Differential diagnosis

Other diseases which lead to muscular wasting, especially of the upper limbs, must be considered:

• syringomyelia - fasciculations are rare; dissociated sensory loss from an early age
• intramedullary tumour - sensory loss usually prominent
• cervical spondylosis - sensory loss is usually present but the upper limb weakness and lower limb spasticity may be remarkably similar to MND. MND has a more rapid myelopathy and cervical disc protrusion will be absent on X-ray. Occasionally, MND may co-exist with cervical spondylosis.
• cervical rib - fasciculation absent, pain prominent, sensory loss usually present, characteristic radiology
• peripheral nerve lesions - localised wasting, usually accompanied by sensory loss.
• peroneal muscular atrophy - sensory loss
• chronic polymyositis - differentiate by electromyography and muscle biopsy
• myasthenia gravis - bulbar signs but rarely muscular wasting; responds rapidly to anticholinesterase

Reference

1. Williams TL. Motor neurone disease: diagnostic pitfalls. Clin Med (Lond). 2013 Feb;13(1):97-100