The primary symptoms of concussion mainly manifest as, initially, disturbances in consciousness such as patient comas, typically lasting no longer than half an hour. The second is recent memory loss, where the patient is unable to recall the circumstances of the injury. At the time of injury, the patient may also appear pale and experience a drop in blood pressure. Post-injury symptoms can include dizziness, headaches, nausea, loss of appetite, poor sleep, reduced memory, lack of concentration, and even tinnitus among various other clinical manifestations.