Quantitative sensory testing: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology.

OBJECTIVE: This assessment evaluates the clinical utility, efficacy, and safety of quantitative sensory testing (QST). METHODS: By searching MEDLINE, Current Contents, and their personal files, the authors identified 350 articles. Selected articles utilized computer operated threshold systems, manually operated threshold systems, and electrical threshold devices. The authors evaluated the use of normal values and the degree of reproducibility between the same and different systems. Articles were rated using a standard classification of evidence scheme. RESULTS: Because of differences between systems, normal values from one system cannot be transposed to others. Reproducibility of results was also an important concern, and there is no consensus on how it should be defined. The authors identified no adequately powered class I studies demonstrating the effectiveness of QST in evaluating any particular disorder. A number of class II and III studies demonstrated that QST is probably or possibly useful in identifying small or large fiber sensory abnormalities in patients with diabetic neuropathy, small fiber neuropathies, uremic neuropathies, and demyelinating neuropathy. CONCLUSIONS: QST is a potentially useful tool for measuring sensory impairment for clinical and research studies. However, QST results should not be the sole criteria used to diagnose pathology. Because malingering and other nonorganic factors can influence the test results, QST is not currently useful for the purpose of resolving medicolegal matters. Well-designed studies comparing different QST devices and methodologies are needed and should include patients with abnormalities detected solely by QST.

Randomized controlled trial of IVIg in untreated chronic inflammatory demyelinating polyradiculoneuropathy.

OBJECTIVE: To determine the efficacy of IV immunoglobulin (IVIg) given patients with untreated chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). METHODS: A randomized, double-blind, multicenter, investigator-initiated study compared IVIg (Aventis Behring LLC, King of Prussia, PA) with placebo (5% albumin). On days 1, 2, and 21, IVIg (1 g/kg) or placebo was given. The primary outcome measure was the change in muscle strength from baseline to day 42, using the average muscle score (AMS). Secondary outcome measures included change from baseline AMS at days 10 and 21, the Hughes' functional disability scale, forced vital capacity (FVC), and nerve conduction studies (NCS) of four motor nerves (median, ulnar, peroneal, and tibial). RESULTS: The patients (n = 33) were randomized. Of these, 30 (14 women, 16 men, aged 54 +/- 20 years, range 13 to 82) received IVIg and 23 were given placebo (12 women, 11 men, aged 50 +/- 18 years, range 23 to 73). Baseline AMS values of the groups were similar (IVIg 7.06 +/- 1.31 versus placebo 7.28 +/- 1.18, p = 0.53). There were two dropouts in placebo group and one in the IVIg group. Mean AMS improved at day 42 comparing IVIg with placebo (0.63 versus -0.1, p = 0.006). Improved strength was seen by day 10. The placebo group lost strength over this same interval. In the IVIg, 11 subjects improved by the functional disability scale; none worsened. This differed (p = 0.019) from those in the placebo-treated group (two improved, two got worse, remainder unchanged). Forced vital capacity did not improve with IVIg treatment. IVIg improved ulnar motor distal latency (p = 0.005), tibial distal compound muscle amplitude (p = 0.003), and peroneal nerve conduction velocity (p = 0.03). CONCLUSIONS: IVIg improves strength in patients with untreated CIDP by day 10 with continued benefit through day 42; more than one third improve by at least a functional grade on a disability scale. This study provides data supporting IVIg as the initial treatment for CIDP.

Sensory neuropathy associated with metronidazole: report of four cases and review of the literature.

OBJECTIVE: To better characterize sensory neuropathy associated with metronidazole. METHODS: We report four patients who developed dysesthesias after metronidazole treatment. One received topical metronidazole only. All four underwent electrodiagnostic studies, including nerve conduction studies (NCS), quantitative sensory testing (QST), and quantitative sudomotor axon reflex testing (QSART). One underwent nerve biopsy. RESULTS: NCS were normal in all patients. QST showed impaired vibration thresholds in three patients. Three of four patients had abnormal tests of small fiber function. Cooling thresholds were abnormal in one; QSART was abnormal in one and borderline in another. The nerve biopsy specimen showed mild loss of small myelinated axons. CONCLUSIONS: This study shows that paresthesias associated with metronidazole exposure may be the result of a relatively mild sensory neuropathy with predominant involvement of small fibers and milder, mostly subclinical involvement of large fibers.

Neuromyotonia: autoimmune pathogenesis and response to immune modulating therapy.

BACKGROUND: Neuromyotonia (NMT) has been postulated to be an autoimmune channelopathy, probably by affecting voltage gated potassium channels (VGKC) leading to excitation and abnormal discharges [Sinha et al., Lancet 338 (1991) 75]. OBJECTIVE: To report three patients with NMT who had other associated immune-mediated conditions, i.e., myasthenia gravis, thymoma and various types of peripheral neuropathies. One patient had peripheral neuropathy and involvement of pre- and post-synaptic neuromuscular junction. RESULTS: All three patients had evidence of polyneuropathy and neuromyotonic discharges on electrodiagnostic studies. Elevated acetylcholine receptor antibodies were noted in all patients and malignant thymoma was found in two patients with metastasis. All three patients showed moderate to marked response to plasma exchange. CONCLUSIONS: These findings strongly suggest a humoral autoimmune pathogenesis of NMT, probably by K(+) channel involvement, affecting acetylcholine quantal release and postsynaptic membrane. Clinicians should be aware of this association of immune-mediated conditions in NMT patients and marked improvement with plasma exchange.

Comparison of different modalities for detection of small fiber neuropathy.

OBJECTIVES: In general, large fiber sensory function is easier to assess than small fiber function both clinically and electrophysiologically. Therefore, small fiber sensory neuropathies are more difficult to diagnose. The relative sensitivities of different electrodiagnostic tests for small fiber neuropathy are not known. We sought to determine and compare the sensitivities of quantitative thermal sensory testing (QST), quantitative sudomotor axon reflex testing (QSART), and cardiovascular autonomic testing for diagnosis in patients with clinically suspected small fiber neuropathy. METHODS: 15 adult patients with clinically suspected small fiber sensory neuropathy underwent neurologic examination, QST, and QSART. Twelve also underwent cardiovascular autonomic testing. RESULTS: 80% had an abnormal neurologic examination consistent with small fiber neuropathy, while 93% had at least one abnormal quantitative test. QSART was most sensitive with 12 of 15 (80%) having abnormal studies while 10 of 15 (67%) had abnormal thermal thresholds by QST. Abnormal heart rate with deep breathing was detected in 9 of 12 (75%) patients. CONCLUSION: Of the modalities tested, QSART was most sensitive in confirming the clinical suspicion of a small fiber neuropathy. Autonomic cardiovascular abnormalities were also common in our patients. Clinical examination and QSART may be optimal for screening patients for small fiber neuropathy.

Fluctuating clinical myotonia and weakness from Thomsen's disease occurring only during pregnancies.

Advances in molecular genetics are allowing better phenotype to genotype correlation of the non-dystrophic myotonic disorders. We report a 32-year-old woman, who first noted myotonia that was associated with weakness during her first pregnancy. The work-up disclosed that she had Thomsen's disease which is not known to be associated with weakness. In addition, her myotonia was of the fluctuating type and occurred (symptomatically) only during two pregnancies. We discuss the evaluation of myotonia in the pregnant woman which led to the diagnosis of Thomsen's disease and we conclude that in exceptional cases, fluctuating myotonia and weakness occurs in autosomal dominant chloride channel myotonia (Thomsen's disease).

Multifocal small fiber sensory neuropathy.

PURPOSE: : To report four patients with unusual multifocal patterns of small fiber sensory neuropathy METHODS: : Four patients who developed multifocal sensory symptoms after infectious illnesses underwent neurologic examinations, nerve conduction studies, and serologic testing. All had one to three types of electrodiagnostic assessments of small nerve fibers by evaluation of thermal and vibratory thresholds. quantitative sudomotor axon reflex testing, or autonomic cardiovascular testing. RESULTS: Nerve conduction and serologic studies were normal. Quantitative sudomotor axon reflex testing, autonomic cardiovascular testing, or both revealed abnormalities of small fiber function in all patients, and thermal thresholds were abnormal in one. Three had progression and fluctuations of symptoms for months. CONCLUSIONS: : Small fiber sensory neuropathies occasionally occur in a multifocal rather than the typical distal distribution and may comprise part of the spectrum of postinfectious sensory neuropathies. Objective testing of small fiber function is useful in distinguishing small fiber sensory neuropathy from other causes of paresthesias in this setting.

Sensory Neuropathy With Sjögren's Syndrome, Thymoma, and Hypogammaglobulinemia.

We report a 63-year-old woman with common variable immunodeficiency (CVID) and an indolent distal sensory neuropathy. Despite having negative serologic tests for Sjögren's syndrome, evaluation of the neuropathy led to a new diagnosis of Sjögren's syndrome based on the presence of sicca symptoms, an abnormal Schirmer's test, and histologic evidence of sialadenitis. In addition, a thymoma was discovered. We conclude that the occurrence of thymoma, CVID, and Sjogren's syndrome reflect a state of systemic autoimmune dysregulation in this patient. We also reiterate the diagnostic importance of salivary gland biopsy in patients with sicca symptoms and sensory neuropathy.

Mononeuropathies associated with liver transplantation.

Mononeuropathies associated with orthotopic liver transplantation were evaluated in a prospective manner. Ten percent of liver transplant recipients were noted to have focal peripheral nerve lesions in the postoperative period. The ulnar nerve was most commonly involved, with intraoperative compression or postoperative trauma as possible mechanisms of injury. Other upper extremity mononeuropathies were likely a result of vascular cannulations. No brachial plexus injuries occurred. Diabetes and alcoholism were not risk factors for the development of a mononeuropathy.

Causes of neuromuscular weakness in the intensive care unit: a study of ninety-two patients.

The spectrum of neuromuscular disorders among intensive care unit (ICU) patients has shifted toward disorders acquired within the ICU and away from "traditional" neuromuscular disorders that lead to ICU admission. We sought to assess this spectrum by determining the causes and relative frequencies of neuromuscular disorders that led to electromyography (EMG) examinations in our ICU population. Ninety-two patients were studied over a 4 1/2-year period. Twenty-six (28%) had neuromuscular disorders (mainly Guillain-Barré syndrome, myopathy, and motor neuron disease) that led to ICU admission. Among patients who developed weakness in the ICU, there was a predominance of organ transplant patients and patients with the systemic inflammatory response syndrome and multiorgan dysfunction. Thirty-nine (42%) developed acute myopathy (consistent with critical illness myopathy in most), and 13% developed acute axonal sensorimotor polyneuropathy (mainly critical illness polyneuropathy). Patients with acute myopathy and acute axonal sensorimotor polyneuropathy had similar functional outcomes. We conclude that among patients who underwent EMG in our ICU population, acute myopathy is three times as common as acute axonal polyneuropathy, and the outcomes from acute myopathy and acute axonal polyneuropathy may be similar.

Oculopharyngeal muscular dystrophy: non-French-Canadian pedigrees.

Oculopharyngeal muscular dystrophy (OPMD) is a late adult onset, autosomal dominant muscular dystrophy characterized by ptosis and dysphagia. The OPMD gene has been localized to chromosome 14q11.2-q13 in French-Canadian pedigrees. We report 2 non-French-Canadian families with OPMD. Affected ancestors were immigrants to the United States from Italy and Normandy. The Norman pedigree does not share the French-Canadian haplotype. OPMD appears to be a heterogeneous disorder with similar phenotypes, but probably with different gene loci.

Neuropathy associated with hyperoxaluria: improvement after combined renal and liver transplantations.

Little is known about oxaluria-associated neuropathy, and no effective treatments have been described. We report two patients with clinically severe and progressive sensorimotor polyneuropathy associated with oxaluria. Electrodiagnostic testing and sural nerve histopathology revealed evidence of severe axon loss and demyelination. In addition, birefringent crystalline deposits were identified within endoneurial and perineurial blood vessel walls, axon cylinders, and perimysial blood vessel walls. Electron probe microscopy confirmed that calcium (consistent with calcium oxalate) was a major constituent of the crystals. Both patients had substantial improvement in neuropathic signs and symptoms after kidney and liver transplantations despite no prior improvement with hemodialysis. Our results confirm previous reports of a mixed axonal and demyelinating neuropathy with calcium oxalate deposition in association with oxaluria. In addition, our findings suggest that renal and liver transplantation may be potential treatments for the associated neuropathy.

Acute myopathy after liver transplantation.

Acute myopathy is a cause of weakness and additional morbidity in a variety of critically ill patients, including transplant recipients. We report the incidence of and risk factors associated with acute myopathy after orthotopic liver transplantation (OLTx). One hundred consecutive adult patients were prospectively assessed for muscle weakness after OLTx. Electrodiagnostic studies and muscle biopsies were performed on consenting affected patients. Potential risk factors for myopathy were evaluated in patients with myopathy versus control subjects. Seven patients developed acute persistent weakness after OLTx. Electrodiagnostic studies were consistent with a necrotizing myopathy. Histopathologic evaluation in five revealed a necrotizing myopathy with loss of myosin thick filaments. A higher initial index of illness severity, dialysis requirement, and higher doses of glucocorticoids were associated with development of myopathy. Patients with myopathy subsequently remained in the intensive care unit (ICU) longer than unaffected patients. In conclusion, acute substantial weakness was a source of additional morbidity in 7% of patients after OLTx. Most had myopathy with loss of myosin thick filaments. Patients with greater severity of illnesses and renal failure requiring dialysis were more likely to be affected. The effect of reducing exposure to corticosteroids in high-risk patients warrants further investigation.

Percutaneous needle muscle biopsy in the evaluation of patients with suspected inflammatory myopathy.

OBJECTIVE: To determine the usefulness of a unique method of percutaneous needle muscle biopsy (NMB) in patients with suspected idiopathic inflammatory myopathy (IIM). METHODS: The yield of percutaneous NMB was studied in 55 patients who were found to have a combination of clinical, laboratory, or electromyographic features of IIM. RESULTS: A diagnosis of IIM was confirmed histopathologically in 29 patients (53%), other specific myopathies were found in 5 (9%), nonspecific myopathic changes were present in 11 (20%), and a neurogenic process was diagnosed in 3 (5%). Nonspecific changes or no abnormalities were present in 7 patients (13%). Followup of the 18 patients with nonspecific histopathologic findings disclosed that only 3 had a subsequent disease course compatible with IIM. CONCLUSION: Percutaneous NMB is a safe, convenient, and relatively inexpensive method of muscle biopsy, with a high diagnostic yield for the pathologic confirmation of IIM. It should be considered as a primary method of acquiring muscle for histopathologic examination in the evaluation of suspected IIM.

Vacuolar myopathies in adults with myalgias: value of paraspinal muscle investigation.

We evaluated 4 women with chronic fatigue and myalgias. Two had proximal weakness. All had elevated serum creatine kinase levels, but none was diagnosed with myopathy until electrodiagnostic studies revealed myotonic or complex repetitive discharges predominantly in paraspinal muscles. Histopathology of paraspinal muscles revealed vacuolar myopathies with glycogen storage; biochemical assays revealed phosphorylase deficiency in 1. Since vacuolar myopathies may affect paraspinal muscles more than limb muscles, electromyographic and histopathologic studies of paraspinal muscles may be required for diagnosis.

Small fiber neuropathy and vasculitis.

Vasculitis-associated neuropathy usually presents as multiple mononeuropathies or sensorimotor polyneuropathies that affect large nerve fibers; painful small fiber sensory neuropathy has not previously been described in association with vasculitis. This report describes 2 patients with small fiber neuropathy in whom vasculitis was found to be present. Patients with small fiber neuropathy for which no other cause has been identified should be evaluated for the presence of vasculitis.

October 1996--rapidly progressive weakness.

One week after a flu-like illness, a 51-year-old woman developed rapidly progressive weakness. Within three weeks, she required mechanical ventilation. A neurological exam revealed severe motor involvement with normal sensory findings confirmed by nerve conduction studies. Five days after intubation a catastrophic brain hemorrhage occurred. Autopsy showed severe loss of axons in the motor roots with periaxonal macrophages and no lymphocytes. These findings are typical of acute motor axonal neuropathy, which is rare in the United States.

Acute onset of colchicine myoneuropathy in cardiac transplant recipients: case studies of three patients.

Colchicine causes both muscle and peripheral nerve toxicity of subacute onset in patients with renal insufficiency. We report three cardiac transplant recipients, treated with colchicine for cyclosporin A (CyA)-induced gout, who developed acute weakness due to colchicine myoneuropathy. The onset of disabling weakness occurred over a 1-2 week period. All three patients had concomitant renal insufficiency and an elevated serum creatine kinase and two elevated CyA levels at the time of presentation. Electromyography revealed features of myopathy and motor axonal neuropathy in all three patients. Two underwent muscle biopsy which confirmed the presence of sarcoplasmic vacuoles characteristic of colchicine-induced myopathy. All patients rapidly improved with either colchicine dose reduction or drug discontinuation. In conclusion, cardiac transplant recipients treated with CyA and colchicine may be at increased risk of developing colchicine-induced myoneuropathy especially in the setting of concurrent renal insufficiency. In patients with post-transplantation gouty arthritis, other treatment modalities are suggested; and if colchicine is administered, the dose should be reduced, CyA levels should be monitored closely and patients should be assessed for signs of neuromuscular toxicity.

Acute myopathy of intensive care: clinical, electromyographic, and pathological aspects.

An acute myopathy of intensive care occurs in critically ill patients treated with intravenous corticosteroids and neuromuscular junction-blocking agents. The full clinicopathological spectrum is uncertain. We evaluated the clinical, electrodiagnostic, and histopathological features of 14 patients who developed acute myopathy of intensive care after organ transplantation or during treatment of severe pulmonary disorders and sepsis. Patients received high-dose intravenous corticosteroids, usually in conjunction with relatively low to moderate doses of neuromuscular junction-blocking agents. After discontinuation of the latter drugs, most had diffuse, flaccid weakness with failure to wean from mechanical ventilation. Electrodiagnostic findings were consistent with a necrotizing myopathy. Muscle histopathology revealed myopathy with loss of thick filaments in 79%, mild myopathic changes in 14%, and atrophy of type 1 and type 2 fibers in 7%. Loss of thick filaments was identified in muscle biopsy specimens obtained 30 +/- 11 days (mean +/- standard deviation) after intravenous corticosteroid treatment but not in those obtained earlier (12 +/- 2 days). Critically ill patients, including those receiving organ transplants, may develop acute myopathy of intensive care after exposure to intravenous corticosteroids and neuromuscular junction-blocking agents, although the exposure to the latter drugs may be minimal. Selective loss of thick filaments is common in acute myopathy of intensive care, especially if the muscle biopsy specimen is obtained 2 weeks or more after intravenous corticosteroid exposure.