Stereotactic subthalamic nucleus lesioning for the treatment of Parkinson's disease.

This study was performed to evaluate the effectiveness and safety of unilateral STN lesioning in 23 patients with PD. L-Dopa intake and dyskinesia, Hoehn & Yahr, Schwab & England, and UPDRS motor scores were recorded pre- and postoperatively. Stereotactic MRI and CT and macrostimulation were used to establish target coordinates. A single RF lesion was performed. All patients underwent postoperative MRI. Contralateral tremor arrest and decrease of rigidity and bradykinesia should be regarded as hallmarks to STN stimulation. All recorded parameters were significantly improved after a mean follow-up of 13.5 months. Patients with STN lateral territory lesioning (alpha <0.05), younger than 61 years and with a duration of the disease between 6 and 9 years (alpha >0.05) did better than the others. The recurrence rate was 10%. Two patients developed dyskinesias which were completely resolved by a Vim/VOp lesion. Other significant complications were rare. The authors conclude that unilateral STN lesioning is a safe and very effective procedure to treat PD.

CT-guided percutaneous punctate midline myelotomy for the treatment of intractable visceral pain: a technical note.

Surgical treatment of intractable visceral pain has always been a challenge. The relatively recent discovery of a specific visceral pain pathway brought a new insight to this matter. The authors describe a new technique to interrupt this pathway, the CT-guided percutaneous punctate midline myelotomy, successfully applied in two patients with intractable pelvic visceral pain. Due to its simplicity, safety and high effectiveness, it may become the treatment of choice for intractable visceral pain.

SPECT-based tailoring of psychosurgical procedures: is it possible?

In contrast to the other areas of functional neurosurgery, psychosurgery has remained basically empiric and unchanged since the seventies, except for the recent suggestion to use chronic stimulation instead of ablative surgery. In this study, the authors investigated the value of SPECT abnormalities to guide psychosurgery and correlated the surgical results with the postoperative SPECT. This new approach, SPECT-based tailored psychosurgery, was applied in 4 of 11 patients referred for surgery, who fulfilled the inclusion criteria adopted. Excellent results were obtained in all of them after a follow-up of 30-52 months. Postoperative SPECT normalized in every case. We conclude, based on this small series, that it is possible to individualize and lateralize (tailor) psychosurgical procedures for every patient and that, to achieve this goal, SPECT is a rather impressive means and that postoperative SPECT closely correlated with the surgical results.

Risk factors for unpleasant paresthesiae induced by paresthesiae-producing deep brain stimulation.

Paresthesiae-producing deep brain stimulation (stimulation of ventrocaudal nucleus-VC, medial lemniscus-ML or internal capsule-IC) is one of the few procedures to treat the steady element of neural injury pain (NIP) currently available. Reviewing the first 60 patients with NIP submitted to deep brain stimulation (DBS) from 1978 to 1991 at the Division of Neurosurgery, Toronto Hospital, University of Toronto, we observed that 6 patients complained of unpleasant paresthesiae with paresthesiae-producing DBS, preventing permanent electrode implantation in all of them. Such patients accounted for 15% of the failures (6 out of 40 failures) in our series. In an attempt to improve patient selection, we reviewed our patients considering a number of parameters in order to determine risk factors for unpleasant paresthesiae elicited by paresthesiae-producing DBS. The results showed that this response happened only in patients with brain central pain complaining of evoked pain, secondary to a supratentorial lesion. Age, sex, duration of pain, quality of the steady pain, size of the causative lesion and site (VC,ML,IC) and type (micro or macroelectrode) of surgical exploration were not important factors. Unpleasant parethesiae in response to dorsal column stimulation, restricted thalamic lesion on computed tomography and the occurrence of associated intermittent pain were considered major risk factors in this subset of patients and the presence of cold allodynia or hyperpathia in isolation and the absence of sensory loss were considered minor risk factors. It is our hope that the criteria here established will improve patient selection and so, the overall results of DBS.

Deep brain stimulation for neuropathic pain.

Paresthesia-producing (PP), but not periventricular grey (PVG) deep brain stimulation (DBS) proved effective in steady neuropathic pain in 25 patients receiving both, regardless of the PP site stimulated, but PVG-DBS suppressed allodynia or hyperpathia in 3 cases of stroke-induced pain. In patients with stroke-induced central pain, PP-DBS was unpleasant in 6 of 17 (35%), all with allodynia and/or hyperpathia, but not in patients with spinal cord central or peripheral neuropathic pain with allodynia or hyperpathia. Of 11 patients in whom prior ineffective dorsal column stimulation (DCS) produced appropriate paresthesia, none responded to PP-DBS; 5 of 7 did so in whom DCS produced no paresthesia or relieved pain. Periaqueductal grey DBS was nearly always unpleasant, PVG-DBS sometimes was.

Thalamic ventrobasal stimulation for pain relief. Probable mechanisms, pathways and neurotransmitters.

Thalamic ventrobasal (VB) stimulation, first performed by Mazars, in 1961, is a valuable means for treating central and deafferentation pain. The way it acts to achieve pain relief, however, is still a matter of controversy. In this paper, the author examines previously proposed hypotheses and suggests that VB stimulation induces pain relief by activation of a multisynaptic inhibitory pathway to the medial thalamus, in which the dopaminergic nigrostriatal system exerts an important role and by modulation of abnormal activity in VB itself. The multisynaptic pathway involved, as well as the neurotransmitters, are suggested: VB stimulation excites somatosensory cortex through the glutaminergic thalamocortical pathway, which in turn, sends excitatory glutaminergic axons to the motor cortex. The sensorymotor cortex originates the excitatory glutaminergic corticostriatal pathway to the anterior putamen. The anterior putamen sends excitatory peptidergic (substance P) pathways to the globus pallidus internus (striatopallidal pathway) and to the substantia nigra reticulata (striatonigral pathway). The globus pallidus internus inhibits the medial thalamus through the pallidothalamic GABAergic pathway. The substantia nigra reticulata sends inhibitory GABAergic projections to the medial thalamus (nigrothalamic pathway) and excites the substantia nigra compacta. The substantia nigra compacta projects excitatory dopaminergic axons to the striatal neurons (nigrostriatal pathway) with output to the globus pallidus internus and substantia nigra reticulata and so on. Data to support this hypothesis are provided by an extensive review of the literature.

Pathways involved in thalamic ventrobasal stimulation for pain relief: evidence against the hypothesis VB stimulation-->rostroventral medulla excitation-->dorsal horn inhibition.

Despite its use for a long time, the way thalamic ventrobasal (VB) stimulation acts to produce pain relief is still unknown. One of the most accepted hypotheses, sponsored by Tsubokawa among others, proposes that VB stimulation excites raphespinal and reticulospinal neurons of the rostroventral medulla which in turn send respectively inhibitory serotonergic and noradrenergic axons through both dorsolateral funiculi (DLF) to the dorsal horn (DHA) nociceptive neurons; this pathway would be the same as is involved in periventricular-periaqueductal gray (PVG-PAG) stimulation induced inhibition of DH nociceptive neurons. This hypothesis implicates the necessity of DLF intactness; in fact, it was showed that section of bilateral DLF inhibits the response of DH nociceptive neurons to VB stimulation. If the above mentioned hypothesis is correct, one could expect that unilateral VB stimulation would produce bilateral pain relief, VB and PVG stimulation would be useful for treating the same modalities of pain and that in patients with central cord-based pain harboring complete cord transection, VB stimulation would not work at all. In order to check these possibilities, the patients with central cord-based pain admitted to the Division of Neurosurgery, Toronto Hospital between June 1978 and July 1991 to undergo deep brain stimulation (DBS) were reviewed. Sixteen patients were operated on. Based on clinical criteria, four out of these sixteen patients were thought to present complete cord transection (all four were men, with an average age of 48 years and pain secondary to cord injury).(ABSTRACT TRUNCATED AT 250 WORDS)