From the Guidelines
Upper motor neuron (UMN) lesions typically cause symptoms such as muscle weakness, increased muscle tone (spasticity), hyperreflexia, Babinski sign, loss of fine motor control, clonus, and difficulty with voluntary movements. These symptoms occur due to damage to the motor neurons in the brain or spinal cord that control voluntary muscle movements, as seen in studies such as 1. The loss of inhibitory signals from upper motor neurons leads to increased muscle tone and hyperactive reflexes. The Babinski sign indicates damage to the corticospinal tract. Weakness and loss of fine motor control result from the reduced ability to activate muscles precisely.
Some key symptoms of UMN lesions include:
- Muscle weakness
- Increased muscle tone (spasticity)
- Hyperreflexia (exaggerated deep tendon reflexes)
- Babinski sign (upgoing plantar reflex)
- Loss of fine motor control
- Clonus (rhythmic muscle contractions)
- Difficulty with voluntary movements
It's essential to note that UMN lesions do not cause muscle atrophy or fasciculations, which are typically seen in lower motor neuron disorders, as discussed in 1. The location of the UMN lesion (brain vs. spinal cord) can affect the distribution of symptoms, with brain lesions often causing contralateral symptoms and spinal cord lesions causing symptoms below the level of injury.
Diagnosis typically involves a thorough neurological examination and may require imaging studies like MRI to identify the location and extent of the lesion, as recommended in 1. Treatment depends on the underlying cause but may include physical therapy, medications to manage spasticity, and addressing the primary condition causing the UMN damage. The most recent and highest quality study, 1, highlights the importance of managing spasticity to improve quality of life and reduce caregiver burden.
From the Research
Symptoms of Upper Motor Neuron (UMN) Lesions
The symptoms of Upper Motor Neuron (UMN) lesions can be categorized into positive and negative signs. The positive signs include:
- Spasticity or hypertonia, which is characterized by increased muscle tone and stiffness 2, 3, 4, 5, 6
- Muscle overactivity, which can lead to spasms and contractures 2, 5, 6
- Associated reactions, which are involuntary movements that occur in response to voluntary movements 2
- Brisk tendon reflexes and extensor plantar response, which are indicative of upper motor neuron dysfunction 4
The negative signs include:
- Voluntary weakness or paresis, which is a loss of muscle strength and control 2, 3, 4, 5
- Loss of dexterity and coordination, which can make it difficult to perform daily activities 3, 6
- Impaired motor performance, which can limit functional capacity and mobility 5
These symptoms can vary in severity and impact, depending on the location and extent of the UMN lesion. Additionally, secondary disabilities such as muscle contractures and bone deformations can develop as a result of the primary symptoms 6.
Clinical Features of UMN Lesions
The clinical features of UMN lesions can be complex and multifaceted, involving both positive and negative signs. The symptoms can be influenced by the level of the lesion, with lesions at different levels of the central nervous system resulting in different patterns of symptoms 4, 5.
Treatment and Management of UMN Lesions
Treatment and management of UMN lesions often focus on reducing muscle tone and spasticity, improving mobility and function, and preventing secondary disabilities such as contractures and bone deformations 3, 6. This can involve a range of interventions, including pharmacological treatments, physical therapy, and surgical interventions.