Toxic neuropathy

Thalidomide upper limb embryopathy - pathogenesis, past and present management and future considerations

This review article provides a comprehensive overview of thalidomide upper limb embryopathy including updates about its pathogenesis, a historical account of the management of the paediatric thalidomide patient, experience with management of the adult patient, as well as creating awareness about early onset age-related changes associated with limb differences. Despite its withdrawal from the market in November 1961, novel discoveries have meant thalidomide is licensed again and currently still in use to treat a variety of conditions, including inflammatory disorders and some cancers. Yet, if not used safely, thalidomide still has the potential to cause damage to the embryo. Recent work identifying thalidomide analogues that retain clinical benefits yet without the harmful effects are showing great promise. Understanding the problems thalidomide survivors face as they age can allow surgeons to support their unique healthcare issues and translate these principles of care to other congenital upper limb differences.

Medikamentös-induzierte Polyneuropathien jenseits von Chemotherapeutika und Antiinfektiva

Zahlreiche in der klinischen Routine eingesetzte Wirkstoffe jenseits von Chemotherapeutika und Antiinfektiva können eine Polyneuropathie verstärken oder hervorrufen. Kenntnis darüber, welche Medikamente mit Polyneuropathien assoziiert sind sowie über Risikofaktoren seitens der Patienten können die Häufigkeit reduzieren. Bei entsprechendem Risiko sollten alternative Präparate eingesetzt oder die Indikation zur Therapie generell überdacht werden.

Medikamentös-induzierte Polyneuropathien durch Chemotherapeutika und Antiinfektiva

Polyneuropathien können durch zahlreiche Wirkstoffe hervorgerufen oder aggraviert werden. Insbesondere die Chemotherapeutika-induzierte Polyneuropathie (CIPN) ist im Alltag von hoher Relevanz. Jedoch kann auch der Einsatz von Antiinfektiva zu neuropathischen Beschwerden führen. Im Folgenden soll ein Überblick über die wichtigsten mit Polyneuropathien assoziierten Wirkstoffe der Substanzklassen sowie die klinischen Charakteristika gegeben werden.

Management of Peripheral Neuropathy Induced by Chemotherapy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is considered a severe side effect of therapeutic agents with limited treatment options. The incidence of CIPN in cancer patients is approximately 3-7% in cytostatic monotherapy and as high as 38% in cases of polychemotherapy. The prevalence of CIPN was found to be 68% within the first month of chemotherapy treatment. In some cases, CIPN can resolve, partially or completely, after completion of the treatment; in other cases, it can remain for a long time and affect the patient's quality of life.

OBJECTIVE

The aim of this study is to present up-to-date data regarding available treatment options for the management of CIPN.

MATERIALS AND METHODS

The up-to-date guidelines of ESMO (European Society for Medical Oncology), ASCO (American Society of Clinical Oncology), ONS (Oncology Nursing Society), NCI (National Cancer Institute), and NCCN (National Comprehensive Cancer Network) were reviewed and included in the manuscript.

RESULTS

The use of tricyclic antidepressant (TCA), selective serotonin norepinephrine reuptake inhibitor (SSNRI), pregabalin, and gabapentin are recommended as first-line treatment. Other treatment options were offered as second and third lines of treatment (lidocaine patches, capsaicin high-concentration patches, tramadol, and strong opioids, respectively); however, lower significance was demonstrated. Inconclusive results were found in the use of cannabinoids, drug combinations, antiepileptics, antidepressants, and topical drugs.

CONCLUSION

TCA, other antidepressants, and opioids could be recommended as treatment. Yet, we could not recommend an ideal therapeutic agent for the prevention or treatment of CIPN. Therefore, CIPN continues to be a challenge to clinicians and our patients.

The use of animal models to study cell transplantation in neuropathic hearing loss

Auditory neuropathy (AN) is a form of sensorineural deafness specifically affecting the conduction of the nerve impulse from the cochlear hair cells to the auditory centres of the brain. As such, the condition is a potential clinical target for 'cell replacement therapy', in which a functioning auditory nerve is regenerated by transplanting an appropriated neural progenitor. In this review, we survey the current literature and examine possible experimental models for this condition, with particular reference to their compatibility as suitable hosts for transplantation. The use of exogenous neurotoxic agents such as ouabain or β-bungarotoxin is discussed, as are ageing and noise-induced synaptopathy models. Lesioning of the nerve by mechanical damage during surgery and the neuropathy resulting from infectious diseases may be very relevant clinically, and we discuss whether there are good models for these situations. We also address genetic models for AN, examining whether the phenotypes truly model the clinical situation in their human counterpart syndromes - we use the example of the hyperbilirubinaemic Gunn rat as a particular instance in this regard.

Custom Orthotics to Mitigate Effects of Chemotherapy-induced Peripheral Neuropathy

Background

Chemotherapy-induced peripheral neuropathy (CIPN) is a complication commonly involving extremities characterized by dysthesias. Given the predilection towards diminished proprioceptive feedback, balance and gait deficits often result, leading to an increase in falls risk. To date there is no published evidence to support the use of orthotics in the treatment of balance dysfunction secondary to CIPN.

Purpose

This report describes custom foot orthotics with a closed cell foam overlay to improve postural stability and mobility in CIPN.

Case Description

An individual experiencing progressive balance dysfunction was provided orthotics when standard interventions were not effective. Expectations were that improved joint contact via midfoot compression and improved bony alignment would alter proprioceptive feedback throughout the kinetic chain and result in greater postural stability. Finding a cosmetically appealing shoe to provide sufficient tactile cues and support, without undue pressure challenged clinical decision making.

Outcome Measures

Computerized dynamic posturography and accelerometry were used to measure postural sway. Three conditions (barefoot, shoes only, and shoe plus orthotics) were tested to differentiate effects of orthotics and shoes. With orthotic use measures of sway velocity and area improved as did his ability to stand unassisted. Timed Up and Go and gait speed measures also improved.

Polymyositis in solid organ transplant recipients receiving tacrolimus

Tacrolimus, also known as FK506, is an immunosuppressive agent widely used for the prevention of acute allograft rejection in organ transplantation and for the treatment of immunological diseases. This study reports two male patients who underwent solid organ transplantation (liver and kidney). After transplant, the patients received continuous immunosuppressive therapy with oral tacrolimus and later presented clinical manifestations and laboratory signs of myopathy. Muscle biopsies of both patients clearly documented an inflammatory myopathy with the histological features of polymyositis including CD8+ T cells which invaded healthy muscle fibers and expressed granzyme B and perforin, many CD68+ macrophages and MHC class I antigen upregulation on the surface of most fibers. Because of the temporal association while receiving tacrolimus and since other possible causes for myopathy were excluded, the most likely cause of polymyositis in our patients was tacrolimus toxicity. We suggest that patients on tacrolimus should be carefully monitored for serum CK levels and clinical signs of muscle disease.

Electroacupuncture for thalidomide/bortezomib-induced peripheral neuropathy in multiple myeloma: a feasibility study

Background

This single-arm study evaluated feasibility, safety, and initial efficacy of electroacupuncture for thalidomide/bortezomib-induced peripheral neuropathy (PN) in cancer patients with multiple myeloma.

Methods

Patients with neuropathy ≥ grade 2 received 20 acupuncture treatments over 9 weeks.

Results

For the 19 evaluable patients, Functional Assessment of Cancer Therapy/Gynecological Oncology Group-Neurotoxicity (FACT/GOG/NTX) mean (SD) scores improved significantly between baseline and week 13 (20.8 [9.6] vs 13.2 [8.5], p = 0.0002). Moderate effect size differences began on week 4, with the largest effect size differences found at week 9 for FACT/GOG/NTX scores, worst pain in the last 24 hours, and pain severity (Cohen’s d = 1.43, 1.19, and 1.08, respectively) and continuing through week 13 (Cohen’s d = 0.86, 0.88, and 0.90, respectively). From baseline to week 13, additional significant improvements were seen as follows: postural stability (1.0 [0.6] vs 0.8 [0.4], p = 0.02); coin test (10.0 [7.4] vs 5.6 [1.9], p < 0.0001); button test (96.1 [144.4] vs 54.9 [47.3], p < 0.0001); and walking test (21.6 [10.0] vs 17.2 [7.7], p = 0.0003). No significant changes were seen with NCS.

Conclusions

Acupuncture may help patients experiencing thalidomide- or bortezomib-induced PN. Larger, randomized, clinical trials are needed.

Trial registration

ClinicalTrials.gov Identifier: NCT00891618.

Association of statin use with peripheral neuropathy in the U.S. population 40 years of age or older

BACKGROUND

Peripheral neuropathy is a serious complication of diabetes and several conditions that may lead to the loss of lower extremity function and even amputations. Since the introduction of statins, their use has increased markedly. Recent reports suggest a role for statins in the development of peripheral neuropathy. The aims of the present study were to assess the association between statin use and peripheral neuropathy, and to determine whether this association varied by diabetes status.

METHODS

Data from the lower extremity examination supplement of the 1999-2004 National Health and Nutrition Examination Survey were used.

RESULTS

The overall prevalence of statin use was 15% and the prevalence of peripheral neuropathy was 14.9%. The prevalence of peripheral neuropathy was significantly higher among those who used statins compared with those who did not (23.5% vs 13.5%, respectively; P < 0.01). Multivariate logistic regression revealed that statin use (adjusted odds ratio 1.3; 95% confidence interval 1.1-1.6; Wald P = 0.04) was significantly associated with peripheral neuropathy, controlling for diabetes status, age, gender, race, height, weight, blood lead levels, poverty, glycohemoglobin, use of vitamin B12 , alcohol abuse, hypertension, and non-high-density lipoprotein-cholesterol. Diabetes status, age, gender, height, weight, blood lead levels, poverty, and glycohemoglobin were also significantly associated with peripheral neuropathy. We found no effect modification between statin use and diabetes status, race, gender, age, vitamin B12 , blood lead levels, or alcohol abuse.

CONCLUSIONS

In the present cross-sectional study, we found a modest association between peripheral neuropathy and statin use. Prospective studies are required to determine the causal direction.

Medication, toxic, and vitamin-related neuropathies

PURPOSE OF REVIEW

Although medication, toxic, and vitamin-related neuropathies are rare causes of neuropathy, they are important to recognize because they are treatable and preventable. It is often difficult to conclusively demonstrate that a particular agent is the cause of neuropathy, but understanding the specific electrodiagnostic and clinical patterns produced by these agents is critical for making these assessments.

RECENT FINDINGS

The clinical and electrodiagnostic features for many of these neuropathies have been well established. The exact mechanism by which some of these agents produce neuropathy is only now beginning to be revealed. These mechanisms are critical for both understanding the normal function of nerves as well as eventually devising specific treatments.

SUMMARY

A large number of medications and toxins can produce neuropathy. This article reviews the clinical characteristics, electrodiagnostic features, and mechanism of action (when known) of those agents that produce the most severe, or perhaps the most unique features of, neuropathy.

Chemotherapy-induced peripheral neuropathy. Part II. Prevention

The incidence of chemotherapy-induced peripheral neuropathy (CIPN) in the population of cancer patients is estimated at 3-7% in cytostatic monotherapy and as high as 38% in the case of polytherapy. While testing drugs that may reduce the damage to the peripheral nervous system, particular attention should be paid to their protective action against the severe and painful complication in the patient. Another aspect, perhaps a more important one, is the confidence that application of preventive drugs will not exert a significant impact on progression of the neoplastic disease or the effectiveness of the causal treatment. Many drugs have been tested for prevention of CIPN; however, none of them have thus far been irrefutably proven to possess preventive properties. No guidelines on chemotherapy-induced peripheral neuropathy preventive action have been established, either. This article is an attempt to present reports from the available literature about the possibilities of prevention of CIPN.

Matrine induces apoptosis of human multiple myeloma cells via activation of the mitochondrial pathway

Multiple myeloma (MM) is a hematological malignancy characterized by the uncontrolled proliferation of clonal plasma cells in bone marrow in the elderly. Although there have been tremendous advances in the treatment of MM, it remains an incurable disease. Matrine, a main alkaloid of the traditional Chinese herb Sophora flavescens Ait, has been shown to inhibit cellular proliferation and induce apoptosis of various cancer cells. The aim of this study was to investigate the possibility of matrine as a novel therapeutic agent for patients with MM. We investigated the effects of matrine for its anti-myeloma activity in vitro, and further examined the mechanisms of apoptosis induced by matrine. Matrine inhibited the proliferation of human myeloma cell lines as well as freshly isolated myeloma cells from patients in a dose- and time-dependent manner. Matrine showed a potent induction of apoptosis of myeloma cells. Mitochondrial membrane potential (Deltapsim) was lost and cytochrome c (cyt c) was released from mitochondria to cytosol in myeloma cells treated by matrine for 24 h in a dose-dependent manner. The ratio of Bcl-2/Bax protein decreased, and the percentage of activated caspase-3 increased in myeloma cells treated by matrine for 48 h, but this matrine-induced activity of caspase-3 was completely canceled by the addition of Z-Asp(O-Me)-Glu(O-Me)-Val-Asp(O-Me) fluoromethyl ketone (Z-DEVD-FMK), a caspase-3 inhibitor. The addition of Z-DEVD-FMK partially blocked the apoptotic effect of matrine on myeloma cells. These data indicated that matrine could exert antiproliferative effects on myeloma cells and induce apoptosis of myeloma cells in vitro. The induction of apoptosis appeared to proceed via the mitochondrial pathway, including down-regulation of Bcl-2/Bax ratio, loss of Deltapsim, release of cyt c from mitochondria to cytosol, and activation of caspase-3. These findings support the view that matrine may be a useful candidate as a chemotherapeutic agent against MM.

Not all neuropathy in diabetes is of diabetic etiology: differential diagnosis of diabetic neuropathy

Diabetic peripheral neuropathy is the most common peripheral neuropathy in the developed world; however, not all patients with diabetes and peripheral nerve disease have a peripheral neuropathy caused by diabetes. Several (although not all) studies have drawn attention to the presence of other potential causes of a neuropathy in individuals with diabetes; 10% to 50% of individuals with diabetes may have an additional potential cause of a peripheral neuropathy and some may have more than one cause. Neurotoxic medications, alcohol abuse, vitamin B(12) deficiency, renal disease, chronic inflammatory demyelinating neuropathy, inherited neuropathy, and vasculitis are the most common additional potential causes of a peripheral neuropathy in these series. The most common disorders in the differential diagnosis of a generalized diabetic peripheral neuropathy are discussed in this article. Prospective studies to investigate the prevalence of other disorders that might be responsible for a peripheral neuropathy in individuals with diabetes are warranted.

Do statins cause myopathy by lowering vitamin E levels?

Statins and other lipid lowering drugs have been repeatedly described to decrease blood levels of minor fat soluble components such as vitamin E (as alpha-tocopherol). Clinical consequences of this secondary state of deficiency have not been described so far, but recent biochemical and molecular evidence on homeostatic and molecular responses to vitamin E deficiency in skeletal muscle cells may suggest the hypothesis presented in this paper of a role as risk factor in the development of statin-associated myopathy. This hypothesis that needs to be further investigated, could suggest the need for precautionary measures during lipid lowering therapy, which include timely diagnosis and active prevention of vitamin E deficiency.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

Systemic cancer therapy: evolution over the last 60 years

The 1940s marked the beginning of an era of important discoveries that contributed to modern concepts underlying the current practice of cancer chemotherapy, such as the log kill hypothesis reported by Skipper, the Norton-Simon hypothesis, and the Goldie-Coldman hypothesis. The early success of nitrogen mustards and antifolates in the treatment of hematologic malignancies paved the way for drug discovery platforms, which resulted in the generation of more drugs that nonetheless predominantly are genotoxic. The turn of the new millennium marked a new phase in the evolution of cancer chemotherapy. Scientific progress in the preceding 60 years elucidated the important ideas behind tumor microenvironment and 'targeted' therapy that had their inception in the late 19th century. Breakthroughs in molecular biology have paved the way for the development of novel agents that modulate the dysregulated molecular pathways implicated in carcinogenesis. The key approaches and evidence pertinent to the clinical development of these novel agents are presented in this review.

Bortezomib-induced peripheral neuropathy in multiple myeloma: a comprehensive review of the literature

Bortezomib has demonstrated significant activity in clinical trials, mainly against recurrent or newly diagnosed multiple myeloma (MM). Peripheral neuropathy is a significant toxicity of bortezomib, requiring dose modification and potential changes in the treatment plan when it occurs. The mechanism underlying bortezomib-induced peripheral neuropathy (BIPN) is unknown. Metabolic changes resulting from the accumulation of bortezomib in the dorsal root ganglia cells, mitochondrial-mediated disregulation of Ca(++) homeostasis, and disregulation of neurotrophins may contribute to the pathogenesis of BIPN. It is increasingly recognized that BIPN may be a proteasome inhibitor class effect, producing primarily a small fiber and painful, axonal, sensory distal neuropathy. Incidence of BIPN is mainly related to various risk factors, including cumulative dose and evidence of preexisting neuropathy. Assessment of BIPN is based primarily on neurologic clinical examination and neurophysiologic methods. To date, apart from the use of dose reduction and schedule change algorithm, there is no effective treatment with neuroprotective agents for BIPN. Analgesics, tricyclic antidepressants, anticonvulsants, and vitamin supplements have been used as symptomatic treatment against bortezomib-associated neuropathic pain with some success. This review looks critically at the pathogenesis, incidence, risk factors, diagnosis, characteristics, and management of BIPN, and highlights areas for future research.

The neuropathic pain triad: neurons, immune cells and glia

Nociceptive pain results from the detection of intense or noxious stimuli by specialized high-threshold sensory neurons (nociceptors), a transfer of action potentials to the spinal cord, and onward transmission of the warning signal to the brain. In contrast, clinical pain such as pain after nerve injury (neuropathic pain) is characterized by pain in the absence of a stimulus and reduced nociceptive thresholds so that normally innocuous stimuli produce pain. The development of neuropathic pain involves not only neuronal pathways, but also Schwann cells, satellite cells in the dorsal root ganglia, components of the peripheral immune system, spinal microglia and astrocytes. As we increasingly appreciate that neuropathic pain has many features of a neuroimmune disorder, immunosuppression and blockade of the reciprocal signaling pathways between neuronal and non-neuronal cells offer new opportunities for disease modification and more successful management of pain.

Up-regulation of apoptosis and regeneration genes in the dorsal root ganglia during cisplatin treatment

Cisplatin is an effective anti-neoplastic drug, but its use is dose-limited due to its association with severe peripheral neurotoxicity. The neurotoxic effect of cisplatin is believed to result from its accumulation in the dorsal root ganglia (DRG), although the mechanism is not completely understood. We used a rat model of cisplatin neurotoxicity to examine changes in gene expression in the DRG. The results indicate that cisplatin affects the expression of several genes associated with apoptosis (Cdkn1a, Ckap2, Bid3, S100a8, S100a9), inflammation (S100a8, S100a9, Cd163, Mmp9), and nerve growth and regeneration (Mmp9, Gfap, Fabp7). The differential regulation of some of these genes may directly contribute to the neurotoxic effect of cisplatin, while others are likely to be representative of the subsequent cellular response to contain damage and initiate recovery. As such, the identified genes may represent candidate processes and pathways that should be considered as targets for therapeutic intervention in cisplatin-induced neuropathy.

The Total Neuropathy Score as an assessment tool for grading the course of chemotherapy-induced peripheral neurotoxicity: comparison with the National Cancer Institute-Common Toxicity Scale

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a major side effect of several antineoplastic drugs. However, despite its clinical importance, there is no agreement as to the best way to assess the severity and changes in CIPN. We have previously demonstrated a correlation between the severity of CIPN, assessed using the Total Neuropathy Score (TNS) or its reduced versions, and several common toxicity scales. In this study, we investigated two series of patients (total number = 173) who were evaluated at baseline and during chemotherapy with the TNS (n= 122) or the TNSc (the TNS version based exclusively on the clinical evaluation of the patients, n= 51) and with the National Cancer Institute-Common Toxicity Criteria (NCI-CTC) 2.0, with the aim of comparing the sensitivity to the changes in CIPN severity. In both series, the TNS and the TNSc had a significant correlation with the NCI-CTC in scoring the severity of CIPN, confirming the results of previous studies. Moreover, both the TNS and the TNSc showed a higher sensitivity to CIPN changes. We, therefore, propose the TNSc as a reliable method for assessing not only the severity but also the changes in CIPN.

Neurotoxicity of bortezomib therapy in multiple myeloma: a single-center experience and review of the literature

BACKGROUND

Bortezomib is active in heavily pretreated multiple myeloma patients; the dose-limiting toxicity is peripheral neuropathy (PN).

METHODS

The authors retrospectively reviewed the incidence, severity, and risk factors for PN in 78 patients who received bortezomib. The median age was 57 years (range, 33-80 years), 62% of patients were men, and 37% of patients were African Americans. Seventeen patients (22%) had diabetes mellitus (DM), and 66 patients (85%) had received thalidomide. Before bortezomib treatment, 37% of the patients reported subjective, grade 1 or 2 PN. Patients received bortezomib alone (n = 10 patients) plus dexamethasone (n = 36 patients) and thalidomide (n = 20 patients) or chemotherapy (n = 12 patients). PN affected 52% of patients, including grade 3 and 4 PN in 15% and 7%, respectively.

RESULTS

Twelve patients stopped bortezomib because of side effects that included PN (n = 9 patients), diarrhea (n = 2 patients) and cytomegalovirus pneumonia (n = 1 patient); 11 patients had dose reductions because of PN. Grade 4 PN affected 6 patients (sensory, n = 4 patients; motor/sensory, n = 2 patients). The onset of grade 4 PN was sudden rather than cumulative. Factors that were predictive of PN grade were baseline PN (P = .002), prior thalidomide use (P = .03), and the presence of DM (P = .03). Multiple myeloma responses included complete, near complete, and partial responses in 5% of patients, 10% of patients, and 27% of patients, respectively. Responses were independent of PN and of whether bortezomib was combined with chemotherapy or thalidomide. Patients remained on therapy longer for a median of 5 cycles (range, 2-36 cycles) when they received bortezomib plus thalidomide versus 3 cycles (range, 1-19 cycles) for the other combinations. PN therapy was mostly supportive. It was noteworthy that 6 of 9 patients with PN who received lenalidomide as salvage therapy after bortezomib had significant improvement in their symptoms.

CONCLUSIONS

The risk of bortezomib-related PN was greater in patients who had PN and DM at baseline. The authors concluded that an unexpected, symptomatic improvement of PN on lenalidomide is worth further investigation.

Thalidomide inhibits pentylenetetrazole-induced seizures

Thalidomide was originally synthesized and tested as a sedative, hypnotic and antiemetic; however, after its teratogenicity was noted its use for treatment of neurological and psychiatric disorders was abandoned. We studied the potential anticonvulsant effect of thalidomide: Different doses of thalidomide were tested against seizures induced by 50 mg/kg or 70 mg/kg of pentylenetetrazole (PTZ); the anticonvulsant effect of thalidomide was also compared with that of valproic acid. Seizures and latency time were individually recorded. Thalidomide in low doses (5-10 mg/kg) prevented seizures in all animals treated with 50 mg/kg PTZ; also, in a dose-dependent manner thalidomide inhibited seizures in rats exposed to a high dose of PTZ (70 mg/kg); thalidomide exhibited an anticonvulsant activity similar to that of valproic acid. Thalidomide is an effective anticonvulsant, and further studies on this potential antiepileptic substance seem warranted.

WIN 55,212-2 prevents mechanical allodynia but not alterations in feeding behaviour induced by chronic cisplatin in the rat

Anorexia, nausea/emesis and peripheral sensorial neuropathy are frequent adverse effects associated with chemotherapy. Cannabinoids have been proposed to alleviate these effects, but their preventive properties in long-term experimental models have not been tested. This study was conducted to determine whether or not a cannabinoid agonist (WIN-55,212-2) can prevent anorexia, pica (an indirect marker of nausea in non-vomiting species, consisting of the ingestion of non-nutritive substances such as kaolin) and mechanical allodynia (a marker of peripheral neuropathy) induced by the antineoplastic drug cisplatin chronically administered. Isolated rats with free access to food and kaolin received either saline, cannabinoid vehicle, WIN-55,212-2 (1-2 mg kg(-1)), cisplatin (1-2 mg kg(-1)), or both drugs once per week for five consecutive weeks. Modifications in temperature, body weight gain, food and kaolin intake, and the threshold for mechanical allodynia were recorded. Additionally, the acute psychoactive effects of the cannabinoid (hypomotility, hypothermia, analgesia and catalepsia) were assayed by means of the cannabinoid tetrad. WIN 55,212-2 prevented the development of mechanical allodynia but not anorexia, pica and reduction in weight gain induced by chronic cisplatin. The effect of WIN 55,212-2 was evident even at a dose lacking activity in the cannabinoid tetrad. The preventive effect on cisplatin-induced mechanical allodynia exerted by the cannabinoid could be due to a neuroprotective role, as has been suggested for other conditions. The present results support the interest in the evaluation of cannabinoids for treatment of patients suffering or likely to suffer neuropathic pain.

Uremic neuropathy: clinical features and new pathophysiological insights

Neuropathy is a common complication of end-stage kidney disease (ESKD), typically presenting as a distal symmetrical process with greater lower-limb than upper-limb involvement. The condition is of insidious onset, progressing over months. and has been estimated to be present in 60%-100% of patients on dialysis. Neuropathy generally only develops at glomerular filtration rates of less than 12 ml/min. The most frequent clinical features reflect large-fiber involvement, with paresthesias, reduction in deep tendon reflexes, impaired vibration sense, muscle wasting, and weakness. Nerve conduction studies demonstrate findings consistent with a generalized neuropathy of the axonal type. Patients may also develop autonomic features, with postural hypotension, impaired sweating, diarrhea, constipation, or impotence. The development of uremic neuropathy has been related previously to the retention of neurotoxic molecules in the middle molecular range, although this hypothesis lacked formal proof. Studies utilizing novel axonal excitability techniques have recently shed further light on the pathophysiology of this condition. Nerves of uremic patients have been shown to exist in a chronically depolarized state prior to dialysis, with subsequent improvement and normalization of resting membrane potential after dialysis. The degree of depolarization correlates with serum K(+), suggesting that chronic hyperkalemic depolarization plays an important role in the development of nerve dysfunction in ESKD. These recent findings suggest that maintenance of serum K(+) within normal limits between periods of dialysis, rather than simple avoidance of hyperkalemia, is likely to reduce the incidence and severity of uremic neuropathy.

Cisplatin-induced peripheral neuropathy: Neuroprotection by erythropoietin without affecting tumour growth

This study examined the dose-dependent efficacy of erythropoietin (EPO) for preventing and/or treating cisplatin (CDDP) induced peripheral neurotoxicity (CINP), and its influence on tumour treatment and growth. Rats received eight intraperitoneal (ip) injections of 2 mg/kg CDDP twice weekly. EPO co-administered (50 or 10 microg/kg ip, three times/week) had a dose-dependent effect, partially preventing CINP, but 0.5 microg/kg ip was not effective. The neuroprotective effect lasted at least 5 weeks after the last dose of EPO and CDDP. In addition, EPO (50 microg/kg ip three times/week) after the last injection of CDDP still induced a significant recovery of CINP. In a separate experiment in rats bearing mammary carcinoma EPO treatment (50 microg/kg ip) given concurrently with CDDP (1.0 and 1.5 mg/kg twice a week for four weeks) was neuroprotective without influencing the effectiveness of the treatment or tumour growth. EPO thus appears to be an effective neuroprotectant that does not interfere with tumour treatment.

The Inherited Neuropathies

Neuropathy is one of the most common referrals to neurologic clinics. Patients often undergo extensive testing for acquired etiologies; inherited causes are common. Increasingly, genetic causes are becoming known and commercial testing available. The rate of recent discovery has been rapid and relates to the extent of single gene disorders of nerve, the ease of peripheral nervous system functional examination, and readily accessible pathologic tissue. Foremost in the rate of recent discoveries is the work and tools of the human genome project. the rapidity of the ongoing discovery requires clinicians to be familiar with molecular biologic discoveries and consider wisely which testing should be performed.

Peripheral nervous system involvement in patients with cancer

Involvement of the peripheral nervous system (PNS) is common in patients with cancer and any part, including motor neurons, sensory ganglia, nerve roots, plexuses, cranial and peripheral nerves, and neuromuscular junctions, can be affected. Different mechanisms can initiate damage associated with cancer-related PNS disorders. These include tumour infiltration, toxicity of treatments, metabolic and nutritional perturbations, cachexia, virus infections, and paraneoplastic neurological syndromes. The type of cancer, lymphoma, or solid tumour is a further determinant of a PNS disorder. In this Review we discuss the different causes and mechanisms of disorders of the PNS in patients with cancer and we will focus on their assessment and diagnosis.

Dixièmes Journées des Maladies du Système Nerveux Périphérique

Sensory ganglionopathies have a frequent association with neoplastic disorders (paraneoplastic subacute sensory neuronopathy, or SSN) or dysimmune disorders, with drugs, such as cisplatin or pyridoxine, and with inherited disorders with degeneration of dorsal root ganglion cells. Unsteady gait and pseudoathetoid movements of the hand are the distinctive signs encountered in these disorders. The chronic disorders are characterized by non-length-dependent abnormalities of sensory nerve action potentials (SNAPs) and differ from other sensory neuropathies in showing a global, rather than distal, decrease in SNAP amplitudes. This review focuses on recent advances in defining the mechanisms involved in sensory ganglionopathies, and describes the differential diagnosis including the rarely encountered hereditary neuronopathies and the infectious causes.

Development of neuropathy in patients with myeloma treated with thalidomide: patterns of occurrence and the role of electrophysiologic monitoring

PURPOSE

Peripheral neuropathy frequently limits the duration of treatment with thalidomide for patients with multiple myeloma. We assessed the time course of occurrence, possible predictive factors, and the utility of serial nerve electrophysiological studies (NES) for detecting onset of neuropathy.

PATIENTS AND METHODS

Seventy-five patients with relapsed/refractory myeloma were enrolled onto a multicenter trial of dose-escalating thalidomide with or without interferon. Patients underwent clinical assessment plus NES at baseline and every 3 months. Time to development of neuropathy according to clinical or NES criteria was compared. Patient and treatment-related factors were compared as predictors of neuropathy.

RESULTS

Thirty-nine percent had some NES abnormalities at baseline. Patients received thalidomide at a median dose-intensity of 373 mg/d. Thirty-one of 75 patients (41%) developed neuropathy during thalidomide treatment; 11 patients (15%) discontinued treatment with thalidomide due to neuropathy. The actuarial incidence of neuropathy increased from 38% at 6 months to 73% at 12 months, with 81% of responding patients developing this complication. Serial NES did not reliably predict the imminent development of clinical neuropathy requiring thalidomide cessation, nor were patient age, sex, or prior therapy predictive. Patients who developed neuropathy had a longer duration of thalidomide exposure (median, 268 v 89 days; P = .0001). Cumulative dose or dose-intensity received was not predictive.

CONCLUSION

The majority of patients will develop peripheral neuropathy given sufficient length of treatment with thalidomide. To minimize the risk of neurotoxicity, therapy should be limited to less than 6 months. Electrophysiologic monitoring provides no clear benefit versus careful clinical evaluation for the development of clinically significant neuropathy.

A Multicenter Retrospective Analysis of Adverse Events in Korean Patients Using Bortezomib for Multiple Myeloma

The proteasome inhibitor bortezomib has demonstrated clinical activity in patients with multiple myeloma (MM). Adverse events, including thrombocytopenia and peripheral neuropathy, have affected 30% to 60% of patients overall, and interrupted therapy in 10% to 20%. No prior toxicity data are available for Asian patients who have used bortezomib for MM. We used National Cancer Institute Common Terminology Criteria for Adverse Events, version 3.0, to review the clinical records of patients with an MM diagnosis from 25 centers in Korea. The included patients were treated with bortezomib alone or in combination with other agents, including thalidomide. Ninety-five MM patients were treated. The patients had a median age of 60 years (range, 42-77 years). The median number of previous treatments was 3 (range, 0-10), and 39% of the patients had been treated with 4 or more major classes of agents, including thalidomide (67%), and autologous stem cell transplantation (51%). Regimens included bortezomib only in 38 patients (40%), bortezomib plus dexamethasone in 34 patients (36%), and bortezomib plus a thalidomide-containing regimen in 23 patients (24%). The analysis of patient response to therapy revealed a complete response (CR) or a near-CR in 31 patients (33%) and a partial response in 30 patients (32%), for an objective response rate of 65% in 93 patients. The most common adverse events reported were thrombocytopenia (47%), sensory neuropathy (42%), anemia (31%), and leukopenia (31%). Thirteen patients (14%) stopped therapy because of adverse events (neuropathy, 8; infection, 4; diarrhea, 1). Neuropathy greater than grade 2 was more frequent in patients who received 4 or more prior therapy regimens (17/37) than in those who received 3 or fewer (14/58). In addition, therapy including thalidomide was significantly correlated with neuropathy of grades 1 to 3 (P = .001). We identified 6 therapy-related deaths (6%) within 20 days after the last dose of bortezomib. The causes of death were infection in 3 patients, disease progression in 2 patients, and suicide in 1 patient. The incidences of thrombocytopenia and neurotoxicity were similar; however, gastrointestinal toxicities were relatively low in Korean patients compared with those reported in Western studies. Significant neuropathy was associated with the number of prior regimens and combination with thalidomide. These findings provide useful information for clinicians and patients using bortezomib.