Concussion is a mild brain injury characterized by immediate transient disturbance of consciousness and retrograde amnesia following the injury.
Mechanism and Pathology
The mechanism underlying concussion remains debated. The prevailing view suggests that the disturbance of consciousness in concussion primarily stems from damage to the brainstem reticular formation. This damage is associated with factors such as cerebrospinal fluid shock (sudden movement of ventricular fluid through the brain's ventricular system), intracranial pressure fluctuations during impact, cerebrovascular dysfunction, and mechanical stretching or twisting of the brainstem. In the affected brain tissue, neuronal mitochondria and axons swell, accompanied by interstitial edema. Elevated concentrations of acetylcholine and potassium ions in the cerebrospinal fluid disrupt axonal conduction or induce cerebral metabolic disturbances. Clinical studies have confirmed organic damage in some concussion patients through abnormal brainstem auditory evoked potential tests. Concussion may represent the mildest form of diffuse axonal injury.
Clinical Manifestations and Diagnosis
Immediately following the injury, there is often a brief loss of consciousness lasting from a few seconds to several minutes, typically no longer than half an hour. In some cases, this may manifest only as transient confusion or disorientation without actual loss of consciousness. Accompanying symptoms may include pallor, pupil changes, cold sweating, low blood pressure, weak pulse, shallow and slow breathing, and signs of autonomic nervous system and brainstem dysfunction. Once consciousness is regained, there is an inability to recall events occurring at the time of and shortly before the injury, a phenomenon known as retrograde amnesia. Common symptoms include headache, dizziness, fatigue, insomnia, tinnitus, palpitations, photophobia, emotional instability, and memory impairment. These symptoms usually last for several days to weeks, though in rare cases, they may persist for a longer duration.
Neurological examination typically does not reveal any significant findings. Lumbar puncture results indicate that intracranial pressure and cerebrospinal fluid (CSF) biochemical markers remain within normal ranges. CT imaging does not show any abnormalities within the cranial cavity.
Treatment
Concussion does not require specific treatment. General management involves bed rest for 5 to 7 days, with the selective use of sedatives or analgesics to alleviate symptoms. Attention to addressing the patient's anxiety is important. Most patients recover fully within two weeks, and the prognosis is generally favorable.