Special Topic - Upper Motor Neuron Lesion (UMNL)
This week we are going to discuss neurology. It could be a complicated topic to discuss at times, but we will keep this as simple as it can. We will start that with two basic facts. When we are trying to initiate any voluntary movement, the ‘thought/signal’ is transmitted via a neural pathway from our brain, down our spinal cord, and then out to our extremities. And an interesting fact to know is that the left side of the brain controls the opposite side of the body and vice versa. That is why when someone could not raise their left arm after a stroke, we suspect the stroke happened on the right side of the brain.
To simplify, the whole neural pathway can be divided into two parts, the neurons from the brain to our spinal cord are called the upper motor neuron, the neurons exiting the spinal cord to the muscles are called the lower motor neurons. When someone has a brain or spinal cord injury that happened along the former pathway, it is referred to as upper motor neuron lesion.
What Could Cause Upper Motor Neuron Lesion?
Injuries to the brain and spinal cord, such as stroke, traumatic brain injury, infections, inflammatory disorders, neurodegenerative disorders, amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), and vitamin B12 deficiency can all cause UMNL.
During a physical examination, clinicians will include a neurological testing as part of the assessment. Below are four major clinical signs and symptoms for someone who has upper motor neuron lesion.
1) Hypertonia (hyper-tonia = high-muscle tone)
High tension in the muscle causes stiffness and tightness. Specifically, patients with UMNL will experience spasticity, where a muscle gets stiff when it is passively stretched in a velocity dependent manner. A classic phenomenon is the clasp knife response, when the clinician rapidly flexes a patient’s arm, the arm will resist at first and give in near the end of range.
2) Hyperreflexia (Increased reflexes)
When the clinician tests for a classic knee jerk reflex during the neurology assessment, the patient response is amplified because of lack of inhibition from the upper motor neuron lesion. Patients will also demonstrate increased response to other reflex testing.
3) Positive Babinski’s Sign
Clinicians suspect an upper motor neuron lesion when patients demonstrate a positive Babinski’s sign. A positive Babinski’s sign is the extension of the big toe and fanning out of the toes when the foot is being struck from the heel towards the big toes.
4) Clonus
Clonus is a series of involuntary contractions when the muscle is suddenly being stretched. Clinicians usually test for clonus by having patients sit on the edge of the bed with the foot dangling off the ground. Then, the clinician rapidly dorsiflexes the ankle thereby creating a sudden stretch of the calf muscle. Repetitive involuntary contractions of the muscle indicate a positive clonus test.
How Can Rehabilitation Help?
Depending on the severity of the disease, therapy that focuses on improving quality of life is the cornerstone of the treatment. Since one of the symptoms of upper motor neuron lesion are muscle contracture (stiffness) and muscle weakness, a daily stretching and muscle strengthening exercise program will benefit the patient. In addition, bowel and potty training is necessary for patients suffering from a more significant injury. A referral to a pharmacist and neurologist for further testing may be also needed.
Consult a health care professional if your loved one has had an upper motor neuron lesion!
Reference: Emos, M. C., & Rosner, J. (2019). Neuroanatomy, Upper motor nerve signs.