You are too focused on brain swelling as a defining condition of concussion or brain injury.

Every concussion is a brain injury . There is diffuse axonal injury, contusions (bruising), etc. CNS leaks require some sort of tearing.

Researchers have tried to create a repeatable matrix of injury forces, immediate symptoms (LOC, amnesia etc. GCS) and treatment protocols,and recovery times and have not been able to show a reliable direct connection. Some people can be knocked out for 5 minutes and regain consciousness with minimal ongoing symptoms. Others can have no LOC and manifest severe symptoms.

Actually, a few years back, the US Department of Defense awarded a multi-million dollar contract to a research clinic to 'define a concussion.' They wanted to be able to accurately diagnose a concussion in clinical situations.

As it stands, a concussion is currently defined as an mTBI resulting from trauma forces to the head/brain resulting in any number of specific symptoms within the cluster of symptoms common to concussion. These trauma forces do not need to be caused by an impact but can be the result of non-contact whipping (whiplash) or jarring.

The delayed symptoms are not limited to swelling. Often, these symptoms are the result of cellular death as the brain shuts down neural pathways that are malfunctioning. There is often damage to the glymph system resulting in a build-up of metabolic waste and waste related to the absorption of dead cells. Often, the capillary system has been damaged or strained resulting is poor blood perfusion. There may be swelling but often all there is is a inability for the brain to control fluid (blood, CNS) pressure within the brain. This is different from inflammatory swelling. Both can occur. Damage to the myelin sheath covering the axons and other neural fibers also causes symptoms.

There is technology to image these different injuries but there is no established protocol for treating these injuries based on those images. They still must rely on symptoms to guide treatment. A neurological exam is used to determine the severity of the injury and the possibility of a need for immediate intervention/investigation to treat a bleed or other focal injury. The mechanism of injury may help direct the investigation but it is an unreliable means of diagnosing.

In your case, it sounds like you suffered a crushing force to your skull and possible impact forces that jarred your brain within your skull. These can combine to cause a complex cluster of symptoms.

btw, We have had people here on NT who have had CNS leaks without elevated ICP (IntraCranial Pressure) .