimulation of the pudendal nerve). We report the first two cases illustrating the value of motor
cortex stimulation (MCS), in this new indication. Methods: The history, decision-making process, intraoperative
findings and results of this technique are presented. The perineal cortical area was identified by intraoperative motor
evoked potentials in the external anal sphincter, confirming its location in the primary motor cortex between the inferi-
or and superior limb positions. As predictive value of repetitive transcranial magnetic stimulation (rTMS) in the identi-
fication of responders to MCS for pain is now established, we performed pre-operative rTMS sessions for both patients.
Results: The first patient was a 74-years-old woman who reported an 11-year history of left lateral perineal pain. The
second patient was a 45-year-old woman who reported a 4-year history of perineal pain following hysterectomy with
ovariectomy. After respectively 40 months and 19 months of follow up, both patients reported an improvement of pain
ranging from 40 to 50%. Time to onset of pain on sitting was markedly improved from a few minutes to 90 minutes, and
largely contributing to improvement of activities of daily living and of quality of life. Conclusion: These two first cases
suggest that motor cortex stimulation constitutes a new treatment for refractory pelvic and perineal pain, and should
be considered after failure of conventional neuromodulation techniques, especially spinal cord stimulation. Neurourol.
Urodynam. 32:53–57, 2013. ? 2012 Wiley Periodicals, Inc.
Key words: motor cortex stimulation; neuropathic pain; pelvic pain; pudendal neuralgia
A very large proportion of cases of chronic pelvic and perineal
pain correspond to pudendal or inferior cluneal neuralgia due to
compression of one or both nerves in one of the several tunnels
described over the course of these nerves (infrapiriformis fora-
men, entrapment between the sacrotuberous and sacrospinatus
ligaments, Alcock’s canal).1,2Anesthetic infiltration (generally li-
docaine) of these nerves at these sites of compression confirms
the entrapment syndrome. Pudendal and/or inferior cluneal
nerve release is therefore logically the first-line surgical option in
these patients3and is effective in about 70% of cases. Failure is
frequently observed in patients who present late, in the elderly,
and at a stage probably corresponding to neuropathic pain relat-
ed to anatomical nerve lesions. In these cases, despite optimal
medical treatment (including antidepressants, antiepileptics,
and combination of these two treatments), neuromodulation
techniques, that have been demonstrated to be effective in
the treatment of some forms of neuropathic pain, are often re-
quired. The techniques reported in the literature are spinal cord
stimulation (dorsal4,5or conus medullaris6), S3 nerve root stimu-
lation7–17and direct stimulation of the pudendal nerve.18These
various techniques can be effective, but a relatively large num-
ber of patients remain refractory. Primary motor cortex stimula-
tion (MCS) has been shown to be effective in the treatment of
neuropathic pain, especially post-stroke central pain and neuro-
pathic trigeminal neuralgia.19–25We report two cases illustrating
the value of primary motor cortex stimulation, a new treatment
option for refractory perineal pain.
A 74-year-old woman reported an 11-year history of left
lateral perineal pain satisfying the criteria for entrapment
syndrome2: territory of the pudendal nerve, accentuated by
sitting, with no nocturnal awakening or sensory deficit, tem-
porary relief by anesthetic block of the pudendal nerve.
Pudendal and inferior cluneal nerve release did not provide
sufficient pain relief and a neuromodulation technique was
considered. Spinal cord stimulation was initially attempted by
surgical implantation of the electrode (Specify 8, Medtronic,
Christopher Chapple led the peer-review process as the Associate Editor responsible
for the paper.
Conflict of interest: none.
*Correspondence to: Dr. Julien Nizard, MD, PhD, Centre d’Evaluation et de Traite-
ment de la Douleur, Centre Fe ´de ´ratif Douleur-Soins de Support-Ethique clinique,
Centre Hospitalier Universitaire Lae ¨nnec, 44093 Nantes, France.
Received 20 January 2012; Accepted 19 April 2012
Published online 5 June 2012 in Wiley Online Library
? 2012 Wiley Periodicals, Inc.
Minneapolis, MN) at T9-T10. Test stimulation via an external
lead successfully covered the perineal territory by paraesthe-
siae, but the analgesic effect was not sufficient and the elec-
trode was subsequently removed. Repetitive Transcranial
Magnetic Stimulation (rTMS) of the motor cortex was per-
formed in order to assess the potential efficacy of motor cortex
stimulation.26During the session, the following parameters
were applied during 20 min: twenty 10-sec trains at 10 Hz at
80% of rest motor threshold, with a 50 sec intertrain interval
(2,000 stimuli). A positive response with marked and transient
pain reduction on the VAS was observed after a single session
of rTMS (Fig. 1). A motor cortex stimulation electrode was
therefore implanted according to a technique that has already
been clearly defined: positioning of a Resume 4-contact elec-
trode in the extradural space.27In line with published results
concerning the location of the perineal region in motor cortex,
we targeted the cortical region situated just anterior to the
central sulcus, between the areas of representation of the up-
per limb and lower limb.28–33Correct positioning of the elec-
trode was confirmed intraoperatively by inducing motor
responses of the anal sphincter by stimulating the electrode
contacts placed anteriorly to the central sulcus (Fig. 2). Pain
gradually improved over the weeks following activation of
the stimulator. Stimulated contacts were detected on a post-
operative CT scan whose images were fused with preoperative
MRI images and clearly corresponded to the contacts at which
intraoperative stimulation induced motor responses of the
anal sphincter.34,35The chronic stimulation parameters were
as follows: bipolar stimulation with the contact placed on M1
(contact 1) used as the cathode and the contact 2 as the anode
(Fig. 3), amplitude 2,5 V, pulse width 60 msec, frequency
40 Hz. Pain remained improved by an average of 45% after
40 months of follow-up. Analgesic intake, calculated by com-
paring pre- and post-operative MQS scores,36decreased by
70% and the time to onset of pain when sitting decreased
from 5 to 90 min. The patient reported a marked improve-
ment of activities of daily living.
A 45-year-old woman reported a 4-year history of perineal
pain following hysterectomy with ovariectomy. She reported
complex pain comprising suprapubic pain, allodynia when
wearing tight clothing, a feeling of vaginal discomfort and
neuropathic pain in the territory of the right pudendal
nerve. These clinical features corresponded to pelvic visceral
pain associated with pudendal neuralgia. This patient also ex-
perienced dysuria. Medical treatment including analgesics in
combination with antiepileptics and antidepressants proved
to be ineffective and the patient consequently stopped taking
virtually all of her medical analgesic treatment. Several argu-
ments in favor of an entrapment cause for pudendal neuralgia
were identified: deterioration when sitting except on a toilet
seat, absence of nocturnal awakening, relief by anesthetic
nerve block, but also atypical signs (sensory loss of the but-
tock). Voiding disorders and suprapubic pain at the insertion
of rectus abdominis muscles were attributed to reflex muscle
hypertonia. MRI investigation demonstrated the presence
of a minimal syringomyelic cavity at T8, which could not
explain the clinical features. Anesthetic infiltrations of the
Fig. 1. Clinical data. a: Course of pain after a trial of repetitive Transcranial Magnetic Stimulation (rTMS) as
reported by the patients. Pain relief was obtained after 1 or 2 days and lasted several days before returning to
baseline. b: Course of pain after motor cortex stimulation, showing persistent post-operative pain relief. c: Course
of time to onset of pain when sitting. Pain-free period when sitting was significantly longer post-operatively.
d: Analgesic intake assessed by Medication Quantification Score (MQS). No modification was observed for patient
2 due to the low level of analgesic intake.
Louppe et al.
Neurourology and Urodynamics DOI 10.1002/nau
pudendal nerve indicated an entrapment syndrome and pu-
dendal nerve release was then performed. Unfortunately, pain
persisted and a neuromodulation technique was considered
1 year after the operation. Due to the anatomical site of the
syringomyelic cavity (T8), spinal cord stimulation was consid-
ered to be inappropriate and motor cortex stimulation was
preferred. Two rTMS sessions were performed with the same
stimulation parameters. A significant improvement of pain
was observed for 3 weeks after the first session and a highly
significant reduction of the VAS was observed for 48 hr after
the second rTMS session (Fig. 1). Placebo stimulation was
negative, confirming the good indication for motor cortex
stimulation. Unlike the first patient, two cortex stimulation
electrodes were used (Fig. 3), and the correct positioning of the
electrodes was confirmed intraoperatively by inducing motor
responses of the anal sphincter. The post-operative result was
rapidly favorable and improvement of pain ranging from 40%
to 50% was still observed 19 months after the operation.
Except for the amplitude (2 V) the parameters used for chronic
stimulation were the same as those used for patient 1. Medi-
cal analgesic treatment, already moderate preoperatively, was
not modified. However, time to onset of pain on sitting was
markedly improved, increasing from 15 to 90 min and largely
contributing to improvement of activities of daily living.
Pudendal neuralgia can be explained by pudendal nerve en-
trapment in one or several narrow passages along the course
of the nerve, corresponding to a tunnel syndrome. The history
of entrapment, the possible sequelae of surgical operations,
and the chronicity of pain can explain why pain gradually
takes on a refractory neuropathic nature, as observed in both
cases reported here. In both, pain was refractory to optimal
medical treatment of neuropathic pain, anesthetic blocks
and pudendal nerve release. Conventional neuromodulation
techniques, such as spinal cord stimulation, either failed
(patient 1) or were considered to be inappropriate (patient 2).
The results of S3 or pudendal nerve stimulation were consid-
ered to be insufficient to consider these techniques.
As the efficacy of motor cortex stimulation (MCS) in the
treatment of refractory central or peripheral neuropathic pain
syndromes, both in animals19,37and humans, even after a fail-
ure of spinal cord stimulation therapy, has been proved by a
number of RCTs,21,22,25,38,39the use of MCS therefore appeared
to be justified in this setting. MCS seems to be technically
Fig. 2. Motor evoked potentials (MEPs) recorded intraoperatively in patient
1. The recording electrodes were placed at the level of the anal sphincter
(SA), the left hand (first dorsal interosseous muscle [MID]) and the left leg
(tibialis anterior muscle [TA]). The motor responses (MEPs) induced by
intraoperative cortical stimulation are represented on the three lines.
Stimulation of contact 1 (primary motor cortex area [M1] corresponding to
the representation of the body and perineal region [Fig. 3]) induces MEPs in
the SA (third line) confirming an adequate targeting for the positioning
of the electrode (four pole-contacts) which will be used for chronic stimula-
tion. MEPS are normally also recorded in the MID (first line) and TA (second
line) whose respective M1 representation are situated from both part from
those corresponding to SA (Fig. 3).
Fig. 3. Site of cortical stimulation electrode contacts in patient 1 (fusion of pre- and post-operative CT scan
images). Representation of the four pole-contact of the electrode. Contacts are numbered from 0 to 3. Contact 1 is
situated just anteriorly to the central sulcus (CS) corresponding to M1. M1 corresponding to the upper limb (UL) is
situated more laterally at the level of the so-called knob (K). M1 corresponding to the inferior limb is situated
medially, near the midline (ML). The M1 representation of the body, including the perineal area is situated in
between these two areas, which was confirmed by intraoperative stimulation (Fig. 2). Chronic stimulation param-
eters were adjusted in order to use contact 1 as the stimulating contact (cathode). SFS, superior frontal sulcus, IFS,
inferior frontal sulcus.
MCS in Refractory Pelvic and Perineal Pain
Neurourology and Urodynamics DOI 10.1002/nau
easier and safer to perform than deep brain stimulation (DBS),
which is an important reason for the current emphasis on de-
velopment of MCS over DBS in the surgical treatment of re-
No case of treatment of pain in the perineal region has been
reported to date.
The work by Tsubokawa, published in 1991,19showed that
motor cortex stimulation could be effective in the treatment
of refractory neuropathic pain, especially post-stroke central
pain. Cortical targets other than the motor cortex have been
proposed in the treatment of refractory neuropathic pain:
some studies have shown pain relief from postrolandic corti-
cal stimulation40,41and some experimental data support the
analgesic effect of primary or secondary somatosensory cortex
stimulation.42,43However, in line with Tsubokawa’s work,
most research teams have found that stimulation using pre-
central contacts was more efficacious than stimulation using
post-central ones, when the MCS lead was positioned perpen-
dicular to the central sulcus. Furthermore, these studies
showed that targeting the motor cortex alone was insufficient
to achieve analgesia—in addition, positioning of the electrode
over the area of somatotopic representation of the painful
zone within the primary motor cortex was also required to
obtain optimal benefit. All studies reported a delay of several
days to several weeks between the onset of stimulation and
The principle of this technique is to chronically stimulate
the motor cortex region corresponding to the painful zone by
implanting one or several electrodes into the extradural space,
which are then connected to a totally implantable pacemaker
type of stimulator.
The mechanisms of action of MCS probably concern differ-
ent neural structures and pathways involved in pain modula-
tion, some of them distant from the site of stimulation,
probably explaining the remarkable analgesic effect of this
technique: the following hypothesis were supported by PET
studies: reduction of the pain-related thalamic hyperactivi-
ty,44suggesting antidromic modulation of the thalamocortical
pathways; enhancement of the release of endogenous opioids
in various brain structures, especially in cingulated cortex
and PAG;45activation of descending pathways, leading to
reinforced or restored inhibitory control of nociceptive trans-
mission in the dorsal horns of the spinal cord;46; activation of
mesencephalic and cortical areas, remote from the site of
stimulation, and involved in the affective and emotional
aspects of pain (insular, cingulated and orbitofrontal corti-
ces);47reinforcement of intracortical GABAergic inhibition.48
MCS is associated with low overall rates of adverse events,
and is considered safer than DBS, as intracranial hemorrhage
does not occur. Complications are mainly related to infections
in the vicinity of the implanted generator. Rare cases of
seizures, which occurred during the immediate post-operative
period, in programming trials (but never during chronic
stimulation), have been reported.49
Identification of the appropriate zone of cortex is a very
important phase of this technique.25This zone is usually
localized intraoperatively by examining the motor responses
obtained by stimulating various cortical zones. In the particu-
lar case of perineal pain, motor responses must be obtained in
the perineal region, which was achieved in both of our
patients by using electrodes implanted in the anal sphincter.
The potential result of the operation is now tested preopera-
tively by using rTMS. The usual protocol consists of detecting
the region of the motor cortex corresponding to the painful
region. This can be easy in the case of upper limb pain, as
motor responses can be observed clinically in the intrinsic
muscles of the hand, but can be much more difficult in the
perineal region. However, several reliable studies33–35have
shown that the area of the primary motor cortex (M1) corre-
sponding to the perineal region is relatively limited and situ-
ated between the area corresponding to the upper limb and
that corresponding to the lower limb (Fig. 2). Classically,29M1
corresponding to the inferior limb is situated at the level of
internal face of the brain but it superior limit regularly reach
the upper part of the convexity,25offering the possibility of
obtaining motor responses in the limb by stimulating the
brain surface near the midline. After locating the cortical
target, conventional rTMS consists of stimulating this zone at
an intensity corresponding to about 80% of the motor thresh-
old during 20 min. The expected result is an improvement of
pain, which is usually observed after an interval of 24–48 hr
and which lasts for 5–8 days. It is recommended to perform
several sessions to facilitate interpretation of the results and,
ideally, one or several ‘‘placebo’’ sessions should be performed
by using appropriate bobbins. Only one rTMS session was per-
formed in our first patient, but three sessions, including a pla-
cebo session, were performed in the second patient. In both
cases, the results of the operation confirmed the results of the
rTMS test sessions. We therefore strongly recommend that the
results of rTMS be evaluated before confirming the indication
for implanted motor cortex stimulation.
Motor cortex stimulation constitutes a new treatment
option for unilateral refractory chronic pelvic and perineal
pain, particularly after failure of conventional neuromodula-
tion techniques (especially spinal cord stimulation) and when
rTMS is effective. Prospective randomized studies in a larger
population using both rTMS and implanted motor cortex
stimulation need to be conducted in order to confirm the good
results obtained in these first two cases.
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MCS in Refractory Pelvic and Perineal Pain
Neurourology and Urodynamics DOI 10.1002/nau