ABSTRACT
A further critical distinction to be made is between upper motor neurone (UMN) weakness and lower motor neurone (LMN) weakness. UMN weakness will be caused by abnormalities of the motor cortex or pyramidal tracts and LMN weakness will arise from diseases affecting the ‘motor unit’, which comprises the motor neurone in the anterior horn of the spinal cord, its axon, the neuromuscular junction and the muscle fibres innervated by that axon.
