Can left carotid artery disease cause right-sided symptoms?

Left Carotid Artery Disease and Right-Sided Symptoms

Yes, left carotid artery disease can cause right-sided symptoms due to the crossing of neural pathways in the brain. According to established guidelines, 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 1.

Anatomical Basis for Contralateral Symptoms

The relationship between carotid artery disease and contralateral symptoms is well-documented in medical literature and is based on the following neuroanatomical principles:

• The left carotid artery supplies blood to the left hemisphere of the brain
• Motor and sensory neural pathways cross at the level of the brainstem (pyramidal decussation)
• Therefore, disruption of blood flow in the left carotid artery affects the left cerebral hemisphere, resulting in neurological deficits on the right side of the body

Clinical Manifestations of Left Carotid Disease

When left carotid artery disease causes cerebral ischemia, the following right-sided symptoms may occur 1:

• Right-sided weakness (hemiparesis)
• Right-sided numbness, paresthesia, or sensory loss
• Aphasia (if the left hemisphere is dominant, which is true for most people)
• Visual field defects affecting the right visual field (right homonymous hemianopsia)

Additionally, left carotid disease may cause:

• Monocular blindness affecting the left eye (ipsilateral to the carotid lesion)
• Cognitive deficits related to left hemisphere function

Diagnostic Considerations

When evaluating patients with right-sided neurological symptoms, the following diagnostic approach is recommended:

1. Initial evaluation: Noninvasive imaging for detection of extracranial carotid and vertebral artery disease (ECVD) is indicated in patients with transient retinal or hemispheric neurological symptoms 1

2. Preferred imaging modalities:

   • Duplex ultrasonography is recommended to detect carotid stenosis in patients with focal neurological symptoms 1
   • MRA or CTA is indicated when ultrasonography cannot be obtained or yields equivocal results 1

3. Additional testing: When extracranial cerebrovascular disease is not severe enough to account for symptoms, echocardiography should be performed to search for cardiogenic embolism 1

Clinical Pearls and Caveats

• The severity of symptoms does not always correlate with the degree of stenosis, as plaque characteristics (ulceration, echolucency, intraplaque hemorrhage, high lipid content) may be more important determinants of stroke risk 1

• Not all strokes in patients with carotid disease are caused by the carotid lesion. In the Framingham Heart Study, fewer than half of stroke events affected the cerebral hemisphere ipsilateral to carotid stenosis 1

• Aphasia may be a sign of ischemia or infarction in the distribution of the right internal carotid artery in ambidextrous or left-handed individuals 1

• Careful assessment of the timing, nature, and distribution of symptoms is essential to determine whether they correspond to the territory supplied by the left carotid artery

• Bilateral carotid disease may be present, so comprehensive vascular assessment is important when evaluating patients with cerebrovascular symptoms

In conclusion, the anatomical organization of the cerebrovascular system and the crossing of neural pathways in the brain explain why left carotid artery disease typically manifests with right-sided neurological symptoms.