A<unk>  is a severe<unk>  to the spine, spinal cord, or brain, and may also include skull or spinal fractures. This is a subset of the definition for the legal term<unk> , which is based on the definition used by the American Medical Association. The National Center for<unk>  Sport<unk>  Research in the United States classifies<unk> es based on the three outcomes associated with them: fatality, those causing permanent severe functional disability, and those causing severe head or neck trauma with no permanent disability. A fatal<unk>  may be a direct result of trauma sustained during an activity, or may occur indirectly. Indirect nonfatal<unk>  may occur as a result of systemic failure from exertion during an activity, such as from cardiovascular conditions, heat illness, exertional hyponatremia, or dehydration, or a complication to a nonfatal<unk> . Indirect fatalities are usually caused by cardiovascular conditions, such as hypertrophic cardiomyopathy and coronary artery disease. Fatal<unk>  may reveal an unknown "underlying anatomical or physiological abnormality". Individuals with certain anatomical anomalies should not participate in some activities. For example, contact sports are contraindicated for individuals with an anomalous odontoid process, as any violent impact may result in a<unk> . This is because a malformed odontoid process may lead to instability between the atlas and axis (the C1 and C2 cervical vertebrae). Those with atlanto-occipital fusion should also avoid contact sports.
Catastrophic injury
Secondary trauma
Nerve injury
Occult fracture
Ischemic compression
Acquired brain injury
Barotrauma
Neurolathyrism