Spotlight On: Neuralgic Amyotrophy
NEURALGIC AMYOTROPHY: DR. VAN ALFEN’S TAKE-HOME POINTS
• NA is not a rare disease and occurs in roughly one per 1,000 in general practice.
• It’s a clinical diagnosis first and foremost, and not just by exclusion.
• Early treatment with a short course of oral steroids may abort the attacks.
• Current standard rehabilitation treatment is often not effective, but a specific approach focusing on scapular coordination and energy management gives promising results in treating the long-term consequences.
Neuralgic amyotrophy (NA), also known as Parsonage Turner syndrome or idiopathic brachial plexus neuropathy, is a painful, focal peripheral nervous system disorder that mainly affects brachial plexus nerves in the shoulder and upper limb. While traditionally thought to be rare, a recent prospective incidence study found an incidence rate of one per 1,000 in general practice, presumably due to increased awareness of the disorder and improved clinical diagnostic skills taught to the participating physicians.1
Neuralgic amyotrophy is generally assumed to be an immune-mediated inflammatory disorder that occurs in people with a genetic predisposition and which can be triggered by both mechanical and immunological events. About half the patients report an antecendent infection, surgical procedure, strain or childbirth preceding their attacks; which all have in common that they activate the immune system in some way. Many different infectious causes have been reported as a trigger, but recently special attention is being paid to hepatitis E virus as a potential trigger.
There are two interesting reports of NA epidemics that underpin the hypothesis that in addition to a preceding infection mechanical factors or a specific genetic background are also prerequisites to trigger an attack. The first epidemic occurred from 1949 to 1953 in the northeast of Czechoslovakia. During this four-year period 265 cases were noted, with an incidence rising from 1.1/1000/year in 1949 to 7.3/1000/year in 1953. The highest incidence rates were found in one particular factory among workers operating a hosiery knitting machine, which involved holding their bent right arm outstretched at 100° elevation for eight hours a day. The number of new cases showed a sharp decline when in November 1953 the main water supply in the lodgings housing factory personnel were replaced. In many affected workers, Coxsackie virus type A2 was isolated from stool.
A second smaller-scale outbreak of NA occurred from April to June 1997 in the southwest of the United States of America in a native American Indian population, in which eight individuals became affected after an antecedent viral illness that was not further specified.
Very recently, there has apparently been a sharp increase in incidence of NA in the North Carolina area in the United States. Physicians at the East-Carolina Brody School of Medicine are currently analyzing these cases in cooperation with the regional Center for Disease Control and Prevention. Hopefully the results will be available soon.
Editor’s Note: See the upcoming November/December edition of Practical Neurology® for a full case report on the recent increase in NA in North Carolina.
Nens van Alfen, MD, PhD, is Medical Director of CNP laboratory at Radboud University Medical Center in Nijmegen, Netherlands. She has co-authored several studies on NA.
1. van Alfen, N., et al. PLoS One. 2015 May 27;10(5).