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| RCVS | Cervical artery dissection | PACNS | SAH |
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| History | Sudden onset headache, often thunderclap | Sudden or subacute, can have thunderclap features | Insidious, constant, progressive, dull | Sudden onset headache, often thunderclap |
| More common in females | No sex predilection | No sex predilection | More common in females |
| Age 20–50 years old | Age less than 50 years old | Age 40–60 years old | Age 40–60 years old |
| Risk increases with age |
| | | Likely to be younger in familial SAH |
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| Risk factors | Drugs, pregnancy, tumours, neuro injury, idiopathic | Atherosclerosis, cervical trauma, connective tissue disease. Can be idiopathic | | Family history
Known cerebral aneurysm |
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| Examination | Presence or absence of neurological deficit | Presence or absence of neurological deficit. Important to rule out in younger patients. | Presence or absence of neurological deficit, 5% spinal involvement | Depends on severity of haemorrhage |
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| CT brain | Majority normal
Cortical SAH, ICH | Normal in the absence of cerebral infarct (60%); crescenteric intramural haematoma on CTA | Majority abnormal—diffuse, multiple small infarcts | Majority abnormal.
SAH, cerebral oedema, hydrocephalus |
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| CSF studies | Majority normal | Normal | Majority abnormal—raised protein, cell count | Abnormal—xanthochromia, raised red cell count |
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| MRI brain | Majority normal | MRA may reveal intramural haematoma as well as demonstrate flow abnormalities. More sensitive than CT or early infarction | Nonspecific changes
Multifocal, cortical or subcortical infarcts, diffuse white matter changes, or leptomeningeal enhancement | Areas of infarct corresponding to vascular territory involved |
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| Cerebral angiography | Considered gold standard.
Useful in recurrent TCH
Diffuse segmental stenosis—medium, large arteries | Long-segmental stenosis, intimal flaps, arterial pseudoaneurysm | Unable to visualise changes in small arteries | Aneurysm, arterio-venous malformation
Vasospasm (not multifocal) at Day 4 |
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| CNS biopsy | Not indicated | | Gold standard.
Skip, segmental vascular lesions | |
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