Middle Cerebral Artery Variants

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Middle Cerebral Artery Variants

• Andy Dimmen

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Outline

• Textbook description
• Variants
• Aneurysms
• Transcranial Doppler Ultrasound

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Circle of Willis1
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Normal Course of Middle Cerebral Artery2

• M1 Segment
• 20 mm long
• 3.35 mm diameter

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M1 Segment
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M1 Bifurcation
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Carotid Artery Angiogram3
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Typical Variants

• Duplicated MCA (0.2-2.9)
• Accessory MCA (0.3-4)
• Fenestrated MCA (0.26-0.47)

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Duplicated MCA

• Arises from distal internal carotid artery

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Accessory MCA

• Originates on proximal anterior cerebral artery

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Fenestrated MCA
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Phylogeny of MCA/ACA

• ACA develops first
• Continuation of primitive internal carotid
• MCA appeared later
• Regarded as a branch of ACA

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Possible Origins of Duplicated Accessory MCAs

• Begin as outpouchings of ICA and ACA
• Proximal branch gtgt Duplication
• Anterior temporal lobe
• Distal branch gtgt Accessory
• Anterior frontal lobe

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Other Hypotheses

• Hypertrophy of Recurrent Artery of Heubner

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Possible Mechanism of Fenestration
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Aneurysm of MCA4
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Accessory MCA Aneurysm

• Not due to weakness of arterial wall
• Recurrent blood flow at ACA-accessory MCA junction

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Accessory MCA Aneurysm
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Fenestration Aneurysm

• Proximal portion is weak
• Strongly associated with aneurysm

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Collateral Circulation with Accessory MCA
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Transcranial Doppler Ultrasound5
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TCD Clinical Applications

• Head injury severity a 1/MCA velocity
• Low velocity gtgt poor prognosis

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Final Thoughts

• Anatomy is variable
• Variants have consequences

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References

• Balaji PS, Varma RG, Kulkarni RN. Microsurgical
  anatomy of the middle cerebral artery. Neurol
  India 2005 53 186-90.
• Fujiwara K, Saito K, Ebina T. Saccular aneurysm
  of the accessory middle cerebral artery. Neurol
  Med Chir (Tokyo) 2003 43 31-4.
• Gailloud P, Albaryram S, Fasel JHD, Beauchamp NJ,
  Murphy KJ. Angiographic and embryologic
  considerations in five cases of middle cerebral
  artery fenestration. AJNR 2002 23 585-7.
• Komiyama M, Nakajima H, Nishidawa M, Yasui T.
  Middle cerebral artery variations duplicated and
  accessory arteries. AJNR 1998 19 45-9.
• Komiyama M, Nishikawa M, Yasui T. The accessory
  middle cerebral artery as a collateral blood
  supply. AJNR 1997 18 587-90.
• Uchino A, Kato A, Takase Y, Kudo S. Middle
  cerebral artery variations detected by magnetic
  resonance angiography. Eur Radiol 2000 10
  560-3.
• Umansky F, Dujovny M, Ausman JI, Diaz FG,
  Mirchandani HG. Anomalies and variations of the
  middle cerebral artery a microanatomical study.
  Neursurgery 1988 22 1023-7.

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Picture Citations

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