From the Guidelines
It is not normal for one side of the body to be noticeably weaker than the other, even in right-hand dominant individuals. While some minor strength difference between dominant and non-dominant sides is expected, a subtle but noticeable weakness affecting the entire left side (both upper and lower body) should be evaluated by a healthcare provider promptly. This pattern of weakness could potentially indicate a neurological issue, possibly involving the right side of the brain or nervous system.
Key Considerations
- The brain's right hemisphere controls movement on the left side of the body, so one-sided weakness patterns are important clinical findings that deserve medical attention.
- Guillain-Barré Syndrome (GBS) is a condition that can cause progressive bilateral weakness of arms and legs, and although it typically presents with bilateral symptoms, some variants can present with asymmetrical or unilateral weakness 1.
- Other conditions such as cerebral palsy can also cause motor dysfunction and weakness, although these typically present in childhood 1.
- Plexopathy, which refers to abnormal neurological symptoms and signs that localize to an anatomically defined network of nerves, can also cause weakness and sensory loss in specific nerve distributions 1.
Recommended Course of Action
- Schedule an appointment with your primary care physician within the next few days for a proper neurological examination.
- They may recommend imaging studies such as an MRI or CT scan of the brain, or refer you to a neurologist for specialized assessment.
- Monitor for any other symptoms like headaches, vision changes, speech difficulties, or worsening weakness, which would warrant immediate emergency care.
- Early intervention for neurological conditions often leads to better outcomes, so prompt evaluation and treatment are crucial.
From the Research
Unilateral Weakness in Healthy Adults
There is no direct evidence to suggest that unilateral weakness on the left side, affecting both upper and lower extremities, in a right-handed individual is considered normal in an otherwise healthy adult.
- The provided studies primarily focus on multiple sclerosis, stroke, and reassurance therapy, which do not directly address the question of unilateral weakness in healthy adults 2, 3, 4, 5.
- One study discusses the concept of clinically benign conditions, such as fever of unknown origin, but does not relate to unilateral weakness 6.
- None of the studies provide information on the normal range of strength or the prevalence of unilateral weakness in healthy adults.
- Therefore, it is not possible to determine if unilateral weakness on the left side is considered normal in an otherwise healthy adult based on the provided evidence.