Naming the segment is the report, not pedantry: the segment, side, and threatened perforators decide clip vs. coil vs. flow-diversion and predict which infarct follows if a vessel is sacrificed. Read anatomy as a map of consequences.
Bottom line
Name the segment because the name is the plan — localization drives clip-vs-coil-vs-flow-divert and predicts which perforator infarct to expect.
Core workstation questions
For an ICA aneurysm: which segment, and is it intradural or extradural? Does 'para-ophthalmic' suffice for the plan?
Post-AComm surgery with a caudate infarct — is this a recurrent artery of Heubner territory complication?
Deep infarct with no named cortical territory — lenticulostriate perforators?
MCA branch occlusion — which division by territory at risk, not by vessel position?
Posterior fossa: is this PICA/AICA (low, together) or SCA (high)? Is that 'donut' just a basilar fenestration?
What changes reporting / management
Localize ICA aneurysms to a segment and state intradural vs. extradural (changes rupture/SAH risk and approach); collapse ophthalmic/hypophyseal/transitional to 'para-ophthalmic' unless a finer split changes the plan (flow diversion treats the zone as one).
Read a focal anteroinferior caudate infarct after AComm aneurysm clipping as a recognized Heubner-territory complication.
For MCA-branch occlusion, name superior vs. inferior division by the territory at risk (superior frontal vs. temporal/inferior frontal), since division dominance is variable and naming is territory-based not position-based.
Anchor reports on the management-relevant junctions: ICA terminus, MCA M1/M2, ACA A1/A2, PCA P1/PComm (the last defining fetal vs. adult supply).
Practical traps
Vague 'ICA aneurysm' localization that doesn't drive treatment — segment + intradural/extradural is required.
Over-precise ophthalmic-vs-hypophyseal-vs-transitional localization where boundaries are indistinct and management is identical (para-ophthalmic).
Inferring MCA superior/inferior division from vessel position rather than supplied territory.
Calling a basilar fenestration (rounded 'donut' duplication) a dissection, aneurysm, or other pathology.
Teaching pearls
'ICA aneurysm' isn't an answer — segment plus intradural/extradural is.
Ophthalmic, hypophyseal, transitional blur together — call it para-ophthalmic and treat it as one.
A caudate infarct after AComm clipping is Heubner's territory.
MCA superior vs. inferior division is about where it goes, not where it sits.
PICA and AICA ride low and together; SCA rides high — and a basilar 'donut' is a fenestration, not disease.
