Anatomy & Blood supply of the brain

Dr. Avinash KMMS, MRCS Ed(UK), Mch (KEM, Mumbai), FINR(Switzerland), FMINS(Germany),

• Interventional & Neurovascular surgeon and Stroke specialist, • Endoscopic Neuro and Spine surgeon, • Minimally invasive Neuro and Spine surgeon (FMINS).

mob: 9740866228, E mail: doc_avin@hotmail.com

Consultant Neurosurgeon and Neurointerventionist

Columbia Asia Hospital, Bangalore.

Blood supply to brain• Healthy young adults have brain size of 1300 to 1400 grams and

have an average whole brain blood flow of approximately 46 mL/100 gram of brain /minute.

• The brain comprises only 2% of body weight, but receives 15% of cardiac output and uses 20% of total body oxygen and 25% of total body glucose.

• In newborn infants, mean global CBF is low, ranging from 6 to 35 mL/100 g /min. Global oxygen utilization in the normal newborn is also very low, with the majority of values less than 1.3 mL/100 g/min. This finding indicates that energy requirements in fetal and newborn brain are minimal.

• Beyond the neonatal period, global CBF, oxygen and glucose utilization progressively increase, reaching a maximum at age 3-10 years (60 to 140 mL/100 g /min , oxygen ranging from 4.3 to 6.2 mL/100 g/min, and Glucose ranging from 49 to 65 μ mol/100 g/min).

• By late adolescence, cerebral flow and oxygen and glucose metabolism decrease to adult levels.

Blood supply to brain•The blood vessels supplying brain are two internal carotid arteries and two vertebral arteries. •Carotid artery contributes approximately 80% to the total cerebral blood flow, the remaining 20% coming from the two vertebral arteries

Pulsations felt when one keeps hand over neck are actually carotid pulsations

Blood supply of Brain

Blood vessels seen from below

Blood supply of the brain

Blood vessels when seen from front of brain

Blood supply of the brain

Blood vessels seen from side

Blood vessels seen from inner side of hemisphere

Blood supply of Brain stem

What happens when blood supply to brain is reduced?

• Certain functional changes occur once blood flow to the brain decreases. Critical values for loss of synaptic transmission, corresponding to loss of neuronal function, are between 15 and 18 ml/100 gram/minute.

• The threshold for membrane pump failure. and thus for loss of cellular integrity and cell death, is approximately 10 ml/100 gram/ minute.

• It is generally assumed that if CBF stays above 18 ml/100 g/min but below 20–25 ml/100 g/min neurons will survive but may not function.