Lower motor neuron disease and signs of dysimmunity

Twenty-two patients (12 men, 10 women, age range 16 to 60) affected with an adult-onset, sporadic, lower motor neuron disease were studied. Motor weak ness was associated with a severe muscular atrophy but never in a periphera l nerve distribution. Weakness predominated in the proximal parts of the li mbs in 3 cases, in distal parts in 10 cases involving predominantly the upp er limbs in 10. It was diffuse in all four limbs in six cases and was monom elic in the last 2 two others. Reflexes were generally lost in weak muscles. Electrodiagnostic findings co nsisted of pure motor axonal features, subtle sensory involvement was prese nt in 3 cases with an IgM monoclonal gammopathy, in only one case the neuro logical syndrome was associated with a lymphoproliferative disorder despite complete investigations. All patients had dysimmune biological features (M GUS or anti-GM1 antibodies). We studied SMN gene in 12 patients and found n o deletion. 16 patients were treated with IVIg and five improved but in 2 c ases the improvement was transcient and lasted less than six months, intrav enous cyclophosphamide (1g/m(2) repeated monthly during 6 to 9 months) was used in six patients and three improved. Among these three patients two rec eived also plasma exchanges on two days before the infusion, in ail three p atients, muscle weakness gradually deteriorated in the months following the end of the treatment Nor the weakness pattern nor the type of biological m arker was predictive of a good response to treatment Lower motor neuron dis eases appear to be much less sensitive to treatment than multifocal motor n europathy with conduction block. However, treatment with IVIg or cyclophosp hamide must be considered in the most severe forms or in case of a young on set.