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Is it upper or lower motor neuron disease? DEBBIE FISCHER, RN, CCRN, MSN Critical Care Consultant

A: Upper and lower motor neurons are cle. When the patient has a lower motor neu- Q: What’s the components of motor pathways—neural ron disease, you’ll note: difference pathways that originate in the brain or I loss of muscle tone between upper brainstem and descend down the spinal I ipsilateral (same side) weakness of indi- and lower cord. These pathways control posture, vidual muscles motor neuron reflexes, muscle tone, and voluntary I flaccidity disease? movements. I atrophy Upper motor neurons originate in the cere- I weak or absent deep tendon plantar bral cortex and descend through the spinal reflexes and abdominal reflexes cord, where they interact with lower motor I fasciculations (muscle twitching). neurons. A patient with an upper motor Bell’s palsy is caused by lower motor neuron disease will exhibit: neuron disease associated with the seventh I weakness with minimal associated cranial nerve, which controls facial expres- atrophy (atrophy may be absent) sion. You’ll see a sagging of the face on the I hyperactive reflexes side of paralysis and constant tearing of the I increased muscle tone eyes. The patient can’t close his eyes, wrin- I spasticity kle his forehead, smile, whistle, or grimace. I rigidity Amyotrophic lateral sclerosis (ALS) is an I minimal paralysis of voluntary example of a mixed upper and lower motor movement neuron disease. It’s characterized by muscle I tremor wasting caused by the destruction of lower I chorea (random involuntary contractions motor neurons in the brainstem and degen- of the extremities) eration of the upper motor neuron pyrami- I athetosis (slow, irregular movements in dal tracts. A patient with ALS will experi- the distal extremities) ence muscle weakness and atrophy followed I dystonia (sustained, involuntary twisting by spasticity and hyperactive reflexes. Other movements). signs and symptoms include dysarthria (un- The patient will also have positive Babin- coordinated speech), dysphagia (difficulty ski’s and Hoffman’s reflexes. To test for Ba- swallowing), and dyspnea. binski’s reflex, run a semisharp object up the When differentiating upper and lower patient’s foot, starting at the heel and curv- motor neuron disease, remember that ing toward the great toe. If you observe upper motor neurons are responsible for plantar flexion of the great toe in response, motor movement, whereas lower motor Babinski’s reflex is present. To test for Hoff- neurons prevent excessive muscle move- man’s reflex, tap on the third finger of the ment. Upper motor disorders usually cause patient’s hand. If the reflex is present, the spasticity; lower motor disorders usually patient will bring his thumb and forefinger cause flaccidity. I together. Lower motor neurons are located in the Learn more about it Smeltzer SC, Bare B. Brunner & Suddarth’s Textbook of Med- central and peripheral nervous systems and ical-Surgical Nursing, 11th edition. Philadelphia, Pa., Lip- are responsible for innervating skeletal mus- pincott Williams & Wilkins, 2007.

64 Nursing made Incredibly Easy! March/April 2007