Growth of myelinated lumbosacral ventral root fibers in kittens after early postnatal dorsal rhizotomy, dorsal rhizotomy and spinal cord hemisection, or sciatic neurectomy.
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Changes of opioid binding density in the rat spinal cord following unilateral dorsal rhizotomy.
Mu, delta and kappa opioid receptors in the vertebrate spinal cord mediate the potent antinociceptive effects of opioid agonists administered onto the spinal cord. The present experiments were conducted to determine the effect of unilateral dorsal rhizotomy on mu, delta and kappa spinal opioid binding sites. Measurements of opioid binding were made at 1, 2, 4 or 8 days after rhizotomy and comparisons were made to intact animals. The changes in mu, delta and kappa opioid binding sites were determined by receptor autoradiography using the highly selective radioligands [3H]sufentanil, [3H]DPDPE and [3H]U69593, respectively. Within autoradiograms of each spinal cord, three regions on each side of the spinal cord were targeted for densitometric analysis: laminae I-II (medial), V (lateral) and X. When effects of unilateral rhizotomy within animals were assessed by comparison of the density of binding on the side ipsilateral to the rhizotomy to the contralateral side, decreases in the binding of all three radioligands were observed in laminae I-II on the side of the spinal cord ipsilateral to the rhizotomy at 2-8 days postlesion. A significant reduction in binding was also noted for mu and delta sites in lamina V after 8 days and for delta binding in lamina X at 2 and 4 days on the side ipsilateral to the rhizotomy. However, when densities of binding sites were compared with the corresponding regions in control, it was clear that dorsal rhizotomy resulted in significant changes in opioid binding on both sides of the spinal cord; changes differed for each type of opioid binding site. On the contralateral side of the spinal cord, rhizotomy caused a significant decrease of mu opioid sites 1 day after the lesion and showed partial recovery by day 8. Delta opioid sites were also significantly decreased as early as 1 day postlesion, but did not recover. Kappa opioid sites did not change at 1 day after the rhizotomy but increased on day 2, decreased on day 4 and fully recovered 8 days after rhizotomy. The present results support the hypothesis that a significant proportion of spinal mu, delta and kappa opioid binding sites are present on the central terminations of primary afferents. Finally the present data are the first to report a contralateral effect of the unilateral rhizotomy on spinal opioid binding sites. The contralateral changes in binding were specific to the type of opioid site examined, time after the surgery and region of the spinal cord examined.
Animals↗
Comparison of surgical treatments for trigeminal neuralgia: reevaluation of radiofrequency rhizotomy.
In this study, we reevaluate the results of radiofrequency rhizotomy and review the effectiveness of other surgical procedures for the treatment of trigeminal neuralgia. Five hundred patients with trigeminal neuralgia underwent radiofrequency rhizotomy at the University of Cincinnati Medical Center, Cincinnati, OH, between 1981 and 1986. Their results are compared with those of patients reported in the literature who underwent radiofrequency rhizotomy (6205 patients), glycerol rhizotomy (1217 patients), balloon compression (759 patients), microvascular decompression (MVD) (1417 patients), and partial trigeminal rhizotomy (250 patients). Comparisons were based on the following outcome parameters: technical success, pain relief and recurrence, facial numbness, dysesthesia, corneal anesthesia, keratitis, trigeminal motor dysfunction, permanent cranial nerve deficit, intracranial hemorrhage or infarction, perioperative morbidity, and perioperative mortality. We found that MVD had the lowest rate of technical success. Radiofrequency rhizotomy and MVD had the highest rates of initial pain relief and the lowest rates of pain recurrence. Glycerol rhizotomy had the highest rate of pain recurrence. Balloon compression had the highest rate of trigeminal motor dysfunction. Balloon compression and MVD had the lowest rates of corneal anesthesia or keratitis. MVD had the lowest rates of facial numbness and dysesthesia. All percutaneous procedures had similar rates of dysesthesia. Posterior fossa exploration had the highest rates of permanent cranial nerve deficit, intracranial hemorrhage or infarction, and perioperative morbidity and mortality. On the basis of our experience and a review of the literature, we conclude the following: 1) percutaneous techniques and posterior fossa exploration offer advantages and disadvantages, 2) radiofrequency rhizotomy is the procedure of choice for most patients undergoing first surgical treatments, and 3) MVD is recommended for healthy patients who have isolated pain in the first ophthalmic trigeminal division or in all three trigeminal divisions and patients who desire no sensory deficit.
Adult↗
Percutaneous controlled radiofrequency rhizotomy in the management of patients with trigeminal neuralgia due to multiple sclerosis.
Between the years 1974 and 1999, 1,672 patients with medically intractable trigeminal neuralgia (TN) were treated by percutaneous controlled radiofrequency (RF) rhizotomy by the senior author and co-workers at the Department of Neurosurgery, Ankara University School of Medicine. Sixteen hundred cases (95.7%) were found to have idiopathic TN, while 72 cases (4.3%) were classified as symptomatic. In the latter group, TN was found to be caused by multiple sclerosis (MS) in 17 cases (23.6%), one of whom had bilateral TN. All patients having TN with MS (17 cases) underwent percutaneous controlled radiofrequency rhizotomy (25 procedures) as the procedure of choice. The MS patients were followed for an average of 60 months (range: 6-141 months). Complete pain relief was achieved with a single procedure in 12 of the 17 MS cases (70.6%). Early (less than 2 weeks) pain recurrence was seen in two patients (11.8%), while the overall recurrence rate was 29.4%. A second procedure was required to control TN in three cases (17.6%), a third in one (5.9%), and twice for each side for the case with bilateral TN (5.9%). Pain was completely relieved in 14 cases (82.4%) with single or multiple RF rhizotomies. In three cases (17.6%), partial pain control was achieved with RF rhizotomy, and the patients continued to receive adjunctive medical therapy. No complications were observed. All 17 patients (100%) were classified to have done well with RF rhizotomy. Satisfactory results and good long-term pain control were obtained in patients having TN due to MS with percutaneous controlled RF rhizotomy. The authors propose that RF rhizotomy may be a safe and effective procedure in the neurosurgical armamentarium for the treatment of patients having TN due to MS.
Adult↗
Extradural sensory rhizotomy in the management of chronic lumbar radiculopathy: a minimum 2-year follow-up study.
STUDY DESIGN: Fifty-one consecutive patients who underwent extradural sensory rhizotomy for chronic radiculopathy after lumbar surgery were reviewed retrospectively. OBJECTIVES: To determine the effectiveness of sensory rhizotomy in the management of chronic radiculopathy in patients selected by extensive imaging techniques and selective nerve root sheath injections. SUMMARY OF BACKGROUND DATA: Results of more central ablative procedures for chronic benign pain problems have been disappointing, with variable reports of pain relief. METHODS: Fifty-one patients were reviewed. All patients underwent extensive evaluation to exclude reversible structural lesions, and all had the diagnosis of chronic radiculopathy confirmed by results of clinical and electrophysiologic examination. Selective nerve root sheath injections under fluoroscopic guidance confirmed the symptomatic nature of the segments. All blocks were repeated at least once. All patients underwent selective sensory rhizotomy or, in some cases, complete rhizotomy. After rhizotomy, 37 patients were available to be observed at selected time intervals for a minimum of 2 years. Clinical results were determined by the presence or absence of pain relief (visual analog scale), sensory and motor deficits, narcotic analgesic usage, and the patient's estimation of the effectiveness of the procedure. RESULTS: At 6 months after surgery, all 51 patients and the outcomes of their surgery were available for review. Fifty-five percent of patients rated were believed to have good or excellent outcomes, whereas the remainder had poor or failed outcomes. For the minimum 2-year follow-up period (range, 2-4.2 years), 37 patients were available for review. At final follow-up examination only 19% of the patients maintained good or excellent outcomes. CONCLUSIONS: The results of the rhizotomy procedures deteriorated over time. Possible reasons for the failure, other than temporal deterioration, were anatomic factors and lack of specificity of diagnostic techniques, specifically selective nerve root sheath injection. At this point rhizotomy cannot be recommended with any confidence whatsoever in the setting of chronic lumbar radiculopathy after lumbar surgery.
Adult↗
Selective dorsal rhizotomy and rates of orthopedic surgery in children with spastic cerebral palsy.
If the spasticity of cerebral palsy (CP) is reduced in children at a young age by selective dorsal rhizotomy, the incidence of lower-extremity deformities requiring orthopedic surgery may be reduced; however, this has never been investigated in detail. The authors examined the effects of selective dorsal rhizotomy on rates of lower-extremity orthopedic surgery in 178 children with CP. Age at selective dorsal rhizotomy ranged from 2 to 19.3 years (mean 5.5 years) with follow-up intervals ranging from 24 to 70 months (mean 44 months). Spastic CP was classified as quadriplegia (33%), diplegia (65%), and hemiplegia (2%). To assess the effects of early versus late rhizotomy on rates of orthopedic surgery, patients were grouped as follows: Group I underwent rhizotomy between 2 and 4 years of age (54 patients), and Group II underwent rhizotomy between 5 and 19 years of age (124 patients). Comparison of Kaplan-Meier plots of lifetime orthopedic surgery rates revealed that Group II underwent orthopedic surgery at a higher rate than Group I (p = 0.037). Analysis by procedure type revealed higher orthopedic surgery rates in Group II than Group I for heel cord releases (p = 0.0025), adductor releases (p = 0.018), and hamstring releases (p = 0.02). Orthopedic surgery rates were no higher for Group II compared to Group I for ankle/foot operations (p = 0.023), femoral osteotomy (p = 0.25), iliopsoas releases (p = 0.35), and "other" operations (p = 0.013). The data indicate that early rhizotomy reduces the need for orthopedic surgery for heel cord, hamstring, and adductor releases.
Adolescent↗
Normal development and the effects of early rhizotomy on spinal systems in the rat.
The normal postnatal development of 4 spinal systems was examined in the dorsal horn of the rat spinal cord using histochemical and immunocytochemical techniques. We used thiamine monophosphatase (TMPase), a marker for dorsal root ganglion cells and their projections, a tachykinin, substance P (SP), which is provided by both dorsal root and intrinsic systems, and two markers for descending systems, serotonin (5-HT) and the synthesizing enzyme for noradrenalin, dopamine B-hydroxylase (DBH). The responses of each of these systems to unilateral dorsal lumbosacral rhizotomy on postnatal day 5 was then examined and quantified using image analysis methods to determine whether the extent of plasticity of spinal systems is different after a neonatal lesion than after a comparable lesion made in the adult. Each system differs in development, distribution, and in response to rhizotomy. TMPase is present in the dorsal horn on the day of birth (DPN0) and reaches adult levels of density by 5 days postnatal (DPN5). SP reaction product is present in a distribution similar to the adult in the dorsal horn on DPN0 and reaches adult levels of density by the second postnatal week. 5-HT is present in the dorsal horn on DPN0, shows a laminar distribution at DPN5, and acquires the adult distribution and density at the end of the second week. DBH is present in the dorsal horn on DPN0, acquires the adult distribution at DPN5 and adult levels of density at the end of the second postnatal week. Unilateral lumbosacral rhizotomy in 5 day old rats completely and permanently abolishes TMPase in the dorsal horn by 4 days postoperatively (4DPO). SP is decreased by 4 DPO (9 DPN) but recovers almost completely by 30 DPO. 5-HT is increased by 10 DPO and remains elevated thereafter. DBH is not changed postoperatively. There is shrinkage of lamina I and II by 10 DPO but the recovery of SP and the increase in density of 5-HT staining is proportionally greater than the extent of shrinkage. Therefore, shrinkage contributes to but does not entirely account for either the apparent recovery of SP staining or the increase in density of 5-HT staining. The responses of the TMPase, 5-HT and DBH systems to neonatal rhizotomy are very similar to the response to rhizotomy in adults and there is therefore no evidence for greater plasticity of these systems after neonatal rhizotomy than after adult rhizotomy. The SP systems show more rapid depletion and a greater and more rapid recovery than after adult deafferentation.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Light microscopic localization of calcitonin gene-related peptide in the normal feline trigeminal system and following retrogasserian rhizotomy.
Calcitonin gene-related peptide (CGRP) is a neuropeptide that has been implicated in the transmission and modulation of primary afferent nociceptive stimuli. In this study, we describe the light microscopic distribution of CGRP immunoreactivity (IR) within the feline trigeminal ganglion and trigeminal nucleus of normal adult subjects and in subjects 10 and 30 days following complete retrogasserian rhizotomy. Within the trigeminal ganglion of normal subjects, cell bodies and fibers showed CGRP-IR, whereas immunoreactive fibers were rare in the central root region. Within the normal spinal trigeminal and main sensory nuclei, CGRP-IR was seen to form a reproducible pattern that varied between the different nuclei. Following rhizotomy, most, but not all, of the CGRP-IR was lost from the spinal trigeminal and main sensory nuclei, except in regions where the upper cervical roots and cranial nerves VII, IX and X project into the trigeminal nucleus. The pattern seen at 10 days contained more CGRP-IR than that seen at 30 days and suggests that degenerating fibers still show CGRP-IR. In contrast to the decrease seen in the nuclei after rhizotomy, examination of the central root that was still attached to the trigeminal ganglion showed an increase in CGRP-IR within fibers, some of which ended in growth conelike enlargements. Rhizotomy induced a dramatic increase in CGRP-IR within trigeminal motoneurons and their fibers, which was strongest 10 days after rhizotomy and weaker at 30 days, which was still stronger than normal. These results indicate that the majority of CGRP-IR found in the trigeminal nucleus originates from trigeminal primary afferents and that an upregulation of CGRP-IR occurs in trigeminal motoneurons and in regenerating fibers in the part of the central root that was still attached to the ganglion. In addition, the persistence of CGRP-IR fibers in the trigeminal nucleus provides one possible explanation for the preservation of pain in humans following trigeminal rhizotomy.
Animals↗
Bladder function before and after selective dorsal rhizotomy in children with cerebral palsy.
PURPOSE: Approximately a third of children with cerebral palsy are expected to present with dysfunctional voiding symptoms. Selective dorsal rhizotomy, which is indicated for managing lower extremity spasticity in children with cerebral palsy, also has the potential of affecting bladder function. We evaluate the impact of selective dorsal rhizotomy on bladder function by comparing preoperative and postoperative symptoms, and urodynamic parameters in children undergoing selective dorsal rhizotomy for spasticity. MATERIALS AND METHODS: We reviewed urodynamic studies in 25 boys and 15 girls with a mean age plus or minus standard deviation of 5.43+/-2.1 years who underwent selective dorsal rhizotomy for spasticity at our institution between January 1992 and September 1995. Urodynamics were performed preoperatively only in 22 patients, preoperative and postoperatively in 13, and postoperatively only in 5. Preoperative urodynamic studies were done within 2 weeks of surgery and postoperative studies were done at least 6 months after surgery (mean 1.32+/-0.65 years). RESULTS: Of the 35 patients with preoperative urodynamic studies total bladder capacity, pressure specific volumes and full resting pressure were abnormal for age in 23 (65.7%). In addition, 17 of the 23 children (74%) were completely asymptomatic. In the group that underwent preoperative and postoperative urodynamic studies there was significant improvement in total bladder capacity (p <0.005) and pressure specific volumes (p <0.005) using the paired Student t test. All children had neurological improvement postoperatively, 5 of 7 (71%) who were incontinent preoperatively became continent and none had deterioration on urodynamics. CONCLUSIONS: At least half of the children with spastic cerebral palsy have clinically silent bladder dysfunction. Selective dorsal rhizotomy improves spasticity and significantly improves bladder storage characteristics. We propose that urodynamic studies be included in the evaluation of children with spastic cerebral palsy who are possible candidates for selective dorsal rhizotomy to treat lower limb spasticity.
Cerebral Palsy↗
Anorectal function in patients with complete spinal transection before and after sacral posterior rhizotomy.
BACKGROUND/AIMS: The implantation of spinal stimulators to facilitate defecation in patients with complete spinal transection involves division of the posterior sacral nerve roots. The aim of this study was to investigate the role of spinal reflexes in anorectal function. METHODS: Anorectal manometry and electromyography were performed in 14 patients with supraconal spinal cord transection (C6-T12) before and after complete sacral posterior rhizotomy and in 30 normal controls. RESULTS: Patients with spinal transection lost conscious control of the external anal sphincter. Reflex responses to intra-abdominal pressure and to rectal distention were eliminated after rhizotomy, indicating that they are spinal reflexes. Rhizotomy also eliminated giant rectal contractions induced by rectal distention in these patients. In contrast, the exaggerated sphincter relaxation induced by rectal distention was not influenced by rhizotomy. Discriminant rectal sensation was lost, but patients with thoracic cord lesions perceived a dull pelvic sensation during rectal distention even after rhizotomy. CONCLUSIONS: The exaggerated anorectal smooth muscle responses and absent conscious control of the anorectum may explain why patients with complete spinal transection experience uncontrollable reflex defecation, and the persistence of external anal sphincter contraction during straining may impair fecal expulsion. The elimination of these responses after posterior rhizotomy prevented reflex defecation while facilitating manual evacuation.
Adult↗
Preservation of pudendal afferents in sacral rhizotomies.
OBJECTIVE: To assess the effectiveness of pudendal afferent mapping as a tool to minimize the risk of postoperative bowel, bladder, and sexual dysfunction in patients undergoing selective posterior rhizotomies in whom the S2 roots are candidates for rhizotomy. METHODS: One-hundred fourteen children with the diagnosis of cerebral palsy and debilitating spasticity were selected to undergo selective posterior rhizotomies at New York University Medical Center during 1991 through 1995. There were 72 male and 42 female patients with a mean age of 3.8 years. At the time of surgery, none of the patients had clinically relevant bladder dysfunction. Dorsal root action potentials were recorded intraoperatively to map the distribution of pudendal afferent fibers in S1-S3 roots bilaterally before performing the rhizotomies. RESULTS: Pudendal afferent mapping was successful in 105 of 114 patients. In the majority of these patients (56%), the distribution was asymmetrical. S1 roots contributed 4%, S2 roots 60.5%, and S3 roots 35.5% of the overall pudendal afferent activity. The pudendal afferent distribution was often confined to a single level in 18% of the patients or even to a single root in 7.6%. Fifty-six percent of the pathologically responding S2 roots during rhizotomy testing were preserved because of the significant afferent activity, as demonstrated during pudendal mapping. None of the 105 patients so mapped developed long-term bowel or bladder complications. CONCLUSIONS: Pudendal afferent mapping identifies S2 roots that carry a significant number of fibers involved with genital sensation. The preservation of such roots during surgical procedures may be important for sexual function and may also contribute to decreasing postoperative bladder and bowel disturbances.
Action Potentials↗
[Experimental study on combining selective rhizotomy of different anterior and posterior sacral roots for restoration of bladder function after spinal cord injury].
OBJECTIVE: To investigate an alternative procedure for complete denervation of bladder in the supra-cone cord injury to restore the bladder function. METHODS: Sixteen dogs were included in this study after their spinal cords were transected above the cone. They were divided into 6 groups and performed the rhizotomy of L7 to S3 root in different combination respectively. The bladder and urethra pressure change by electrostimulation during operation and cystometrogram change after operation were tested. RESULTS: 1. Electrostimulation study: for bladder innervation, S2 was the most important and S1 was secondary. While for urethra innervation, S1 was more important than S2. When the anterior and posterior roots of S1 and S2 were intact with rhizotomy of posterior roots of L7 and S3, stimulated the common or posterior root of S1 and S2, the change of pressure in bladder and urethra was the same. When the anterior roots of S1 and S2 were resected with rhizotomy of posterior roots of L7 and S3, the pressure in bladder and urethra was significant decreased compared to stimulating the corresponding posterior roots. 2. Cystometrogram (CMG) study: in the complete deafferented group, resecting the posterior roots of L7 to S3, the bladder became flaccid. While resecting the posterior root of S2 and anterior root of S1 or, resecting the posterior root of S1 and anterior root of S2, combining with rhizotomy of posterior roots of L7 and S3, the CMG curve was similar to the complete deafferented group. In the S1 and S2 intact group, the bladder became spastic. CONCLUSION: Combining rhizotomy of anterior and posterior sacral root in different level has the same effects on bladder as complete deafferentation.
Animals↗
Does gait continue to improve 2 years after selective dorsal rhizotomy?
Although changes in the gait pattern of children with spastic diplegia 1 year after selective dorsal rhizotomy have been well documented, minimal information exists regarding the continued changes in the gait pattern over time. Despite improvements in gait after rhizotomy, 66-75% of patients still require orthopaedic surgery for residual deformities. The optimal timing of the orthopaedic surgery after selective dorsal rhizotomy is not well established because of the lack of information regarding changes in gait over a long term. Using three-dimensional gait analysis, the gait pattern of 23 children was evaluated preoperatively, 1 and 2 years postoperatively. There were significant improvements in hip, knee, and ankle motion at 1 year after surgery. Although improvements in the gait pattern were found between 1 and 2 years after surgery, the changes were not significant. Therefore orthopaedic intervention may be undertaken at 1 year after rhizotomy to enhance function, as changes in gait from 1 to 2 years after rhizotomy are minimal.
Cerebral Palsy↗
How frequent is anesthesia dolorosa following spinal posterior rhizotomy? A retrospective analysis of fifteen patients.
Anesthesia dolorosa has been considered an infrequent complication of spinal posterior rhizotomy. We reviewed the data of all patients who underwent rhizotomy between 1962 and 1972 (15 cases). Thirteen were affected by cancer and 2 by non-neoplastic conditions. Eight developed a typical deafferentation pain (i.e., anesthesia dolorosa) (53%) while 3 who were found to have a brain (frontal 2; parietal 1) metastasis did not. Anesthesia dolorosa developed 1.5-8 months after rhizotomy. We conclude that anesthesia dolorosa following rhizotomy is more frequent than usually stated and that rhizotomy should be restricted to patients with a less than 3-month life expectancy.
Adult↗
Effects of dorsal bilateral rhizotomy treatment on transmitter systems in the spinal cord of normal and spastic dogs.
The high-affinity uptakes of [3H]serotonin, [3H]-glutamate, and gamma-[3H]aminobutyric acid were studied using a myelin-free crude synaptosomal fraction prepared from the spinal cords of normal dogs and spastic dogs following sham treatment or dorsal bilateral rhizotomy surgery. Compared to sham-operated controls, rhizotomy surgery of normal dogs produced, after 1 week, a 30% reduction in the Vmax value of [3H]glutamate, but did not alter the uptake of gamma-[3H]aminobutyric acid. This treatment also produced a 60% decrease in the Vmax value of [3H]serotonin. Comparison of the effect of rhizotomy surgery on normal and spastic dogs revealed that the spastic group had 60% higher Vmax values for uptakes of [3H]glutamate and gamma-[3H]aminobutyric acid. Comparison of sham-operated spastic dogs and rhizotomy-treated spastic animals showed that there was a 25% decrease in the uptake of both amino acids in the rhizotomy-treated spastic group. Overall, the data (a) support the hypothesis that glutamate is the neurotransmitter from some of the primary afferents, and (b) suggest that sprouting of interneuronal amino acid transmitter systems may occur in the spinal cords of spastic dogs.
Animals↗
Inability of dorsal spinal rhizotomy to prevent renal wrap hypertension in rats.
Renal hypertension has been shown to be prevented and reversed by renal denervation. It has been postulated that the afferent nerves from the kidney are responsible for mediating the hypertensive stimulus that activates the sympathetic nervous system and increases arterial pressure. This study was designed to directly test the hypothesis that the afferent renal nerves are necessary for the development and maintenance of renal hypertension. In the first experiment, dorsal spinal rhizotomies or sham rhizotomies were performed in rats between T9 and L1, through which afferent renal nerves have been shown to traverse. After the one-kidney, one-wrap procedure, the increase in systolic arterial pressure and water intake was similar in the two groups of rats. To determine whether the removal of afferent renal nerves reversed the hypertensive process, animals with established renal hypertension were subjected to dorsal rhizotomy or the sham-rhizotomy procedure. Again, there was no significant effect on systolic arterial pressure and water intake. Although combined dorsal and ventral rhizotomy and subdiaphragmatic vagotomy did not affect the onset of hypertension, spinal transection at the level of C8 effectively prevented the rise in arterial pressure. Although efferent neural mechanisms contribute to the hypertensive process, these studies suggest that afferent renal nerves are not directly involved in the development and maintenance of one-kidney, one-wrap renal hypertension.
Afferent Pathways↗
An experimental study of reflex variability in selective dorsal rhizotomy.
Significant problems regarding the measurement technique currently used to choose nerve roots for sectioning in the selective dorsal rhizotomy procedure have recently been reported. To better understand the source of these problems, a series of six experiments was performed in which the selective rhizotomy technique was applied to cats that were either intact, decerebrate, or spinalized. Measurements were made before and after partial rhizotomy. In decerebrate preparations, large, spontaneous changes in reflex threshold were observed over short periods of time, especially after partial rhizotomy was performed, and threshold changes greater than 1000% could be observed over 10-minute periods. Using constant-current stimulation of the dorsal root at threshold, the response of each ipsilateral leg muscle demonstrated frequent changes, and changes coincided with the variability in threshold estimation. In addition, very low thresholds were measured (0.1 to 0.25 mA) in half (3 of 6) of these experiments, these measurements being well below the currents customarily used for intraoperative decision making. Stimulation at twice threshold was found to consistently increase the pathological quality of the responses observed. Although intact animals never displayed contralateral responses when stimulated at threshold, such contralateral responses could readily be elicited at twice threshold. These laboratory results raise further doubts regarding the reliability of the measurement techniques now widely used for selective dorsal rhizotomy.
Animals↗
Changes in hip migration after selective dorsal rhizotomy for spastic quadriplegia in cerebral palsy.
Selective dorsal rhizotomy is increasingly used for management of spastic quadriplegic cerebral palsy but rates of hip stability following the operation have not been reported. Determining hip stability by radiographic measurement of lateral migration of the femoral head beyond a lateral edge of the acetabulum after dorsal rhizotomy allows an objective assessment of the outcome of the operation. This prospective study examined the effect of selective dorsal rhizotomy on lateral migration of the femoral head in 45 children with spastic quadriplegic cerebral palsy. The children ranged in age from 2 to 9 years (average 5 years 1 month) and were grouped according to their ages with 23 children in the 2- to 4-year-old group and 22 children in the 5- to 9-year-old group. Postoperative follow up ranged from 7 to 50 months (average 20 months). The Reimers migration percentage (MP), a measure of the lateral migration of the femoral head, was calculated from anteroposterior hip radiographs taken prior to the operation and at the last follow-up examination. Of the 90 hips involved, 9% improved, 80% remained unchanged, and 11% worsened, yielding a radiographic stability rate of 89%. The hips with postrhizotomy worsening of the MP had an average preoperative MP of 14% (range 9% to 38%) and an average postoperative increase in MP of 18% (range 11% to 37%). Of the 45 children, four subsequently underwent unilateral derotational femoral osteotomies for persistent or worsening hip subluxation. There was a significant tendency for the MP to worsen in patients with lower prerhizotomy MP values (chi 2 = 20.74, df = 4, p = 0.001), but the age of patients and their ambulatory status at the time of rhizotomy had no bearing on postoperative hip stability. The data indicate that selective dorsal rhizotomy prevents progressive lateral migration of the femoral head in the majority of children who undergo the operation for spastic quadriplegia.
Cerebral Palsy↗