Concussion has been derived from Latin word which means Contutere (to shake violently) or concussion (action of  striking  together).It is  the most common type of   traumatic brain injury and  presently  the  word is  interchangeable  with mild  traumatic brain  injury (MTBI). Concussion includes variety of physical, cognitive and emotional symptoms. In head injury there is temporary loss of brain function. Concussion falls under the classification of mild traumatic brain injury. Injuries such as intracranial hemorrhage (e.g. such as intracranial hematoma, subdural hematoma, epidural hematoma) are not included into MTBI, but neuroimaging may be considered as complication of MTBI.

Mechanism of Concussion

Brain is surrounded by Cerebrospinal fluid (CSF), which mainly functions to protect the brain from light trauma. Impact of striking forces on the brain causes, linear rotation and angular movement of the brain. In rotational movement  the  head  turns  around  the  center of  gravity and  in angular  movement  the head turns  around  the axis. The rotational forces may be thought to be major component in concussion and severity.  The midbrain and diencephalon are most affected. The forces disrupt the normal cellular activity in the reticular activity system; the individual becomes unconscious when upper part of the brain system, corpus callosum, temporal lobe and frontal lobe are affected.

Diagnosis of Concussion 

In assessing  the patient  of  concussion, it  is  mandatory to assess the  Airways, breathing  and  Circulation (ABC). Examination of  cervical spine, which may found  to be injured in unconscious  person. Patient may be thoroughly examined for other serious injuries, the signs are at high risk for serious brain injuries are as follows:-

1. Persistence headache, and vomiting
2. Gradual increase in disorientation or deteriorating level of consciousness
3. Seizures
4. Unequal pupil size

Brain imaging may be done to detect lesion that are frequently in 24-48 hours. Diagnosis of MTBI is based on the physical and neurological examination, duration and  level of unconsciousness (usually less 30 minutes), and in   Post Traumatic Amnesia (PTA) less than 24 hours. Glasgow coma scale less (13 to 15) is indicative of MTBI.

• Neurophysiological Test: are used to measure cognitive functions. If Glasgow coma scale is less than 15 in two hour and less than 14 at any time, CT scan is recommended. Most complication with concussion cannot be diagnosed by CT scan and MRI.
• Post Concussional syndrome may be associated with abnormality which is visible on SPECT and PET scan. Mild head injury may or may not produce abnormality on EEG.

Signs and symptoms of Concussion

Concussion is associated with variety of Symptoms the most common are:

1. Headache. It is the most common MTBI symptom.
2. Other Symptoms include. Dizziness, nausea, vomiting, lack of motor coordination, and difficulty in balancing.
3. Visual symptoms:  includes, light sensitivity, seeing bright light, blurred vision, double vision,
4. Ear Symptoms: tinnitus, or ringing of ear.
5. Cognitive and Emotional Symptoms: The patient feels disoriented in time and space and is unable to concentrate.
6. Post Traumatic  Amnesia: In the  event of  injury ,the individual is  unable  to be recall, confusion and  other concussion  is  the  hallmark which may  developed immediately or  takes  Several  minutes.

Grading of Concussion

In order to simplify the process; three systems of grading are widely followed:-

	Grade I	Grade II	Grade III
Cantu	Post-traumatic amnesia <30 minutes, no loss of consciousness	Loss of consciousness <5 minutes or amnesia lasting 30 minutes–24 hours	Loss of consciousness >5 minutes or amnesia >24 hours
Colorado Medical Society	Confusion, no loss of consciousness	Confusion, post-traumatic amnesia, no loss of consciousness	Any loss of consciousness
American Academy of Neurology	Confusion, symptoms last <15 minutes, no loss of consciousness	Symptoms last >15 minutes, no loss of consciousness	Loss of consciousness (III a, coma lasts seconds, III b for minutes)