Abstract

We report the case and functional MRI imaging findings of a patient who, following a diagnosis of acute motor and sensory axonal neuropathy (AMSAN) reported supernumerary phantom limbs of both arms and legs. A 55 year old female, having presented with neuromuscular weakness requiring ventilatory support, was diagnosed with AMSAN, confirmed following lumbar puncture and nerve conduction studies. Early during inpatient rehabilitation the patient reported an unusual sensation of having ‘two extra arms and legs’. Symptoms persisted for many weeks, with improvement slowly tracking her neurological recovery. Visualising her normal limbs helped reduce the awareness of the ‘phantom’ limb resulting in a subjective improvement in her motor function. A functional MRI was undertaken during which a motor paradigm task was performed both with and without sight of the respective arms. As expected, both tasks demonstrated activity within the respective primary motor and supplementary motor cortical areas. However, increased activity was demonstrated when performing these tasks with sight of the normal limb. We discuss the interpretation of these findings alongside a review of supernumerary phantom limbs in neurological practice.