From the Guidelines
Reduced cranial blood flow can result from various conditions, with atherosclerosis, carotid artery stenosis, and hypertension being prominent causes, as evidenced by the 2021 American College of Rheumatology/Vasculitis Foundation guideline 1.
Causes of Reduced Cranial Blood Flow
The causes of reduced cranial blood flow are multifaceted and can be attributed to several factors affecting the cardiovascular system and cerebral circulation. Some of the key causes include:
- Atherosclerosis, where plaque buildup narrows blood vessels supplying the brain
- Hypertension, which damages blood vessels over time
- Hypotension, where low blood pressure fails to push adequate blood to the brain
- Carotid artery stenosis, which specifically narrows the major arteries in the neck that supply blood to the brain
- Heart conditions like atrial fibrillation, heart failure, and valve disease, which can reduce cardiac output and decrease overall blood flow to the brain
- Blood disorders such as anemia, polycythemia, and hypercoagulable states, which affect oxygen delivery and blood viscosity
- Structural issues like arteriovenous malformations and intracranial masses, which can physically obstruct blood flow
- External compression from tight neckwear or improper neck positioning, which can temporarily reduce cerebral circulation
- Certain medications, particularly antihypertensives, vasoconstrictors, and some psychiatric drugs, which may reduce cerebral perfusion as a side effect
- Lifestyle factors including smoking, dehydration, and excessive alcohol consumption, which can compromise cranial blood flow through various mechanisms affecting vascular health and blood composition.
Clinical Assessment and Management
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, clinical assessment of patients with focal cerebral ischemic symptoms should follow guidelines for stroke care. The guideline emphasizes the importance of establishing the cause and pathophysiology of the event and risk stratification. The 2021 American College of Rheumatology/Vasculitis Foundation guideline 1 also highlights the potential benefits of aspirin in preventing ischemic events in patients with vascular narrowing causing decreased cerebral blood flow. Therefore, it is crucial to consider these factors when assessing and managing patients with reduced cranial blood flow, prioritizing interventions that address the underlying causes and minimize the risk of further complications.
From the FDA Drug Label
- Hunt and Hess Grade † p=0.03 Patients Study Dose Grade * Number AnalyzedAny Deficit Due to Spasm Numbers with Severe Deficit ... Delayed Ischemic Deficits (DID) Permanent Deficits Nimodipine n (%) Placebo n (%) Nimodipine n (%) Placebo n (%) DID Spasm Alone 8 (11) * 25 (31)5 (7)* 22 (27)
The causes of reduced cranial blood flow include vasospasm, as evidenced by the reduction in spasm-related deficits in patients treated with nimodipine. Key points include:
- Delayed ischemic deficits are often caused by spasm
- Spasm can contribute to permanent deficits
- Nimodipine has been shown to reduce the severity of neurological deficits resulting from vasospasm in patients with subarachnoid hemorrhage (SAH) 2
From the Research
Causes of Reduced Cranial Blood Flow
- Atherosclerosis: a condition in which the buildup of plaque in the arteries can lead to reduced blood flow to the brain 3
- Aging: normal aging phenomena can cause a decrease in cerebral blood flow, leading to decreased neuronal activity and potentially Alzheimer's disease 4
- Cardiovascular disease: conditions such as coronary artery bypass graft and chronic atrial fibrillation can increase the risk of reduced cranial blood flow 5
- Endothelial dysfunction: damage to the inner lining of blood vessels can impair blood flow to the brain 3
- Increased risk of bleeding: the use of aspirin for primary prevention of cardiovascular disease has been shown to have a neutral net benefit or even harm due to an increased risk of bleeding, which can lead to reduced cranial blood flow 6, 7