From the Guidelines
Ischemic stroke in the medial right cerebral artery can lead to hypotonia (low muscle tone) in the contralateral (left) side of the body, which may eventually evolve into spasticity (increased tone) due to damage to upper motor neurons and subsequent changes in spinal reflex activity and neuroplasticity mechanisms. This occurs because the upper motor neurons in the motor cortex of the right hemisphere normally exert inhibitory control over lower motor neurons in the spinal cord, and damage to these pathways disrupts this balance, initially causing hypotonia in the affected limbs 1. The prevalence of poststroke spasticity in any limb is in the range of 25% to 43% over the first year after stroke, highlighting the potential long-term impact on muscle tone and motor function 1.
Key aspects of the impact of ischemic stroke on muscle tone and motor neurons include:
- Damage to upper motor neurons in the motor cortex, leading to disrupted inhibitory control over lower motor neurons
- Initial hypotonia (decreased muscle tone) in the contralateral side of the body, which may evolve into spasticity (increased tone) over time
- Changes in spinal reflex activity and neuroplasticity mechanisms contributing to the transition from hypotonia to spasticity
- Potential long-term effects on muscle tone, motor function, and quality of life, with spasticity correlated with activity limitations and increased caregiver burden 1
Management of post-stroke tone abnormalities should focus on:
- Early physical therapy to prevent contractures during the hypotonic phase
- Medications such as baclofen, tizanidine, or botulinum toxin injections for spasticity
- Rehabilitation emphasizing maintenance of range of motion, strengthening exercises, and functional training to optimize recovery and prevent secondary complications like joint contractures and pain.
From the Research
Ischemic Stroke and Motor Neurons
- An ischemic stroke in the medial right cerebral artery can affect motor neurons, leading to various complications, including changes in muscular tonus and hipotonia (low muscle tone) 2, 3.
- The primary cerebral injury due to acute ischemic stroke occurs in the first hours, and early reperfusion is crucial for patient outcome, which may also impact the recovery of motor functions 2.
Effects on Muscular Tonus
- There is limited direct evidence on the specific effects of an ischemic stroke in the medial right cerebral artery on hipotonia and muscular tonus in relation to motor neurons.
- However, a study on a patient with spastic hemiparesis due to ischemic stroke reported the development of a Pisa-like syndrome after introduction of Baclofen, which reduces spasticity by stimulating GABA-B receptors, suggesting that changes in muscular tonus can occur after an ischemic stroke 4.
Artery Involvement and Lesion Location
- The involvement of the middle cerebral artery (MCA) in an ischemic stroke can result in significant changes in speech and language functions, and response to speech and language therapy may be better in patients with MCA involvement 5.
- While this study does not directly address the effects on muscular tonus and hipotonia, it highlights the importance of considering artery involvement and lesion location in the management of post-stroke complications.