Below what cerebral blood flow value will first signs of cerebral ischemia appear on EEG?

Below what cerebral blood flow value will first signs of cerebral ischemia appear on EEG?

• A. 6 mL/100 g/min
• B. 15 mL/100 g/min
• C. 22 mL/100 g/min
• D. 31 mL/100 g/min

Answer: (C)

When cerebral perfusion starts to fall below normal levels, neurons struggle to meet their metabolic needs, and EEG activity slows before it completely stops. Normal cerebral blood flow is roughly 50–60 mL/100 g/min, and as flow declines, the EEG shows progressive slowing: fast activity diminishes, and delta/theta activity becomes more prominent. The first signs of ischemia on EEG occur once flow has dropped into the low 20s. Around 22 mL/100 g/min this early slowing and attenuation of background activity appear, signaling the onset of ischemic changes. If flow falls further, the EEG becomes more suppressed, eventually reaching isoelectric (is when complete loss of detectable activity occurs with severe ischemia). So the value around 22 mL/100 g/min represents the threshold where early EEG signs of ischemia emerge.

When cerebral perfusion starts to fall below normal levels, neurons struggle to meet their metabolic needs, and EEG activity slows before it completely stops. Normal cerebral blood flow is roughly 50–60 mL/100 g/min, and as flow declines, the EEG shows progressive slowing: fast activity diminishes, and delta/theta activity becomes more prominent. The first signs of ischemia on EEG occur once flow has dropped into the low 20s. Around 22 mL/100 g/min this early slowing and attenuation of background activity appear, signaling the onset of ischemic changes. If flow falls further, the EEG becomes more suppressed, eventually reaching isoelectric (is when complete loss of detectable activity occurs with severe ischemia). So the value around 22 mL/100 g/min represents the threshold where early EEG signs of ischemia emerge.