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sumably removes the segmental pool of hyperexcitable
neurons and denervation hypersensitivity, eliminating
convergence and severing the ascending intranuclear
pathways. Th e technique has been well described [31].
In brief, patients undergo surgery under neuroleptic an-
algesia, with the head fully fl exed within a stereotactic
frame. Electrical stimulation clearly identifi es the tri-
geminal region, with its rostral dermatome located ven-
trolaterally and its caudal dermatome dorsomedially. It
is usually possible to further defi ne the dorsal border of
the nucleus by ipsilateral responses induced from the
cuneatus tract and its ventral border by contralateral
responses elicited from the spinothalamic tract, or at
times by motor responses obtained from a posteriorly
located corticospinal tract [68].
In addition, threshold stimulation often mim-
ics the patient’s neuropathic pain. Th is procedure al-
lows for the placement of accurate stereotactic lesions
with concomitant electrophysiological control of cranial
nerves V, VII, IX, and X, as well as of the second and
third cervical roots, at the nucleus caudalis (Fig. 3). Sch-
varcz has used this technique since 1971, terming the
Fig. 3. Postsurgical magnetic resonance image after stereotactic trigeminal nucleotomy. Arrows show that the radiofrequency lesion is entirely within the nucleus caudalis area: (a) axial view, (b) coronal view.
a b
Surgical Treatment for Neuropathic Pain 443
procedure trigeminal nucleotomy to emphasize the
signifi cance of lesioning primarily the second-order
neurons at the oral pole of the nucleus caudalis, which
are heavily involved in intrinsic mechanisms pertain-
ing to dysesthetic facial pain [65,71]. From a series of
204 consecutive nucleotomies performed on 196 pa-
tients, 143 underwent this procedure for deaff erenta-
tion pain [57]. In this study, Piedimonte and Schvarcz
reported abolition of allodynia and a marked reduc-
tion of deep background pain in 75.0% of patients with
postherpetic dysesthesia, 71.7% of those with dyses-
thesia, 66.7% of those with anesthesia dolorosa, and
77.8% of those with posttraumatic neuropathy [57].
Siqueira described a method for open surgical
trigeminal nucleotomy [84], and Kanpolat et al. devel-
oped an elegant computed tomography–guided per-
cutaneous technique for trigeminal nucleotomy [35];
both of these methods were for deaff erentation pain.
Grigorian and Slavin also reported good results with
ultrasound-guided trigeminal nucleotomy for deaff er-
entation pain [21]. Even though stereotactic trigeminal
nucleotomy is a reasonably straightforward technique,
especially suitable for elusive dysesthetic facial pain
phenomena, its use has been diminished with the de-
velopment of neuromodulation techniques.
Dorsal Root Entry Zone Lesions
In the 1960s, several neurophysiological investigations
showed that the dorsal horn is the fi rst, and an impor-
tant, level of modulation for pain sensation. Th is was
popularized in 1965 by the gate-control theory [49],
which drew neurosurgeons’ attention to this area as a
possible target for augmentative (spinal cord stimula-
tion) and ablative pain surgery.
Sindou and colleagues have attempted a micro-
surgical DREZotomy procedure in patients with neuro-
pathic pain syndromes, such as those associated with
paraplegia and brachial plexus avulsion, since 1972,
owing to encouraging early results with malignancies
na injury, phantom limb and stump pain, intercostal
neuralgia, postherpetic neuralgia [79], and painful legs
and moving toes [60].
Th e majority of electrode leads selected for
implant are percutaneous. Surgical leads (plate elec-
trodes) are considered to be less likely to dislocate and
are greatly preferred when a percutaneous cable lead
has been dislocated several times or when scar tissue
prevents the passing of such an electrode to the tar-
get area (Fig. 5). A stimulation trial using temporary
percutaneous extension cables is an indispensable step
Fig. 4. Postsurgical frontal (a) and lateral (b) X-ray control images showing tetrapolar electrodes for the synergic stimulation of the spheno-palatine ganglion (SPG) and great occipital nerve (GON).
a b
Surgical Treatment for Neuropathic Pain 449
in deciding whether or not a complete stimulation sys-
tem should be permanently implanted [22]. In many
countries, a period of trial stimulation is required for
reimbursement.
Motor Cortex Stimulation
Th e use of motor cortex stimulation (MCS) to con-
trol central pain was introduced by Tsubokawa et al.
especially for poststroke pain in 1991 [96], by Mey-
erson et al. for trigeminal neuropathic pain in 1993
[50], and by Katayama et al. for Wallenberg syndrome
in 1994 [37]. Despite encouraging results, the mecha-
nisms of MCS have yet to be elucidated. Th e surgical
technique consists of a small craniotomy performed
around the area identifi ed as the precentral gyrus
during preoperative planning. Somatosensory evoked
potentials are obtained with the use of electrode grids
to identify the central sulcus and its orientation via
the detection of N20-P20 phase reversal. Stimulation
is attempted with individual contacts of the grid. Th e
goal is to locate the contact that produces motor re-
sponses in the painful area. Th e positions of the iden-
tifi ed electrodes can be marked on the corresponding
dura mater, indicating the position and orientation
for electrodes to be implanted.
According to Tsubokawa et al., the best loca-
tion and orientation of the electrode array corresponds
to the site where bipolar stimulation produces muscle
twitches in the painful area with the lowest threshold
[97]. After identifi cation of the appropriate location,
the electrode array is sutured tightly on the dural sur-
face, and the stimulation system is internalized. On the
following days, the parameters for chronic stimulation
are selected to achieve optimal pain control. Outcomes
from series in the literature indicate that positive results
can be accomplished with this method and may be long
lasting.
Sindou et al. reported the results of 127 opera-
tions from diverse published series [80]. A total of 86
patients had pain after stroke, 29 presented with tri-
geminal neuropathic pain, and 12 experienced pain of
miscellaneous origin. Pain relief of >50% was obtained
after a 1-year follow-up in two-thirds of the patients
with poststroke pain and in patients with neuropathic
trigeminal pain. In most patients, relief persisted on
long-term follow-up (1–6 years; average 2 years).
ab
Fig. 5. Radiograph showing spinal cord stimulation surgical lead electrodes in a patient with failed back surgery sydrome after spinal lumbar fusion: (a) frontal view, (b) lateral view.
450 Fabián C. Piedimonte
A double-blind assessment of a group of pa-
tients with implanted motor cortex stimulators has
corroborated the efficacy of this method [102]. In
this study, stimulation was randomized to the off
mode for a period of 30 days at 60 or 90 days post-
implantation with active stimulation, and pain levels
were reassessed. The results indicated that pain lev-
els were significantly reduced by stimulation and sig-
nificantly increased when the stimulation was turned
off. In all series, complications were limited to occa-
sional seizures by the time intensity parameters were
adjusted. In conclusion, MCS is recommended for
treating poststroke pain and trigeminal pain of neu-
ropathic origin.
Deep Brain Stimulation
Deep brain stimulation (DBS) has been used to treat in-
tractable pain for more than 50 years. Heath and Mick-
le [30] and Pool et al. [58] reported analgesic eff ects
in patients receiving stimulation in the septal region.
By the 1970s and 1980s, thalamic and periaqueductal
gray/periventricular gray stimulation were common-
ly used for the treatment of chronic refractory pain
[32,48,63,91,98]. Th ough no proper studies comparing
the outcomes of DBS in diff erent targets have been con-
ducted, the general consensus is that neuropathic pain
is more likely to respond to stimulation of the sensory
thalamus, whereas nociceptive pain responds better to
[43]. Patients with mixed pain may be implanted with
electrodes in both structures.
In addition to these more common targets,
DBS of the internal capsule has been routinely off ered
to poststroke patients with signifi cant thalamic atro-
phy [2,40]. Other targets leading to good outcomes in
small clinical series or case reports are the septal re-
gion [67,69], medial thalamus (including the centro-
median-parafascicular nuclei) [6,66,94], and cingulate
gyrus [87]. Within the past decades, there has been
a progressive decrease in the number of published
studies and the number of patients with chronic pain
treated with DBS. Th is has been partially attributed
to the development and use of less-invasive alterna-
tives for the management of neuropathic pain includ-
ing catheters and pumps for drug administration, new
pharmacological agents, and spinal cord and motor
cortex stimulation. Despite these facts, DBS continues
to be off ered routinely to patients with chronic refrac-
tory neuropathic pain.
Boccard et al. recently reported 85 patients
who underwent DBS for chronic neuropathic pain of
diff erent etiologies, targeting the periventricular gray
area in 33 patients, the ventral posterior nuclei of the
thalamus in 15, or both in 37. Almost 70% of the pa-
tients retained implants 6 months after surgery. A to-
tal of 39 of 59 (66%) of those who retained implants
gained benefi t and effi cacy, depending on etiology,
improving outcomes by 89% for amputation pain and
70% for stroke pain [11].
Final Remarks
As John Bonica presciently expressed, we should try to
know all the therapeutic options available for pain con-
trol, even if we are not the ones who will carry out these
techniques. Functional neurosurgery provides the nec-
essary tools for those complex cases that have not found
the solution with pharmacological treatment or less-
invasive techniques. Success depends on accurate diag-
nosis, adequate patient selection, proper choice of the
technique to be used, and its correct implementation.
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Correspondence to: Prof. Fabián C. Piedimonte, MD, Presi-dent, Fundación CENIT para la Investigación en Neuro-ciencias, Juncal 2222, 5º Piso, CABA, C1125ABD Argentina. Email: [email protected].