PracticeUpdate: Neurology - Winter 2018

CONFERENCE COVERAGE 26

Immune Globulins Continue to Be theMost Effective Treatment for Multifocal Motor Neuropathy Most patients still deteriorate over the long term I mmune globulins continue to be effective, but most patients still deteriorate over the long term. Dr. Oberreiter explained that multifocal motor neuropathy is a rare immune-mediated neuropathy that leads to slowly progressive, asymmetric muscle weaknesses. Electrophysiological motor con- duction block is the hallmark of the disorder.

Eva-Maria Oberreiter, MD, of the Medical University of Inns- bruck, Austria, and colleagues surveyed Austrian individuals with multifocal motor neuropathy to review epidemiological and clini- cal features and their response to treatment. They also compared results with those of published studies. Austrian neurologists were contacted through the Austrian Neu- rological Society and asked to provide anonymized data on individuals with multifocal motor neuropathy in their care. A total of 57 individuals reported were diagnosed between 1993 and 2017. Clinical, electrophysiological, and laboratory data, as well as IV immune globulin use and treatment outcomes were assessed. The point prevalence of multifocal motor neuropathy in Austria was found to be 0.65 out of 100,000. The male-to-female ratio was 2.2:1, and median age of symptom onset was 45 years. Mean diagnostic delay was 5.4 ± 8.33 years. Mean diagnostic delay was 17 years when symptoms began between 1982 and 1986, and 0.9 years when symptom onset was between 2012 and 2017. Multifocal motor neuropathy typically began in the upper extremity (77.2%) and in distal muscles (87.7%). Conduction block was found in 95% of individuals, most frequently in the ulnar and median nerves. Forty-three percent showed immune globulin M antibod- ies against GM1. Overall, 51 of 57 individuals were treated with IV immune globu- lin at median intervals of 4 weeks at a mean dosage of 1.55 g/kg of body weight. High muscle strength was a favorable prognos- tic factor. Elevated serum immune globulin M anti-GM1 antibody titer, muscle atrophy, and long intervals of treatment were nega- tive prognostic factors. Duration of treatment correlated with outcome: the longer the treatment, the worse the outcome. IV immune globulin improved muscle strength but frequently lost effectiveness after >7 years.

With early diagnosis and treatment with intravenous immune glob- ulins, multifocal motor neuropathy is treatable, at least during the first years of disease. The rarity of multifocal motor neuropathy has limited the number of studies of clinical features and response to long-term treatment. Dr. Oberreiter concluded that the prevalence of multifocal motor neuropathy in Austria is similar to the few reports from other coun- tries. The present results corroborate previous results in terms of clinical, electrophysiological, and laboratory features of multifocal motor neuropathy. Intravenous immune globulins continue to be the most effective treatment for multifocal motor neuropathy. In most cases, however, deterioration occurs over the long term. Jung Im Suk, MD, of the Catholic University of Daegu, School of Medicine in Daegu, South Korea, and colleagues described a case of multifocal motor neuropathy that highlighted the complemen- tary role of ultrasonography. A 40-year-old man presented with a 2-year history of progressive left-sided weakness without sensory symptoms. A nerve con- duction study revealed partial conduction block in two nerves. Anti-GM1 antibody was negative and other laboratory studies, unremarkable. Ultrasonography showed focal nerve enlargement of the right median nerve at the forearm and left ulnar nerve at the elbow. His weakness improved completely after intravenous immune glob- ulin. Ultrasonography revealed focal enlargement of the median and ulnar nerves. Cross-sectional areas of the right and left median nerves at the wrist were normal, as were those of the left median nerve at the forearm, the right and left median nerves at the upper arm, and the right ulnar nerve at the elbow. However, cross-sectional areas of the right median nerve at the forearm and the left ulnar nerve were increased at 15.2 mm 2 and 11.1 mm 2 , respectively. Cross-sectional area of the right and left median nerves at the upper arm was normal. Cross-sectional area of the right and left ulnar nerves at the wrist was normal. Cross-sectional area of the right ulnar nerve at the elbow was normal (3.5 mm 2 ), but of the left ulnar nerve, increased at 11.1 mm 2 . Dr. Im Suk explained that multifocal motor neuropathy is treatable, and its differentiation from lower motor neuron disease is crucial. Evidence of conduction block or positive immune globulin M anti-GM1 is considered an important diagnostic marker. Some indi- viduals with atypical multifocal motor neuropathy, however, exhibit no detectable conduction block nor anti-GM1 antibodies. Dr. Im Suk concluded that ultrasonography can be valuable in sup- porting the diagnosis of multifocal motor neuropathy. www.practiceupdate.com/c/70783

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