The Duke experience with nucleus caudalis DREZ coagulation.

The results of 46 nucleus caudalis DREZ coagulations performed at Duke in the preceding 5 years are reviewed retrospectively, with a mean follow-up of 32 months. Fifteen (38%) of 39 patients with complete data indicated that they would undergo the procedure again. Fifteen (38%) described improved quality of life. Outcome was fair or better in 18 (46%). Complications in the form of ataxia were present in 21 (54%).

Spontaneous and evoked dysesthesias observed in the rat after spinal cordotomies.

Thirty-six rats have received surgical spinal cord lesions, 7 at a thoracic and 29 at a cervical level. More than 70% of rats with lesions which involved the lateral column (spinothalamic tract) developed spontaneous dysesthesias in the contralateral limb. Only high cervical (C1-C2) lateral column lesions were followed frequently by forelimb signs. Lesions restricted to the dorsal columns were not followed by dysesthesias.

A new design of radiofrequency lesion electrodes for use in the caudalis nucleus DREZ operation. Technical note.

Two new right-angled electrodes have been designed for use at the dorsal root entry zone (DREZ) of the caudalis nucleus to provide relief of chronic facial pain. The electrode design was based on an anatomical study of the human caudalis nucleus at the cervicomedullary junction. Previously, caudalis nucleus DREZ operations were often followed by ipsilateral ataxia, usually in the arm. The new electrodes have significantly reduced this complication. A group of 21 patients with varied types of chronic facial pain have been treated, with pain relief in 70%.

The expression of deafferentation dysesthesias reduced by dorsal root entry zone lesions in the rat.

Extensive longitudinal lesions of the dorsal root entry zone (DREZ) are effective in relieving some chronic deafferentation pain in humans. A deafferentation syndrome follows C5-T2 dorsal root ganglionectomies in rats. The syndrome consists of biting and scratching the completely and partially denervated limb areas, respectively. This study examines the effect of DREZ lesions on the deafferentation syndrome in the rat. Of 37 rats, 24 underwent C5-T2 ganglionectomies only, five received C4-T3 micromechanical DREZ lesions only, and eight underwent ganglionectomies plus simultaneous DREZ lesions. The animals were observed for 45 days post-operatively. Histological analysis of the spinal cord lesions was performed. All rats with ganglionectomies alone exhibited the deafferentation syndrome; however, no rats with DREZ lesions alone showed this feature. Only 25% of rats with combined ganglionectomies and DREZ lesions exhibited the deafferentation syndrome in the first 30 days, whereas 80% of the animals with ganglionectomies only did so. Although 75% of the animals with combined lesions eventually bit the insensitive forepaw, this behavior was significantly attenuated: the day of onset was delayed and the extent of self-mutilation was reduced. Postmortem histological examination of the DREZ lesions indicated a close association between the completeness of the dorsal horn destruction and the reduction or prevention of self-mutilation. These data support the validity of the animal model and also the hypothesis stating that the deafferentation syndrome results from abnormal spontaneous neural activity in the dorsal horn. Moreover, the variability of the histological findings in these experiments stresses the importance of making contiguous and complete dorsal horn lesions in human DREZ surgery.

Deafferentation syndrome in the rat: effects of sex, age, and lesion type.

A deafferentation syndrome can be produced in Sprague-Dawley rats following dorsal root sections. The behavior may be objective evidence of dysesthesias, thus serving as an experimental model to study chronic dysesthesias caused by deafferentation in humans. This article examines the effects of sex, age, and lesion type on the expression of the deafferentation syndrome in Sprague-Dawley rats. No significant differences were found in the expression of the deafferentation syndrome with respect to age and weight in male rats within the ranges studied. Sex and lesion type did alter the expression of the syndrome.

Trigeminal nucleus caudalis dorsal root entry zone: a new surgical approach.

New radiofrequency lesion dorsal root entry zone (DREZ) electrodes for relief of facial pain were designed based on a neuroanatomic study in man of the trigeminal nucleus caudalis at the cervicomedullary junction. The human brainstems of 3 normal postmortem specimens were sectioned with measurements and relationships of the trigeminal nucleus caudalis, segmental tracts, spinocerebellar tracts and dorsal columns. Two right-angle DREZ electrodes were made by Radionics for producing DREZ lesions in the trigeminal nucleus caudalis to treat deafferentation facial pain.

Swallowing in torticollis before and after rhizotomy.

To determine risk factors for dysphagia after ventral rhizotomy, videofluoroscopic barium swallowing examinations were done on 41 spasmodic torticollis patients before and after surgery. Radiologic abnormalities were present in 68.3% of the patients before surgery, but these were only mildly abnormal in the majority. After surgery 95.1% showed radiologic abnormalities which were moderate or severe in one-third of the patients. Swallowing abnormalities correlated significantly with duration of torticollis and subjective complaints of swallowing difficulty both before and after surgery, but not with age, sex, or type of torticollis. The major acute postoperative finding was aggravation of preexisting pharyngeal dysfunction. Follow-up from about half of our original sample showed that gradual improvement occurred from 4 to 24 weeks after surgery by subjective report. We review the innervation of intrinsic and extrinsic pharyngeal musculature, and suggest that C1-3 rhizotomies and selective sectioning of the spinal accessory nerve are responsible for aggravation of pharyngeal swallowing dysfunction in the acute postsurgical period.

The deafferentation syndrome in the rat: effects of intraventricular apomorphine.

A deafferentation syndrome, produced in rats by dorsal root ganglionectomies, is expressed as scratching of partially deafferented limb areas and/or biting of anesthetic limb areas. This self-mutilation may be objective evidence of dysesthesias, thus serving as an experimental model to study chronic dysesthesias and/or pain from deafferentation in man. This study included behavioral observations of the syndrome and the effects of intraventricular apomorphine, a dopamine agonist, on its expression. Thirty-eight female Sprague-Dawley rats underwent unilateral C5-T2 dorsal root ganglionectomies followed immediately by stereotactically guided cannulation of the right lateral ventricle in 20 of the rats. For 2 weeks continuously via an osmotic minipump, 10 rats received apomorphine (5 micrograms/h) and 10 others received L-ascorbate (the vehicle). Rats with ganglionectomies only, as well as those receiving L-ascorbate, demonstrated early onset, more severe and later onset, less severe biting groups (P less than 0.05 Mann-Whitney U). Animals receiving apomorphine exhibited low autotomy scores irrespective of time of bite onset. Among the control groups, but not the experimental animals, the earlier the onset of biting, the more severe was the autotomy. The rats receiving vehicle via the minipump had earlier bite onsets than the rats in the ganglionectomy only group. This may indicate that the presence of the minipump is a stress which can accelerate the onset of biting. Intraventricular apomorphine can affect the deafferentation syndrome in the rat; it seems to decrease the level of autotomy and disrupt the relationship of bite onset with degree of biting.

Intraoperative somatosensory evoked potentials. A localizing technique in the DREZ operation.

The localization of neural pathology by the evoked potential technique through the use of the Nicolet compact four-signal averager is reviewed. Stimulating electrode application on facial nerves and peripheral nerves of the limbs is described, as well as spinal cord and medullary recording electrode type and placement. Several pathological lesions causing pain are presented and the intraoperative evoked potentials prior to and after lesion production are examined and analyzed.

Abnormal physiology of the dorsal horn as related to the deafferentation syndrome.

The spinal cord dorsal horn has been implicated in the generation of pain and dysesthesias following nerve and nerve root damage and/or avulsion, as well as following damage in adjacent spinal cord regions. Alterations in the functional properties of dorsal horn neurons occur after deafferentation and may underlie the occurrence of abnormal sensations referred to the denervated body part. Abnormal activity following deafferentation has also been noted at thalamic and cortical levels. Some of these post-denervation functional changes, determined anatomically and/or electrophysiologically, are reviewed as well as the results of behavioral studies of the deafferentation syndrome in the rat.

The deafferentation syndrome in the rat: effects of intraventricular neurotensin and cholecystokinin.

A deafferentation syndrome can be produced in rats by dorsal root ganglionectomies. This syndrome consists of scratching and/or biting of the anesthetic limb to the point of amputation. This behavior may serve as an experimental model to study certain aspects of chronic dysesthesias and/or pain caused by deafferentation in man. In this study, we made behavioral observations on the deafferentation syndrome and examined the possibility that intraventricular neurotensin and cholecystokinin alter the course of this syndrome. We found that neurotensin accelerated the scratching component without affecting the biting behavior. Cholecystokinin, however, attenuated the release of both components of the syndrome.

Electrical impedance recording for localization in functional neurosurgery of the spinal cord and lower brain stem.

Functional neurosurgery aims to modify or abolish neural messages. Established techniques use confirmatory electrical stimulation prior to ablation and require local anesthesia. Recently developed procedures take place under general anesthesia increasing the chance of damage to adjacent neural structures with postoperative morbidity. We describe a laboratory study correlating changes in measured electrical impedance with transition from white to grey matter in the brain and spinal cord of two mammalian species; this has not previously been easy to undertake, nor felt reliable. Impedances can now be measured simply and reliably. This study confirms our operating theater experience. We recommend that when stimulation cannot be used, impedance can and should be utilized to indicate the need for an electrode to be resited.

Intraoperative evoked potentials recorded in man directly from dorsal roots and spinal cord.

Direct spinal cord surface recordings of evoked spinal cord potentials have been made in 26 patients during neurosurgical procedures for intractable pain. Monopolar recordings at the dorsal root entry zone after peripheral nerve stimulation have been made at multiple levels for segmental localization and to monitor the state of the afferent path and dorsal horn. Dorsal root and dorsal column conduction has been tested on diseased and intact sides. Normal afferent conduction velocity was found to have an overall mean of 61.33 m/sec for cervicothoracic and lumbosacral peripheral nerves, and 50 m/sec for the dorsal columns. The normal mean amplitude for the slow negative wave (N1) recorded at the root entry was 52.54 muV, while that for the dorsal column conducted response recorded within 4 cm of the stimulus point on the dorsal columns was 347.5 muV. Several different placements of stimulating and recording electrodes are described, as well as their application. An interpretation of the resulting data is proposed.

Dorsal root rhizotomy and avulsion in the cat: a comparison of long term effects on dorsal horn neuronal activity.

We performed an extracellular microelectrode analysis of the neuronal activity of cells located in deeper laminae of dorsal horns that had been deafferented by ipsilateral lumbar dorsal root rhizotomy or avulsion. Special attention was given to those cells that were recorded in preparations that were more than 6 weeks chronic. We compared the results to those obtained in nondenervated controls and in experiments in which the spinal cord was acutely transected at a midthoracic level, but had intact dorsal roots. There was an increase in ipsilateral flank and contralateral input in the chronically deafferented as compared to nondenervated controls. Differences were observed between long term rhizotomized and avulsed dorsal horns. Receptive fields extended on to flank and thoracic dermatomes after rhizotomy, often requiring only light cutaneous stimuli. Receptive fields were more restricted with avulsion injury, generally requiring moderate to strong, superficial or deep pinch. Histological analysis revealed consistent differential damage to the medial portion of Lissauer's tract with avulsion injury and subsequently more gliosis in the substantia gelatinosa. The loss of this propriospinal pathway may explain the lack of receptive field expansion on to the thoracic dermatomes and the stronger natural stimuli that were required. A higher percentage of cells with bilateral and inhibitory receptive fields was found in experiments in which the spinal cord was transected at a midthoracic level than in the controls. Ipsilateral excitatory receptive fields were also expanded as compared with control observations, but were not found on the flank.(ABSTRACT TRUNCATED AT 250 WORDS)

Dorsal root entry zone lesions for the treatment of post-herpetic neuralgia.

Post-herpetic pain was treated in 12 patients using dorsal root entry zone ( DREZ ) lesions. All patients had failed to receive adequate pain relief from conservative therapy consisting of transcutaneous nerve stimulation, carbamazepine, and/or amitriptyline. Dorsal root entry zone lesions were made to include the involved dermatomes plus one-half of the dermatomes above and below the painful areas. Eight patients reported good pain relief with follow-up periods ranging from 6 to 21 months. A ninth patient obtained satisfactory pain relief, but the superior 1 cm of the original painful area was not included in the distribution of the DREZ lesions. Patients whose lesions were performed using a thermally controlled lesion probe suffered no significant postoperative neurological deficit. Dorsal root entry zone lesions appeared to be a satisfactory treatment for post-herpetic neuralgia in patients who have failed to respond to more conservative modes of therapy.

Increase in nociceptive input to spinocervical tract neurons following chronic partial deafferentation.

Recordings from antidromically identified spinocervical tract (SCT) cells in the partially deafferented spinal cord of chloralose-anesthetized cats have revealed reorganization of their input from peripheral receptors in the skin. Immediately after dorsal rhizotomy of segments L5, L6, S1, and S2, (sparing L7), units in L6 had a lower than normal probability of responding to moderate pressure, mechanical nociceptive, noxious heat, and cooling inputs. This persisted for about 6 weeks, after which normal or even larger than normal proportions of SCT units could be driven by these inputs. The proportion of units driven by hair deflection remained large throughout this period. Responses in the L7 segment with intact L7 dorsal root were unchanged. We suggest that afferent fibers from different receptor types differ in the extent of their normal functional projection, accounting for the selective changes after acute deafferentation. The chronic changes may reflect a differential ability of surviving afferent fibers to undergo compensatory changes in their projection (e.g., sprouting) after chronic rhizotomy.