Does right hemiparesis (right-sided weakness) indicate right-sided symptoms or right cerebral hemisphere involvement?

From the Guidelines

Right hemiparesis (right-sided weakness) typically indicates left cerebral hemisphere involvement, not right-sided symptoms or right cerebral hemisphere involvement. This is because the nerve pathways in the brain cross over, meaning that damage to one side of the brain affects the opposite side of the body. According to the 2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS guideline on the management of patients with extracranial carotid and vertebral artery disease 1, symptoms and signs that result from ischemia or infarction in the distribution of the left internal carotid artery or middle cerebral artery may cause right-sided weakness, right-sided paresthesia or sensory loss, aphasia, and monocular blindness that affects the left eye or left visual field.

Key Points to Consider

• The crossing of nerve pathways in the brain means that damage to one side of the brain affects the opposite side of the body
• Right-sided weakness is typically caused by left cerebral hemisphere involvement, not right-sided symptoms or right cerebral hemisphere involvement
• The 2011 guideline provides evidence for the relationship between cerebral artery distribution and resulting symptoms, including right-sided weakness 1

Clinical Implications

• Understanding the relationship between cerebral hemisphere involvement and resulting symptoms is crucial for determining appropriate treatment and rehabilitation approaches
• Clinicians should consider the possibility of left cerebral hemisphere involvement when diagnosing and treating patients with right-sided weakness, rather than assuming right-sided symptoms or right cerebral hemisphere involvement.

From the Research

Right Hemiparesis and Cerebral Hemisphere Involvement

• Right hemiparesis, or right-sided weakness, is typically associated with left cerebral hemisphere involvement, not right-sided symptoms or right cerebral hemisphere involvement 2, 3.
• The brain's motor control is generally contralateral, meaning that the left hemisphere controls the right side of the body and vice versa.
• Studies have shown that lacunar strokes, which are a type of stroke that affects the small vessels in the brain, can cause hemiparesis on the contralateral side of the body 4, 5, 6.

Lacunar Strokes and Hemiparesis

• Lacunar strokes are often associated with small vessel disease and can cause a range of symptoms, including hemiparesis, depending on the location and severity of the stroke 4, 5.
• The presence of cerebral small vessel disease can increase the risk of intracerebral hemorrhage during thrombolysis, but it is not an absolute exclusion criterion for treatment 4.
• Treatment with intravenous thrombolysis, such as alteplase, has been shown to be effective in patients with lacunar infarcts, with a favorable outcome observed in 59% of patients in one study 6.

Diagnostic Considerations

• Neuroimaging, such as magnetic resonance imaging (MRI), is essential in diagnosing and evaluating patients with suspected lacunar stroke or hemiparesis 2, 3.
• The use of MRI can help identify the location and extent of the stroke, as well as any underlying small vessel disease or other conditions that may be contributing to the patient's symptoms 4, 6.