By Radhika Sundararajan, M.D., Ph.D
Faculty Peer Reviewed
A healthy 18 year-old female presents to Urgent Care after slipping and falling this morning in the bathroom and hitting her head on the tile floor. She denies any loss of consciousness, vomiting, or current neurological deficits, but does have a mild occipital headache where she struck her head. She has heard a lot about recent research regarding concussions in young athletes and asks if you think she suffered a concussion and what this means for her.
What is a concussion?
The term concussion has been used in the medical literature as a synonym for mild traumatic brain injury (TBI). Mild TBI is a common and typically benign type of injury, though there are risks of serious short- and long-term sequelae.
In 1997, the Quality Standards Subcommittee of the American Academy of Neurology defined concussion as a trauma-induced alteration in mental status that may or may not involve loss of consciousness.1 However, this term had been loosely applied to a range of presentations. In 2004, an international multidisciplinary conference on concussion convened to provide further clarification.2 A concussion is therefore defined as a complex pathophysiological process affecting the brain, induced by traumatic forces and involving the following characteristics:
1) rapid onset of short-lived impairment of neurologic function that resolves spontaneously
2) neuropathological changes, but with acute clinical symptoms largely reflecting a functional disturbance rather than structural injury
3) a graded set of clinical syndromes that may or may not involve loss of consciousness
4) resolution of the clinical and cognitive symptoms typically following a sequential course
5) grossly normal structural neuroimaging studies
Mild TBI occurs with head injury due to contact and/or acceleration/deceleration forces and may result in cortical contusions with varying degrees of axonal damage depending on the force of the trauma. Disruption of axonal neurofilament organization can impair axonal transport and lead to swelling, Wallerian degeneration, and possible transection. In addition, the release of the excitatory neurotransmitters acetylcholine, glutamate, and aspartate, and generation of free radicals contribute to secondary injury.3
There are approximately 1.4 million reported incidents of TBI in the United States every year, with the overwhelming majority being mild.4 In the United States, estimates of the relative causes of TBI are as follows: motor vehicle accidents (45%), falls (30%), occupational accidents (10%), recreational accidents (10%), and assaults (5%). Mild TBI also occurs from contact; in American football alone, an estimated 10% of college and 20% of high school players sustain brain injuries each season.5
Patients who have sustained a concussion or mild TBI should be evaluated with a neurologic assessment and mental status testing. Clearly, patients who present with prolonged unconsciousness, persistent mental status alterations, or abnormalities on neurologic examination require urgent neuroimaging and neurosurgical consultation. The Standardized Assessment of Concussion (SAC) was developed as a tool for the sideline evaluation of athletes who suffer a head injury.6 The SAC includes measures of orientation, immediate memory, concentration, delayed recall, neurologic screening, and exertional maneuvers. Its efficacy has been studied in cohorts of high school and college athletes sustaining concussions where patients with concussion were found to have significantly lower scores as measured by the SAC than those without.
The indication for neuroimaging depends primarily on the patient’s clinical presentation. Studies suggest a prevalence of CT scan abnormalities of 5% among patients presenting to a hospital with a normal Glasgow Coma Scale (GCS) score of 15, and of 30% for those presenting with a GCS score of 13, with the incidence of abnormalities leading to neurosurgical intervention at 1%.7 The American College of Emergency Physicians has endorsed the New Orleans criteria for adult patients with suspected mild TBI.8 These criteria apply to patients with a GCS score of 15 and indicates CT scanning if there is headache, vomiting, age >60 years, drug or alcohol intoxication, persistent anterograde amnesia, or visible trauma above the clavicle. Evidence suggests that patients with a normal GCS score, normal examination and head CT, and no predisposition to bleeding are less likely to suffer subsequent neurologic deterioration.8,9 Therefore outpatient observation may be permitted for the patient whose neurologic condition is very unlikely to deteriorate.
Sequelae and Prognosis
Patients who have suffered a concussion are at risk for numerous short-term and long-term sequelae. Second impact syndrome describes diffuse cerebral swelling thought to occur if a second concussion takes place while an athlete is still symptomatic from an earlier concussion. This is a rare but potentially fatal complication of mild head injury caused by cerebrovascular congestion and edema with increased intracranial pressure.10 More commonly experienced is postconcussion syndrome (PCS), which generally includes symptoms such as headaches, dizziness, fatigue, irritability, anxiety, insomnia, loss of concentration/memory, and noise sensitivity. It is estimated that 30 to 80% of patients with mild to moderate brain injury will experience some symptoms of PCS.2,6 Such symptoms typically develop in the first days after the trauma and generally resolve within a few weeks to a few months. Even more commonly occurring are post-concussion headaches, which occur in anywhere from 25 to 78% of patients after mild TBI, most often within one week of the injury.11
Based on the New Orleans criteria, neuroimaging was not indicated for this patient. She was educated regarding the definition of a concussion, the fact that it is often diagnosed without neuroimaging, and the possible sequelae of postconcussion syndrome and headaches. She was also given strict instructions to return should her headache worsen or her condition deteriorate.
Dr. Sundararajan is a recent graduate of NYU School of Medicine
Peer reviewed by Robert Staudinger, MD, Associate Professor, Department of Neurology, NYU Langone Medical Center
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