Segmental mixed nerve conduction studies in ulnar neuropathy at the elbow.

Conventional nerve conduction and electromyography may not be adequate in localizing ulnar neuropathy at the elbow, particularly in longstanding lesions with severe axon loss. Ratios of wrist to elbow and elbow to axilla segmental ulnar mixed nerve amplitudes were determined in 11 patients with ulnar neuropathy at the elbow. In 20 control subjects, the mean ratio was 1.06 +/- 0.25 (standard deviation). All patients had ratios less than two standard deviations of the control mean ratio. This method is a useful adjunct to conventional nerve conduction techniques in the localization of ulnar neuropathy at the elbow.     

Calf hypertrophy in spinal muscular atrophy.

Two unusual variants of spinal muscular atrophy with gross calf hypertrophy of adolescent onset were studied clinically, electrophysiologically and histologically. There have been reports of several variants within this group of spinal muscular atrophies. In Singapore we encountered 2 patients who had an unusual variant of spinal muscular atrophy not well recognised previously with only 3 reports recorded to date. Our cases presented with gross calf hypertrophy and a slowly progressive clinical course. Nerve conduction studies were normal but electromyogram and muscle biopsies revealed a chronic denervation problem of probable central origin.     

Dose-dependent protective effect of coffee, tea, and smoking in Parkinson's disease: a study in ethnic Chinese

INTRODUCTION: Few studies have examined the relationship of coffee and tea in Parkinson's disease (PD). The potential protective effect of coffee intake and risk of PD has not been studied in a Chinese population. There is a high prevalence of caffeine takers among Chinese in our population. OBJECTIVE: We undertook a case control study to examine the relationship between coffee and tea drinking, cigarette smoking, and other enviromental factors and risk of PD among ethnic Chinese in our population. METHODS AND RESULTS: 300 PD and 500 population controls were initially screened. Two hundred case control pairs matched for age, gender, and race were finally included in the analysis. Univariate analysis revealed significant association of PD with coffee drinking (p<0.0005), tea drinking (p=0.019), alcohol drinking (p=0.001), cigarette smoking (p<0.0005), and exposure to heavy metals (p=0.006). Conditional logistic regression analysis demonstrated that amount of coffee drunk (OR 0.787, 95%CI 0.664-0.932, p=0.006), amount of tea drunk (OR 0.724, 95%CI 0.559-0.937, p=0.014), number of cigarettes smoked (OR 0.384, 95%CI 0.204-0.722, p=0.003), history of heavy metal and toxin exposure (OR 11.837, 95%CI 1.075-130.366, p=0.044), and heart disease (OR 5.518, 95%CI 1.377-22.116, p=0.016) to be significant factors associated with PD. One unit of coffee and tea (3 cups/day for 10 years) would lead to a 22% and 28% risk reduction of PD. One unit of cigarette smoke (3 packs/day for 10 years) reduced the risk of PD by 62%. CONCLUSIONS: We demonstrated a dose-dependent protective effect of PD in coffee and tea drinkers and smokers in an ethnic Chinese population. A history of exposure to heavy metals increased the risk of PD, supporting the multifactorial etiologies of the disease.     

Adult onset polymyositis/dermatomyositis: clinical and laboratory features and treatment response in 75 patients.

OBJECTIVES--To determine possible similarities and differences in clinical and laboratory features and treatment response between patients in Singapore with polymyositis (PM) and dermatomyositis (DM) and reported series. METHODS--Case records of adult patients (16 years old and above) referred to the 3 main electromyographic (EMG) laboratories in Singapore between 1 June 1986 and 31 May 1991 were reviewed if the referring diagnosis was myositis or myopathy for investigation. A computer search for adult patients with a diagnosis of PM/DM (ICD codes 710.3, 710.4, 517.8) who attended the main rheumatology and neurology centre during this period was also carried out. The criteria for PM/DM proposed by Bohan and Peter was adopted. RESULTS--The incidence of PM/DM was 7.7 cases per million population per year. There were 35 PM and 40 DM cases with a median age at diagnosis of 50.7 years (SD: 16.7) and significantly more females in the PM group (p < 0.05). At presentation, 86.7% had proximal myopathy, 34.7% had arthralgia/arthritis and 18.7% had cutaneous vasculitis. The creatine kinase level was elevated in 89.3% of patients and positive EMG and muscle biopsy in 79.4% and 76.4% respectively. Systemic lupus erythematosus was the commonest associated connective tissue disease. The percentage of patients with malignancy was higher in DM compared with PM (p < 0.01) and they were significantly older (mean age 61.8 years) (p < 0.001). Patients who achieved remission were significantly younger (mean age 46.4 years, p < 0.05). The overall mortality rate was 26.7% with infection and malignancy as the main causes of death. CONCLUSION--The results of the study suggest ethnicity does not influence the expression of PM/DM in view of the considerable similarities in frequency and clinical expression of disease in the population studied compared with series from other countries.     

Absence of A673T amyloid-β precursor protein variant in Alzheimer's disease and other neurological diseases

The rare variant A673T in the amyloid-β precursor protein (APP) gene has been shown to reduce the risk of cognitive impairment. We genotyped the variant in 8721 Asian individuals comprising 552 with Alzheimer's disease and vascular dementia, 790 with Parkinson's disease, and 7379 controls. The A673T variant was absent in all of the subjects. Our finding suggests that the A673T protective variant is not relevant in our Asian population. Studies in other ethnic populations would clarify whether this variant is specific to specific races/ethnicities.     

Superficial peroneal sensory and sural nerve conduction studies in peripheral neuropathy.

The objective of this study was to prospectively evaluate sensory nerve conduction studies (NCS) in the distal lower limbs in the electrodiagnosis of peripheral neuropathy. We prospectively studied 316 consecutive patients with surface stimulation and recording, in comparison with 90 control subjects. A total of 310 patients were found to have lower limb sensory NCS abnormalities. In these patients, the rate of detection of peripheral neuropathy with superficial peroneal NCS (88.5%) was significantly higher (P<0.001) compared with sural NCS (75%). The superficial peroneal NCS appeared to have a higher detection rate for peripheral neuropathy in our study, and its study can be adjunctive to sural NCS.     

Analysis of 14 LRRK2 mutations in Parkinson's plus syndromes and late-onset Parkinson's disease.

The pleomorphic pathology of postmortem LRRK2-positive patients and the frequent association with late-onset Parkinson's disease (LOPD) symptoms suggest that LRRK2 mutations may play a role in Parkinson's Plus disorders and LOPD. Published studies primarily focus on the common G2019S mutation. Analysis of a spectrum of LRRK2 mutations in Parkinson's Plus disorders has yet to be reported. We investigated 14 leucine-rich repeat kinase 2 (LRRK2) mutations in a cohort of Parkinson's Plus disorders and LOPD. A total of 458 patients with progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal ganglionic degeneration (CBGD), atypical Parkinsonism (AP), and LOPD were screened for 14 mutations that span exons 19 to 41 of the LRRK2 gene. Among the LOPD cases, 1 patient was found to harbor the R1441C mutation. He presented with typical features of PD at age of 58 years old and responded well to levodopa. We did not detect any of the 14 mutations in PSP, MSA, CBGD, and AP patients. We highlight the first case of LRRK2 R1441C mutation in late onset sporadic PD of non-European ancestry. Furthermore, extensive mutational screen found LRRK2 mutations to be rare among patients who presented with PSP, MSA, CBGD, and AP.     

Clinical and electrophysiological aspects of distal ulnar neuropathy

OBJECTIVES: To evaluate the use of fixed distance side to side comparison of abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) studies in the diagnosis of distal ulnar neuropathy. MATERIALS AND METHODS: Thirty normal controls underwent ADM and FDI CMAP studies bilaterally at a fixed ADM recording to stimulating point distance of 6 cm. Side to side mean latency differences to both muscles were calculated. Twenty patients with suspected unilateral distal ulnar neuropathy from routine nerve conduction studies had positive results when compared with controls. RESULTS: The upper limit of normal for side to side mean latency difference at 3 SD above the mean was 0.394 and 0.474 ms for ADM and FDI, respectively. All 20 patients had side to side mean CMAP latency difference above 3 SDs in the ADM, FDI or both muscles. Fifty percent of cases had involvement of the superficial sensory branch. CONCLUSIONS: Fixed distance side to side CMAP latency comparison is a useful electrodiagnostic adjunct for distal ulnar neuropathy. Trauma was the most common aetiology in the 20 reported cases. Correlation was found between aetiological factors and sites of lesions as localized with this method.