Isolated pure motor involvement of the shoulder and arm muscles is extremely rare after stroke, and up to now has been documented by magnetic resonance imaging (MRI) in only one patient.¹

The corticospinal system is known to exert a greater influence over distal than proximal upper limb muscles, and the mechanisms that induce better recovery from stroke of proximal muscles are debated. The contribution of ipsilateral corticospinal fibres from the unaffected hemisphere, or of corticoreticulospinal projections, has been hypothesised.^2,3

A 65-year-old right-handed man awoke unable to abduct the right arm. Examination showed a strength of 0/5 (Medical Research Council scale) in the right deltoid, 2/5 in the biceps and 4/5 in the triceps. Strength in the remaining upper and lower limb muscles as well as the sensory examination were completely normal. Tendon jerks were normal except in the right biceps, where they were reduced. Electromyography showed no voluntary activity in the right deltoid muscle, and a reduced recruitment pattern with motor units of low firing frequency in the biceps brachii. A computed tomography scan showed a small hypodense lesion in the left precentral gyrus. Two months later, the patient was able to abduct the arm against gravity and the strength in the biceps was 4/5. Biceps tendon jerk was hyperactive. At 7 months, the patient was able to hold the right arm abducted against resistance (4+/5).

Standard and functional magnetic resonance imaging (fMRI) was performed 2 months after stroke. fMRI was carried out using the blood oxygenation level-dependent contrast technique. To explore the cortical activity of the primary and secondary motor cortices, a self-paced finger-tapping task at a frequency of about 1 Hz was used. The experimental paradigm was a block design …