Physiological evidence of bilateral spinal projections of pain fibers in cats and monkeys

An overview of interventional strategies for the management of oncologic pain

Pain is a ubiquitous part of the cancer experience. Often the presenting symptom of malignancy, pain becomes more prevalent in advanced or metastatic disease and often persists despite curative treatment. Although management of cancer pain improved following publication of the WHO's analgesic ladder, when used in isolation, conservative approaches often fail to control pain and are limited by intolerable side effects. Interventional strategies provide an option for managing cancer pain that remains refractory to pharmacologic therapy. The purpose of this review is to investigate these strategies and discuss the risks and benefits which must be weighed when considering their use. Therapies anticipated to have an increasingly important role in the future of cancer pain management are also discussed.

The surgical treatment of chronic pain: destructive therapies in the spinal cord

Stereotactic pain surgery is accepted as a group of procedures. These are usually highly sophisticated and technically risky procedures. In practice, the most important part of this discipline is not the technical abilities of the surgeon, but selection of the most appropriate patients for the available procedures. We must remember that we are performing all these procedures with the cooperation of patients. The energy that is used for lesioning can be stopped when desired. The target we want to approach can be definitely and anatomically visualized and demonstrated, and the function of the target is evaluated with neurophysiologic impedance techniques and stimulation. Thus, if we are able to understand the language of the central nervous system, these are available, effective, and safe procedures in neurosurgical practice. We must remember that if intractable pain can be controlled by minimally invasive destructive techniques, the patients will not be dependent on implantable systems, drugs,and medical units. This independent lifestyle is a critical goal central to quality of life for patients having intractable pain.

Computerized tomography-guided percutaneous extralemniscal myelotomy

Extralemniscal myelotomy (ELM) is a procedure performed at the cervicomedullary junction of the spinal cord in which the central cord is lesioned to treat intractable pain. The neurophysiological mechanism of pain relief after ELM remains unclear. The authors present a series of 14 patients with intractable cancer pain who were managed by CT-guided, percutaneous ELM. In six of the cases (42.8%), total pain relief was achieved; partial satisfactory pain relief was attained in four cases (28.5%), and no pain control was achieved in four cases (28.5%). No complications due to ELM were observed. The authors believe that ELM is a safe and effective procedure in the management of intractable cancer pain for selected cases; computerized tomography guidance is an essential part of the procedure to achieve morphological localization of the target in the cervicomedullary junction. More research is needed to understand the neurophysiological mechanism of pain relief after ELM and to standardize the lesion volume.

Spinal cord conduction pathway for cerebellar evoked potentials from C-fibers

Evoked responses from saphenous nerve C fiber stimulation were identified on the ipsilateral intermediate cerebellar cortex. This late potential has a latency between 180 and 250 msec, duration 50-70 msec, and an amplitude 10-20 micro V. The potential is conducted in the ipsilateral dorsal quadrant as determined by differential section of the spinal cord. The probable pathway is assigned to the dorsal spinocerebellar tract.

High cervical commissural myelotomy in the treatment of pain

High cervical myelotomy was carried out on 10 patients. Commissurotomy was performed at the C1-3 level by a combined procedure of deep electrocogulation and sharp splitting of the posterior columns. The immediate results were excellent in all patients, but relapse of pain took place shortly in six of them; there was apparently no relation with the location of pain. No long-term favourable results were observed in this series. Only three patients exhibited a well-defined band of mild hypalgesia from C2 to T 10 dermatome, but it lasted for only three to four weeks. Transient lower or four limb ataxia was observed in seven patients. Different pain conducting systems seem to be affected by commissural myelotomy, but not to a sufficient extent to give permanent or long-lasting relief of pain. The indications for high cervical myelotomy are very limited: this procedure should be considered only in patients with unilateral or bilateral arm and/or upper chest pain, respiratory impairment, and short life expectancy.

Stereotactic extralemniscal myelotomy

A procedure is reported in which radiofrequency lesions were stereotactically placed in the central cord region at the cervicomedullary junction to interrupt selectively the extralemniscal system. Physiological recognition of the target site was based upon the homuncular organization of the dorsal funiculi, which is analysed. Only subjective (segmentally unrelated) analgesia was achieved, usually without demonstrable sensory loss. Stimuli were not painful, while ability to localize it and the discrimination between sharp and blunt components were preserved. A rational approach is offered to certain central pain phenomena which resulted in abolition of hyperpathia and disappearance of, or marked reduction in, deep background pain. Both upper and lower body pain were easily dealt with. Pathways for automatic respiration or for micturition were not encroached upon. Therefore it was electively used for cases with diminished respiratory reserve and for cases with midline and/or bilateral pain.

C-fiber responses in the ventrolateral column of the cat spinal cord

Saphenous nerve C-fiber volleys generate, in the ventrolateral column of the cat spinal cord, a conducted postsynaptic response revealed by averaging the integrated temporally dispersed axonal discharges. This finding is compatible with the hypothesis that the feline ventrolateral column includes a major pathway related to nociception.