Effects of x-irradiation on the proliferation of cells in peripheral nerve during Wallerian degeneration in the rat

Voice Changes of Patients With Nasopharyngeal Carcinoma in Eleven Years After Radiotherapy: A Cross-Sectional Study

OBJECTIVES

The objective of this study was to assess voice changes in patients with nasopharyngeal carcinoma (NPC) using subjective and objective assessment tools and to make inferences regarding the underlying pathological causes for different phases of radiotherapy (RT).

METHODS

A total of 187 (123 males and 64 females) patients with post-RT NPC with no recurrence of malignancy or other voice diseases and 17 (11 males and 6 females) healthy individuals were included in this study. The patients were equally divided into 11 groups according to the number of years after RT. The acoustic analyses, GRBAS (grade, roughness, breathiness, asthenia, and strain) scales, and Voice Handicap Index (VHI)-10 scores were collected and analyzed.

RESULTS

The fundamental frequency (F0) parameters in years 1 and 2 and year 11 were significantly lower in patients with NPC than in healthy individuals. The maximum phonation times in years 1 and 11 were significantly shorter than those in healthy individuals. The jitter parameters were significantly different between year 1 and from years 8 to 11 and the healthy individuals. The shimmer parameters were significantly different between years 1, from years 9 to 11, and healthy individuals. Hoarseness was the most prominent problem compared to other items of the GRBAS. The VHI-10 scores were significantly different between years 1 and 2 and year 11 after RT in patients with NPC.

CONCLUSIONS

Voice quality was worse in the first 2 years and from years 8 to 11 but remained relatively normal from years 3 to 7 after RT. Patient-reported voice handicaps began during year 3 after RT. The most prominent problem was perceived hoarseness, which was evident in the first 2 years and from years 9 to 11 after RT. The radiation-induced mucous edema, laryngeal intrinsic muscle fibrosis, nerve injuries, upper respiratory tract changes, and decreased lung capacity might be the pathological reasons for voice changes in post-RT patients with NPC.

The role of surgery in the management of radiation-induced brachial plexopathy: a systematic review

This systematic literature review of the clinical characteristics of radiation-induced brachial plexopathy and outcomes after intervention includes 30 trials with 611 patients. The mean radiation dose to the brachial plexus was 56 Gy, and the mean duration of radiation was 4 weeks. The mean time from radiation to the onset of symptoms was 35 months. The most commonly reported symptom was sensory loss (n = 323, 62%), followed by motor deficits (n = 294, 56%) and neuropathic pain (n = 284, 54%). In total, 65 (56%) patients had panplexus involvement and 51 (44%) patients had partial plexus involvement. The most common surgical procedure was neurolysis with flap coverage (n = 108, 6%), followed by neurolysis alone (n = 71, 30%). Of the 237 patients who underwent surgery, 125 (53%) reported an improvement in pain. Motor and sensory deficits were improved in 46 (19%) and 39 (16%) patients, respectively, suggesting that surgery is beneficial in relieving pain, but not as beneficial in restoring motor and sensory function.

A distal ileum malignant peripheral nerve sheath tumour after abdominal radiation therapy: case report of a rare tumour

Malignant peripheral nerve sheath tumours (MPNSTs) are malignant tumours arising from a peripheral nerve or displaying nerve sheath differentiation. Most MPNSTs are found on the head, body trunk and extremities, whereas cases in the gastrointestinal are extremely rare. About half arise in neurofibromatosis type 1 patients and 10% arise post-irradiation. This is probably the first small bowel MPNST post-radiation therapy case reported. A 72-year-old female who received radiotherapy 30 years ago for cervical cancer was admitted with progressive abdominal pain and weight loss. Computed tomography revealed a mass with inhomogeneous enhancement in the lumen of the small intestine. Tumour excision was performed with ileocecal and sigmoid colon resection due to suspicion for peripheral tissue invasion. Histopathological examination revealed spindle-shaped cells with focal cartilage differentiation. Together with immunochemistry stain showing complete loss of H3K27me3, a final diagnosis of MPNST was made. The patient is presently under regular follow-ups, and has remained disease-free for 24 months.

Case report: Brachial plexopathy caused by malignant peripheral nerve sheath tumor and review of the literature

Brachial plexopathy (BP) is easily misdiagnosed due to its complexity and varying clinical presentation. Malignant peripheral nerve sheath tumors (MPNST) can accumulate in the brachial plexus and share symptoms with BP, which may hinder the differential diagnosis between BP induced by radiation or metastases, and MPNST-derived BP, in patients with a history of breast cancer and radiation exposure. A 34-year-old Chinese female presented with MPNST. The tumor involved the brachial plexus. She had a history of breast cancer and radiotherapy. The first consideration was radiation- or breast cancer metastasis-derived BP. Clinical examination was performed. Finally, a diagnosis of MPNST of the brachial plexus was made, which guided an accurate treatment plan. This report highlights the importance of correctly diagnosing BP etiology for guiding precise treatment. BP caused by MPNST needs to be considered in clinical practice, and biopsy plays a central role in the differential diagnosis. Complete local surgical resection can prolong survival of patients with MPNST and improve treatment prognosis.

'Triton' Tumor of the Lower Alveolus: An Aggressive Variant of Malignant Peripheral Nerve Sheath Tumour

Malignant Triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor which harbingers a poor prognosis owing to its aggressive behavior. We report a case of a gentleman, who presented with MTT of the lower alveolus, and management with extensive extirpative surgery and adjuvant radiotherapy.

Hyperbaric oxygen therapy for radiation-induced brachial plexopathy, a case report and literature review

Aim

To report a case of radiation-induced brachial plexopathy (RIBP) with significant radiographic and clinical improvement after a course of hyperbaric oxygen (HBO).

Background

RIBP is a rare complication after radiotherapy to the neck and axilla. There are no standard treatment options, with empirical use pharmacotherapy being predominately used, which has had mixed results.HBO is efficacious for the treatment of other severe radiation-induced side effects, however, its benefit in RIBP has conflicting reports.

Case Presentation

A 45-year-old male, with a 33 pack-year smoking history, presented with a 6-month history of a progressive left neck mass. The final diagnosis was unknown primary squamous cell carcinoma of the head and neck. He received intensity-modulated radiation therapy (IMRT) with 70 Gy prescribed to the gross tumor volume (PTV HR) and 56 Gy to the oropharynx, nasopharynx, and bilateral lymphatics (PTV SR) in 35 daily fractions with three cycles of concurrent cisplatin at 100 mg/m².Fifteen months following therapy completion, the patient began to endorse symptoms of left brachial plexopathy. Decadron was prescribed for 2 weeks, trental and vitamin E for 6 months, and HBO. The patient returned for follow-up 2 months after completing 30 dives of HBO at 2.4 atmospheres for 2 hours per session. He reported pain resolution and full range of motion of his left arm.

Conclusions

The best management strategy of RIBP is prevention by reducing total RT doses and close follow-up. However, when RIBP occurs, we recommend treatment with HBO therapy, steroids, trental, and vitamin E as tolerable.

Radiation-Induced Schwannomas of the Neuraxis. Report of Three Cases

We report 3 cases of possible radiation-induced schwannomas observed in our Department. Their salient clinical and pathogenetic features are analyzed and the role of radiation therapy in the oncogenesis of these lesions is discussed. Several cases of radiation-induced tumors, including some of the nervous system, have been reported, but schwannomas have only occasionally been reported in connection with ionizing radiation. The possible adjuvant role of antineoplastic drugs is also discussed, and the literature on this topic is reviewed.

Radiation-Induced Schwannomas and Neurofibromas: A Systematic Review

OBJECTIVE

Radiation-induced benign peripheral nerve sheath tumors are uncommon late complications of irradiation. We conducted the largest systematic review of individual patient data.

METHODS

We performed a systematic search of PubMed databases and compiled a comprehensive literature review. Kaplan-Meier analysis was used to investigate survival, and statistical significance was assessed with a log-rank test.

RESULTS

We analyzed 40 cases of radiation-induced benign peripheral nerve sheath tumors. The histologic distributions were 28 schwannomas, 11 neurofibromas, and 1 ganglioneuroma. The average age of radiation exposure for development of primary lesions was 14.9 ± 15.5 years, and the latency period between radiotherapy to the onset of secondary tumors was 24.5 ± 12.7 years. The average irradiation dose delivered was 26.3 ± 20.3 Gy. The median overall survival for all cases was not reached (95% confidence interval, 22-not reached) months, with 10-year survival rates of 65.2%. Surgical negative margin was a positive prognostic factor for radiation-induced benign peripheral nerve sheath tumors.

CONCLUSIONS

The risk of incidence of secondary benign peripheral nerve sheath tumors in patients treated with radiotherapy should be considered in long-term follow-up periods. At present, complete surgical resection is the main stay for the treatment of radiation-induced benign peripheral nerve sheath tumors.

Anti-VEGF treatment improves neurological function and augments radiation response in NF2 schwannoma model

Hearing loss is the main limitation of radiation therapy for vestibular schwannoma (VS), and identifying treatment options that minimize hearing loss are urgently needed. Treatment with bevacizumab is associated with tumor control and hearing improvement in neurofibromatosis type 2 (NF2) patients; however, its effect is not durable and its mechanism of action on nerve function is unknown. We modeled the effect anti-VEGF therapy on neurological function in the sciatic nerve model and found that it improves neurological function by alleviating tumor edema, which may further improve results by decreasing muscle atrophy and increasing nerve regeneration. Using a cranial window model, we showed that anti-VEGF treatment may achieve these effects via normalizing the tumor vasculature, improving vessel perfusion, and delivery of oxygenation. It is known that oxygen is a potent radiosensitizer; therefore, we further demonstrated that combining anti-VEGF with radiation therapy can achieve a better tumor control and help lower the radiation dose and, thus, minimize radiation-related neurological toxicity. Our results provide compelling rationale for testing combined therapy in human VS.

Pediatric and adult malignant peripheral nerve sheath tumors: an analysis of data from the surveillance, epidemiology, and end results program

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas that arise predominantly from Schwann cells. Despite the fact that MPNSTs have high local recurrence rates and are generally associated with poor prognosis, little is known about prognostic factors or effective clinical management for this tumor type. The purpose of this study was to describe the distributions of patient and tumor characteristics and to identify predictors of cause-specific survival among MPNST cases reported to SEER between 1973 and 2008. Patient and tumor characteristics were compared between pediatric and adult MPNST cases. Cox regression and tree-based survival analysis were used to examine factors associated with MPNST-related mortality separately among adults and children. A total of 1,315 MPNST cases were isolated from the 1973-2008 SEER dataset. Among pediatric cases, sex, race, and radiation therapy predicted MPNST survival, whereas among adults, tumor site, tumor grade, number of primary tumors, and tumor size were significant predictors. As tumor size at diagnosis/resection may be the only somewhat "modifiable" prognostic factor, future studies should aim to identify biological and social attributes associated with tumor size at diagnosis, separately among individuals with and without NF-1, in order to help identify earlier opportunities for clinical intervention.

Laryngeal electromyography findings of vocal fold immobility in patients after radiotherapy for nasopharyngeal carcinoma

BACKGROUND

The clinical features of vocal fold immobility (VFI) after radiotherapy for nasopharyngeal carcinoma (NPC) have seldom been reported.

METHODS

We retrospectively reviewed laryngeal electromyography (LEMG) and tumor study findings to elucidate the common clinical features of patients who presented with VFI after radiotherapy for NPC. The LEMG signals obtained from the cricothyroid and thyroarytenoid muscles were used to confirm superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN) injury.

RESULTS

The medical records of 13 patients were reviewed and 11 of them had evidence of RLN injury. Six of the 11 patients also had SLN injury, indicating possible vagus nerve (VN) injury. Two patients had cricoarytenoid joint fixation without evidence of nerve injury. None of the nerve injuries were caused by skull base recurrence or tumor metastasis.

CONCLUSION

VFI is usually caused by nerve injury, but it is not a malignant sign of tumor recurrence or metastasis.

Radiation-induced neuropathy in cancer survivors

Radiation-induced peripheral neuropathy is a chronic handicap, frightening because progressive and usually irreversible, usually appearing several years after radiotherapy. Its occurrence is rare but increasing with improved long-term cancer survival. The pathophysiological mechanisms are not yet fully understood. Nerve compression by indirect extensive radiation-induced fibrosis plays a central role, in addition to direct injury to nerves through axonal damage and demyelination and injury to blood vessels by ischaemia following capillary network failure. There is great clinical heterogeneity in neurological presentation since various anatomic sites are irradiated. The well-known frequent form is radiation-induced brachial plexopathy (RIBP) following breast cancer irradiation, while tumour recurrence is easier to discount today with the help of magnetic resonance imaging and positron emission tomography. RIBP incidence is in accordance with the irradiation technique, and ranges from 66% RIBP with 60Gy in 5Gy fractions in the 1960s to less than 1% with 50Gy in 2Gy fractions today. Whereas a link with previous radiotherapy is forgotten or difficult to establish, this has recently been facilitated by a posteriori conformal radiotherapy with 3D-dosimetric reconstitution: lumbosacral radiculo-plexopathy following testicular seminoma or Hodgkin's disease misdiagnosed as amyotrophic lateral sclerosis. Promising treatments via the antioxidant pathway for radiation-induced fibrosis suggest a way to improve the everyday quality of life of these long-term cancer survivors.

Late radiation injury to peripheral nerves

Although the peripheral nerve has often been considered as radioresistant, clinical practice demonstrates the occurrence of radiation-induced peripheral neuropathies. Because these complications appear late, usually several years after the course of radiotherapy, their occurrence is explained by improvement in the prognosis of several cancers. Their physiopathology is not fully understood. Compression by radio-induced fibrosis probably plays a central role but direct injury to nerves and blood vessels is probably also involved. The most frequent and best known form of postradiation neuropathy is brachial plexopathy, which may follow irradiation for breast cancer. Recent reports demonstrate that postradiation neuropathies show a great heterogeneity, particularly in the anatomical sites, but also in the clinical, electrophysiological, and neuroimaging features. The link with radiotherapy may be difficult for the clinician to establish. Patients with radiation-induced lumbosacral radiculoplexopathy may be misdiagnosed with amyotrophic lateral sclerosis as they often present with pure lower motor neuron syndrome, or with leptomeningeal metastases since nodular MRI enhancement of the nerve roots of the cauda equina and increased CSF protein content can be observed. From a pathophysiological perspective, radiation-induced neuropathy offers an interesting model for deciphering the mechanisms of peripheral neuropathies due to environmental factors. Recent developments show promising strategies for the prevention and treatment of these complications, which have a considerable impact on a patient's quality of life.

[Radiation-induced neuropathies: collateral damage of improved cancer prognosis]

INTRODUCTION

Because of the improvement of cancer prognosis, long-term damages of treatments become a medical and public health problem. Among the iatrogenic complications, neurological impairment is crucial to consider since motor disability and pain have a considerable impact on quality of life of long cancer survivors. However, radiation-induced neuropathies have not been the focus of great attention. The objective of this paper is to provide an updated review about the radiation-induced lesions of the peripheral nerve system.

STATE OF THE ART

Radiation-induced neuropathies are characterized by their heterogeneity in both symptoms and disease course. Signs and symptoms depend on the affected structures of the peripheral nerve system (nerve roots, nerve plexus or nerve trunks). Early-onset complications are often transient and late complications are usually progressive and associated with a poor prognosis. The most frequent and well known is delayed radiation-induced brachial plexopathy, which may follow breast cancer irradiation. Radiation-induced lumbosacral radiculoplexopathy is characterized by pure or predominant lower motor neuron signs. They can be misdiagnosed, confused with amyotrophic lateral sclerosis (ALS) or with leptomeningeal metastases since nodular MRI enhancement of the nerve roots of the cauda equina and increased cerebrospinal fluid protein content can be observed. In the absence of specific markers of the link with radiotherapy, the diagnosis of post-radiation neuropathy may be difficult. Recently, a posteriori conformal radiotherapy with 3D dosimetric reconstitution has been developed to link a precise anatomical site to unexpected excess irradiation.

PERSPECTIVES AND CONCLUSION

The importance of early diagnosis of radiation-induced neuropathies is underscored by the emergence of new disease-modifying treatments. Although the pathophysiology is not fully understood, it is already possible to target radiation-induced fibrosis but also associated factors such as ischemia, oxidative stress and inflammation. A phase III trial evaluating the association of pentoxifylline, tocopherol and clodronate (PENTOCLO, NCT01291433) in radiation-induced neuropathies is now recruiting.

Prognostic factors for the malignant triton tumor of the head and neck

BACKGROUND

Malignant triton tumors are rare neoplasias consisting of a malignant peripheral nerve sheath tumor with additional rhabdomyoblastic differentiation. These tumors are highly aggressive and prognosis is poor. Our aim is to describe the outcome and to identify potential prognostic factors.

METHODS

From 1993 to 2005, 7 patients with a malignant triton tumor of the head and neck were treated at our institution. A literature search revealed another 46 published cases. All these cases were analyzed for outcome and prognostic factors.

RESULTS

Patients with primary tumors involving the nose and paranasal sinuses have better, patients involving the neck a poor prognosis. All other locations show an intermediate course. Complete surgical removal is of crucial importance. Additional radiation or chemotherapy show little effect.

CONCLUSION

Location of the primary tumor is a key factor for prognosis. Complete surgical removal is the only treatment associated with survival.

Malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are a rare variety of soft tissue sarcoma of ectomesenchymal origin. MPNSTs arise from major or minor peripheral nerve branches or sheaths of peripheral nerve fibers and are derived from Schwann cells or pluripotent cells of neural crest origin. Arthur Purdy Stout played a pivotal role in the development of our current understanding of the pathogenesis of peripheral nerve sheath tumors by identifying the Schwann cell as the major contributor to the formation of benign and malignant neoplasms of the nerve sheath. Although this fact remains essentially true, the cell of origin of the MPNST remains elusive and has not yet conclusively been identified. Some have suggested these tumors may have multiple cell line origins. In the present review, MPNSTs and their epidemiology, diagnosis, management, and treatment are discussed.

Malignant trigeminal schwannoma extending into the anterior skull base

Malignant schwannomas are rare tumours that seldom grow in the head and neck and their occurrence is even rarer in patients not affected by neurofibromatosis. The authors report a 40 year old woman with a left trigeminal malignant schwannoma (arising from V2), involving the infratemporal fossa and subsequently extending into the maxillary, sphenoid and ethmoidal sinuses, the orbit, and the intracranial compartment. Given the complex location of this tumour, the patient initially underwent radiation treatment; however due to a poor response to this form of treatment as well as disease progression, surgical resection requiring a combined Neurosurgical, ENT and Plastic Surgery was recommended. The planned operation included sacrificing the internal carotid artery and cavernous sinus, ipsilateral orbit exenteration and reconstruction with a free flap from the latissimus dorsi muscle. In this report, we discuss the sporadic occurrence of these tumours, the histo-pathological features and the management strategy along with a review of the literature.

Malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas of ectomesenchymal origin. The World Health Organization coined the term MPNST to replace previous heterogeneous and often confusing terminology, such as “malignant schwannoma,” “malignant neurilemmoma,” “neurogenic sarcoma,” and “neurofibrosarcoma.” Malignant peripheral nerve sheath tumors arise from major or minor peripheral nerve branches or sheaths of peripheral nerve fibers, and are derived from Schwann cells or pluripotent cells of neural crest origin.

The Schwann cell is thought to be the major contributor to the formation of benign as well as malignant neoplasms of the nerve sheath. While this fact remains essentially true, the identity of cell of origin of the MPNST remains elusive, and has not yet been conclusively identified. It has been suggested that these tumors may have multiple cell line origins. In this review, the authors discuss the epidemiology, diagnosis, management, and treatment of MPNSTs.

Radiation induced peripheral nerve tumors: case series and review of the literature

PURPOSE

Radiation induced peripheral nerve tumors (PNT) are a rare but known complication of radiotherapy. The clinical and pathologic features of six cases of post-radiation PNT's are reported here, more than doubling the number of known cases reported in the literature.

METHODS

We reviewed six cases of radiation induced PNT and performed a review of the current literature on radiation induced neurofibromas.

RESULTS

Patient's ranged in age from 18 months to 49 years at the time of their original diagnosis, with radiation doses to the primary tumor ranging from 24 to 40 Gy with post radiation intervals from 10 to 50 years. The majority of PNT's identified were neurofibromas (3) and schwannomas (3). Nuclear atypia, S100 positive staining and mild-moderate cellularity were common pathologic findings.

CONCLUSIONS

There are only a handful of neurofibromas in the 60 cases of PNT's thus far reported. This case series broadens the post-radiation neurofibroma literature. While the pathology of PNT induced transformation is still poorly understood, experiments and pathology are congruent on the possibility of malignant transformation, especially for the "atypical neurofibroma". On the clinical level, this case series lends its support to some, but not all, of the risk factors thought to predispose to the formation of radiation induced neurofibromas. Though rare, the complication of radiation-induced neurofibroma cannot be ignored, especially with the increasing use of focused radiosurgical techniques.

Radiotherapy-induced malignant peripheral nerve sheath tumor of the cauda equina

STUDY DESIGN

Case report.

OBJECTIVES

To report a rare case of radiation-induced malignant peripheral nerve sheath tumor of the cauda equina 10 years after treatment for testicular seminoma.

SUMMARY OF BACKGROUND DATA

Development of malignant peripheral nerve sheath tumor after irradiation is well recognized and often associated with a dismal prognosis. There have been isolated reports of malignant peripheral nerve sheath tumor developing in sites of previous irradiation for testicular seminoma.

METHODS

Retrospective review of case records and imaging.

RESULTS

A 38-year-old man presented with signs of cauda equina syndrome. Ten years previously, he had undergone right radical inguinal orchidectomy and adjuvant para-aortic radiotherapy as treatment for Stage I testicular seminoma. Magnetic resonance imaging demonstrated an inoperable intra- and extradural tumor leading to significant cauda equina compression. CT-guided biopsy revealed a diagnosis of malignant peripheral nerve sheath tumor, most likely due to previous radiotherapy. His clinical condition did not improve, and he underwent a course of palliative chemotherapy.

CONCLUSIONS

Postirradiation malignant peripheral nerve sheath tumors are rare and occur in a population at high risk of developing second malignancies. The authors report the fourth case resulting from adjuvant radiotherapy for testicular seminoma, with the present report being the first report of extensive intradural tumor leading to cauda equina syndrome.

Effects of External Beam Radiation in the Rat Tibial Nerve after Crush, Transection and Repair, or Nerve Isograft Paradigms

INTRODUCTION

In head and neck surgery, radiation therapy is often administered to an injured nerve. Previous studies have examined the effects of either preoperative or postoperative radiation on nerve regeneration in rodents. In these studies, histomorphometric analysis was performed up to 8 month postoperatively. Given the exceptional neuroregenerative capacity of rodents, significant differences in nerve regeneration may go undetected if nerves are evaluated at such distant postoperative time points. This study is designed with a more appropriate model and investigates the effects of radiation after three common nerve injury paradigms.

METHODS

Sixty-four Lewis rates were randomized to 8 groups corresponding to uninjured, tibial nerve crush, transection and repair, or reconstruction with isografts. Half of the animals in each of these paradigms (n = 8 per group) were treated with 10 Gy of external beam radiation to the site of nerve injury at 7 days postoperatively. On postoperative day 28, functional recovery and histomorphometric assessment was performed.

RESULTS

For a given paradigm of nerve injury, no significant differences in nerve fiber number, neural density, neural debris, or fiber width were noted between the control and radiated groups, and radiation did not affect functional recovery.

CONCLUSION

Radiation had no discernible effect on nerve regeneration or functional recovery in the rodent nerve injury models studied. All assessments were made at time points suitable for detecting differences in nerve regeneration between groups. These findings suggest that administration of radiation to fields containing injured peripheral nerve is unlikely to adversely affect functional outcomes.

Multiple recurrences in malignant peripheral nerve sheath tumor of the orbit: a case report and a review of the literature

PURPOSE

To report the onset of malignant peripheral nerve sheath tumor of the orbit 8 years after irradiation in a patient with neurofibromatosis type-1.

METHODS

Case report of a young man with neurofibromatosis type-1 who received irradiation for presumed bilateral optic nerve and chiasmal gliomas and in whom a malignant peripheral nerve sheath tumor later developed. Exenteration with extirpation of the entire contents of the orbit was performed 6 times.

RESULTS

Complete recurrence of the tumor occurred after each surgical procedure until the patient died of malignancy.

CONCLUSIONS

Our case underscores the risk of irradiation, especially in children with neurofibromatosis type-1, and emphasizes that radiotherapy should never be given as an empirical therapy. The authors believe that irradiation and neurofibromatosis type-1 may, in combination, pose a significant risk for the development of malignancies. Clear-cut indications and a precise tissue diagnosis are desirable before the initiation of radiotherapy, particularly in the pediatric population. We recommend that if irradiation is necessary in persons with neurofibromatosis type-1, regular follow-up is imperative. In view of the hostile nature of malignant peripheral nerve sheath tumor, early aggressive treatment appears to be the only viable alternative at present.

Double-blind randomized phase II study of hyperbaric oxygen in patients with radiation-induced brachial plexopathy

BACKGROUND

Radiation-induced brachial plexopathy (RIBP) is an untreatable complication of curative radiotherapy for early breast cancer, characterized by chronic neuropathic pain and limb paralysis. Hyperbaric oxygen (HBO2) therapy is known to promote healing of tissue rendered ischaemic by radiotherapy, but is untested in RIBP.

METHODS

Thirty four eligible research volunteers suffering from RIBP were randomized to HBO2 or control group. The HBO2 group breathed 100% oxygen for 100 min in a multiplace hyperbaric chamber on 30 occasions over a period of 6 weeks. The control group accompanied the HBO2 group and breathed a gas mixture equivalent to breathing 100% oxygen at surface pressure. All volunteers and investigators, except the operators of the hyperbaric chamber and the trial statistician, were blind to treatment assignments. The warm sensory threshold, which measures the function of small sensory fibres, was selected as the primary endpoint.

FINDINGS

Pre-treatment neurophysiological tests were grossly abnormal in the affected hand compared to the unaffected hand in both HBO2 and control groups, as expected, but no statistically significant differences were noted in either group at any time up to 12 months post-treatment. However, normalization of the warm sensory threshold in two of the HBO2 group was reliably recorded. Two cases with marked chronic arm lymphoedema reported major and persistent improvements in arm volume for at least 12 months after treatment with HBO2. IINTERPRETATION: There is no reliable evidence to support the hypothesis that HBO2 therapy slows or reverses RIBP in a substantial proportion of affected individuals, although improvements in warm sensory threshold offer some suggestion of therapeutic effect. Improvement in long-standing arm lymphoedema was not anticipated, and justifies further investigation.

Function of skeletal muscle tissue formed after myoblast transplantation into irradiated mouse muscles

1. Pretreatment of muscles with ionising radiation enhances tissue formation by transplanted myoblasts but little is known about the effects on muscle function. We implanted myoblasts from an expanded, male-donor-derived, culture (i28) into X-ray irradiated (16 Gy) or irradiated and damaged soleus muscles of female syngeneic mice (Balb/c). Three to 6 months later the isometric contractile properties of the muscles were studied in vitro, and donor nuclei were visualised in muscle sections with a Y chromosome-specific DNA probe. 2. Irradiated sham-injected muscles had smaller masses than untreated solei and produced less twitch and tetanic force (all by about 18 %). Injection of 106 myoblasts abolished these deficiencies and innervation appeared normal. 3. Cryodamage of irradiated solei produced muscle remnants with few (1-50) or no fibres. Additional myoblast implantation led to formation of large muscles (25 % above normal) containing numerous small-diameter fibres. Upon direct electrical stimulation, these muscles produced considerable twitch (53 % of normal) and tetanic forces (35 % of normal) but innervation was insufficient as indicated by weak nerve-evoked contractions and elevated ACh sensitivity. 4. In control experiments on irradiated muscles, reinnervation was found to be less complete after botulinum toxin paralysis than after nerve crush indicating that proliferative arrest of irradiated Schwann cells may account for the observed innervation deficits. 5. Irradiation appears to be an effective pretreatment for improving myoblast transplantation. The injected cells can even produce organised contractile tissue replacing whole muscle. However, impaired nerve regeneration limits the functional performance of the new muscle.

Effects of intraoperative irradiation (IORT) and intraoperative hyperthermia (IOHT) on canine sciatic nerve: histopathological and morphometric studies

PURPOSE/OBJECTIVE

Peripheral neuropathies have emerged as the major dose-limiting complication reported after intraoperative radiation therapy (IORT). The combination of IORT with hyperthermia may further increase the risk of peripheral nerve injury. The objective of this study was to evaluate histopathological and histomorphometric changes in the sciatic nerve of dogs, after IORT with or without hyperthermia treatment.

METHODS AND MATERIALS

Young adult beagle dogs were randomized into five groups of 3-5 dogs each to receive IORT doses of 16, 20, 24, 28, or 32 Gy. Six groups of 4-5 dogs each received IORT doses of 12, 16, 20, 24, or 28 Gy simultaneously with 44 degrees C of intraoperative hyperthermia (IOHT) for 60 min. One group of dogs acted as hyperthermia-alone controls. Two years after the treatment, dogs were euthanized, and histopathological and morphometric analyses were performed.

RESULTS

Qualitative histological analysis showed prominent changes such as focal necrosis, mineralization, fibrosis, and severe fiber loss in dogs which received combined treatment. Histomorphometric results showed a significantly higher decrease in axon and myelin and small blood vessels, with a corresponding increase in connective tissue in dogs receiving IORT plus hyperthermia treatment. The effective dose for 50% of nerve fiber loss (ED50) in dogs exposed to IORT only was 25.3 Gy. The ED50 for nerve fiber loss in dogs exposed to IORT combined with IOHT was 14.8 Gy. The thermal enhancement ratio (TER) was 1.7.

CONCLUSION

The probability of developing peripheral neuropathies in a large animal model is higher when IORT is combined with IOHT, when compared to IORT application alone. To minimize the risk of peripheral neuropathy, clinical treatment protocols for the combination of IORT and hyperthermia should not assume a thermal enhancement ratio (TER) to be lower than 1.5.

Peripheral nerve regeneration: the effects of postoperative irradiation

The purpose of this study was to evaluate the effects of postoperative external cobalt-60 beam irradiation on nerve regeneration. Sixty-five 250-gm male Sprague-Dawley rats were studied. Peripheral nerve regeneration was measured by walking track analysis and histomorphology of the proximal, graft, and distal nerve segments. These 65 animals underwent a 1.5-cm interpositional nerve graft into the right posterior tibial nerve. The left leg served as a control. Each animal was then randomly allocated into one of four groups. Group 1 served as control. Groups 2 through 4 were subjected to external cobalt-60 gamma-ray irradiation through a 2.5-cm circular portal for a total fractionated dose of 30, 50, and 70 Gy beginning on postoperative day 3. Radiation was administered in 2-Gy fractions, 5 fractions per week, with a top-up dose of 16 Gy given at the end of the fractionated irradiation. Walking track analysis was performed at 30, 60, 90, and 120 days after nerve grafting. At the conclusion of 120 days, sections of the proximal, grafted, and distal nerve were harvested, stained, and examined histomorphologically. Hematoxylin and eosin stains also were obtained. Evaluation of the print-length index demonstrated no statistical difference between the unirradiated controls and the irradiated groups. The total number of axons per square millimeter and nerve fiber density per square millimeter were significantly decreased in the distal segment of all the irradiated groups when compared with controls. Despite the reduction in myelinated regenerating fibers, no reduction in function was observed, as measured by walking track analysis. We would therefore recommend immediate reconstruction of peripheral nerve defects in the face of postoperative irradiation.

Effects of intraoperative irradiation and intraoperative hyperthermia on canine sciatic nerve: neurologic and electrophysiologic study

PURPOSE

Late radiation injury to peripheral nerve may be the limiting factor in the clinical application of intraoperative radiation therapy (IORT). The combination of IORT with intraoperative hyperthermia (IOHT) raises specific concerns regarding the effects on certain normal tissues such as peripheral nerve, which might be included in the treatment field. The objective of this study was to compare the effect of IORT alone to the effect of IORT combined with IOHT on peripheral nerve in normal beagle dogs.

METHODS AND MATERIALS

Young adult beagle dogs were randomized into five groups of three to five dogs each to receive IORT doses of 16, 20, 24, 28, or 32 Gy to 5 cm of surgically exposed right sciatic nerve using 6 MeV electrons and six groups of four to five dogs each received IORT doses of 0, 12,16, 20, 24, or 28 Gy simultaneously with 44 degrees C of IOHT for 60 min. IOHT was performed using a water circulating hyperthermia device with a multichannel thermometry system on the surgically exposed sciatic nerve. Neurologic and electrophysiologic examinations were done before and monthly after treatment for 24 months. Electrophysiologic studies included electromyographic (EMG) examinations of motor function, as well as motor nerve conduction velocities studies.

RESULTS

Two years after treatment, the effective dose for 50% complication (ED50) for limb paresis in dogs exposed to IORT only was 22 Gy. The ED50 for paresis in dogs exposed to IORT combined with IOHT was 15 Gy. The thermal enhancement ratio (TER) was 1.5. Electrophysiologic studies showed more prominent changes such as EMG abnormalities, decrease in conduction velocity and amplitude of the action potential, and complete conduction block in dogs that received the combination of IORT and IOHT. The latency to development of peripheral neuropathies was shorter for dogs exposed to the combined treatment.

CONCLUSION

The probability of developing peripheral neuropathies in a large animal model was higher for IORT combined with IOHT, than for IORT alone. The dose required to produce the same level of late radiation injury to the sciatic nerve was reduced by a factor of 1.5 (TER) if IORT was combined with 44 degrees C of IOHT for 60 min.

Effects of intraoperative hyperthermia on canine sciatic nerve: histopathologic and morphometric studies

Failure to achieve local control in the treatment of pelvic and retroperitoneal tumours results in a high rate of recurrences. The objective of intraoperative hyperthermia (IOHT) is to enhance the effect of intraoperative radiation therapy and to increase local tumour control. The tolerance of peripheral nerves to heat may limit the heat dose that can be applied to tumours. Histopathologic and histomorphometric changes of canine sciatic nerve after 60-min IOHT were studied in three groups of five dogs each for temperatures of 43, 44 and 45 degrees C. IOHT was performed using a water-circulating hyperthermia device with a multichannel thermometry system on surgically exposed sciatic nerve. Histopathologic and histomorphometric studies were done immediately, 3 weeks and 12 months after IOHT. Histologic changes observed immediately after treatment were minimal but at 3 weeks following 60-min 45 degrees C IOHT both axon and myelin loss and an increase in endoneurial fibrous tissue were observed. Twelve months after treatment a statistically significant decrease in axon, myelin and small vessel percentages as well as an increase in endoneurial and epineural connective tissue were observed for dog treated to 45 degrees C. Dog treated to 44 degrees C for 60 min had similar statistically significant but less severe changes. Twelve months after 43 degrees C IOHT for 60 min, nerve fibres appeared normal and endoneurial connective tissue was only increased mildly around small and medium-sized vessels. These results suggest that temperatures to the peripheral nerve > 44 degrees C for 60 min are likely to cause significant histopathologic changes that can be found 12 months after treatment. A hypothesis of the mechanism of heat injury to peripheral nerves was developed.

Intraoperative radiation (IORT) injury to sciatic nerve in a large animal model

Peripheral nerve appears to be a dose-limiting normal tissue in the clinical application of intraoperative radiation therapy (IORT). To assess IORT injury to peripheral nerve, three groups of five beagle dogs received doses of 12, 20 or 28 Gy to the surgically exposed and isolated right sciatic nerve in the mid-femoral region using 6 MeV electrons. The left sciatic nerve of each dog served as its own control. As a surgical control five dogs received surgical exposure of the nerve only. Monthly neurologic exams, electromyogram and nerve conduction studies were performed following treatment for 12 months. After that dogs were euthanatized and histologic studies of nerves were done to define the degree of axon and myelin loss as well as presence of fibrosis and vascular lesions for different doses of IORT. Results showed that the threshold dose most likely related to expression of severe radiation damage to the nerve in this model is between 20 and 25 Gy. Radiation injury to peripheral nerve appears to be the result of direct radiation effects on Schwann cells and nerve vasculature and secondary effects resulting from damage to regional muscle and vasculature. A theoretical mechanism of radiation injury to peripheral nerve is proposed.

Cranial nerve length predicts the risk of delayed facial and trigeminal neuropathies after acoustic tumor stereotactic radiosurgery

PURPOSE

To test the hypothesis that length of cranial nerve irradiated is a major factor predicting the risk of cranial nerve injury following radiosurgery and to identify any other significant related treatment factors.

METHODS AND MATERIALS

Ninety-two patients (93 acoustic tumors) were treated with a 201 source Cobalt-60 gamma unit from 1987 to 1990 and prospectively followed. The range of minimum tumor dose was 12-20 Gy and maximum dose 24-50 Gy. Univariate and multivariate analyses were used to evaluate any correlations between tumor measurements and treatment factors, with the development of trigeminal and facial neuropathies following radiosurgery.

RESULTS

The risks of trigeminal and facial neuropathy following radiosurgery were associated with the pon-petrous distance and mid porous transverse tumor diameters respectively (anatomically related to the irradiated length of cranial nerves V and VII respectively) in both univariate (p = .002 for V and p = .026 for VII) and multivariate (p = .004 for V and p = .055 for VII) analyses. Tumor volume, other tumor measurements, maximum dose, minimum tumor dose, and tumor dose inhomogeneity were not significantly related to either trigeminal or facial neuropathy in univariate and multivariate analyses.

CONCLUSION

Within a minimum tumor dose range of 12-20 Gy, the incidence of delayed trigeminal or facial neuropathy depended more on the estimated length of nerve irradiated than the tumor dose or tumor volume. In the future, the risk of delayed facial or trigeminal cranial neuropathy may be reduced significantly by performing radiosurgery when the tumor still has both a small mid-porous transverse diameter and a small pons-petrous distance.

Latent X-ray damage in the rat sciatic nerve results in delay in functional recovery after a heat treatment

The influence of X-irradiation on the sensitivity of the rat sciatic nerve to local hyperthermia was investigated. A 10 or 20 mm long segment of the nerve was irradiated intraoperatively using 50 kV X-rays. Hyperthermia (30 min at 45 degrees C), was applied to the irradiated part (over a length of 5 mm) of the nerve using a brass thermode. Functional damage to the nerve was assessed using the toe-spreading test, which mainly assesses the motor function of the sciatic nerve. Radiation alone (doses up to 70 Gy) did not lead to detectable damage for at least 90 weeks. Hyperthermia alone (30 min at 45 degrees C) resulted in complete loss of motor function. This function loss was transient and complete recovery took place in about 4 weeks. Recovery time was scored as the number of days between hyperthermia and the day on which 50% of the motor function had returned. Irradiation (35 Gy) of a nerve segment, which included the heated part, resulted in a delayed recovery from the heat treatment compared to controls (heat only). The time interval and sequence between irradiation and hyperthermia hardly influenced the recovery delay. The size of the irradiated nerve segment did influence the recovery delay. Irradiation of a 20 mm nerve segment led to longer recovery delays than irradiation of a 10 mm segment (a delay of 5-10 days and 1-5 days respectively). A dose-response relation for the irradiation-induced delay in recovery was observed when a large segment (20 mm) of the nerve was irradiated immediately after heat with a dose ranging from 5 to 40 Gy. The delay in heat recovery was dose-dependent below 20 Gy, but after radiation doses above 20 Gy the recovery delay remained almost constant.

Malignant peripheral nerve sheath tumors of the buttock and lower extremity. A study of 43 cases

Using strict clinical and pathologic criteria for the inclusion of cases, the authors have reviewed the clinicopathologic features of 43 malignant peripheral nerve sheath tumors of the buttock and extremity seen over a 35-year period. Twenty-three (53%) of the patients had neurofibromatosis (VRN), whereas 20 (47%) did not. Fifty-one percent of the patients were women. The mean age at presentation was 36 years for patients with VRN and 44 years for patients without VRN. A nerve of origin was identified for 72% of the cases and an associated neurofibroma for 44% (65% with VRN and 20% without VRN). The mean greatest dimension of the tumors was 12.3 cm, and this did not differ significantly between the two groups. The predominant histologic pattern in 86% of the tumors was that of tightly packed spindle cells in an interlacing and woven pattern; heterologous sarcomatous elements were noticed in 12% of the cases. Surgical resection was the main modality of treatment for all patients; 65% also received adjuvant therapy. Follow-up evaluation was done in every case. An unexpected finding was the absence of a significant difference in survival rates between patients with and without VRN. Overall, 63% of the patients died of tumor: 65% of the patients with VRN and 60% of the patients without VRN. Large tumor size and high mitotic rate (greater than 20 per 10 high-power fields) portended a poor prognosis, as did the need for resection by amputation. Adjuvant radiation therapy and chemotherapy did not affect survival rates.

Transient and chronic neurological complications of fast neutron radiation for adenocarcinoma of the prostate

The records of 132 patients participating in clinical trials using fast neutron (n = 94), mixed neutron and photon (n = 16), or conventional photon (n = 22) irradiation for primary management of prostatic cancer were retrospectively reviewed to assess treatment-related neurological complications. With a median follow-up of 14 months (range 1 to 101 months), 31/132 patients (26 neutron, 3 mixed beam, 2 photon) have experienced either sciatica beginning during or shortly after treatment, or diminished bladder or bowel continence that developed at a median time of 6.5 months following treatment. Sciatica responded to oral steroids and was usually self-limited, whereas sphincter dysfunction appears to be permanent. Pre-treatment risk factors for complications included a history of hypertension, diabetes, cigarette smoking or peripheral vascular disease, with 81% of affected patients having one or more risk factors compared with 55% of unaffected patients (p = 0.01). Seven patients have moderate (5) or severe (2) residual problems, all in the cohorts receiving neutrons (6/7) or mixed beam therapy (1/7).

Regeneration in the peripheral nervous system

Mammalian peripheral nerve fibres can regenerate after injury. Repair is most likely to succeed if axons are simply crushed or have only a very short (less than 0.5 cm) interstump gap to cross and most likely to fail if the interstump gap is long (greater than 1 cm) and associated with soft tissue damage. Whereas reactive axonal sprouting appears to be an intrinsic neuronal response to injury, the subsequent organization of the axonal sprouts, in particular their orderly outgrowth in minifascicles towards a distant distal stump does not occur unless Schwann cells are present. During the injury response, Schwann cells proliferate; co-migrate with regrowing axons (when the proximal stump is separated from the distal stump); respond to axonal cues by transient upregulation or re-expression of molecules which provide a favourable substrate for axonal extension; and attract bundles of regrowing axons and their associated Schwann cells across interstump gaps up to 1 cm in length. Recruited macrophages remove myelin debris from the Schwann cell tubes; they probably interact with Schwann cells in other ways during the injury response, e.g. by presenting mitogens and cytokines.

X-irradiation impairs regeneration of peripheral nerve across a gap

The effects of X-irradiation on the regeneration of peripheral nerve across a gap were studied in the mouse. The right sciatic nerve was transected and 3 days later a 20-Gy dose of X-rays was administered to the hind limb, which was shielded so that the irradiation affected either the proximal, the distal or both parts of the nerve. Within a few hours of irradiation, the proximal and distal nerve stumps were inserted into a polythene tube within which they were separated by a 5-mm gap. After 1 or 2 months the sciatic nerves were processed for examination by light and electron microscopy. Irradiation affected axonal growth, differentiation of Schwann cells and formation of a perineurium. These effects were most marked when both the proximal and distal stumps had been exposed to X-rays. At 2 months there were fewer axons in the irradiated than in control nerves (P less than 0.01), but all of the larger axons which had regenerated were myelinated, albeit more thinly than in the controls. The changes in the pattern of regeneration in the irradiated nerves are interpreted as being largely due to radiation damage to Schwann cells.

Malignant peripheral nerve sheath tumors. A clinicopathologic study of 120 cases

A review was done of 120 cases of malignant peripheral nerve sheath tumor (MPNST) seen during a 71-year period. Of the 120 patients, 52 were males and 68 were females with a mean age at diagnosis of 35.3 years; 12 patients were younger than 20 years. The series included 62 (52%) patients with neurofibromatosis, 13 (11%) with postradiation sarcomas, and 19 (16%) with metaplastic foci. The incidence of MPNST arising in neurofibromatosis was 4.6% in the current series and 0.001% in the general clinic population. Tumors greater than 5 cm and the presence of neurofibromatosis adversely affected the prognosis (P less than 0.05). When both features were present, survival was greatly decreased. Patients with tumor in the extremities did better than those with head or neck lesions. Metaplastic foci or previous radiation at the tumor site did not alter the prognosis. Each tumor was graded 1 to 4 on the basis of cellularity, pleomorphism, mitotic index, and necrosis. No significant correlation was noted between survival and either grade or mitotic rate. Survival was improved when total rather than subtotal resection was done. This was most marked in patients with a small lesion, which may reflect the difficulty in adequately excising large tumors. Adjuvant radiation or chemotherapy did not appear to affect survival. The MPNST is an aggressive uncommon neoplasm, and large tumor size, the presence of neurofibromatosis, and total resection are the most important prognostic indicators.

Chronic demyelination in mouse peripheral nerve produced by lysophosphatidyl choline and X-irradiation: ultrastructural observations

The effects of X-irradiation on demyelination and remyelination were studied in the peripheral nerve of the mouse. Three days after injection of lysophosphatidyl choline into one sciatic nerve, a 20 Gy dose of X-rays was administered to the hind limb. At survival times ranging from 4 days to 6 months after injection, the nerves were examined by light and electron microscopy. Removal of myelin debris was retarded and remyelination delayed or prevented. The myelin sheaths which did form were thin and the configuration of Schmidt-Lanterman incisures and nodes of Ranvier was abnormal. Some of the chronically demyelinated fibres formed focal node-like complexes: patches of finely granular material coated the inner aspect of the axolemma, the external surface was covered by slender processes of Schwann cell cytoplasm, and an electron-dense lamina was present in the enlarged periaxonal space. Elsewhere demyelinated axons and their ensheathing Schwann cells were separated by gap junctions or transverse bands. The present findings indicate that the morphological differentiation of structures thought to be characteristic of nodes of Ranvier can take place in the absence of remyelination.

Morphometric effects of vincristine on nerve regeneration in the rat

Administration of vincristine (200, 100 or 50 micrograms/kg/week) for 6 months during regeneration of the sciatic nerve after crush injury caused a dose-dependent reduction in nerve fibre size and failure of removal of myelin debris. Successfully regenerating neurites showed an unusual amount of shape distortion. The ratio of myelin sheath thickness to axon circumference was reduced, but the ratio of myelin sheath thickness to axon area was normal. Microtubule concentration was diminished in axons, but neurofilament density was unaffected. Unmyelinated axons were reduced in number but their axon diameter distribution was not affected. Fibres on the non-crushed side appeared normal. The toxicity of vincristine to regenerating nerves is probably related to increased blood-nerve permeability occurring both at the site of crush and along the degenerating nerve.

The effect of vincristine on nerve regeneration in the rat. An electrophysiological study

Weekly injections of vincristine to produce a dose-dependent delay in regeneration following sciatic nerve crush. With 20 micrograms/kg/wk recovery was similar to that in control animals. With 50 and 100 micrograms/kg/wk electrophysiological evidence of reinnervation of the foot muscles was significantly delayed and muscle action potential amplitude increased at a slower rate. However, once begun the increase in motor nerve conduction velocity was closer to that in control animals. With 200 micrograms/kg/wk no evidence of reinnervation of the foot muscles was found even after 6 months. These doses produced no abnormality of muscle action potential amplitude or of nerve conduction velocity on the opposite non-crushed side.

Malignant peripheral nerve sheath tumors in childhood

Malignant peripheral nerve sheath tumor (MPNST) is an uncommon sarcoma in the pediatric population; however, its presence should be considered in a child with an enlarging or painful soft-tissue mass. Diagnosis of this neoplasm depends on either the demonstration of its origin within a peripheral nerve or the association with a contiguous neurofibroma. We have identified 16 cases of MPNST involving children 16 years of age or less, which represent 12.8% of the total cases seen at the Mayo Clinic. Most of the lesions arose in children with von Recklinghausen's disease and were associated with a contiguous neurofibromatous component. The mean survival of patients who were known to have died of tumor was only 1.8 years. This sarcoma requires prompt aggressive therapy utilizing wide surgical excision. Because of the association of MPNST with von Recklinghausen's neurofibromatosis, a careful workup and family history should be obtained for the potential prognostic value and for the purpose of genetic counseling.

Effects of experimental radiation-induced hypomyelinating neuropathy on motor end-plates and neuromuscular transmission

Morphological and physiological techniques were used to study the effects of radiation-induced hypomyelinating neuropathy on the innervation of skeletal muscle in the mouse. The right sciatic nerve was crushed focally and 3 days later the hind limb exposed to 20Gy X-rays. After reinnervation of original end-plate sites there was extensive formation of ultraterminal sprouts and of new end-plates characterized by small nerve terminals and rudimentary postsynaptic folds. In vitro examination of soleus nerve-muscle preparations showed reduced frequency of spontaneous miniature end-plate potentials and low quantal content of evoked potentials. The findings indicate that hypomyelinating neuropathy may cause reduction in quantal release of neurotransmitter.

Postirradiation neurofibrosarcoma

A known risk of radiation therapy is the induction of secondary neoplasms, most commonly osteosarcoma and fibrosarcoma. A recent addition to the list of postirradiation neoplasms is neurofibrosarcoma, a Schwann cell or fibroblastic malignancy arising in peripheral nerves, often associated with von Recklinghausen's disease. In a clinicopathologic review of 109 patients with neurofibrosarcoma seen at the Mayo Clinic from 1912 to 1981, the tumors in 12 cases were found to originate in areas that had previously been irradiated for benign or malignant disease. Seven of the 12 patients demonstrated stigmata of von Recklinghausen's disease. The mean latency period between irradiation and clinical presentation of the sarcoma was 15.6 years (range, 5-26 years). Eight patients experienced at least one recurrence; metastases were present in two, and nine patients died of their disease. The mean interval between initial diagnosis and death was 3.4 years. In summary, neurofibrosarcoma may arise secondary to radiation; animal studies on the effects of radiation on peripheral nerves support this concept. It is the authors' opinion that patients with von Recklinghausen's disease should not be unnecessarily irradiated, and that those who do receive radiation therapy should be carefully observed for the development of secondary neurofibrosarcoma.

The effects of acrylamide on beta-glucuronidase and acid phosphatase activities in rat sciatic nerve above and below a ligature

The enzymes beta-glucuronidase and acid phosphatase have been assayed by histochemical and by fluorimetric methods above and below a tightly tied ligature on the rat sciatic nerve over the subsequent 10 days. These findings have been compared with similarly treated animals also given four daily doses of acrylamide (50 mg/kg). The following have been found: 1 during this time, acrylamide at this dose causes slight increases in beta-glucuronidase in untied sciatic nerves, detectable both histochemically and fluorimetrically; 2 below the ligature both enzyme activities were greatly increased and this was slightly reduced in the acrylamide-dosed animals; 3 there was a mild rise in beta-glucuronidase activity in the 1.0 cm above the ligature in undosed animals demonstrable both histochemically and fluorimetrically; 4 that in the acrylamide-dosed animals there was a marked rise in beta-glucuronidase activity both 1.0 cm and 2.0 cm above the ligature which was intensified at 7 days and at 10 days after dosing. This was demonstrated both histochemically and fluorimetrically. These results are discussed in the light of the known sheath cell and axonal responses to acrylamide intoxication.

Effects of x-irradiation on axonal sprouting induced by botulinum toxin

The effect of X-irradiation on axonal sprouting of motor nerves induced by botulinum toxin was examined. Muscles of one leg in the mouse were X-irradiated (15 Gy) prior to the injection of a locally paralysing dose of botulinum toxin. It was found that axonal sprouting occurred as expected, but the sprouts remained unmyelinated and many degenerated. Fewer new end-plates were formed, muscles remained more severely atrophied and supersensitive to acetylcholine and recovery of neuromuscular transmission was greatly delayed when compared with the effects of botulinum toxin alone. The experiments show that X-irradiation did not prevent sprouting but, probably by impairing Schwann cell proliferation, altered axon-Schwann cell relationships and prevented the maturation of newly-formed axons and the differentiation of new end-plates.

Retardation of Schwann cell division and axonal regrowth following nerve crush in experimental lead neuropathy

In experimental lead neuropathy, Schwann cells undergo segmental demyelination and possible cell death and, concurrently, remyelination and multiplication to create new internodes of myelin and onion bulb formations. In rats fed 4% lead carbonate for three months, the ability of Schwann cells to divide (percentage showing mitotic figures, labeling index, n total number per millimeter of fascicular length of nerve) was studied serially for four weeks. Schwann cell events were also compared in sural nerve distal to crush with and without resection of an intervening length of nerve. In both cases, Schwann cell multiplication as a result of axotomy was retarded in lead-intoxicated as compared to control animals. On the average, regrown myelinated axons four weeks after and 10 mm below the point of crush in lead-treated animals were similar in number and smaller in caliber, but they exhibited a normal relationship of myelin thickness to axonal area compared with control animals. These studies provide evidence that Schwann cell division and axonal regrowth after crush are retarded in experimental lead neuropathy.