Symptoms of concussion can be mild to severe, and in some cases emergency treatment may be needed.

The most common symptoms of concussion are:

• confusion, such as being unaware of your surroundings, a delay in answering questions, or having a blank expression 
• headache
• dizziness
• nausea
• loss of balance
• feeling stunned or dazed
• disturbances with vision, such as double vision, blurred vision or "seeing stars" or flashing lights
• difficulties with memory

Difficulties with memory can mean:

• you are unable to remember events that occurred before the concussion happened (this usually only affects the minutes immediately leading up to the concussion) – retrograde amnesia  
• you are unable to remember any new information or events after the concussion happened – anterograde amnesia

Both types of memory loss usually improve within a few hours.

Less common symptoms

Less common symptoms include:

• loss of consciousness
• slurred speech
• changes in behaviour, such as feeling unusually irritable
• inappropriate emotional responses, such as suddenly bursting into laughter or tears

When to seek medical advice

As a precaution, it is recommended that you visit your nearest accident and emergency (A&E) department if you or someone in your care has a head injury resulting in concussion and then develops any of the following signs and symptoms:

• loss of consciousness from which the person then recovers
• amnesia (memory loss), such as not being able to remember what happened before or after the injury
• persistent headaches since the injury
• changes in behaviour, such as irritability, being easily distracted or having no interest in the outside world – this is a particularly common sign in children under the age of five
• confusion
• drowsiness that goes on for longer than an hour when you would normally be awake
• a large bruise or wound to the head or face
• prolonged vision problems, such as double vision
• reading or writing problems
• balance problems or difficulty walking
• loss of power in part of the body, such as weakness in an arm or leg
• clear fluid leaking from the nose or ears (this could be cerebrospinal fluid, which normally surrounds the brain)
• a black eye with no other damage around the eye
• sudden deafness in one or both ears

Anyone taking warfarin should seek medical assistance after a head injury, even if they feel well. 

Anyone who is drunk or high on recreational drugs should also go to A&E if they have a head injury. It's often easy for others around them to miss signs of a more severe head injury.

Certain things make you more vulnerable to the effects of a head injury, such as:

• being aged 65 or older
• a previous history of brain surgery
• having a condition that makes you bleed more easily, such as haemophilia, or having a condition that makes your blood more prone to clotting, such as thrombophilia
• taking anticoagulant medication (such as warfarin) to prevent blood clots, or taking low-dose aspirin

When to seek emergency medical treatment

You should phone 999 for an ambulance immediately if the person:

• remains unconscious after the initial injury
• is having difficulty staying awake, speaking or understanding what people are saying
• is having a seizure or fit
• has been vomiting since the injury
• is bleeding from one or both ears