Chapter 21 Neurosurgical Procedures for Treatment of Intractable Pain

Question 1

Methods used to lesion the nervous system

Answer 1

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

Question 2

Criterias for patients selecting patients for Neurosurgical procedures

Answer 2

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

Question 3

DORSAL ROOT ENTRY ZONE LESIONS/CAUDALIS DORSAL ROOT ENTRY ZONE

Answer 3

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

Question 4

DORSAL ROOT ENTRY ZONE LESIONS indications

Answer 4

treatment of pain due to traumatic brachial plexus root avulsions.

Question 5

DORSAL ROOT ENTRY ZONE LESIONS/CAUDALIS DORSAL ROOT ENTRY ZONE PROCEDURE

Answer 5

1. 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.

Question 6

How does the fibers travel in the DREZ?

Answer 6

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.

Question 7

How are lesions created in the DREZ?

Answer 7

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

Question 8

treatment of facial pain

Answer 8

the lesions may be made in the trigeminal nucleus caudalis

Question 9

What is the trigeminal nucleus caudalis?

Answer 9

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.

Question 10

Lesions of the trigeminal nucleus caudalis

Answer 10

these lesions are made from the upper rootlets of C2 to a point just above the obex.

Question 11

How are cells organized in the nucleus caudalis?

Answer 11

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

Question 12

Great care must be exercised in targeting DREZ lesions

due to

Answer 12

the presence of the corticospinal tract just laterally to the dorsal horn

Question 13

The limited series of results of DREZ lesioning for

Answer 13

phantom limb pain

Question 14

The best indication for caudalis DREZ is

Answer 14

postherpetic facial pain

Question 15

Most common adverse effect of caudalis DREZ

Answer 15

high incidence of postoperative ataxia due to the location of the nucleus caudalis deep in the
spinocerebellar tract

Question 16

Resection of a peripheral nerve found its most significant use in the treatment of

Answer 16

trigeminal neuralgia and

peripheral neuromas

Question 17

NEURECTOMY PROCEDURE

Avulsion of the peripheral branches of V1 (supraorbital and supratrochlear nerves) was often used in the treatment of

Answer 17

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.

Question 18

Supraorbital and infraorbital neurectomy procedure

Answer 18

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

Question 19

Neurectomy has also been used for

Answer 19

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

Question 20

Ganglionectomy is intended to avoid the

Answer 20

issue of peripheral
nerve regeneration, which may follow peripheral RF
ablation or avulsion.

Question 21

The dorsal root ganglion contains

Answer 21

the cell bodies of the sensory neurons whose central projections enter the dorsal horn of the spinal cord.

Question 22

dorsal root ganglion exposure

Answer 22

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.

Question 23

C2 ganglion has been resected as a therapy for

Answer 23

intractable occipital neuralgia. In this procedure, the ganglion
is located ventral to the copious venous plexus in
between the laminae of C1 and C2

Question 24

the most common indication for sympathectomy

Answer 24

palmar hyperhidrosis

Question 25

interruption of the sympathetic chain has been performed | for a variety of pain syndromes, such as

Answer 25

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

Question 26

sympathetically mediated pain

Answer 26

the phenomenon of pain abolition due to cessation | (temporary or permanent) of sympathetic transmission

Question 27

In determining a patient’s candidacy for sympathectomy, a determination must be made as to the relative contributions of

Answer 27

``` sympathetically mediated pain (SMP) and sympathetically independent pain (SIP) to the overall level of pain ```

Question 28

Sympathectomy is offered to those patients with appropriate | pain syndromes who have

Answer 28

failed other therapies and have demonstrated substantial temporary relief from these injections (Intravenous phentolamine (a2, adrenergic blockade) and guanethidine Bier block (adrenergic depletion))

Question 29

Posterior Approach of Thoracic sympathectomy

Answer 29

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

Question 30

Posterior Approach of Thoracic sympathectomy

Answer 30

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

Question 31

Lumbar sympathectomy is perfomed for

Answer 31

relief of pain in the lower extremities.

Question 32

Approach to Lumbar sympathectomy

Answer 32

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

Question 33

RF thoracic sympathectomy.

Answer 33

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

Question 34

Complications of thoracic | sympathectomy

Answer 34

pneumothorax, Horner’s syndrome, vascular injury, and intercostal neuralgia

Question 35

Complications of Lumbar sympathectomy

Answer 35

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

Question 36

CORDOTOMY

Answer 36

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

Question 37

the spinothalamic tract, the sacral fibers and cervical fibers are location

Answer 37

Within the spinothalamic tract, the sacral fibers are located more dorsolaterally and the cervical fibers more ventromedially

Question 38

at any spinal level, axons composing the spinothalamic | tract are primarily projections from cells located

Answer 38

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

Question 39

Caution must be taken in lesioning the upper cervical cord due to

Answer 39

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

Question 40

CORDOTOMY Procedure open procedure,

Answer 40

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

Question 41

Percutaneous cordotomy

Answer 41

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

Question 42

Pial penetration is heralded by

Answer 42

an increase in the impedance | from around 300 ohms to over 500 ohms. Patients may also report pain with this maneuver.

Question 43

In cordotomy Low frequency electrical stimulation is used to obtain a

Answer 43

motor threshold | for approximation of the distance to corticospinal tract.

Question 44

In cordotomy High frequency stimulation should produce

Answer 44

contralateral | sensations covering the painful region

Question 45

In cordotomy the most common complications are

Answer 45

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.

Question 46

Commisural myelotomy

Answer 46

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

Question 47

Myelotomy is considered primarily for patients with

Answer 47

intractable pain in the lower body and pelvis.

Question 48

Commisural myelotomy Procedure

Answer 48

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

Question 49

Intracranial lesioning is often intended to accomplish one of several well-defined goals

Answer 49

: 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

Question 50

lesioning of the spinothalamic tract in the midbrain is intended to

Answer 50

produce hemibody analgesia in patients with intractable pain that involves the head and neck

Question 51

MIDBRAIN TRACTOTOMY utility has been severely hampered by

Answer 51

disturbing postoperative dysesthesias and other complications, such as auditory and visual disturbances due to the approach through the colliculus. gaze palsy, and hemiparesis

Question 52

In MIDBRAIN TRACTOTOMY disturbing dysesthesias are often associated with

Answer 52

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

Question 53

Several thalamic nuclei have been targeted, either singly or in isolation, to achieve pain control, including the

Answer 53

medial/intralaminar thalamus, | ventrocaudal (Vc) nucleus and pulvinar

Question 54

In the medial thalamus, most commonly lesioned due to their large input from the spinothalamic tract and diffuse cortical projections

Answer 54

the central lateral (CL) and centromedian/parafascicular complex (CM/Pf). Lesioning the medial thalamic complex (CL or CM/Pf) does not produce sensory deficits.

Question 55

HYPOPHYSECTOMY

Answer 55

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

Question 56

HYPOPHYSECTOMY complications

Answer 56

panhypopituitarism

Question 57

CINGULOTOMY target

Answer 57

Lesions of the anterior cingulate gyrus target the affective components of pain, rather than the pain transmission itself.

Question 58

CINGULOTOMY Procedure

Answer 58

The procedure typically involves bilateral stereotactically placed RF or radiosurgical lesions in the bilateral anterior cingulate gyrus