Concussion: Pathophysiology, Causes, Symptoms and Treatment, Animation

(USMLE topics, neurology) Concussion (mild traumatic brain injury): Pathophysiology, Causes, Signs and Symptoms, Treatment.

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Voice by: Ashley Fleming

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Concussion is a MILD traumatic brain injury that affects normal brain functions. It occurs as a result of a forceful blow, either DIRECT or INdirect to the head. An example of an INdirect blow is a whiplash-type injury that causes the brain to SHAKE quickly back and forth inside the skull. In a direct blow, injury may develop on the side of contact with the force, or on the OPPOSITE side of the head. Concussion may be caused by falls, contact sports, motor vehicle accidents, or physical abuse. Brain injury can occur with translational, rotational or angular movements of the head. Rotational and/or angular forces cause the brain to TWIST against the BRAINSTEM - the thin stalk that connects the brain to the spinal cord, and damage the structures within. Because the brainstem controls many VITAL bodily functions, including consciousness, rotational and angular injuries usually result in LOSS of consciousness and are often more serious.
Concussion is a FUNCTIONAL injury, rather than structural. A concussed brain usually looks NORMAL on a brain-imaging test. The damage occurs at a MICROSCOPIC level and generally affects a LARGE area of the brain. The mechanical impact exerted by the blow sends shock waves that diffuse through the brain tissues, STRETCHING and possibly SHEARING membranes of neurons, especially along the long axons that are responsible for transmitting signals from one neuron to another. The events that take place during and after concussion are complex and not fully understood, but likely to involve IONIC IMbalances and ENERGY CRISIS due to REDUCED blood flow. Ionic disturbances, such as ABnormal potassium EFflux and calcium INflux, INTERFERE with action potential dynamics, DISRUPTING normal communication between neurons. Reduced blood supply IMPAIRS cellular functions and makes the brain MORE vulnerable to further damage.
Children and teens are at GREATER risks for brain injury because their brain is STILL DEVELOPING and therefore more susceptible to insults. Axons in young brains are not FULLY myelinated, EASIER to get damaged and take LONGER to recover. Brain development may also STOP for some time after sustaining a concussion.
Signs and symptoms of concussion can be SUBTLE and may NOT appear immediately. It is common for the first signs to show up after 20 minutes to hours from the time of impact. COMMON symptoms include headache, drowsiness, dizziness, sensitivity to light, loss of memory, difficulty concentrating and feeling slowed down. Patients should be observed for at least 48h for worsening signs such as loss of consciousness, INcreasing headache, REPEATED vomiting, slurred speech, confusion, unusual behaviors, seizures, and limb weakness or numbness. Any of these would require emergency care.
Concussion usually revolves on its own, with PROPER physical and cognitive REST. The majority of people fully recover after a couple of weeks but some may take longer. During recovery the brain is MUCH more vulnerable to further insults and any activities that may potentially cause another impact SHOULD be avoided. A REPEATED injury while the brain is recovering may exacerbate symptoms, result in PERMANENT brain damage, and can be fatal.