Differentiating features of UMN and LMN disease
| Feature | Upper Motor Neuron Lesion | Lower Motor Neuron Lesion |
|---|---|---|
| Site of the lesion | Cerebral hemispheres, cerebellum, brainstem, spinal cord | Anterior horn cell, nerve roots, peripheral nerves, neuromuscular junction, muscles |
| Muscle weakness | Quadriplegia, hemiplegia, diplegia, paraplegia | Proximal (myopathy) Distal (neuropathy) |
| Muscle tone | Spasticity, rigidity | Hypotonia |
| Fasiculations | Absent | Present (particularly tongue) |
| Tendon reflexes | Hyperreflexia | Hypo/areflexia |
Abdominal reflexes | Absent (depending on the involved spinal level) | Present |
| Sensory loss | Cortical sensations | Peripheral sensations |
Electromyography (EMG) | Normal nerve conduction Decreased interference pattern and firing rate | Abnormal nerve conduction Large motor units Fasciculations and fibrillations |
Note. Reprinted from “Concise outline of the nervous system examination for the generalist,” by Jan MM, Al-Buhairi AR, Baeesa SS. Neurosciences (Riyadh). 2001;6:16–22 (https://nsj.org.sa/content/6/1/16). CC BY-NC.