Slee M, Selvan A, Donaghy M. Neurology 2007; 69:1680-1687.
Authors look at 47 patients retrospectively and found that strict adherence to consensus criteria was a barrier to treatment. Neither conduction block nor antibody status is a reliable predictor of treatment responsiveness.
Some of the pearls in the article: Conduction block was present in 66%; GM1 antibody in a minority (25 %) and was not associated with conduction block. 27 % had lower limb onset, bu tin those patients, arm weakness typically developed subsequently. Patients may have an acute or subacute onset with spontaneous resolution. MMN can be PRECIPITATED by the use of steroids, and is usually not helped by steroids. It "is evident from our study and others (Pakkiam AS, Perry GJ, Multifocal motor neuropathy without overt conduction block. Muscle Nerve 1998; 21: 243-245) that IVIG responsive MMN occurs regularly without conduction block being demonstrated." "A redefinition of conduction block which eliminates temporal dispersion as a restrictive factor and which helps predict IVIG responsiveness, (see Ghosh and Busby, JNNP 2005) categorized a further 15 % of our patients with conduction block." "Our study suggests a decrement if IVIG responsiveness over time." Using higher doses of 1.92 g/kg/6 weeks does better than Utrecht group of .54 g/kg /mo. Disability self reports were more accurate than MRC scale scores with overall clinical change.
"Recognition of the clinical picture is the mainstay of diagnosis of MMN outside the researchg setting. Weakness in nonwasted muscles and differential weakness across a common terminal motor nerve are the cardinal features. Differential finger extension weakness is a frequent early manifestation likely reflecting vulnerabilities of the terminal branches of the posterior interosseous nerve."
Blogger note-- this citation is extremely important for dealing with insurance companies to obtain approval for IVIG.
Take away-- to take care of the patient, don't look at the test, be a doctor and a neurologist.