I am writing a novel in which a child suffers a head trauma after
falling from a tree, after which he remains in a coma or coma-like
state for a period of three days before dying. Is this feasible, and
if so what sort of things would happen "inside the head" that could
cause this?

Hi writer (Hi "thewriter" sounds awkward, no?,

     There are two types of coma associated with head injury. Head
injury patients often suffer internal organ damage as well, which can
contrubute to coma and death. The type you describe in your scenario,
which is credible, by the way, would be of a brainstem injury :
?Laborious breathing, pinpoint pupils, quadrispasticity with arms
flexed and trunk and legs extended, but without intracranial pressure
(elevated blood pressure).  Such cases almost always imply severe
brain damage and carry a poor prognosis.
Since severe head injuries are often accompanied by thoracic damage,
pulmonary edema (some of which is undoubtedly neurogenic), hypoxia,
and an unstable circulation often complicate the neurologic problems
created by the injury.  Damage to the cervical spine also a common
accompaniment, can cause fatal respiratory paralysis or permanent
quadriplegia from spinal cord injury; other cord damage can be almost
as disastrous.? And ?The most common cause of death and disability in
young people in the age of one to 44 is head injury.  In other words,
every ten minutes head injury claims the life of yet another child.?
http://www.headinjury.com/coma.htm


Since a child?s brain has a higher water content than an adult, it
more prone to acceleration-deceleration injuries. Head trauma from car
accidents, falls, and abuse, is a leading cause of death in children.
This site presents a slide show (click the screen with the mouse to
advance the slides) of head trauma in children.
Warnings:
The photos in this slide show are very intense and graphic.
This is a slow download, even with high-speed internet
http://pedsccm.wustl.edu/All-Net/media/slides/head/hdtrauma/hdtrauma.ppt


?At the moment of impact, the patient's brain is violently thrusted
back and forth inside the skull, tearing blood vessels and pulling
nerve fibers. These injuries cause the brain to swell, blocking the
flow of oxygen-carrying blood. Such a condition could result in
massive strokes and/or brain death. There's this period of time which
can last from a few days to a week -- It can even last up to months --
where there's no conscious behavior?
http://www.planetmobility.com/news/headinjury/coma.htm

?According to the National Center for Health Statistics, the mortality
rate from head trauma is 29% in the pediatric population. These data
are based on death certificate information, and 29% could be an
underestimation of the actual rate. Data reported by studies in trauma
centers show that head injury represents 75-97% of pediatric trauma
deaths.?
eMedicine
http://www.emedicine.com/ped/topic929.htm 
?Children with massive generalized brain oedema had the poorest
prognosis (37% died, 25% had impairment of consciousness).?
You can see the abstract on this site, but to read the entire article,
you will need to sign up for a free account.
http://www.blackwell-synergy.com/links/doi/10.1046/j.1460-9592.2002.00837.x/abs/


?What is the prognosis?
The outcome of TBI depends on the cause of the injury and on the
location, severity, and extent of neurological damage: outcomes range
from good recovery to death. Doctors often use the Glasgow Coma Scale
to rate the extent of injury and chances of recovery. The scale (3-15)
involves testing for three patient responses: eye opening, best verbal
response, and best motor response. A high score indicates a good
prognosis and a low score indicates a poor prognosis.?
http://www.doctorhealthynet.com/diseases/diseases_A-Z/diseases_P-T/traumatic_brain_injury.htm


Additional Reading:

Head Trauma in Children
http://www.cps.ca/english/statements/EP/ep90-01.htm#Severe%20injury

Head Injury
http://www.nlm.nih.gov/medlineplus/ency/article/000028.htm
Pediatric Head Trauma
http://surgclerk.med.utoronto.ca/Phase2/Paediatric/HeadTrauma/LearnIss.htm


Hope this provides you with sufficient background for your novel!

If any part of my answer is unclear, or if I have duplicated
information you already had, please request an Answer Clarification,
before rating. This will enable me to assist you further, if possible.

Regards, 
crabcakes

Search Terms
Coma death brain injury
Head trauma children

This is my first time using this service and I'm pretty well pleased.
The amount of information was sufficient for my needs. The answer was
well-written, concise and easy to read.

You might try searching Google for the PDF document "Fatal Pediatric
Head Injuries Caused by Short-Distance Falls" by John Plunkett, M.D.
published in the March 2001 issue of Lancet (copyrighted).  Included
are 18 case summaries and post mortems on children ranging from 12
months to 13 years who died from head trauma -- most injured on
playground equipment.  One of these scenarios might fit your story
parameters.

Best of luck,
V