How do you differentiate a parietal (lobe) bleed from a basal ganglia bleed on computed tomography (CT) or magnetic resonance imaging (MRI) scans in a patient with a history of intracranial hemorrhage (ICH), cardiovascular disease, and stroke?

Differentiating Parietal Lobe Hemorrhage from Basal Ganglia Hemorrhage on Neuroimaging

Parietal lobe hemorrhages are located in the cortical/subcortical regions of the parietal lobe (superficial, near the skull), while basal ganglia hemorrhages are deep, centrally located structures adjacent to the lateral ventricles—these are easily distinguished on CT or MRI by their anatomic location alone. 1, 2

Anatomic Location: The Primary Distinguishing Feature

Basal Ganglia Hemorrhage Characteristics

• Deep, central location within the brain parenchyma, specifically involving structures such as the putamen, caudate nucleus, globus pallidus, or internal capsule 3, 4
• Located adjacent to the lateral ventricles in the deep gray matter structures 5, 6
• Accounts for approximately 50% of all spontaneous intracerebral hemorrhages and is the most common site 5, 3
• Strongly associated with chronic hypertension as the underlying etiology 3, 4, 6

Parietal Lobe Hemorrhage Characteristics

• Superficial/lobar location in the cortical or subcortical white matter of the parietal lobe 1
• Located peripherally, near the skull rather than deep central structures 3
• More likely to be secondary hemorrhages from underlying vascular lesions (arteriovenous malformations, aneurysms, tumors, or cerebral amyloid angiopathy) rather than hypertensive hemorrhage 1, 6
• May show unusual hematoma shape (non-circular) or edema out of proportion to the hemorrhage timing, suggesting secondary causes 1

Imaging Approach

Initial Non-Contrast CT Scan

• CT is the gold standard for identifying acute hemorrhage with 100% sensitivity and immediately distinguishes location 1, 2
• Basal ganglia bleeds appear as hyperdense (bright) blood in deep central structures 3
• Parietal bleeds appear as hyperdense blood in superficial cortical/subcortical regions 1

Advanced Imaging for Secondary Causes

• CT angiography (CTA) or MR angiography should be obtained for parietal/lobar hemorrhages to exclude underlying vascular lesions (AVMs, aneurysms) 1, 2
• Consider CT or MR venography if parietal hemorrhage shows unusual features suggesting cortical vein thrombosis, such as ipsilateral dural thickening/enhancement or cortical vein "cord sign" 1
• Catheter angiography may be needed if non-invasive studies are inconclusive but clinical suspicion remains high for vascular malformation 1

Clinical Context That Aids Differentiation

Factors Suggesting Basal Ganglia (Hypertensive) Hemorrhage

• History of chronic hypertension 3, 4, 6
• Older age and typical vascular risk factors 4
• No prodromal symptoms before sudden onset 1

Factors Suggesting Parietal (Secondary) Hemorrhage

• Younger age (<55-65 years), female sex, non-smoker, no hypertension history 2, 6
• Prodrome of headache or neurological symptoms before hemorrhage 1, 2
• Associated subarachnoid hemorrhage on imaging 1, 6
• Ipsilateral dural thickening and enhancement on MRI (suggests cortical vein thrombosis) 1

Critical Pitfalls to Avoid

• Do not assume all deep hemorrhages are hypertensive: Even basal ganglia hemorrhages in young patients without hypertension warrant vascular imaging to exclude secondary causes 6
• Do not miss cortical vein thrombosis: Parietal hemorrhages with unusual features (dural enhancement, cord sign, disproportionate edema) require venographic studies 1
• Do not delay imaging: Both CT and advanced vascular imaging should be obtained emergently, as 28-38% of patients scanned within 3 hours will have hematoma expansion 1, 2
• Do not rely on clinical features alone: Neuroimaging is mandatory to distinguish hemorrhage location and etiology 1, 7