The dearth of evidence-based data for ablative pain procedures can be attributed to the advent of intrathecal opioids. As intrathecal drug delivery became the procedure of choice for visceral cancer pain, the number of destructive procedures performed dwindled, eliminating training opportunities, and reducing industry investment in technology.

A review of the relevant neurosurgical literature is notable for various individual case reports of treating pain by making a targeted destructive lesion. In 1973, Andy described successful unilateral anterior thalamotomy with a bipolar electrode for a 37-year-old woman with hysterical pain and chronic severe visceral disturbances [4]. Targeting the thalamus for pain treatment was rather common in the 1970s as this approach was suggested and tried for treatment of all kinds of intractable pain syndromes [5–7]. Nevertheless, the majority of destructive neurosurgical procedures for abdominal pain have targeted spinal cord pathways. These techniques include anterolateral cordotomy, commissurotomy, and midline myelotomy.

Cordotomies are generally effective for unilateral somatic or neuropathic pain while midline myelotomy is more useful for treating bilateral, diffuse visceral pain. Cordotomies aim to interrupt the ascending anterolateral spinothalamic spinal cord tracts and are most appropriate for unilateral nociceptive somatic pain below the neck as well as neuropathic pain. Cordotomy may reduce the severity of visceral pain but is not the best surgical option. Pain relief from cordotomy is unilateral (affecting the contralateral side of the body) but because visceral pain is frequently bilateral, it becomes necessary to perform cordotomies on both sides when trying to treat visceral pain patients. For this and other reasons mentioned below, midline myelotomy is currently the most effective ablative neurosurgical procedure for midline visceral pain and for deep, diffuse visceral abdominal pain.

There is more published evidence for cordotomy than any other procedure for cancer pain. Although none are Class I reports and none of the current prospective or retrospective cohorts qualified as Class II evidence, a recent meta-review identified 47 papers including 3,601 patients with the majority reporting excellent lasting relief from cancer pain [8]. This review clearly shows that most of the papers reported greater than 50 % pain reduction for more than 6 months with less than 1 % risk of postoperative weakness. Moreover, hospital stays are brief and charges are low relative to implanting drug delivery or stimulation devices. For these reasons, the cordotomy procedure has a definite role for patients with terminal cancer with unilateral somatic abdominal pain.

Bilateral anterolateral cordotomies have seen success in treating some patients with midline visceral pain [9]. However, there are significant risks of complications such as incontinence and respiratory disorders. Malignant visceral pain cannot be eliminated with bilateral anterolateral cordotomy and there are risks of serious complications. Nevertheless, there are reports of successful bilateral cordotomies for pain related to pelvic cancer.

Midline myelotomy was originally designed to achieve bilateral spinothalamic lesions without damaging other functional fiber tract systems in the anterolateral quadrant of the spinal cord. Early midline myelotomy procedures were performed to interrupt the midline commissure over a retrocaudal length to sever the bilateral crossing fibers of the anterolateral ascending pain tracts. This commissural myelotomy for visceral pain was found to carry significant risk of loss of proprioception, dysesthesias, bowel and bladder dysfunction, and even death. When Armour in 1927 introduced open spinal midline myelotomy to achieve the same effect as bilateral cordotomy without the complications, he intended to interrupt the spinothalamic fibers as they decussate but the operation was abandoned because of unacceptable morbidity and mortality [10].

Hirshberg and colleagues postulated that the success of midline myelotomy in treating pain was due to coincidental lesioning of the midline dorsal columns. Using their own autopsies and clinical reports, they showed that some successful myelotomies were not deep enough or at incorrect levels [11]. This concept made more sense when in the 1990s Al-Chaer and colleagues discovered a new visceral pain pathway ascending in the posterior dorsal column (Fig. 24.1b) [12–14].

Hitchcock introduced the limited midline myelotomy with the intent of severing crossing spinothalamic tract fibers at only a single level. Even though the lesions were limited to the midline at a single level, lesions at C-1 and T-10 were reported to achieve widespread relief from chronic visceral abdominal pain yet spared proprioception and sensation [15, 16]. Schvarcz suggested that the pain relief resulted from destruction of a polysynaptic ascending pain tract in the central cord [17, 18] and it was soon discovered that the true culprit was in the midline of the posterior columns, an area incidentally damaged during myelotomy procedures.

With these developments in mind, Nauta et al. described a modified punctate midline myelotomy for chronic malignant lower abdominal pain in a 39-year-old woman with malignant abdominal pain from radiation damage to the bowel, bladder, and ureter in the setting of multiple abdominal surgeries. The lesion was made at the T8 level via open laminectomy. Prior to surgery, the patient reported a constant pressure in the right lower abdomen with a severe “ripping” pain after bowel movements. Afterwards, the patient reported 100 % resolution of her disabling lower abdominal pain and this effect persisted for at least 10 months postoperatively [19].

The first punctate midline myelotomies were performed via open laminectomy using an operative microscope to create a midline punctate incision with a needle inserted to a depth of 5 mm. The exact midline was determined by measuring and bisecting the distance between the two root entry zones since the dorsal vein and the septum posticum are not reliable markers of the true dorsal midline of the spinal cord.

Additional reports of successful punctate midline myelotomy were quick to follow Nauta’s success with punctate midline myelotomy. Becker, Sure, and Bertalanffy reported success in treating a patient with severe visceral abdominal pain in the epi- and mesogastric regions of a 41-year-old man with multiple anaplastic carcinomas of the small intestine, peritoneal carcinosis, and retroperitoneal lymphomas. His pain was reduced from VAS 10 to 2–3 postoperatively [20]. Kim and Kwon reported performing high thoracic midline dorsal myelotomy for eight patients with severe visceral pain due to advance stomach cancer. All eight patients enjoyed relief from their preoperative abdominal pain and there were no reports of mortality. One patient suffered permanent paresthesias below the level of the myelotomy and two patients exhibited transient paresthesias that improved with corticosteroid treatment. They chose to lesion both the central gray area and the medial portion of the spinal cord and used a microdissector instead of a 16-gauge needle. They reiterate that the procedure is more effective for pain from diffuse abdominal metastases rather than patients with a large mass producing focalized pain [21].

The appropriate level for the punctate lesion is determined based on the level of the abdominal pain and the lesion level was usually made one segment above the level of the spinal cord that innervates the region causing the diffuse pain. Kim and Kwon made the lesion at T1-T4 for pain from stomach cancer [21] while Huang et al. did myelotomy at T4-5 for patients with hepatobiliary and pancreatic cancers [22]. However, based on a review of published cases, Hong et al. argue that the myelotomy should be performed several levels above the corresponding spinal cord level. For example, pain from cancers of the genitalia, rectum, or colon the dorsal midline pathway might be treated with a lesion at the T7-T8 spinal cord level [23].

Punctate midline myelotomy has been successfully performed for pain from pelvic cancer as well as pancreatic, and hepatobiliary cancer [22]. The procedure can be performed using local anesthesia with a 1–2 day hospital stay. Since the patient remains awake during the procedure, they can report sensory and motor changes, thereby reducing the risk of neurologic deficit [23].

Most case reports describe a lesion made to a depth of 5–6 mm when in reality the anterior–posterior diameter of the thoracic spinal cord varies along the length of the cord and between individuals [23]. This depth may not be appropriate based on several anatomic studies including Japanese postmortem data showing that the sagittal diameter of the spinal cord at the T4 and T10 segments is 7.59 ± 0.31 mm and 7.81 ± 0.25 mm, respectively [23–25]. For this reason, magnetic resonance imaging (MRI) must be used to calculate the depth of myelotomy. The surgeon must account for both individual anatomical variation as well as pathological changes.

Punctate midline myelotomy is the least destructive of the neuroablative procedures, however it still carries a risk of unintended injury to the dorsal column-medial lemniscus pathway. Therefore, the risks of this procedure include loss of sensation of touch, pressure, vibration, and proprioception. Bowl and bladder incontinence are also potential complications. Because the dorsal vein meanders along its course, using CT-guidance increases the risk of injuring the dorsal vein and causing a subarachnoid hemorrhage.

Despite having fewer neurological complications and proven efficacy, punctate midline myelotomy has not been standardized. Good surgical candidates have prominent visceral pain with poor pain control or intolerable side effects and a stable disease state with life expectancy greater than 3 months. They should also be in stable medical condition to minimize the risk of morbidity or mortality. Patients who have undergone radiation therapy and complain of diffuse, rather than local, visceral pain may be good candidates for neuroablation of the dorsal pain pathway [19].

Although outcome measures for myelotomy are generally less favorable then for cordotomy, myelotomy is consistently superior for relieving midline visceral cancer pain for cervical, pancreatic, and gastric cancers. While only Class III evidence exists for myelotomy for cancer pain relief, the anecdotal literature clearly supports its efficacy and highlights the potential for further development [8]. There are no prospective randomized studies of punctate midline myelotomy for abdominal pain and it has not yet become popular in the United States or Europe. Nevertheless, there is convincing empiric evidence that punctate midline myelotomy is an effective neurosurgical strategy for certain patients with diffuse visceral abdominal pain.

The need to minimize invasiveness of pain relieving procedures became obvious long time ago. Back in 1963, Mullan introduced a percutaneous alternative to open cordotomy when he reported using a strontium needle to create the lesions during radiography-based percutaneous interventions [26]. Introduction of CT scanning further advanced the field enabling the practitioner to directly visualize the spinal cord and account for the differences in spinal cord diameter and shape between individual patients. CT guidance for stereotactic pain procedures dates to 1987 when first developed by Kanpolat and his colleagues [27]. They showed that CT measurements of the cervical cord are reliable and can be used to perform pain procedures such as percutaneous cordotomy.