Incidence of distal symmetric (sensory) neuropathy in NIDDM. The San Luis Valley Diabetes Study.

OBJECTIVE: To determine the incidence and risk factors for distal symmetric sensory neuropathy (DSN) in people with NIDDM. RESEARCH DESIGN AND METHODS: Prospective follow-up was conducted from 1988 to 1992 on 231 people free of DSN during the baseline period 1984-1988 (mean follow-up, 4.7 years). Subjects with incident DSN (n = 66) were defined by any two of three criteria: 1) bilateral paresthesia in legs or feet; 2) bilateral decreased or absent ankle reflexes; and/or 3) bilateral decreased or absent cold temperature discrimination in feet. Of all 66 cases, 42 had one positive follow-up visit; 14 cases had 2 positive follow-up visits. RESULTS: The overall incidence rate of DSN was 6.1 per 100 person-years (95% CI, 4.7-7.8). The rate for Hispanics (n = 164) and non-Hispanic whites (n = 67), adjusted for age, sex, and NIDDM duration, was 5.3 per 100 person-years (95% CI, 3.9-7.0) and 5.0 per 100 person-years (95% CI, 2.8-8.1), respectively. Adjusting for age and sex, higher glycohemoglobin level and lower C-peptide secretion were associated with increased DSN but were no longer predictive after accounting for duration of diabetes. Logistic regression models found significantly increased risk of DSN for insulin treatment, current smoking, and history of myocardial infarction. Duration was related to DSN incidence until insulin treatment was included. Other risk factors, including height, weight, family history of diabetes, peripheral vascular disease, hypertension, urinary albumin, protein:creatinine ratio, retinopathy, and alcohol use, were not significantly related to incident DSN. CONCLUSIONS: Hispanic and non-Hispanic whites with NIDDM have similar risks of DSN. Current cigarette smoking and a history of myocardial infarction may represent independent risk factors for DSN in addition to glycemic control.

Risk factors for distal symmetric neuropathy in NIDDM. The San Luis Valley Diabetes Study.

OBJECTIVE: To investigate risk factors for distal symmetric (sensory) neuropathy among prevalent cases of non-insulin-dependent diabetes mellitus (NIDDM) in a population-based study in southern Colorado. RESEARCH DESIGN AND METHODS: Prevalent neuropathy was identified in 77 of 277 people with NIDDM by a standardized history and neurologic examination. Fifteen known or suspected risk factors for neuropathy were determined without knowledge of neuropathy status. RESULTS: Older age at examination, longer duration of diabetes, higher glycohemoglobin percentage, lower fasting C-peptide, insulin use, and presence of retinopathy and nephropathy (microalbumin > or = 200 micrograms/ml) were all significantly associated with neuropathy. Sex, ethnicity (Hispanic versus non-Hispanic white), height, systolic blood pressure, peripheral vascular disease, cigarette and alcohol use, and serum lipid levels were not significantly associated with neuropathy. In a multivariate logistic model, increasing age (odds ratio [OR] = 1.3, 95% confidence interval [CI] = 1.1-1.6), longer duration of diabetes (OR = 1.3, CI = 1.0-1.6), increased glycohemoglobin percentage (OR = 1.5, CI = 1.1-2.1), and insulin use (OR = 2.8, CI = 1.3-6.1) were associated with neuropathy. Retinopathy (OR = 3.0, CI = 1.2-7.7), but not nephropathy, was important when added to this model. CONCLUSIONS: Worse glycemic control and insulin use were independently associated with neuropathy in people with NIDDM. Whether insulin use represents another marker for severity of the metabolic disturbance or is an independent risk factor for neuropathy requires further study. We could not confirm associations of neuropathy with height, with nephropathy, or with retinopathy, independent of duration of diabetes.

Genetic polymorphisms of microsomal and soluble epoxide hydrolase and the risk of Parkinson's disease.

Oxidative stress is hypothesized to play a major role in the destruction of dopaminergic neurons, which is associated with Parkinson's disease. Epoxides are potentially reactive intermediates formed through the oxidative metabolism of both exogenous and endogenous substances that contribute to cytotoxic damage mediated by oxidative stress. The microsomal (EPHX1) and soluble (EPHX2) epoxide hydrolases function to regulate the oxidation status of a wide range of xenobiotic- and lipid-derived substrates; therefore, interindividual variation in these pathways may mitigate epoxide-related cellular injury. In this investigation, we examined the potential association between the risk of Parkinson's disease and genetic variation within the EPHX1 and EPHX2 genes. Fluorescent 5' nuclease-based assays were developed to identify the allelic status of individuals with respect to specific single nucleotide polymorphisms in exons 3 and 4 of the EPHX1 gene and exons 8 and 13 of the EPHX2 gene. EPHX1 and EPHX2 genotype data were obtained from 133 idiopathic Parkinson's disease patients and 212 control subjects matched on age, gender and ethnicity. No statistically significant differences were found in the distribution of the reference and variant alleles between Parkinson's disease and control subjects, or when results were stratified by gender. Therefore, common polymorphisms within EPHX1 and EPHX2 do not appear to be important risk factors for Parkinson's disease.

Field testing of a minimal record of disability in multiple sclerosis: the United States and Canada.

The IFMSS Minimal Record of Disability (MRD) in Multiple Sclerosis was field tested at eight medical centers in the U.S. and Canada. The goals were to conduct a qualitative and quantitative evaluation of the MRD. Assessment were completed on 249 patients with definite MS by neurologists and allied health professionals. Effective administration required some study and practice. Refinement of some unclear wording and awkward format will improve ease of administration. The MRD fit well into clinic routines and was accepted by staff and patients. Scoring presented few problems and these were related to overlap among the MRD scales, poor wording, and content not appropriate to MS. Quantitative evaluation of the MRD indicated that Incapacity Status primarily reflects disability in mobility and self-care when used as a composite score. Heterogeneity of content in Incapacity Status suggests that summed scores be used cautiously. Both Incapacity and Environmental Status had high levels of reliability and high correlations with established measures of impairment in MS. Inter-rater agreement of the ISS and ESS were also high. Once some necessary revisions are made, the MRD should be well on its way to achieving the IFMSS goal of developing a brief, reliable, valid, and appropriate instrument acceptable to a wide variety of workers in MS.

A comparison of dementia in Alzheimer's disease and multiple sclerosis.

We compared results of comprehensive neuropsychological testing in 42 patients with clinically diagnosed Alzheimer's disease (AD) and in an equal number of patients with clinically definite chronic-progressive multiple sclerosis. Age, sex, and education were controlled using demographically corrected T scores based on a large normal sample. Both groups showed significant impairment on the test battery, but the degree of dementia was more severe in the patients with AD. A deviation score analysis, controlling for overall level of cognitive impairment, revealed significant differences between the groups. Alzheimer's disease was associated with relatively greater impairment of learning, memory, and verbal skills, whereas the MS group showed greater relative impairment of attention, incidental memory, and psychomotor functions. These data suggest that both the degree and pattern of mental impairement differ in patients with AD and patients with multiple sclerosis. Our results support a distinction between "gray matter" and "white matter" dementia, and may help clarify the issue of "cortical" vs "subcortical" dementia by demonstrating neuropsychological differences based on secure neuropathologic distinctions.

Cognitive loss in multiple sclerosis. Case reports and review of the literature.

Neuropsychological and neuroradiologic evidence of cerebral lesions is described for 12 patients with multiple sclerosis in whom cognitive disability was far greater than any other neurologic disability. Cognitive dysfunction resulted in significant functional impairment at work or home in three fourths (9 of 12) of the patients described here, despite mild physical disability (mean Kurtzke Expanded Disability Status Scale score, 3.2). A unique feature of the neurologic examination in these patients was the presence of prominent frontal release signs (gait apraxia and placing response) in the lower extremities. Two new scales, a Cognitive Function Scale and a Frontal Release Scale, were adapted for the investigation of these patients. The extensive literature relating to cognitive dysfunction in multiple sclerosis is reviewed and discussed with regard to its clinical relevance.

Neurology practice patterns in Colorado.

Eighty-one percent (47/58) of private-sector neurologists in Colorado responded to a mail survey of practice patterns. We evaluated patient load, degree of principal versus consultative care, and use of neurodiagnostic tests. Broad areas of neurologic education that were perceived to have been lacking during residency training were also addressed. Eight-four percent (41/49) of responding neurologists agreed to participate in a more comprehensive prospective study of neurology practice patterns. The prospective data will provide information to determine how many neurologists are needed and the applications for neurologic education.

Outcome of surgery for thoracic outlet syndrome in Washington state workers' compensation.

OBJECTIVE: To determine the predictors of outcome of thoracic outlet syndrome (TOS) surgery in a population-based cohort of injured workers. METHODS: All injured workers in the Washington State Workers' Compensation system who received TOS surgery during 1986 to 1991 were identified by computerized bill payment records and validated by medical record review (n = 158). The main outcome measure was work disability status 1 year after surgery. Additional functional status and quality of life outcomes were determined by telephone survey an average of 4.8 years after operation. A sample of workers with a TOS diagnosis who did not receive surgery during 1987 to 1989 were identified as a comparison group (n = 95). RESULTS: Sixty percent of workers were still work disabled 1 year after surgery. The strongest predictors of remaining disabled were the amount of work disability before surgery (OR = 1.85; 95% CI, 1.51 to 2.28), longer time between injury and TOS diagnosis (OR = 1.34; 95% CI, 1.09 to 1.64), and older age at injury (OR = 1.07; 95% CI, 1.00 to 1.13). There was no relationship between type of surgery, presence of any provocative tests, or experience of surgeon and work disability outcome. In follow-up surveys an average of 4.8 years after surgery, 72.5% of workers still reported they were "limited a lot" in vigorous activities. Compared with a nonsurgical sample of TOS patients, those receiving surgery had 50% greater medical costs and were three to four times more likely to be work disabled. CONCLUSIONS: The outcome of TOS surgery among injured workers is worse than has generally been reported. The nonspecific neurogenic TOS diagnosis, the complexity of workers' compensation cases, and the adverse event profile are likely substantial contributors to the worse outcomes reported here. Well-designed prospective studies and randomized trials are required to elucidate any role of TOS surgery in nonspecific TOS.

A prospective study of principal care among Colorado neurologists.

We initially surveyed the practice patterns of 24 private sector neurologists in Colorado between June and September, 1985, having chosen representative practices from each of 4 practice types (solo [6], nonsolo single discipline [11], nonsolo multispecialty [4], and nonsolo HMO [3]) and from both urban (14) and rural (10) practice locations. Among 2,373 consecutive new patient visits initially surveyed, we reexamined 2,359 (99%) charts 1 year later to investigate patterns of principal care. We defined principal care as 2 or more follow-up visits in the year following the initial office visit. One-fifth of initial visits received principal care, and the mean number of follow-up visits per year among those receiving principal care was 4 (range, 2 to 32 visits). The best indicators of principal care were Medicare coverage, a classic neurologic diagnosis (seizure, stroke), rural practice location, and solo neurology practice. The best indicators of consultative care were self-pay coverage, a diagnosis of musculoskeletal, psychiatric, or pain disorder, urban practice location, and HMO neurology practice. Age, sex, race, and type of referring physician were unimportant in determining subsequent principal care. Projections of future manpower needs must reflect both consultative as well as principal care services provided by neurologists, as well as the cost-effectiveness of such care.

Correlation of neuropsychological and MRI findings in chronic/progressive multiple sclerosis.

Sixty patients with chronic/progressive MS received a newly assembled neuropsychological screening battery (NSB) and a brain MRI. A neuroradiologist blinded to NSB findings quantified cerebral lesions on MRI. We developed weighted brain area lesion scores according to number and size of cerebral lesions. Patients who were impaired on NSB testing had a significantly higher mean bihemispheric lesion score (X = 26.1) than those who were unimpaired (X = 17.4); this MRI lesion rating score correlated significantly with the cognitive summary score of the NSB (r = 0.35, p less than 0.01). However, we did not find a significant correlation between the Kurtzke Expanded Disability Status Scale and any MRI or NSB summary measures. Compared with the Mini-Mental State Exam (MMSE), the NSB cognitive summary score yielded a prevalence estimate for cognitive impairment that is more consistent with previous findings in chronic/progressive MS. The NSB is a useful screening test for cognitive dysfunction in chronic/progressive MS because of its relationship to cerebral lesions on MRI and its greater sensitivity than the frequently used MMSE.

The effects of pregnancy in multiple sclerosis: a retrospective study.

We reviewed the medical records of 178 women with multiple sclerosis to evaluate the number of completed pregnancies, current disability status, and relationship of pregnancy to onset of MS symptoms. We found no differences in the long-term disability of women with no pregnancies, one pregnancy, or two or more pregnancies. Women who had initial symptom onset in pregnancy experienced less subsequent disability than women whose symptoms began before or after pregnancy. Therefore, pregnancy per se or number of pregnancies has no effect on subsequent disability.

Multiple sclerosis sibling pairs: clustered onset and familial predisposition.

We evaluated 48 relapsing-remitting multiple sclerosis (R/R MS) sibling pairs derived from 44 families for age and date of onset of MS symptoms, clinical course, and family history of MS. Age- and sex-matched R/R MS clinic patients provided a statistical comparison group. The age of onset tended to cluster within multiplex families. The initial symptom of MS occurred within 5 years of age in 30/48 sibling pairs compared with 16/48 controls. A positive family history of MS (other than siblings) was present in 43% of the multiplex families compared with 20% among simplex controls. In 1st-, 2nd-, and 3rd-degree relatives who had lived into the age at risk, 22/1,134 family members of multiplex sibling pairs had probable or definite MS compared with 10/1,215 control family members. Age of onset clustering in siblings concordant for R/R MS and an increased risk of MS in other family members suggest that factors influencing disease onset may be in part inherited in these kindreds.

A genetic polymorphism of MAO-B modifies the association of cigarette smoking and Parkinson's disease.

In a population-based case-control study, we found a reversal of the association of cigarette smoking with Parkinson's disease (PD) in relation to the monoamine oxidase B intron 13 genetic polymorphism. A reduced PD risk related to pack-years of smoking was detected for persons with the G allele, whereas an opposite effect was found among persons with the A allele. These results indicate an unexplained interaction between cigarette smoking and this genetic polymorphism.

MR nerve imaging in a prospective cohort of patients with suspected carpal tunnel syndrome.

OBJECTIVES: To evaluate the reliability and diagnostic accuracy of high-resolution MRI of the median nerve in a prospectively assembled cohort of subjects with clinically suspected carpal tunnel syndrome (CTS). METHODS: The authors prospectively identified 120 subjects with clinically suspected CTS from five Seattle-area clinics. All subjects completed a hand-pain diagram and underwent a standardized nerve conduction study (NCS). The reference standard for determining CTS status was a classic or probable hand pain diagram and NCS with a difference >0.3 ms between the 8-cm median and ulnar peak latencies. Readers graded multiple imaging parameters of the MRI on four-point scales. The authors also performed quantitative measurements of both the median nerve and carpal tunnel cross-sectional areas. NCS and MRI were interpreted without knowledge of the other study or the hand pain diagram. RESULTS: Intrareader reliability was substantial to near perfect (kappa = 0.76 to 0.88). Interreader agreement was lower but still substantial (kappa = 0.60 to 0.67). Sensitivity of MRI was greatest for the overall impression of the images (96%) followed by increased median nerve signal (91%); however, specificities were low (33 to 38%). The length of abnormal signal on T2-weighted images was significantly correlated with nerve conduction latency, and median nerve area was larger at the distal radioulnar joint (15.8 vs 11.8 mm(2)) in patients with CTS. A logistic regression model combining these two MR variables had a receiver operating characteristic area under the curve of 0.85. CONCLUSIONS: The reliability of MRI is high but the diagnostic accuracy is only moderate compared with a research-definition reference standard.

Environmental chemical exposures and disturbances of heme synthesis.

Porphyrias are relatively uncommon inherited or acquired disorders in which clinical manifestations are attributable to a disturbance of heme synthesis (porphyrin metabolism), usually in association with endogenous or exogenous stressors. Porphyrias are characterized by elevations of heme precursors in blood, urine, and/or stool. A number of chemicals, particularly metals and halogenated hydrocarbons, induce disturbances of heme synthesis in experimental animals. Certain chemicals have also been linked to porphyria or porphyrinuria in humans, generally involving chronic industrial exposures or environmental exposures much higher than those usually encountered. A noteworthy example is the Turkish epidemic of porphyria cutanea tarda produced by accidental ingestion of wheat treated with the fungicide hexachlorobenzene. Measurements of excreted heme precursors have the potential to serve as biological markers for harmful but preclinical effects of certain chemical exposures; this potential warrants further research and applied field studies. It has been hypothesized that several otherwise unexplained chemical-associated illnesses, such as multiple chemical sensitivity syndrome, may represent mild chronic cases of porphyria or other acquired abnormalities in heme synthesis. This review concludes that, although it is reasonable to consider such hypotheses, there is currently no convincing evidence that these illnesses are mediated by a disturbance of heme synthesis; it is premature or unfounded to base clinical management on such explanations unless laboratory data are diagnostic for porphyria. This review discusses the limitations of laboratory measures of heme synthesis, and diagnostic guidelines are provided to assist in evaluating the symptomatic individual suspected of having a porphyria.

Association of a polymorphism in intron 13 of the monoamine oxidase B gene with Parkinson disease.

Monoamine oxidase B (MAO-B) is an enzyme that has relevance for Parkinson disease (PD) because of its roles in catabolizing dopamine and potentially activating exogenous neurotoxicants. A polymorphism of the gene encoding MAO-B has been identified as a single base change (A or G) in intron 13 of the X chromosome. The A allele was previously associated with an approximately twofold risk of PD. The present study compared A and G allele frequencies between newly diagnosed idiopathic PD cases and a control group free of neurodegenerative diseases. All study subjects were Caucasian. Cases were 37 men and 25 women, age 37-80 years; controls were 50 men and 29 women, age 45-82 years. MAO-B genotype was determined by the allele-specific polymerase chain reaction on DNA extracted from peripheral lymphocytes. In complete contrast to previous studies, elevated risks were detected with the G allele. The age-adjusted odds ratio for the G allele in males was 1.87 ((95% confidence interval) 0.78-4.47). Among females the age-adjusted odds ratios were 5.00 ((95% confidence interval) 1.13-22.1) for the GA genotype and 5.60 ((95% confidence interval) 1.01-30.9) for the GG genotype. These findings, although of limited statistical precision, suggest that the G allele of this MAO-B polymorphism may relate to PD risk.

Referral bias in multiple sclerosis research.

Referral bias is a significant problem affecting the generalizability of clinical studies conducted in a university setting. To examine referral bias in our university-based multiple sclerosis referral center, we analyzed the characteristics of referral center patients compared to the population-based group of multiple sclerosis patients from which the referral center patients originated. The referral center patient group differed from those that remained in the population-based group in the following important ways: (1) they were younger, (2) they had more mobility impairment for their age, (3) disabled females were overrepresented compared to disabled males, (4) they more often reported recent disease worsening, (5) they had a higher frequency of early diagnosis supported by laboratory tests, and (6) they more often relied on neurologists and therapists for routine care of their disease. The multiple sclerosis referral center setting would appear to be ideal for the conduct of intervention trials, but inadequate for collecting representative natural history data.

The EcoRV genetic polymorphism of human monoamine oxidase type A is not associated with Parkinson's disease and does not modify the effect of smoking on Parkinson's disease.

We previously observed an association with Parkinson's (PD), and modification of the effect of smoking on PD, by a polymorphism of the monoamine oxidase B (MAO-B) gene. The A form of monoamine oxidase (MAO-A) shares with MAO-B many characteristics that could be relevant to PD, especially proneuroxicant bioactivation and dopamine metabolism. MAO-A is also inhibited by tobacco smoke, which bears an apparent protective effect on PD. We investigated the possibility that MAO-A genetic variants may also be involved in predisposition to PD and in modification of the effect of smoking. Three-hundred and seventy-one subjects--145 idiopathic PD cases and 226 age/gender-matched controls--were genotyped for the EcoRV polymorphism of MAO-A gene which has been related to increased enzyme activity. MAO-A EcoRV polymorphism was neither significantly associated with PD nor did it modify the inverse relationship with smoking. These results suggest that the EcoRV polymorphism of MAO-A is not an important biomarker of PD risk.

A pilot study of occupational and environmental risk factors for Parkinson's disease.

Increasingly, the etiology of Parkinson's disease (PD) has been linked to exposures to environmental toxicants. This epidemiologic pilot study used a self-administered questionnaire among 34 PD cases and 22 other neurology clinic control patients. All subjects were at least 40 years old. Risk factors investigated included occupation, well-water use, pesticide use, metal exposures, medical history, smoking, alcohol consumption, and drug use. Twenty-six percent of the male PD cases reported having been employed in farming versus eleven percent for male controls (OR = 3.1, 95% C.I. = 0.3 to 35). Sixteen percent of male cases versus none of the controls reported employment as welders. No clear trends involving exposure to either occupational or home pesticides emerged. In assessing occupational exposures to metals, aluminum and copper exposures tended to be more common among male cases than male controls. Additionally, as reported in other studies, smoking showed an inverse relationship with PD. Although the findings reported here are provocative, these results are statistically imprecise and must be interpreted cautiously because of the small number of subjects included in the study.

Mitochondrial ND1 sequence analysis and association of the T4216C mutation with Parkinson's disease.

Mitochondrial dysfunction originating from mutations in Complex I genes may play a role in the pathogenesis of Parkinson's disease (PD). In this study, the entire ND1 coding sequence was sequenced in 84 newly diagnosed PD cases and 127 age/gender-matched controls. Numerous missense mutations were found at low frequency (<5%), whereas a thymidine to cytosine missense mutation at position 4216 that results in the replacement of tyrosine with histidine was found in 25% of the PD case samples and in 18% of the controls. When calculated according to gender, the 4216 mutation was observed in 26% of the male cases versus 16% of male controls (Odds Ratio [OR] = 1.85; 95% CI = 0.79-4.34). In contrast, females exhibited approximately equal frequencies among cases (22.5%) and controls (21%), yielding an OR of 1.08 (95% C.I. = 0.36-3.22). The findings indicate only a weak association of this genetic variant with PD.