The correct answer is:

Failure of neuronal membrane pumps.

Educational Objective:

Identify appropriate levels of cerebral blood flow (CBF).

Key Point:

The normal cerebral blood flow (CBF) is approximately 40 to 60 mL/100 g of brain tissue per minute. When CBF drops below 15 to 18 mL/100 g of brain per minute, the brain becomes electrically “silent,” although neuronal membrane integrity initially remains intact.

Explanation:

Clinically, the areas of the brain that are electrically silent manifest a neurologic deficit that is indistinguishable from a stroke; however, the brain cells are viable in this low flow, electrically silent area and can be salvaged with knowledgeable stroke care in the first hour that optimizes the restoration of flow to these at-risk areas.

At or below low flow states of 10 mL/100g brain tissue per minute, brain cell membrane failure occurs due to a critical degree of ATP depletion and a resulting lack of energy to operate the various membrane pumps.

Sustained low flow rates and membrane pump failure lead to an increase in extracellular potassium, intracellular calcium, intracellular acidosis, and ultimately, cell death. This additional cell death and enlargement of the stroke area can be prevented with paying close attention to “time is brain” and reversing major vessel occlusion in the most timely manner possible,

References:

Powers WJ, Rabinstein AA, et al. 2018 Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2018;49:e46–e99.

Andersen KK et al. Hemorrhagic and Ischemic Strokes Compared: Stroke Severity, Mortality, and Risk Factors. Stroke. 2009;40:2068–2072.

Crocco TJ. Stroke. (Chapter 91) In: Walls R, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice.9th ed., 2018: 1241-1255.e3