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Optic neuritis (ON) is associated with a 38% ten-year risk of developing multiple sclerosis (MS) in Western populations, but the corresponding risk in non-Western populations is unclear. We conducted this study to estimate the risk of progression to MS after an episode of ON in a South Asian population.
Two hundred and fifty-three patients with idiopathic ON were identified by reviewing records of visual evoked potentials and chart notes from a single academic center spanning the years 1990-2007. A structured telephone interview was then conducted to identify patients who had subsequently received a diagnosis of MS. The diagnosis was corroborated from chart notes, where possible. Cumulative probability of conversion to MS was calculated using Kaplan-Meier survival analysis.
The five-year risk of developing MS was 14.6% and the ten-year risk was 24%. Patients (N=218) who had one or more typical demyelinating lesions on baseline brain magnetic resonance imaging (MRI) had a 68% 10-year risk; those with no lesions or non-typical lesions had a 14% risk (p<0.001). Female gender, recurrent ON, and occurrence of ON in winter months were also associated with increased risk (p≤ 0.001). Severity of ON and likelihood of detecting cerebrospinal fluid (CSF) oligoclonal bands were higher in patients who developed MS.
Idiopathic ON in Pakistan carries a lower risk of progression to MS compared with Western data. As in Western populations, however, presence of abnormal baseline brain MRI and CSF oligoclonal bands correlate with increased MS risk.
Electromyography (EMG) for suspected cervical or lumbosacral root compression is often negative, producing expense and physical discomfort that could have been avoided. To improve patient selection for testing, we sought to identify clinical features that would accurately predict presence of radiculopathy on EMG.
Adult patients consecutively evaluated for suspected cervical or lumbosacral root compression at an academic clinical neurophysiology laboratory were prospectively enrolled. Presence of clinical features suggesting root disease (neck or back pain, dermatomal pain or numbness, myotomal weakness, segmental reflex loss, and straight leg-raising) was recorded prior to testing. EMG examination to confirm root compression was conducted per standard protocols. Analysis was based on computation of sensitivity, specificity, predictive values, and accuracy.
A total of 200 patients (55% male; mean age 46.4 years; 38% suspected of cervical and 62% of lumbosacral disease) were included. EMG evidence of root disease was detected in 31% of cervical and 62% of lumbosacral referrals. Dermatomal pain was the most sensitive, and segmental reflex loss and myotomal weakness the most specific individual predictors of root disease. Combined presence of dermatomal pain or numbness with segmental reflex loss and myotomal weakness approached specificities of 78% (lumbosacral disease) and 99% (cervical disease). In all cases, myotomal weakness was the most accurate predictor of root disease.
The diverse symptoms and signs of cervical and lumbosacral root compression predict a positive electrodiagnosis of radiculopathy with varying degrees of accuracy, and may be used to guide patient selection for EMG testing.
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