Chapter 21 Neurosurgical Procedures for Treatment of Intractable Pain Flashcards
1. Ablative techniques have been used for many decades to control intractable pain. While they continue to have some well-defined indications, they have largely been replaced by neurostimulation procedures. 2. The results of ablative procedures for pain tend to be highly variable, with a substantial proportion of patients obtaining relief early and then experiencing recurrence of pain. 3. Ablative procedures such as cordotomy may be useful in treating pain of malignant origin, given the limite
Methods used to lesion the nervous system
avulsion/resection of a peripheral nerve or cranial nerve branch. Thermocoagulation
(TC) or radiofrequency (RF) lesioning has been most
often used in the CNS, including the creation of ganglionic, spinal cord, and intracerebral lesions. Cryoablation
Criterias for patients selecting patients for Neurosurgical procedures
patient should have chronic pain that has failed to adequately respond to multiple other
conservative nonsurgical treatments. These may include rehabilitation, oral medications (anti-inflammatories, opioids,
anticonvulsants, antidepressants), and injections
DORSAL ROOT ENTRY ZONE LESIONS/CAUDALIS DORSAL ROOT ENTRY ZONE
lesioning of the dorsal root entry zone (DREZ) was seen as a way to
remove the portions of the CNS that had already undergone central sensitization in response to a peripheral lesion, such as malignancy or nerve injury. The lesions
are intended to injure Lissauer’s tract and preserve fibers
subserving proprioception and certain aspects of touch
that travel in the dorsal rootlets to the dorsal columns
DORSAL ROOT ENTRY ZONE LESIONS indications
treatment of pain due to traumatic brachial plexus root avulsions.
DORSAL ROOT ENTRY ZONE LESIONS/CAUDALIS DORSAL ROOT ENTRY ZONE PROCEDURE
- Intradural exposure of the intended anatomic levels is accomplished, 2. followed by microsurgical dissection of the dorsal rootlets to free them from each other. 3. After identifying the correct anatomic levels, either by electrical stimulation or the presence of avulsed rootlets, lesions are created on the inferolateral aspect of the
rootlet entry zone.
How does the fibers travel in the DREZ?
The small lightly or unmyelinated fibers that carry pain signals to the dorsal horn enter
from the lateral aspect of the DREZ while the medial side contains primarily those fibers destined for the dorsal
columns.
How are lesions created in the DREZ?
Lesions are created either by coagulating and opening the pia on the lateral aspect of the dorsal
rootlets followed by microbipolar coagulation of the DREZ (Sindou’s method) or by using a DREZ RF needle
(0.25-mm diameter) to make 1-mm–spaced lesions at 75oC for 15 s
treatment of facial pain
the lesions may be made in the trigeminal nucleus caudalis
What is the trigeminal nucleus caudalis?
a cranial continuation of the dorsal horn, extending from the brainstem down into the upper cervical spinal cord, and receives much of the nociceptive signaling from the
trigeminal system.
Lesions of the trigeminal nucleus caudalis
these lesions are made from the upper rootlets of C2 to a point just above the obex.
How are cells organized in the nucleus caudalis?
In the nucleus caudalis, cells receiving
input from the first division are located in a more ventrolateral position while cells receiving input from the third division are located in a more dorsomedial position. Moreover,
the third division is only represented in the more
cranial aspect of the nucleus while the first division has a
much broader extent
Great care must be exercised in targeting DREZ lesions
due to
the presence of the corticospinal tract just laterally to the dorsal horn
The limited series of results of DREZ lesioning for
phantom limb pain
The best indication for caudalis DREZ is
postherpetic facial pain
Most common adverse effect of caudalis DREZ
high incidence of postoperative ataxia due to the location of the nucleus caudalis deep in the
spinocerebellar tract
Resection of a peripheral nerve found its most significant use in the treatment of
trigeminal neuralgia and
peripheral neuromas
NEURECTOMY PROCEDURE
Avulsion of the peripheral branches of V1 (supraorbital and supratrochlear nerves) was often used in the treatment of
trigeminal neuralgia in this region so as to selectively cause cutaneous anesthesia and spare the corneal anesthesia
that often results from RF trigeminal ganglionolysis that includes V1.
Supraorbital and infraorbital neurectomy procedure
Supraorbital most commonly performed via an incision through the eyebrow while infraorbital
neurectomy uses an approach to the maxilla via the gingivolabial
margin. Once the nerve is located, it is wound
around a small instrument and avulsed
Neurectomy has also been used for
orbital pain, thoracic pain, shoulder pain, and pelvic pain. It is sometimes applied as a treatment for postoperative neuropathic pain that afflicts people undergoing hernia repair
Ganglionectomy is intended to avoid the
issue of peripheral
nerve regeneration, which may follow peripheral RF
ablation or avulsion.
The dorsal root ganglion contains
the cell bodies of the sensory neurons whose central projections enter the dorsal horn of the spinal cord.
dorsal root ganglion exposure
It maybe exposed by resection of the lateral portion of the facet joint and inferior aspect of the lamina of the superior vertebral segment overlying the target root. Opening the root sleeve exposes the ganglion, which can be separated from the underlying ventral root and resected.
C2 ganglion has been resected as a therapy for
intractable occipital neuralgia. In this procedure, the ganglion
is located ventral to the copious venous plexus in
between the laminae of C1 and C2
the most common indication for sympathectomy
palmar hyperhidrosis
interruption of the sympathetic chain has been performed
for a variety of pain syndromes, such as
complex regional pain syndrome (I and II) and angina pectoris, as well as painful vasospastic disorders such as syndrome X and Raynaud’s syndrome. Often these conditions are characterized by pain that does not conform to traditional peripheral nerve or dermatomal innervation patterns and whose intensity is out of proportion to the inciting event and/or imaging findings. Vascular and dystrophic changes
often accompany the pain
sympathetically mediated pain
the phenomenon of pain abolition due to cessation
(temporary or permanent) of sympathetic transmission
In determining a patient’s candidacy for sympathectomy, a determination must be made as to the relative contributions of
sympathetically mediated pain (SMP) and sympathetically independent pain (SIP) to the overall level of pain
Sympathectomy is offered to those patients with appropriate
pain syndromes who have
failed other therapies and have demonstrated substantial temporary relief from these injections (Intravenous phentolamine (a2, adrenergic blockade) and guanethidine Bier block (adrenergic depletion))
Posterior Approach of Thoracic sympathectomy
resecting the T2 and T3 ganglia for the treatment
of upper extremity pain. This region is approached
either anteriorly via a small thoracotomy or, most typically,
via thoracosopic approaches. In the thoracoscopic procedure, ports are placed after deflating the ipsilateral lung. After elevating or opening the pleura, the sympathetic chain is identified on the paramedial posterior thoracic wall. The chain is coagulated and sectioned above and below the intended ganglia and the specimen is removed
Posterior Approach of Thoracic sympathectomy
approached posteriorly, via costotransversectomies
at T2 and T3. The pleura is dissected away from the
underside of the rib heads and transverse processes prior
to their resection. The chain is located over the pleura
near the lateral vertebral body. where its clipped/coagulated
and resected
Lumbar sympathectomy is perfomed for
relief of pain in the lower extremities.
Approach to Lumbar sympathectomy
Typically the ganglia at L2 and L3 are resected. This may be approached via an open, muscle splitting retroperitoneal approach through a flank incision,
sweeping the peritoneal sac away from the vena cava or
aorta (depending on the side of symptoms). The chain is
found at the junction of vertebral body and psoas muscle
RF thoracic sympathectomy.
This involves fluoroscopically placing RF needle electrodes
at the levels of the T2 and T3 sympathetic ganglia. The
ganglion is located near the dorsal half of the vertebral
body near the craniocaudal midpoint of the vertebral body.
Multiple lesions are created in the craniocaudal direction to
ensure appropriate lesioning. Intraprocedural monitoring
of limb termperature may be used to determine the procedural endpoint. A 2oC rise in temperature in the ipsilateral
limb is considered significant
Complications of thoracic
sympathectomy
pneumothorax, Horner’s syndrome, vascular injury, and intercostal neuralgia
Complications of Lumbar sympathectomy
carries the risk of ejaculation problems in men. Rarely patients may experience “postsympathectomy neuralgia,” a constant, aching pain in the proximal portion of
the targeted limb. This is almost always self-limited to
several months
CORDOTOMY
interruption of the spinothalamic and spinoreticular pathways in
the anterolateral quadrant of the cord carrying pain inputs to the brain from the periphery. These lesions are intended to preserve fine touch and proprioceptive tracts
the spinothalamic tract, the sacral fibers and cervical fibers are location
Within the spinothalamic tract, the sacral fibers are located more dorsolaterally and the cervical fibers more ventromedially
at any spinal level, axons composing the spinothalamic
tract are primarily projections from cells located
in the contralateral cord beginning two or three spinal segments below the specific level. Therefore, a lesion should produce pain relief beginning two or three dermatomes below the level of the lesion
Caution must be taken in lesioning the upper cervical cord due to
respiratory fibers of the reticulospinal tract lying medial to the spinothalamic tract. For this reason, bilateral upper cervical cordotomy is often not performed and patients with tenuous respiratory function are often considered unsuitable
candidates
CORDOTOMY Procedure
open procedure,
intradural exposure is first accomplished, followed by sectioning of the dentate ligament at the appropriate level. Grasping the free end of the dentate ligament allows the surgeon to gently rotate the cord away from the operative side and expose the ventral cord. A cordotomy hook with a 45-degree angle is inserted into the anterolateral quadrant and may be taken to the medial
pia before sweeping ventrally. Care is taken to not violate
the medial pia and risk injury to the anterior spinal vessels
Percutaneous cordotomy
performed in the upper cervical (C1–C2) region to treat hemibody malignant pain.
done using either CT or fluoroscopic guidance
combined with contrast myelography. Following dural
puncture from a lateral approach, contrast is instilled into the CSF, allowing identification of the dentate ligament and definition of the ventral hemicord. A stimulating/ lesioning electrode is advanced through the needle and impedance mapping is used to signal entry into the cord. Serial RF lesions are
then created until the area of pinprick analgesia encompasses
the patient’s area of pain
Pial penetration is heralded by
an increase in the impedance
from around 300 ohms to over 500 ohms. Patients may also report pain with this maneuver.
In cordotomy Low frequency electrical stimulation is used to obtain a
motor threshold
for approximation of the distance to corticospinal tract.
In cordotomy High frequency stimulation should produce
contralateral
sensations covering the painful region
In cordotomy the most common complications are
ataxia or paresis due to collateral lesioning of the nearby spinocerebellar
and corticospinal tracts, respectively. Severe respiratory
failure was noted and some
have advocated an anterior transdiscal approach in the lower cervical region as a method of avoiding this complication. Unfortunately, one particularly devastating complication is the late onset of new pain following cordotomy.
Commisural myelotomy
involves severing the fibers of the spinothalamic tract where they cross the spinal cord in
the anterior commissure. It is expected that interrupting
the flow of nociceptive information in this fashion will
produce analgesia at the spinal level of the myelotomy and just below
Myelotomy is considered primarily for patients with
intractable pain in the lower body and pelvis.
Commisural myelotomy Procedure
The spinal cord is exposed over the spinal neural level
(rather than the bony spinal segment) corresponding to the
pain. A small probe is inserted just lateral to the fibrous
septum in the dorsal midline between the posterior columns. Traditionally, this is then used to carefully section
the midline crossing fibers until the anterior cleft of the
cord is noted, taking care not to injure the ventrally located
anterior spinal artery and other epidural veins. For lower
body and pelvic pain, the cord is often exposed via a T9
laminectomy
Intracranial lesioning is often intended to accomplish one of several well-defined goals
: capture pain involving the face, head, and neck that cannot be treated with spinal ablative lesions, treat a wider area of the body, treat the affective nature of pain, or reduce hormonal drivers of malignancy
lesioning of the spinothalamic tract in the midbrain is intended to
produce hemibody analgesia in patients with intractable pain that involves the head and neck
MIDBRAIN TRACTOTOMY utility has been severely hampered by
disturbing postoperative dysesthesias and other complications, such as auditory and visual disturbances due to the approach through the colliculus. gaze palsy, and hemiparesis
In MIDBRAIN TRACTOTOMY disturbing dysesthesias are often associated with
abolition of the SSEP signals, indicating unintended lesioning of the medial lemniscal fibers in addition
to the spinothalamic fibers.
Intraoperative stimulation
may help identify the spinothalamic fibers from the
lemniscal fibers by the painful sensations evoked by stimulating the former and the more vibratory or pleasant sensations from stimulating the latter tract
Several thalamic nuclei have been targeted, either singly or in isolation, to achieve pain control, including the
medial/intralaminar thalamus,
ventrocaudal (Vc) nucleus and pulvinar
In the medial thalamus, most commonly lesioned due to their large input from the spinothalamic tract and diffuse cortical projections
the central lateral (CL) and centromedian/parafascicular complex (CM/Pf). Lesioning the medial thalamic complex (CL or CM/Pf) does not produce sensory deficits.
HYPOPHYSECTOMY
The pituitary gland may be ablated via either a standard
craniotomy or a less invasive transphenoidal approach.
The gland is destroyed either via direct resection, instillation
of alcohol into the sella, RF, cryotherapy, or interstitial
brachytherapy. Stereotactic radiosurgery
HYPOPHYSECTOMY complications
panhypopituitarism
CINGULOTOMY target
Lesions of the anterior cingulate gyrus target the affective components of pain, rather than the pain transmission itself.
CINGULOTOMY Procedure
The procedure typically involves bilateral stereotactically placed RF or
radiosurgical lesions in the bilateral anterior cingulate gyrus
