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Repetitive Head Injury Syndrome David Cifu, MD, eMedicine.com (page 2 of 8) Page 2 of 8

Schulz et al reported on a prospective cohort study of North Carolina high-school athletes followed from 1996–1999.²³ Subjects were clustered by school and sport, and the sample included 15,802 athletes, with 1–8 seasons of follow-up per athlete. Concussion rates ranged from 9.36 concussions per 100,000 athlete-exposures in cheerleading to 33.09 concussions per 100,000 athlete-exposures in football, where "athlete-exposure" is one athlete participating in one practice or game. The overall rate of concussion was 17.15 concussions per 100,000 athlete-exposures.

Cheerleading was the only sport for which the practice rate of concussions was greater than the game rate.²³ Almost two thirds of cheerleading concussions involved two-level pyramids. Concussion rates were elevated for athletes with a history of concussion, and they increased with the increasing level of body contact permitted in the sport.

Powell and Barber-Foss reported a two-year review of 235 US certified athletic high-school training records. The authors estimated a total of 62,816 cases of mild traumatic brain injury (TBI) annually among high-school varsity athletes, with football accounting for approximately 63% of these cases and a varied incidence among 10 other popular sports.²⁴

Matser et al showed that 23% of the amateur soccer players they studied had 2-5 concussions during their career.16 Boden et al found that the overall prevalence of college soccer-related concussions was 0.6 cases per 1000 athlete-exposures for men and 0.4 cases per 1000 athlete-exposures for women.17 The authors reported that the vast majority (72%) of these concussions were grade 1, and none were grade 3.¹⁷

The actual number of athletes who may be affected by repeated minor head injuries is largely unknown.

Functional Anatomy

SIS is thought to occur because of a loss of autoregulation of the cerebral blood flow, which leads to vascular engorgement, increased intracranial pressure (ICP), and eventual herniation. This herniation may involve the medial temporal lobe and may occur medially across the falx cerebri or inferiorly through the tentorium. Herniation can also force the cerebellar tonsils to move inferiorly through the foramen magnum. The athlete's condition rapidly worsens, and brainstem failure occurs in 2-5 minutes.

Sport-Specific Biomechanics

The brain is protected by bone and is cushioned by tough meninges and cerebrospinal fluid. Despite these protective surroundings, blunt-force trauma to the head can cause injury to the site of impact (coup injury) and the site immediately opposite of the impact (contrecoup injury). Factors that dissipate the force (eg, equipment, neck muscle strength) can minimize this trauma.

Clinical

History

The history is a key element in evaluating an athlete with a suspected head injury. However, the athlete may not be able to provide a good history because of slowed mentation or confusion. In such cases, obtain the history from a teammate, coach, or observer. Symptoms of a head injury may include the following:

• Headache
• Memory impairment
• Confusion
• Diplopia
• Fatigue
• Photophobia, phonophobia, or both
• Blurred vision
• Dizziness
• Hemiplegia
• Nausea
• Sensory loss
• Impairment of hand-eye coordination
• Irritability
• Depression

Physical

The goals of the physical evaluation are to (1) recognize that a head injury may have occurred, (2) determine which athletes require immediate transport to a medical facility, and (3) decide when the athlete can return to competition. Emergency management includes the ABCs of first aid. That is, assess and manage the individual's airway, breathing, and circulation. Signs of head injury include the following:

• Altered levels of consciousness
• Posttraumatic or retrograde amnesia
• Gait abnormalities
• Weakness
• Visual abnormalities
• Sensory loss
• Pupillary concordance and/or accommodation
• Poor concentration
• Apprehension
• Increased symptoms with exertion
• Focal symptoms – Facial or extremity twitching, smelling of atypical odors, tasting of atypical tastes
• Generalized symptoms – Tonic-clonic movements of body, incontinence, altered level of arousal

The brief neurologic examination should be performed without moving the athlete until the patient's ABCs and spine are deemed stable. The following are assessed:

• Verbal quality and appropriateness
• Memory (eg, to event), orientation (eg, to date), cognitive (eg, ability to perform the serial 7s test)
• Visual findings – Pupillary size and reaction, tracking, nystagmus, gross visual fields, diplopia
• Motor findings – Coordination (finger to nose), strength (focal findings), balance (eg, single-leg stance, heel to toe)
• Romberg test results
• Tone
• Reflexes
• Sensory abnormalities – Touch, pinch, and pain

Causes

Factors that may increase the risk of a poor outcome with a repetitive head injury include the following:

• Previous head injury
• Persistence of symptoms from a previous head injury
  • Headache
  • Labyrinthine dysfunction (balance disorder)
  • Visual, motor, or sensory changes
  • Mental difficulties that affect thought and memory processes
• Alcohol or illicit drug use

Differentials

Other Problems to Be Considered

• Brain mass (eg, tumor, abscess, infection, congenital abnormality)
• Cerebral contusion
• Dehydration / Hyperthermia
• Diffuse axonal injury
• Epidural hematoma
• Intoxication (alcohol or illicit drug use)
• Medication effect (pain, allergy)
• Meningeal irritation/infection
• Seizure disorder
• Psychiatric disorder
• Subarachnoid hemorrhage
• Subdural hematoma or intracerebral hematoma

WorkUp

Lab Studies

No laboratory tests help in diagnosing repetitive head injury. Most cases are diagnosed on the basis of the clinical findings.

From eMedicine.com. Reprinted with permission. www.emedicine.com/sports/TOPIC113.HTM.

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