Janice Ovelmen-Levitt

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.

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.

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 Lissauers 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)

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.

Self-mutilation following brachial plexus injury sustained at birth

Self-mutilation after deafferentation injuries has been reported only rarely in adult humans. This behavior has been found to be similar to that observed in animals that have been subjected to experimental deafferentation. We present a child with a brachial plexus injury sustained at birth who began to bite her analgesic digits. Self-mutilation behavior in humans is reviewed and its relevance to current deafferentation pain animal models is examined. This behavior in humans further validates the current animal model of deafferentation 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.

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%).

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.

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.