Soon after Sally is born, the top part of her head begins to enlarge drastically

Question

Soon after Sally is born, the top part of her head begins to enlarge drastically, a relatively common condition called hydrocephalus (or “water on the brain”), caused by a blockage in the passages which normally drain cerebrospinal fluid (CSF) from the cranial cavity. If untreated for long enough, hydrocephalus can cause brain damage or death. Fortunately, Sally’s condition is caught early. Surgeons implant a shunt tube to drain the CSF into her abdominal cavity, and she grows up to lead a normal life with normal brain function.

But as (bad) luck would have it, Sally’s grandmother, Sarah, falls and hits her head on a doorframe. One of the many complications from this is that Sarah develops cerebral edema (that is, swelling of the brain and fluid buildup within the skull).

While hydrocephalus in newborns is serious, cerebral edema in older children or adults is critically dangerous and requires emergency treatment to reduce pressure within the skull. Why is this? (Hint: look back at the bones chapter.)

As one part of the complex treatment Sarah receives for her injury, she’s given hypertonic IV saline. Explain why this could be helpful in this situation. (Hint: osmosis again. It’s everywhere!)

Explanation / Answer

While hydrocephalus in newborns is serious, cerebral edema in older children or adults is critically dangerous and requires emergency treatment to reduce pressure within the skull. Why is this?

Answer- The skull being a not flexible syructure ot cannot accomodate the increased pressure. An increase in pressure, most commonly due to head injury leading to cerebral edema, can crush brain tissue, shift brain structures, cause hydrocephalus, cause brain herniation, and restrict blood supply to the brain. It also causes reflex bradycardia.

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As one part of the complex treatment Sarah receives for her injury, she’s given hypertonic IV saline. Explain why this could be helpful in this situation.

Answer- administration of hypertonic IV saline is called as osmotherapy. Hypertonic saline has increase serum osmolality which shifts excess fluid from intracellular or extracellular space of the brain to intravascular compartment. This results in brain shrinkage effectively reduces intracranial volume and decreases the intracranial pressure.

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