**3. Vestibular system**

The vestibular system is a complex network that includes small sensory organs of the inner ear (utricle, saccule, and semicircular canals) and connections to the brainstem, cerebellum, cerebral cortex, ocular system, and postural muscles [4, 5].

The vestibular system is distinctive from other systems because it becomes immediately multisensory and multimodal [4]. For example, the vestibular system intercorrelates with the somatosensory system through the vestibulospinal reflex that is responsible for postural control and with the visual system controlling the vestibulo-ocular reflex (VOR), that maintains visual stability during head movements.

These linked group of systems allows the brain to differentiate active from passive head movements and provide information regarding head movements and positions to maintain visual and balance control. Furthermore, visual and somatosensory systems interact with the vestibular system throughout the central vestibular pathways and are essential for gaze and postural control. This interaction *Concussion and Balance in Sports DOI: http://dx.doi.org/10.5772/intechopen.97024*

of multisensory and multimodal pathways is important for higher level of function such as self-motion perception and spatial orientation [2, 4–6].

Usually, individuals who present impairments related to the vestibulo-ocular reflex complain about dizziness and visual instability, this is due the organization and neurophysiology of the vestibular system [4].

Inversely, vestibulo-spinal dysfunction (correlated to the vestibulo-spinal reflex - VSR) normally present as consequences imbalance. Since these reflexes do not share the same neuronal circuitry, it is possible to have damages one without affecting the other [4, 6].

## **4. Sport-related concussion**

Traumatic Brain Injury (TBI) occurs in subjects of all age groups and is a significant public health issue [7].

The Post-Concussive Syndrome (PCS) defines the set of symptoms and signs present frequently in a persistent mild TBI [8]. The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) presents the clinical criteria for PCS [9]. The symptoms include headache, fatigue, vision changes, disturbances in balance, confusion, dizziness, insomnia, neuropsychiatric symptoms, and difficulty with concentration [7–9].

Disturbances in balance and dizziness are described in literature by 23–81% [8, 10–13] of concussed athletes [and is correlated with a 6.4-times higher risk to have another concussion if not treated, comparing to any other on-field symptom [11, 14]. Currently, several studies have presented that imbalance and dizziness are usual after a TBI have a correlation with the time to recovery (protracted recovery superior to 21 days), causing a delay comparing to the ones who did not present those symptoms [10–14].

Cohort studies and analysis had shown that women are at greater risk for persistent PCS. Besides, they are more likely to present headache, irritability, fatigue, and concentration problems post-concussion. Increases in age are also associated with a higher risk of PCS [15].

#### **5. Assessment**

The assessment of an injured player is facilitated by the presence of a certified athletic trainer, team physician, or other health care provider at the location where the injury occurred. It is important to mention that balance symptoms may not become apparent for several hours after injury bringing an additional obstacle to identification. Thus, the follow up for SRC is crucial to assess any balance dysfunction and treatment during the patient's recovery. Hence, vestibular and balance evaluations must be included in the concussion assessment battery and when available, objective tests may be used [16].

The assessments strategies present in this chapter were noted in scientific literature to be used as part of the concussion evaluation as well as a preseason baseline. The same tools for assessment are applied and can benefit other individuals with vestibular and ocular/oculomotor disorders as well [16–18].

Among the recommended assessments are physical examinations, clinical interviews, symptom reports, and neurocognitive and balance tests. For that reason, is recommended to use the Symptom Checklist. It is a self-report graded symptom checklist validated for concussion assessment. One example is the Sport Concussion Assessment Tool 5 (SCAT-5). The SCAT-5 contain 22 items and corresponding 0 to 6 points where higher numbers indicate greater symptom severity [19].

Below, it is described some assessments that can be applied in case of vestibular impairments after concussions:

Balance Error Scoring System (BESS) Sensory Organization Test (SOT) Head Shake-Sensory Organization Test (HS-SOT) Concussion Balance Test (COBALT) Vestibulo-Ocular Reflex and Vestibular/Ocular Motor Screen (VOMS) Dynamic Visual Acuity Test (DVAT) Head Impulse Test (HIT) Post-Concussion Symptom Scale (PCSS) Dizziness Handicap Inventory (DHI) Dix-Hallpike Maneuver
