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Symptoms do not identify the lesion by themselves

A brain AVM may be found incidentally, after a seizure or during assessment of a hemorrhage or another neurological problem. Headache, weakness, sensory changes, speech or vision problems can occur, but none proves that an AVM is present or explains a symptom without assessment. Symptoms depend partly on the affected tissue and whether bleeding has occurred. Some people have no recognized symptoms when the lesion is found.1

Sudden severe headache, new weakness, trouble speaking or seeing, or abrupt loss of balance needs immediate local emergency assessment. A first seizure or collapse is also a reason for urgent medical attention. A familiar headache history or an existing AVM diagnosis should not be used to dismiss new neurological symptoms. Emergency assessment is different from arranging an elective opinion about a stable scan.2 3

What the clinical assessment asks

The clinician considers the symptoms, timing, neurological examination, prior hemorrhage and relevant health history. Imaging is interpreted alongside that information. A bleed near an AVM may require assessment of the nidus and any associated aneurysm; they are related findings but different structures. A nidus-type brain AVM also differs from a dural fistula, cavernous malformation or vein of Galen malformation. The exact diagnosis matters before applying a treatment study.4 1

Imaging answers different questions

CT can be useful in assessing acute hemorrhage; MRI helps show brain tissue and the lesion's surroundings. CT angiography and MR angiography show vascular anatomy noninvasively. Catheter digital subtraction angiography, or DSA, provides detailed information about individual feeding arteries, shunting and venous drainage over time. The SNIS report recommends DSA in pretreatment assessment, but that is not an instruction for every reader to arrange a test independently.4

Catheter angiography is a procedure with its own risks. The team should explain why it is needed, what uncertainty it can resolve and the risks relevant to the person. The choice and sequence of tests depend on the clinical question. A scan image or report shared online cannot substitute for that assessment.4

Grading is a tool for a particular question

Spetzler-Martin grading combines nidus size, relationship to eloquent brain and venous drainage to estimate the risk of surgical resection. “Eloquent” describes tissue important for functions such as movement or language. Supplementary systems add clinical or anatomical information for surgical selection; other models address radiosurgery or embolization. The same numerical grade can cover different lesion configurations.5 6

A surgical grade is not a cancer stage, an individualized annual hemorrhage probability or an automatic instruction to operate. Rupture history, symptoms, age, anatomy, procedural goals and the team's experience still matter. Adult unruptured trial evidence cannot simply be transferred to a child or an acutely ruptured lesion.5 4

Questions to take to the appointment

Ask what the confirmed diagnosis is, whether there is evidence of prior bleeding and which finding explains the proposed next test. Ask what the reported grade predicts and what it leaves out. If additional imaging is proposed, ask how its result could change the decision.

References

National Institute of Neurological Disorders and Stroke. Arteriovenous Malformations (AVMs). Patient information. Source ↩
US Centers for Disease Control and Prevention. Signs and Symptoms of Stroke. Patient information. Source ↩
NHS. Epilepsy. Patient information; reviewed 6 March 2025. Source ↩
De Leacy R et al. J NeuroIntervent Surg. 2022;14:1118–1124. doi:10.1136/neurintsurg-2021-018632. Source ↩
Derdeyn CP et al. Stroke. 2017;48:e200–e224. doi:10.1161/STR.0000000000000134. Official Top Things to Know summary. Source ↩
Graffeo CS et al. Neurosurgery. 2020;87:442–452. doi:10.1093/neuros/nyaa004. Source ↩