[Treatment of trigeminal neuropathic pain by motor cortex stimulation]. / Traitement des douleurs trigéminales neuropathiques par stimulation corticale.

The neurosurgical procedures currently available for the treatment of trigeminal neuralgia can induce trigeminal neuropathic pain. Severe forms of trigeminal neuropathic pain correspond to the classical facial anesthesia dolorosa, whose treatment is known to be very difficult. Chronic stimulation of the ventral posterolateral nucleus (VPL) of the thalamus was, in the past, the only neurosurgical therapy available to treat this complication. The long-term results have been disappointing, which opened the field to the development of other techniques, including stimulation of the motor cortex for which there is now sufficient experience showing long-term results that are satisfactory in more than 70% of patients. Meanwhile, some authors have proposed directly stimulating the nerve branches concerned, such as the supraorbital nerve, or discussing indications for thalamic stimulation. In this chapter, only the cortical stimulation procedure will be developed.

Motor cortex rTMS restores defective intracortical inhibition in chronic neuropathic pain.

OBJECTIVE: To assess cortical excitability changes in patients with chronic neuropathic pain at baseline and after repetitive transcranial magnetic stimulation (rTMS) of the motor cortex. METHODS: In 22 patients with unilateral hand pain of various neurologic origins and 22 age-matched healthy controls, we studied the following parameters of cortical excitability: motor threshold at rest, motor evoked potential amplitude ratio at two intensities, cortical silent period (CSP), and intracortical inhibition (ICI) and intracortical facilitation. We compared these parameters between healthy subjects and patients at baseline. We also studied excitability changes in the motor cortex corresponding to the painful hand of patients after active or sham rTMS of this cortical region at 1 or 10 Hz. RESULTS: At baseline, CSP was shortened for the both hemispheres of patients vs healthy subjects, in correlation with pain score, while ICI was reduced only for the motor cortex corresponding to the painful hand. Regarding rTMS effects, the single significant change was ICI increase in the motor cortex corresponding to the painful hand, after active 10-Hz rTMS, in correlation with pain relief. CONCLUSION: Chronic neuropathic pain was associated with motor cortex disinhibition, suggesting impaired GABAergic neurotransmission related to some aspects of pain or to underlying sensory or motor disturbances. The analgesic effects produced by motor cortex stimulation could result, at least partly, from the restoration of defective intracortical inhibitory processes.

Neurogenic pain relief by repetitive transcranial magnetic cortical stimulation depends on the origin and the site of pain.

OBJECTIVE: Drug resistant neurogenic pain can be relieved by repetitive transcranial magnetic stimulation (rTMS) of the motor cortex. This study was designed to assess the influence of pain origin, pain site, and sensory loss on rTMS efficacy. PATIENTS AND METHODS: Sixty right handed patients were included, suffering from intractable pain secondary to one of the following types of lesion: thalamic stroke, brainstem stroke, spinal cord lesion, brachial plexus lesion, or trigeminal nerve lesion. The pain predominated unilaterally in the face, the upper limb, or the lower limb. The thermal sensory thresholds were measured within the painful zone and were found to be highly or moderately elevated. Finally, the pain level was scored on a visual analogue scale before and after a 20 minute session of "real" or "sham" 10 Hz rTMS over the side of the motor cortex corresponding to the hand on the painful side, even if the pain was not experienced in the hand itself. RESULTS: and discussion: The percentage pain reduction was significantly greater following real than sham rTMS (-22.9% v -7.8%, p = 0.0002), confirming that motor cortex rTMS was able to induce antalgic effects. These effects were significantly influenced by the origin and the site of pain. For pain origin, results were worse in patients with brainstem stroke, whatever the site of pain. This was consistent with a descending modulation within the brainstem, triggered by the motor corticothalamic output. For pain site, better results were obtained for facial pain, although stimulation was targeted on the hand cortical area. Thus, in contrast to implanted stimulation, the target for rTMS procedure in pain control may not be the area corresponding to the painful zone but an adjacent one. Across representation plasticity of cortical areas resulting from deafferentation could explain this discrepancy. Finally, the degree of sensory loss did not interfere with pain origin or pain site regarding rTMS effects. CONCLUSION: Motor cortex rTMS was found to result in a significant but transient relief of chronic pain, influenced by pain origin and pain site. These parameters should be taken into account in any further study of rTMS application in chronic pain control.

Pain relief induced by repetitive transcranial magnetic stimulation of precentral cortex.

Chronic electrical stimulation of the precentral (motor) cortex using surgically implanted electrodes is performed to treat medication-resistant neurogenic pain. The goal of this placebo-controlled study was to obtain such antalgic effects by means of a non-invasive cortical stimulation using repetitive transcranial magnetic stimulation (rTMS). Eighteen patients with intractable neurogenic pain of various origins were included and underwent a 20 min session of either 10 Hz, 0.5 Hz or* sham rTMS over the motor cortex in a random order. A significant decrease in the mean pain level of the series was obtained only after 10 Hz rTMS. This study shows that a transient pain relief can be induced by 10 Hz rTMS of the motor cortex in some patients suffering from chronic neurogenic pain.

[Treatment of central and neuropathic facial pain by chronic stimulation of the motor cortex: value of neuronavigation guidance systems for the localization of the motor cortex]. / Traitement des douleurs centrales et neuropathiques faciales par stimulation chronique du cortex moteur. Intêret des systèmes de neuronavigation pour le repérage du cortex moteur]

Thirty two patients with refractory central and neuropathic pain of peripheral origin were treated by chronic stimulation of the motor cortex between May 1993 and January 1997. The mean follow-up was 27. 3 months. The first 24 patients were operated according to the technique described by Tsubokawa. The last 13 cases (8 new patients and 5 reinterventions) were operated by a technique including localization by superficial CT reconstruction of the central region and neuronavigator guidance. The position of the central sulcus was confirmed by the use of intraoperative somatosensory evoked potentials. The somatotopic organisation of the motor cortex was established peroperatively by studying the motor responses at stimulation of the motor cortex through the dura. Ten of the 13 patients with central pain (77%) and nine of the 12 patients with neuropathic facial pain had experienced substantial pain relief (75%). One of the 3 patients with post-paraplegia pain was clearly improved. A satisfactory result was obtained in one patient with pain related to plexus avulsion and in one patient with pain related to intercostal herpes zoster. None of the patients developed epileptic seizures. The position of the stimulating poles effective on pain corresponded to the somatotopic representation of the motor cortex. The neuronavigator localization and guidance technique proved to be most useful identifying the appropriate portion of the motor gyrus. It also allowed the establishment of reliable correlations between electrophysiological-clinical and anatomical data which may be used to improve the clinical results and possibly to extend the indications of this technique.

Motor cortex stimulation in the treatment of central and neuropathic pain.

BACKGROUND: Motor cortex stimulation has been proposed for the treatment of central pain. METHODS: Thirty-two patients with refractory central and neuropathic pain of peripheral origin were treated by chronic stimulation of the motor cortex between May 1993 and January 1997. The mean follow-up was 27.3 months. The first 24 patients were operated on according to the technique described by Tsubokawa. The last 13 cases (8 new patients and 5 reinterventions) were operated on by a technique including localization by superficial CT reconstruction of the central region and neuronavigator guidance. The position of the central sulcus was confirmed by the use of intraoperative somatosensory evoked potentials. The somatotopic organization of the motor cortex was established preoperatively by studying the motor responses at stimulation of the motor cortex through the dura. RESULTS: Ten of the 13 patients with central pain (77%) and 10 of the 12 patients with neuropathic facial pain experienced substantial pain relief (83.3%). One of the three patients with post-paraplegia pain was clearly improved. A satisfactory result was obtained in one patient with pain related to plexus avulsion and in one patient with pain related to intercostal herpes zoster. None of the patients developed epileptic seizures. CONCLUSIONS: Our results confirm that chronic stimulation of the motor cortex is an effective method in treating certain forms of refractory pain.

Cortical stimulation and epileptic seizure: a study of the potential risk in primates.

OBJECTIVE: The recent successful development of chronic stimulation of the motor cortex as a treatment for neuropathic and central pain does not exclude the possibility of eventual side effects, such as epileptic seizure or a lowering of the epileptic threshold. This study evaluates the behavioral and electroencephalographic impact of this treatment in three normal monkeys. RESULTS: None of the monkeys presented epileptic behavior or abnormal electroencephalographic activity at parameters of stimulation currently used in clinical series, i.e., frequency and pulse duration of approximately 40 Hz and 90 microseconds, respectively, and an intensity just under the threshold for inducing muscle twitch in painful areas. Higher intensities did, however, induce reversible epileptic seizure. There was, nonetheless, no modification of the epileptic threshold, because even after these seizures, intermittent light stimulation elicited no abnormal electroencephalographic activity. CONCLUSION: It thus seems that motor cortex stimulation does not induce epileptic complications when the classic clinical criteria of stimulation are respected. Nevertheless, it would be wise to subject candidates for implantation to intermittent light stimulation before and after a period of stimulation to ascertain the innocuousness of the cortical stimulation.

Treatment of deafferentation pain by chronic stimulation of the motor cortex: report of a series of 20 cases.

Twenty patients with deafferentation pain were treated by chronic stimulation of the motor cortex. The central fissure was localized using stereotactic MRI and the motor cortex was mapped using intra-operative somatosensory evoked potentials. Seven patients with trigeminal neuropathic pain experienced definite pain relief varying between 40 and 100%. Ten patients had central pain secondary to central nervous system lesions. A satisfactory long-lasting pain control (pain relief > 40%) was obtained in five of them (50% of cases). One patient with pain from peripheral nerve injury obtained more than 80% pain relief. Two patients had pain from spinal cord lesions. One did not respond but the other obtained an excellent long-term result. The location of the effective stimulation plots was in agreement with the somatotopic maps of the primary motor cortex. One patient developed a small extradural haematoma which resolved spontaneously. None of the patients developed seizure activity. This study confirms the potential value of motor cortex stimulation in the treatment of certain forms of intractable pain, especially in cases with trigeminal neuropathic pain.

Is electrostimulation preferable to surgery for upper limb ataxia?

Ataxic syndromes of the upper limbs are observed in various situations but are usually a result of lesions involving the efferent pathways of the cerebellum, the superior cerebellar peduncles and midbrain. The commonest causes are multiple sclerosis, brain injury and focal neoplastic or vascular lesions. Cerebellar tremor, which usually comprises a postural and intentional component, is the commonest clinical form. In this review, we assess the value of the various surgical techniques in the treatment of this particular form of ataxia of the upper limbs.

[Neurosurgical treatments of chronic pain]. / Traitements neurochirurgicaux de la douleur chronique.

During these last years the methods and the indications of analgesic neurosurgery have respectively changed toward greater multiplicity and more selectivity. The conservative methods of neurostimulation have acquired a prominent place in some types of pain from neuropathic origin. Their aim is to reinforce inhibitory fibre function. Whatever the technique used, stimulation of peripheral nerves, of posterior funiculi of the spinal cord, of the thalamus or the cerebral cortex, it will be effective only if the target structures are not totally, anatomically and functionally, destroyed. Intrathecal morphine administration, has been shown to be useful to control some cancer-induced pain. Lastly, the techniques of interrupting the pathways of pain, achieving greater selectivity in their effects, remain the preferred treatment for some types of localised pain having precise mechanisms.

[Phrenic stimulation in C1-C2 tetraplegia. Apropos of a case]. / Stimulation phrénique dans les tétraplégies C1-C2. A propos d'un cas.

The authors report a case of post traumatic tetraplegia at the C1-C2 level in a young man of 16 with total respiratory paralysis treated with mechanical ventilation and a tracheotomy. Thirty months after the accident, an Avery S 232(1) diaphragmatic pacemaker was surgically implanted by the mediastinal approach. The technique was rapidly successful and enabled satisfactory ventilation and phonation two months after the implantation. The patient is currently treated at home with no signs of diaphragmatic fatigue 20 months after the implantation of the stimulator.

Microsurgical procedures in the peripheral nerves and the dorsal root entry zone for the treatment of spasticity.

When spasticity becomes severe and harmful, in spite of physical and medical therapy, neurosurgery can give functional improvement. This paper deals with the long term results of Selective Peripheral Neurotomies of the Tibial Nerve and Selective Posterior Rhizotomies in the Dorsal Root Entry Zone, in 123 patients with spastic disorders localized to the limbs. The micro-techniques and intra-operative electro-stimulation for identification of the nervous structures responsible for the spastic components, can give a substantial reduction of the harmful spasticity, without suppressing the useful muscle tone and impairing the residual motor and sensory functions. The results were effective, with a 1 to 13 year follow-up (5 on average), in 89% of 47 Selective Peripheral Neurotomies of the tibial nerve for spastic foot, in 92% of 53 Selective Posterior Rhizotomies for paraplegia and in 87% of 23 Selective Posterior Rhizotomies for hemiplegia. In the most severe situations ("comfort" indications), correction of the abnormal postures and relief of pain facilitated nursing and physiotherapy. Sometimes there was reappearance of some useful voluntary movements. In the less affected patients ("functional" indications), the suppression of the harmful spastic components made the persistant capacities more effective.

[Pain relief through transcutaneous electrical nerve stimulation (TENS). Results on painful neurological disorders in 180 cases (author's transl)]. / Analgésie par la méthode d'électrostimulation transcutanée. Résultats dans les douleurs d'origine neurologique. A propos de 180 cas.

A series of 180 patients with painful neurological disorders were treated with TENS. The findings most frequently encountered when the treatment was successful are analyzed. Depending upon the etiology of the primary disorder, good results (i.e. pain relief of 20% or higher) were obtained as follows : -- Peripheral Nerve Involvement : Amputation - 35 cases; Traumatism - 13 cases ; Miscellaneous - 7 cases. (87 %). -- Radicular Syndromes : Epidural scar and/or Arachnoiditis - 19 cases; Miscellaneous - 9 cases. (60 %). -- Post Herpetic Pain : 34 cases. (67 %). -- Brachial Plexus Lesions (Avulsions) : 12 cases. (25 %). -- Spinal Cord Disorders : 17 cases. (11 %). --Thalamic Pain : 5 cases. (0 %). -- Post-Radiation Pain or Carcinomatous Pain : 16 cases. (30 %). Satisfactory long-term results (over 3 years) were maintained in 80 % of cases of peripheral nerve involvement. In all other cases the percentage of pain relief decreased with follow-up. In this series the likelyhood of good results was associated with the following objective data : 1) Pain is generally secondary to deafferentation. 2) Pain is localized. 3) TENS application in close contact with the nervous structure innervating the painful area is more productive. 4) A relative preservation of lemniscal fibers to superior centers must be present so that stimulation can be transmitted.