Pr Patrick MERTENS

Pain Assessment and Treatment Center (CETD)

The pain assessment and treatment center takes care of chronic pain that is refractory to the usual treatments that can be offered in other centers.

Pr Patrick Mertens

University professor in Anatomy Hospital practitioner in Neurosurgery

  • Head of department of functional neurosurgery, spinal cord and nerve surgery peripheral devices.
  • Coordinator of the HCL Neurosurgery Federation Head of department of the HCL pain assessment and treatment center Head of the Anatomy laboratory at the Lyon-est Faculty of Medicine
  • Former president of the French Society of Neurosurgery.
  • Member of the board of the World Federation of Neurosurgical Societies and the World Society of Stereotactic and Functional Neurosurgery

Axes de recherche récents :

Member of the INSERM 1024 – CNRS UMR 5292 team “Central integration of pain in humans” within the LYON Neurosciences Research Center

Clinical research on the evaluation of innovative surgical techniques in neuromodulation for the treatment of chronic pain (neurostimulation – analgesic medicinal infusions).

Evaluation of surgical techniques for the treatment of spastic motor disabilities.

Study of the microsurgical anatomy of the spinal cord.

Links with other national or international teams

  • Within the FHU InnovPain: the neurosurgical and medical pain teams of University Hospital of NICE, MARSEILLE, SAINT ETIENNE, CLERMONT FERRAND, POITIERS
  • Within common research protocols: CETD FOCH Hospital and ROTSCHILD PARIS, CETD ANGERS, CHU NANTES – AP-HP BEAUJON
  • Internationally: Neurosurgical team Pr. BROWN HARVARD University – USA, Dr DELTOMBE University of LIÈGE – BELGIUM, Team Dr CUBILLOS Santiago de CHILE University, Pr FERREIRA University of LISBON- PORTUGAL, Dr SUN JIAO TONG University SHANGHAY – CHINA.


Centre d’évaluation et de traitement de la douleur (CETD)

1. Spinal cord stimulation for chronic refractory pain: long-term effectiveness and safety data from a multicentre registry.

BRINZEU A, CUNY E, FONTAINE D, MERTENS P, LUYET PP, VAN DEN ABEELE C, DJIAN MC; French SCS study group. Eur J Pain. 2019 May;23(5):1031-1044

Spinal cord stimulation for chronic refractory pain — Abstract


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Background: Spinal cord stimulation (SCS) is an established therapy for refractory
neuropathic pain. To ascertain the balance between treatment benefits and risks, the
French National Authority for Health requested a post-market registry for real-world
evaluation of the long-term effectiveness and safety of the therapy.

Methods: A total of 402 patients undergoing implantation with a Medtronic SCS
device as either a primo-implant (n = 264) or replacement implant (n = 138) were
enrolled across 28 representative sites in France. Outcome measures at 2 years
included pain intensity, satisfaction with treatment, improvement of pain relief and
daily life activity, willingness to undergo the treatment again and use of pain
treatments. A patient was considered a responder if, compared to baseline,
predominant pain reduction was ≥50%.
Results: At the 2-year follow-up visit, predominant pain intensity for primo-implant
patients had decreased from baseline (p < 0.001), with responder rates of 55%, 36%
and 67% for the lower limbs, back and upper limbs, respectively. Most patients
acknowledged an improvement in pain relief (89%) and daily life activity (82%) were
satisfied with treatment (91%) and willing to undergo the treatment again (93%). A
significant decrease (p < 0.01) in the proportion of patients receiving pain treatment
was observed for all drug and non-drug treatments. Reported adverse events were in
line with the literature. Pain intensity at 2 years was comparable for patients in the
replacement group, supporting the long-term stability and effectiveness of SCS.
Conclusion: Real-world evaluation of the use of spinal cord stimulation under the
recommendations of the French Health Authority shows that two years after the first
implantation of an SCS device close to 60% of the patients retain a significant pain
reduction and 74% show improvement in pain scores [of at least 30%] with significant
decreases in drug and non-drug pain treatments.
Significance: This observational, prospective study in a real-life setting followed a
large cohort of patients suffering from chronic pain and implanted with SCS devices
in France. The study assessed the long-term effectiveness and safety of SCS
therapy in a representative sample of implanting sites in France.

2. Anatomy of the human spinal cord arachnoid cisterns: applications for spinal cord surgery.

DAULEAC C, JACQUESSON T, MERTENS P. J Neurosurg Spine. 2019 Jul 12:1-8.

Anatomy of the human spinal cord arachnoid cisterns — Abstract


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Objective: The goal in this study was to describe the overall organization of the
spinal arachnoid mater and spinal subarachnoid space (SSAS) as well as its
relationship with surrounding structures, in order to highlight spinal cord arachnoid
Methods: Fifteen spinal cords were extracted from embalmed adult cadavers. The
organization of the spinal cord arachnoid and SSAS was described via macroscopic
observations, optical microscopic views, and scanning electron microscope (SEM)
studies. Gelatin injections were also performed to study separated dorsal
subarachnoid compartments.

Results: Compartmentalization of SSAS was studied on 3 levels of axial sections.
On an axial section passing through the tips of the denticulate ligament anchored to
the dura, 3 subarachnoid cisterns were observed: 2 dorsolateral and 1 ventral. On an
axial section passing through dural exit/entrance of rootlets, 5 subarachnoid cisterns
were observed: 2 dorsolateral, 2 lateral formed by dorsal and ventral rootlets, and 1
ventral. On an axial section passing between the two previous ones, only 1
subarachnoid cistern was observed around the spinal cord. This
compartmentalization resulted in the anatomical description of 3 elements: the
median dorsal septum, the arachnoid anchorage to the tip of the denticulate
ligament, and the arachnoid anchorage to the dural exit/entrance of rootlets. The
median dorsal septum already separated dorsal left and right subarachnoid spaces
and was described from C1 level to 3 cm above the conus medullaris. This septum
was anchored to the dorsal septal vein. No discontinuation was observed in the
median dorsal arachnoid septum. At the entrance point of dorsal rootlets in the spinal
cord, arachnoid trabeculations were described. Using the SEM, numerous arachnoid
adhesions between the ventral surface of the dorsal rootlets and the pia mater over
the spinal cord were observed. At the ventral part of the SSAS, no septum was
found, but some arachnoid trabeculations between the arachnoid and the pia mater
were present and more frequent than in the dorsal part. Laterally, arachnoid was
firmly anchored to the denticulate ligaments' fixation at dural points, and dural
exit/entrance of rootlets made a fibrous ring of arachnoidodural adhesions. At the
level of the cauda equina, the arachnoid mater surrounded all rootlets together-as a
sac and not individually.
Conclusions: Arachnoid cisterns are organized on each side of a median dorsal
septum and compartmentalized in relation with the attachments of denticulate
ligament and exit/entrance of rootlets.
Keywords: AVM = arteriovenous malformation; DREZ = dorsal root entry zone; SEM
= scanning electron microscope; SSAS = spinal subarachnoid space; anatomy;
arachnoid; cistern; spinal cord; subarachnoid space.

3. Ziconotide for spinal cord injury-related pain.

Eur J Pain. 2019 Oct;23(9):1688-1700.

Ziconotide for spinal cord injury-related pain — Abstract


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Background: Central neuropathic pain related to spinal cord injury is notoriously
difficult to treat. So far most pharmacological and surgical options have shown but
poor results. Recently ziconotide has been approved for use both neuropathic and
non-neuropathic pain. In this cohort study, we assessed responder rate and long-
term efficacy of intrathecal ziconotide in patients with pain related to spinal cord
Methods: Patients presenting chronic neuropathic related to spinal cord lesions that
was refractory to medical pain management were considered for inclusion. Those

accepting were tested by lumbar puncture injection of ziconotide or continuous
intrathecal infusion and if a significant decrease in pain scores (>40%) was noted
they were implanted with a continuous infusion pump. They were then followed up for
at least 1 year with constant assessment of the evolution of pain and side effects.
Results: Out of the 20 patients tested 14 had a decrease in pain scores of more than
40% but only 11 (55%) were implanted with permanent pumps due to side effects
and patient choice. These were followed up on average for 3.59 years (±1.94) and in
eight patients an above threshold decrease in pain scores was maintained. Overall in
patients that responded to the test baseline VAS was 7.91 and 4.31 at last follow-up
with an average dose of 7.2 μg of ziconotide per day. Six patients (30%) did not
respond to any test and in three patients side effects precluded pump implantation.
No significant long-term effects of the molecule were noted.
Conclusion: This study shows response to intrathecal ziconotide test in 40% of the
patients of a very specific population in whom other therapeutic options are not
available. This data justifies the development further studies such as a long-term
randomized controlled trial.
Significance: Intrathecal Ziconotide is a posible alternative for the treatment of pain
in patients with spinal cord injury and below level neuropathic pain.

4. Anatomical and Histological Analysis of a Complex Structure Too Long Considered a Simple Ligament: The Filum Terminale.

World Neurosurg. 2019 Sep;129: 464-471.

Anatomical and Histological Analysis of a Complex Structure Too Long Considered a Simple Ligament — Abstract


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Background: The intradural filum terminale (iFT) connects the conus medullaris
(CM) with the dural sac (DS), and the extradural filum terminale (eFT) connects the
DS to the coccyx. The aim of the present study was to update the description of the
FT and integrate these data in a physiological and pathological context.
Methods: Anatomical measurements and histological investigations were performed
on 10 human cadavers.
Results: The mean length of the iFT and eFT was 167.13 and 87.59 mm,
respectively. The mean cranial diameter of the iFT was 1.84 mm. It was >2 mm in 2
specimens. The mean half and caudal diameter of the iFT was 0.71 and 0.74 mm,
respectively. The cranial diameter of the eFT correlated with the caudal diameter of
the eFT (ρ = 0.94; P = 0.02). The level of the CM-iFT junction correlated significantly
with the iFT length (ρ = -0.67; P = 0.03). The mobilization of the iFT was not
transmitted to the extradural elements and vice versa. The iFT contained axons and
ependymal cells, which were dense in the first third and then randomly arranged
caudally in islets. This could explain why ependymomas can occur all along the iFT.
Ganglion cells were abundant around the junction with the DS. The eFT contained
smooth muscle cells, adipocytes, and axons. A mechanoreceptor was identified in 1

Conclusions: Consistently with their common embryological origin, a real
anatomical and histological continuum is present between the CM and FT. The FT
should, therefore, no longer be considered a simple ligament but, rather, a complex
fibrocellular structure.
Keywords: Anatomy; Ependymoma; Filum terminale; Histology; Spine; Tethered
cord syndrome.

5. – Stimulation of the motor cerebral cortex in chronic neuropathic pain: the role of electrode localization over motor somatotopy.

J Neurosurg Sci. 2020 Sep 18. doi: 10.23736/S0390-5616.20.04991-7. Online ahead of print.PMID: 32951416

Stimulation of the motor cerebral cortex in chronic neuropathic pain — Abstract


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Background: Previous studies have reported the pain-relieving effect of chronic
electrical motor cortex stimulation (eMCS) in various types of neuropathic pain. The
study aimed to explore the potential relationship between the clinical efficacy of
eMCS for the treatment of chronic neuropathic pain and the precise localization of
the contacts over the motor cortex somatotopic representation of the painful area.
Methods: A total of 22 patients with neuropathic pain were implanted with eMCS
electrodes. Implantation of the electrodes was performed using intraoperative 1)
anatomical identification by neuronavigation software using 3D-MRI; 2) monitoring of
somesthetic evoked potentials to check the potential reverse over the central sulcus;
and 3) electrical stimulations through the dura to identify the motor responses and its
somatotopy. Image fusion of postoperative 3D-CT and preoperative MRI images
allowed postoperative location of the electrodes.

Results: Analgesic effects were obtained in 18 (81.81%) out of 22 patients.
Postoperative 3D-CT analysis showed a correspondence between localization of the
contacts and the motor cerebral cortex somatotopy in the patients with postoperative
good analgesic effects. No correspondence was found between localization of the
contacts and the motor cerebral cortex somatotopy in the four patients with no
analgesic effects. In three out of these four patients, analgesic effects were obtained
after new surgery allowed repositioning of the electrode over the motor cortex
somatotopy of the painful area.

Conclusions: The findings of this study suggest that eMCS provides analgesic
effects when the stimulated cortex corresponds to the somatotopy of the painful area.

6. Overcoming challenges of the human spinal cord tractography for routine clinical use: a review.

Neuroradiology. 2020 Sep;62(9):1079-1094.

Overcoming challenges of the human spinal cord tractography for routine clinical use — Abstract


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The spinal cord (SC) is a dense network of billions of fibers in a small volume
surrounded by bones that makes tractography difficult to perform. We aim to provide
a review collecting all technical settings of SC tractography and propose the optimal
set of parameters to perform a good SC tractography rendering.

database was searched for articles reporting “spinal cord” “tractography” in
“humans”. Studies were selected only when tractography rendering was displayed
and MRI acquisition and tracking parameters detailed. From each study, clinical
context, imaging acquisition settings, fiber tracking parameters, region of interest
(ROI) design, and quality of the tractography rendering were extracted. Quality of
tractography rendering was evaluated by several objective criteria proposed herein.
According to the reported studies, to obtain a good tractography rendering, diffusion
tensor imaging acquisition should be performed with 1.5 or 3 Tesla MRI, in the axial
plane, with > 20 directions; b value: 1000 s mm -2 ; right-left phase-encoding direction
for cervical SC; isotropic voxel size; and no slice gap. Concerning the tracking
process, it should be performed with determinist approach, fractional anisotropy
threshold between 0.15 and 0.2, and curvature threshold of 40°. ROI design is an
essential step for providing good tractography rendering, and their placement has to
consider partial volume effects, magnetic susceptibility effects, and motion artifacts.
The review reported herein highlights that successful SC tractography depends on
many factors (imaging acquisition settings, fiber tracking parameters, and ROI
design) to obtain a good SC tractography rendering.

Keywords: Diffusion tensor imaging; Fiber tracking; Review; Spinal cord;

7. – Predictors of functional outcome after spinal cord surgery: Relevance of intraoperative neurophysiological monitoring combined with preoperative
neurophysiological and MRI assessments.

7053(22)00019-3. doi: 10.1016/j.neucli.2022.03.004.

Predictors of functional outcome after spinal cord surgery — Abstract


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Objectives: To assess the accuracy of intraoperative neurophysiological monitoring
(IONM) in predicting immediate and 3-month postoperative neurological new deficit
(or deterioration) in patients benefiting from spinal cord (SC) surgery; and to identify
factors associated with a higher risk of postoperative clinical worsening.

Methods: Consecutive patients who underwent SC surgery with IONM were
included. Pre and postoperative clinical (modified McCormick scale), radiological
(lesion-occupying area ratio), and electrophysiological features were collected.
Results: A total of 99 patients were included: 14 (14.1%) underwent extradural
surgery, 50 (50.5%) intradural extramedullary surgery, and 35 (35.4%) intramedullary
surgery. Cumulatively, multimodal IONM (motor and somatosensory evoked
potentials, D-wave whenever possible) significantly predicted postoperative deficits
(p<0.001), with a sensitivity, specificity, positive predictive value, and negative
predictive value of 0.81, 0.93, 0.83, and 0.92, respectively. Sixty (60.6%) patients
displayed no IONM change, whereas 39 (39.4%) displayed IONM worsening. In
multivariate analysis, predictors for postoperative clinical worsening were: abnormal
preoperative electrophysiological assessment (p=0.03), intramedullary tumor
(p<0.001), lesion-occupying area ratio ≥0.7 (p<0.001), and IONM alterations
(p<0.001). Three months after the surgical procedure, in patients presenting at least
one of the risk factors described above, 45/81 (55.6%) and 19/81 (23.5%) were
clinically and electrophysiologically improved, respectively; while 13/81 (16.0%) and
10/81 (12.3%) were clinically and electrophysiologically worsened.

Conclusion: Multimodal IONM is an essential tool to guide SC surgery, and enables
the accurate prediction of postoperative neurological outcome. Specific attention
should be given to patients presenting with preoperative electrophysiological
abnormalities, large tumor volume, and intramedullary tumor location.
Keywords: D-wave; Intraoperative neurophysiological monitoring; Motor evoked
potentials; Somatosensory evoked potentials; Spinal cord.

8. Anatomical study of the thoracolumbar radiculomedullary arteries (the Adamkiewicz artery and supporting radiculomedullary arteries).

JNS Spine, 2022

Anatomical study of the thoracolumbar radiculomedullary arteries— Abstract


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Objective: The aim of this paper was to identify and characterize all the segmental
radiculomedullary arteries (RMAs) that supply the thoracic and lumbar spinal cord.
Methods: All RMAs from T4 to L5 were studied systematically in 25 cadaveric
specimens. The RMA with the greatest diameter in each specimen was termed the
artery of Adamkiewicz (AKA). Other supporting RMAs were also identified and

Results: A total of 27 AKAs were found in 25 specimens. Twenty-two AKAs (81%)
originated from a left thoracic or a left lumbar radicular branch, and 5 (19%) arose
from the right. Two specimens (8%) had two AKAs each: one specimen with two
AKAs on the left side and the other specimen with one AKA on each side. Eight
cadaveric specimens (32%) had 10 additional RMAs; among those, a single additional RMA was found in 6 specimens (75%), and 2 additional RMAs were found in each of the remaining 2 specimens (25%). Of those specimens with a single additional RMA, the supporting RMA was ipsilateral to the AKA in 5 specimens (83%) and contralateral in only 1 specimen (17%). The specimens containing 2 additional RMAs were all (100%) ipsilateral to their respective AKAs.

Conclusions: The segmental RMAs supplying the thoracic and lumbar spinal cord
can be unilateral, bilateral, or multiple. Multiple AKAs or additional RMAs supplying a
single anterior spinal artery are common and should be considered when dealing
with the spinal cord at the thoracolumbar level.

Keywords: anatomy; artery of Adamkiewicz; degenerative; hairpin turn;
radiculomedullary artery.

9. eDOL mHealth App and Web Platform for Self-monitoring and Medical Follow-up of Patients With Chronic Pain: Observational Feasibility Study.

Form Res. 2022 Mar 2;6(3):e30052. doi: 10.2196/30052

eDOL mHealth App and Web Platform for Self-monitoring and Medical Follow-up of Patients With Chronic Pain — Abstract


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Background: Chronic pain affects approximately 30% of the general population,
severely degrades quality of life (especially in older adults) and professional life
(inability or reduction in the ability to work and loss of employment), and leads to
billions in additional health care costs. Moreover, available painkillers are old, with
limited efficacy and can cause significant adverse effects. Thus, there is a need for
innovation in the management of chronic pain. Better characterization of patients
could help to identify the predictors of successful treatments, and thus, guide
physicians in the initial choice of treatment and in the follow-up of their patients.
Nevertheless, current assessments of patients with chronic pain provide only
fragmentary data on painful daily experiences. Real-life monitoring of subjective and
objective markers of chronic pain using mobile health (mHealth) programs can
address this issue.

Objective: We hypothesized that regular patient self-monitoring using an mHealth
app would lead physicians to obtain deeper understanding and new insight into
patients with chronic pain and that, for patients, regular self-monitoring using an
mHealth app would play a positive therapeutic role and improve adherence to
treatment. We aimed to evaluate the feasibility and acceptability of a new mHealth
app called eDOL.

Methods: We conducted an observational study to assess the feasibility and
acceptability of the eDOL tool. Patients completed several questionnaires using the
tool over a period of 2 weeks and repeated assessments weekly over a period of 3
months. Physicians saw their patients at a follow-up visit that took place at least 3
months after the inclusion visit. A composite criterion of the acceptability and

feasibility of the eDOL tool was calculated after the completion of study using
satisfaction surveys from both patients and physicians.

Results: Data from 105 patients (of 133 who were included) were analyzed. The rate
of adherence was 61.9% (65/105) after 3 months. The median acceptability score
was 7 (out of 10) for both patients and physicians. There was a high rate of
completion of the baseline questionnaires and assessments (mean 89.3%), and a
low rate of completion of the follow-up questionnaires and assessments (63.8%
(67/105) and 61.9% (65/105) respectively). We were also able to characterize
subgroups of patients and determine a profile of those who adhered to eDOL. We
obtained 4 clusters that differ from each other in their biopsychosocial characteristics.
Cluster 4 corresponds to patients with more disabling chronic pain (daily impact and
comorbidities) and vice versa for cluster 1.

Conclusions: This work demonstrates that eDOL is highly feasible and acceptable
for both patients with chronic pain and their physicians. It also shows that such a tool
can integrate many parameters to ensure the detailed characterization of patients for
future research works and pain management.

Trial registration: NCT03931694;

Keywords: chronic pain; eHealth; feasibility study; mHealth; self-monitoring.

10. Evaluation of Selective Tibial Neurotomy for the Spastic Foot Treatment Using a Personal Goal-Centered Approach: A 1-Year Cohort Study.

DAULEAC C, LUAUTE J, RODE G, AFIF A, SINDOU M, MERTENS P. Neurosurgery. 2022 Dec 23. doi: 10.1227/neu.0000000000002287. Online ahead of print.

Animal Feasibility Study of a Novel Spinal Cord Stimulation Multicolumn Lead (Heron Lead).

Mertens P, Cantone MC, Antonini A, Ferrari S, Ferpozzi V, Abd-Elsayed A. Discov Med. 2023 Aug;35(177):632-641.

Evaluation of Selective Tibial Neurotomy for the Spastic Foot Treatment Using a Personal Goal-Centered Approach — Abstract


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Background: Selective tibial neurotomy (STN) has already demonstrated its effectiveness to reduce foot deformities and spasticity, but assessment according to a goal-centered approach is missing.

Objective: To evaluate the effectiveness of STN associated with a postoperative rehabilitation program for the treatment of the spastic foot, according to a goal- centered approach.

Methods: Interventional study (before-after STN and rehabilitation program) with observational design including consecutive adult patients with spastic foot, who received STN followed by a rehabilitation program, was performed. The primary outcome measure was the achievement of individual goals at the 1-year follow-up using the Goal Attainment Scaling methodology (with T-score). The secondary outcomes measures were the Modified Ashworth Scale and the modified Rankin Score.

Results: A total of 104 patients were included. At the 1-year follow-up, 228/252 (90.5%) goals were achieved: 62/252 (24.6%) were achieved as initially expected, 86/252 (34.1%) were achieved better than initially expected, and 80 (31.7%) were achieved much better than initially expected. The mean T-score was significantly increased at the 1-year follow-up (61.5 ± 10.5) compared with the preoperative period (38.1 ± 2.9, P &lt; .00001), and 95/104 (91.3%) patients had a T-score ≥50, meaning that these patients have achieved their goals. At follow-up, spastic deformities were all significantly decreased ( P &lt; .0001), the Modified Ashworth Scale was significantly lower for each muscle targeted ( P &lt; .0001), and the modified Rankin Score was significantly decreased ( P &lt; .0001) allowing the patient population to improve from a moderate to a slight disability status.

Conclusion: This study showed that STN, associated with a postoperative
rehabilitation program, successfully achieve personal goals in patients with spastic