Review Article
Volume 2, No.2
October 1998
 Marc Sindou
 Patrick Mertens

 Dept of Neurosurgery
 University of Lyon
 France

 Correspondence:
 Mark Sindou, M.D.,D.Sc.
 Dept. of Neurosurgery
 Neurological Hospital P.
   Wertheimer
 University of Lyon
 France
 
Neurosurgical Management of Neuropathic Pain: Decision-Making


Keywords: Dorsal column stimulation, dorsal root entry zone surgery, intrathecal morphinethereapy, neuropathic pain, neurostimulation, pain surgery, precentral cortex stimulation
   INTRODUCTION
The authors present, in the form of simplified schematic views, the guidelines they use for treating neuropathic pain. Neuropathic pain is the pain associated with primary injury of neural tissues; peripheral or central, according to the definition given by MJ Gybels and WH Sweet in the recent book "Neurosurgical treatment of persistent pain" (Fig. 1).

Main causes and clinical aspects of neuropathic pain
The neurosurgical methods considered are: anatomical, augmentative (neurostimulation of peripheral nerves, spinal cord, thalamus or precentral cortex), pharmacological (through implanted delivery systems) or (especially DREZ-lesions) ablative Fig. 2.

The algorythms proposed are based on the author's experience and the literature reports (Fig. 3 and 4).

1. Pain due to peripheral nerve lesions
When the causal lesion involves a distal and sensory nerve, and if there is reasonable evidence that the pain is related to scar tissue adhesions and/or a "true" neuroma formation, a direct surgical approach of the lesional site can be justified. The nerve is freed and if there is a neuroma its resection achieved. When the lesion involves a proximal and/or a mixed nerve trunk, the same attitude may be adopted, but even more prudently because of the greater functional importance of such nerves. If there is no reason for a so-called "anatomic" surgical treatment, Peripheral Nerve Stimulation (PNS) or the more commonly used Dorsal Column Stimulation (DCS) method can be indicated.

When several nerves are involved, DCS at the corresponding spinal cord segments is the first choice, because of the conservative nature of the method. If DCS fails, DREZotomy may be considered, but only if the main component of pain is of paroxysmal or the allodynic type.

A Complex Regional Pain Syndrome of Type II (CRPS-II i.e., causalgia) may accompany peripheral nerve lesions especially when severe. When CRPS II is present, same management applies.

 
 

 
 


2. Pain due to plexus or root lesions
In cases of plexus or root lesions, it is of prime importance to know the exact location of the lesion: distal or central to the dorsal root ganglion, as well as the completeness, or not, of the anatomical-functional interruption of the fibres. This can be checked by studying the nerve conduction velocity (NCV) and the somesthetic evoked potentials (SEP). If the interruption is central and total, DCS will not be effective, because of degeneration of the axons all along the spinal cord, up to the brain stem sensory relay nuclei. If one wants to apply neurostimulation, the target has to be at the level of thalamic sensory nucleus (namely the ventro-postero-lateral nucleus deep brain stimulation (DBS) or at the level of the precentral motor) using stereotactic cortex, using extra-dural cortical stimulation (CORT).

In cases of "deafferentation" pain with hyperactivity of the dorsal horn cells, like after brachial plexus avulsion (or lumbo-sacral avulsion) or severe plexus-root or cauda equina injuries, DREZotomy is particularly indicated and effective.

Post-herpetic pain corresponds to lesions both of the spinal ganglion cells and related axons going to and conveyed by the spinal cord and of the dorsal horn itself. DCS can be tried if sufficient lemniscal fibres are still valid. DREZotomy may be indicated when the pain components of pain are of the paroxysmal and/or of the allodynic types.

3. Pain due to spinal cord lesions
The same applies for pain in the territory below the spinal cord lesion. When the lemniscal fibres are totally interrupted, DCS cannot be efficient even if the electrodes are implanted above the spinal cord lesion. Imaging and SEP may be useful to check the integrity of the dorsal columns. For pain in the territory corresponding to the injured and neighbouring segments, DCS may be effective, though very inconstantly.

DREZotomy is only effective on the pain corresponding to the lesioned segments. Pain corresponding to the territory below the lesion is not influenced by DREZotomy, even if performed at the lower levels.

4. Central pain due to brain Iesions
These types of pain are classically not accessible to neurosurgical procedures. Nevertheless, some attempts are under evaluation, especially the newly introduced precentral (motor cortex) cortical stimulation.

CONCLUSION

Provided that patient selection is rigorous, neurosurgical procedures can be attempted in neuropathic pain syndromes, when pain has resisted all medical and psychotherapic treatments.

SUGGESTED READING
1. Head injury, Graham M Teasdale, J. of Neurology, Neurosurgery, and Psychiatry, 1995, 58: 526-539.
2. Jeanmonod D. Sindou M (1991) Somatosensory function following dorsal root entry zone lesions in patients with neurogenic pain or spasticity J. Neurosurgy 74: 916-932
3. Jeanmonod D. Sindou M. M. Mauguiere F (1991) The human cervial and lumbo -sacral evoked electrospinogram. Data from intra-operative spinal cord surface recordings. Electroencephalogr Clin Neurophysiol 80: 477 -489
4. Losser JD Ward AA Jr White EL Jr .White LE Jr(1968) Chronic defferentation of human spinal cord neurons of human spinal cord neurons. J Neurosurg 29: 48 -50
5. Melzach R. wall PD ( 1965) Pain mechanism A new theory Since 150: 971-979
6. Sindou M (1972) Study of the dorsal root - spinal cord junction. A target for pain surgery. These Doctorat Medicine Lyon 182 pp
7. Sindou M. Quoex C. Baleydier C. ( 1974) Fiber organization at the posterior spinal cord-rootlet junction in man J. Comp Neurol 153:15-26
8. Sindou M. Fisher G Mansuy L/ Manusy L. (1976) Posterior spinal rhizotomy and selective posterior rhizidiotomy. In:Krayenbuhl H. Maspes PE Sweet WH (eds) Progress in neurological surgery. Vol7 Karger. Basel pp 201-250
9. Sindou M. Goutelle A ( 1983) Surgical posterior .rhiziotomies for the reatment of pain. Krayenbuh H(ed) Advanced and technical standards in neuro surgery. Vo110 Springer. Wien New York pp 147-185
10. Sindou M. Daher A (1988) Spinal cord ablation procedures for pain. In Dubner A. Gebbart GF Bond MR (eds) Proceedings of the Fifty World Congress on Pain Elsevier. Amsterdam pp 477 - 495
 


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