5 Monomelic Amyotrophy and Parkinson’s disease: Possible correlations?

Benign Monomelic Amyotrophy (BMA) is a sporadic condition characterized by a neurogenic amyotrophy that affects a single either upper or lower limb; typically the disease is confined to second motoneuron involvement without cerebellar, pyramidal and cognitive signs; extrapyramidal features are not reported in BMA. We describe the case of a patient who experienced weakness and muscle atrophy in the right limb which starts approximately 5 years ago and progressed over the following 4 years. There was no history of poliomyelitis or familial neuromuscolar diseases. He denied any sensory symptoms; neurological examination showed marked amyotrophy of the right calf and mild amyotrophy of the right thigh with mild-to-moderate weakness; cranial nerves, sensory, pyramidal and cerebellar systems were normal. Needle electromyography revealed fibrillation potentials (acute denervation), polyfasic action potential, increased amplitude and long-duration of MUAPs and reduced recruitment pattern (chronic partial denervation and reinnervation). Transcranial magnetic stimulation was normal. MRI of the lower limbs detected severe right leg muscle atrophy and muscular replacement with adipose tissue. After one year extrapyramidal signs were observed as follows: hypomimia, bradykinesia, akinesia, axial and bilateral arm rigidity with decreased arm swing, postural instability, without cerebellar signs or cognitive decline. SPECT DAT SCAN examination showed reduced dopaminergic innervation in the striatum on both sides. We observed improvement of extrapyramidal features with Levodopa replacement therapy. Extrapyramidal dysfunctions are uncommon but recognized feature in motor neuron disease for which the pathological substrate is uncertain. To our knowledge this is the first description of BMA associated with Parkinsonism.