In the case of a head injury with brief loss of consciousness and no focal neurological deficits, what is the diagnosis?

A head injury that results in a brief loss of consciousness, accompanied by a lack of focal neurological deficits, is most consistent with a concussion. A concussion is a type of mild traumatic brain injury that typically occurs due to a blow to the head, which can disrupt the normal functioning of the brain temporarily.

The hallmark symptom of a concussion is a transient alteration in mental status, which can include confusion or loss of consciousness, but it does not typically result in persistent neurological deficits in a physical examination right after the event. Patients may recover completely and cognitive symptoms can resolve over time, making the diagnosis of concussion appropriate in cases where brief loss of consciousness occurs without ongoing neurological issues.

In contrast, a contusion generally involves bruising of the brain tissue and can lead to focal neurological deficits or prolonged symptoms. A subdural hematoma involves bleeding and can present with more severe symptoms, again often including focal neurological deficits, making it less likely in this scenario. Concussion syndrome refers to prolonged symptoms persisting beyond the expected recovery time after a concussion, but the initial acute diagnosis remains concussion based on the presentation described.