Amnesia and vomiting are some of the more rare symptoms of a concussion.

Many who suffer an impact to the head will not even notice any symptoms beyond the first few seconds or minutes until some time has passed. This can be anywhere from the next day to even a few weeks later.

This is why:

One expert suggests all impacts to the head be recorded in the patients medical records so that later manifestation of symptoms can be considered as possible PCS. Without this possible concussion in the medical record, the later manifestation of a cluster of PCS symptoms can be confusing to the doctor and patient leading to errant diagnoses.

The following International Code of Diagnostics are recommended for the patients' medical record.

2012 ICD-9-CM Diagnosis Code 850.9
Concussion, unspecified
A violent jar or shock, or the condition which results from such an injury.

2012 ICD-10-CM S06.0X0A Concussion without loss of consciousness, initial encounter