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

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.

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

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

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

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

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.

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!

Bilateral Carotid-ACA anastomoses Bilateral case is extremely rare.

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

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

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.

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

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

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

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

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

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

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

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

Completely duplicated BA!

Double BA fenestrations?

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

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

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

Persistent hypoglossal artery

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

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

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.

Stereoscopic projection Left SCA arising from the lateral type PTA

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

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

Thank you very much for your attention !!! References Uchino A, et al (1996) MR imaging and MR angiography of persistent trigeminal artery and its variant. Clin Imaging 20:247-252 Uchino A, et al (2000) Middle cerebral artery variations detected by magnetic resonance angiography. Eur Radiol 10:560-563 Uchino A, et al (2000) Persistent trigeminal artery variants detected by MR angiography. Eur Radiol 10:1801-1804 Uchino A, et al (2001) Basilar artery fenestrations detected by MR angiography. Radiat Med 19:71-74 Uchino A, et al (2001) Persistent primitive olfactory artery: diagnosis with MR angiography. Clin Imaging 25:258-261 Uchino A, et al (2002) Extreme fenestration of the basilar artery associated with cleft palate, nasopharyngeal mature teratoma, and hypophyseal duplication. Eur Radiol 12:2087-2090 Uchino A, et al (2002) Congenital absence of the internal carotid artery diagnosed during investigation of trigeminal neuralgia. Eur Radiol 12:2339-2342 Uchino A, et al (2002) Moyamoya disease associated with an anterior inferior cerebellar artery arising from a persistent trigeminal artery. Eur Radiol 12 Suppl 3:S14-S17 Uchino A, et al (2002) Extreme fenestration of the right vertebral artery: magnetic resonance angiographic demonstration. Eur Radiol 12 Suppl 3:S32-S34 Uchino A, et al (2003) Variations of the superior cerebellar artery: MR angiographic demonstration. Radiat Med 21:235-238 Uchino A, et al (2003) MR angiography of anomalous branches of the internal carotid artery. AJR Am J Roentogenol 181:1409-1414 Uchino A, et al (2004) Carotid-anterior cerebral artery anastomosis: MR angiographic features and literature review. Clin Imaging 28:377-380 Uchino A, et al (2006) Fenestrations of the middle cerebral artery detected by MR angiography. Magn Reson Med Sci 5:51-55 Uchino A, et al (2006) Anterior cerebral artery variations detected by MR angiography. Neuroradiology 48:647-652 Uchino A, et al (2006) Intracavernous fenestration of the internal carotid artery. Eur Radiol 16:1623-1624 Thank you very much for your attention !!!