Chapter 75. Neurosurgical Treatment of Pain

Indications for surgical interventions in the treatment of chronic pain continue to evolve as we learn more about the pathophysiology and mechanisms of chronic pain. Recent advances in technology and availability of newer and better analgesics have also helped us rely more on neuromodulation and neuroaugmentation rather than neuroablation. Establishment of multidisciplinary pain centers, formal fellowship training in pain medicine, and popularity of minimally invasive techniques has enabled clinicians from various disciplines to perform procedures that were once performed only by neurosurgeons. Surgical procedures that are used to relieve pain, and are not discussed in detail elsewhere in this book, can be divided into three major categories (Table 75-1).

• I. Techniques that attempt to correct the disordered physiology of nerves without creating a lesion.

• II. Destructive procedures.

• • • A. Procedures that transsect primary afferent fibers at the level of peripheral nerve, root, or ganglion.

    • B. Operations that interrupt ascending sensory tracts in the spinal cord or brainstem.

    • C. Stereotactically placed lesions of deep brain structures.

    • D. Operations that inactivate a portion of the sympathetic system.

    • E. Destruction of the anterior lobe of the pituitary gland.

    • F. Cutting cerebral cortical structures.

• III. Procedures in which a device is implanted to stimulate an analgesia-producing mechanism in the central nervous system.

The first category of neurosurgical procedures for pain control includes operations designed to relieve constriction of peripheral nerves, spinal nerve roots, dorsal root ganglia, or cranial nerves. These decompressive operations are sometimes elegant and often curative. Their use is restricted to specific well-defined syndromes in which the site of disordered nerve physiology can be predicted. The prediction usually is based on radiologic studies, electromyography, nerve conduction studies, and after careful clinical examination. Most procedures of this type have high success rates. Whenever possible, they should be used in preference to destructive lesions.

The reason for the success of nerve decompression is not entirely clear since it is not always understood why pressure on a nerve causes pain. Not all sites of nerve distortion are associated with chronic pain. For example, in a large series of patients investigated for possible acoustic nerve tumors, myelograms frequently showed incidental disc protrusions. Asymptomatic lesions severe enough to distort spinal nerve roots were identified in one third of cases.2 These well-defined disc protrusions with nerve root compression were not painful, ...