1. Intracranial arterial variations diagnosed by MR angiography
Akira Uchino, MD, PhD
Department of Diagnostic Radiology
Saitama Medical University International Medical Center
Hidaka, Saitama, JAPAN

2. Learning Objectives Background
To illustrate various types of cerebral arterial variations
diagnosed by MR angiography.
Background
Because image quality of MR angiography improved,
many types of cerebral arterial variations can be detected
incidentally. These variations should be diagnosed
correctly in order to avoid complications during procedure
of the interventional neuroradiology or neurosurgery.

3. Variations presented here
IC agenesis, IC fenestrations
Carotid-ACA anastomoses
ACA variations
MCA variations
PCA variations
Intracranial vertebrobasilar artery variations
Carotid-vertebrobasilar anastomoses

4. Right IC agenesis
This is the most frequently observed type of IC agenesis,
and there is right side predominance.

5. Right IC agenesis with intercavernous anastomosis
This is an extremely rare variation.
Transnasal pituitary surgery is dangerous!

6. The supraclinoid (L) and cavernous (R) IC fenestrations.
The latter is extremely rare.

7. Carotid-ACA anastomosis
(infraoptic course of ACA, interoptic course of ACA)
An anomalous artery is arising from right IC ophthalmic segment.
This variation is relatively rare, and there is right side predominance.

8. Stereoscopic projection
Right carotid-ACA anastomosis with normal A1 segment
This case shows that “infraoptic-” or “interoptic course of ACA” is
inadequate, because there is normal A1 segment!

9. Bilateral Carotid-ACA anastomoses
Bilateral case is extremely rare.

10. ACA variations (L) Azygos (unpaired) ACA
(R) Triple ACA (median artery of the corpus callosum)

11. ACA, ACoA fenestrations
ACA fenestrations are most frequently found
at the distal A1 segment.

12. Right persistent olfactory artery
There is an anomalously anteroinferior course of proximal ACA
with hairpin tern.
There is no laterality in frequency, and bilateral type is rare.

13. MCA variations 3 4 2 5 1 Schematic illustration of several types of
the middle cerebral artery (MCA) variation.
(antero-posterior projection)
1: Duplicated MCA
2: Early bifurcated MCA
3: Distal A1 origin of accessory MCA
4: Proximal A1 origin of accessory MCA
5: Fenestration of MCA

14. (L) Early bifurcated right MCA
(R) Duplicated left MCA

15. (L) Proximal A1 origin of left accessory MCA
(R) Distal A1 origin of right accessory MCA

16. (L) M1 fenestration
(R) M2 fenestration
MCA fenestration is most frequently found at the proximal M1 segment.

17. PCA variations Duplicated right PCA
The right PCA is fetal origin, and duplicated completely.

18. (L) Hyperplastic anterior choroidal artery supplies calcarine artery.
(R) Left PCA fenestration

19. Intracranial VB systen variations (L) Cervical origin of right PICA
(R) Large left VA fenestration

20. (L) Proximal BA fenestration
(R) Distal BA fenestration
VB junction〜proximal BA fenestrations are most frequently observed.

21. Completely duplicated BA!

22. Double BA fenestrations?

23. (L) Common trunk of left PCA and SCA, or duplicated terminal BA
(R) Duplicated left SCA

24. Schematic illustration of several types of carotid-vertebrobasilar anastomoses (lateral projection)
1: Proatlantal artery type 1
2: Proatlantal artery type 2
3: Persistent hypoglossal artery
4: Persistent otic artery ?
5: Persistent trigeminal artery (PTA)
6: Cerebellar artery arising from the PTA
7: PTA variant (cerebellar artery arising from the ICA)
The persistent otic artery (4) may not exist, because
previously reported cases are regarded as low origin
of PTA. 7 6 5 4 3 2 1

25. Proatlantal artery type 2, and low origin of persistent trigeminal artery
Extremely large left occipital artery connects with left VA.

26. Persistent hypoglossal artery

27. 2 3 1 4
Schematic illustration of several types of persistent trigeminal artery (PTA) (caudo-cranial projection)
1: Lateral type, and Salzman type 2 (ipsilateral P1 hypoplasia)
2: Medial type, and Salzman type 1 (ipsilateral posterior communicating artery hypoplasia)
3: PTA variant (cerebellar artery arising from the ICA)
4: Cerebellar artery arising from the lateral type PTA

28. Lateral type persistent trigeminal artery (PTA)
Salzman type 1
This is the most frequent type of carotid-VB anastomosis.

29. Medial type persistent trigeminal artery (PTA)
Salzman type 2
This type of PTA is also called “intrasellar PTA” or
“transhypophyseal PTA”. Transnasal pituitary surgery
is dangerous in this variation.

30. Stereoscopic projection
Left SCA arising from the lateral type PTA

31. (L) PTA variant (AICA)
(R) PTA variant (PICA)

32. Conclusion
Cerebral arterial variations are frequently detectable
during daily clinical practice. Diagnostic radiologist
should pay attention to diagnose these variations
correctly.
Keywords
Cerebral artery, Arterial variation, MR angiography

33. Thank you very much for your attention !!!
References
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Thank you very much for your attention !!!