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Concussion and dizziness and balance

Timothy C. Hain, MD

Most recent update: October 19, 2014 : This page is not written for or intended for use in legal endeavors.


Concussion comes from the Latin word, "to shake violently" (Webster). Most concussions in adults are caused by direct blows to the head. However, it is also accepted that occasionally, such as in the "shaken baby" syndrome, concussions can occur without a direct blow to the head after a very forceful acceleration/decelerations.

The American Academy of Neurology (AAN) defined concussion in 1997 as "any trauma-induced alteration in mental status that may or may not include loss of consciousness". In other words, they defined it as the combination of a change in mental status associated with "trauma". (Practice Parameter, 1997). We think that this definition is so all-inclusive as to be almost meaningless as by this a "concussion" could be a change in one's mood after an acorn fell on one's head. Another attempt was made in 2001.

Criteria for concussion proposed by the 2001 "Concussion in Sport" international symposium are as follows:

  1. Concussion may be caused either by a direct blow to the head, face, neck, or elsewhere on the body with an “impulsive” force transmitted to the head.
  2. Concussion typically results in the rapid onset of short-lived impairment of neurological function that resolves spontaneously.
  3. Concussion may result in neuropathological changes, but the acute clinical symptoms largely reflect a functional disturbance rather than structural injury.
  4. Concussion results in a graded set of clinical syndromes that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course.
  5. Concussion is typically associated with grossly normal structural neuroimaging studies.

(Aubry et al, 2001).

As shown above, sports researchers in 2001, also used an immense number of vague words to "define" concussion. In #1, they specified that a concussion must be caused by trauma that transmits an "impulsive" force to the head. At least they are saying that the head must be affected. What isn't so clear is how "impulsive" force is defined.

In criteria 2, they suggest that concussion "typically" results in the "rapid" onset of short-lived impairment. The "typically" qualifier as well as the use of the term "neurological function" here make this criterian vague. We prefer the AAN definition that requires a change in mental status rather than "impairment of neurological function". Otherwise, by the sports criterian, an injury to a nerve in the big toe associated with an "impulsive" type force, might qualify as a concussion. We think the injury in concussion should be limited to the brain.

They also indicated that concussion is typically associated with normal structural imaging studies. In other words, a normal MRI and CT scan of the brain. Logically, one might both have a bleed of the brain as well as additional disruption of the brain due to "concussion". We think the "typically" word is justified here.

Whether or not a concussion occurred after in a "whiplash" type accident, where there was no or minimal force to the head, is often debated by attorneys. Considering the vagueness of the definitions adopted by the groups above, nearly anything (including feeling distressed after a ping-pong ball dropping on one's head) would qualify.

The neck is more vulnerable than the brain -- and it takes almost an order of magnitude more force to cause a significant brain injury than a neck injury (see whiplash page).

We prefer a more constrained definition of a concussion as a mental disturbance (including poor memory, slowed or otherwise disturbed thinking) which follows an impact of the head (within 24 hours at the most), and that is without a new imaging abnormality. The obvious difficulty with this definition is that it depends on a subjective judgement (concerning memory or abnormal thinking), and thus is vulnerable to bias. Thus to conclude someone has a concussion, one must also accept that the individual is reporting their internal thought processes accurately.

Post concussion syndrome is often attributed to "Traumatic Brain Injury", or TBI, which is a general term for a head injury caused by trauma, affecting the brain. Again, there is considerable looseness to this term.

One must differentiate "significant", or maybe "real" concussions from events that meet the literature's criteria, but that no reasonable person would accept as being a cause impairment or disability. For example, one might be involved in a motor vehicle collision and not remember the second of impact.

Our general impression is that "significant" concussions are unlikely to be consequences of whiplash mechanism accidents. We are also dubious that "significant" cognitive symptoms should persist for long periods of time after a head injury unaccompanied by a loss of consciousness. Not impossible, but uncommon.


Theories regarding the source of cognitive symptoms in concussion fall into several broad categories (Choe et al, 2012).

Each theory has its advocates.

Signoretti et al(2011) suggested that "energetic metabolism disturbances caused by the initial mitochondrial dysfunction seem to be the main biochemical explanation for most postconcussion signs and symptoms.".

Johnson et al (2013) suggested that diffuse axonal injury was one of the "most common and important pathological features of traumatic brain injury). McAllister et al (2014) compared concussed to nonconcussed athletes, and suggested that diffusion tensor imaging diffusivity on MRI correlates with both the magnitude of impact as well as neuropsychological measures. In most instances however, a pre-injury MRI with DTI is not available for comparison, making inference regarding the source of DTI changes difficult in individuals.

Len et al (2011) reviewed blood flow abnormalities post mild traumatic brain injury.

Some studies suggest that there is increased amyloid accumulation in individuals who have had brain injuries. This would suggest a link between Alzheimer's disease and cognitive disturbances after brain injury.

Diagnosis of concussion:

Concussion diagnosis is a combination of screening for other diagnoses (like bleeding in the brain), and assessment of vulnerable brain systems such as thinking and balance.

Neuropsychological testing is the preferred method of assessing thinking. Recently, a short neuropsychological test called the "IMPACT" test has become widely available for sports concussions. It is much quicker (and cheaper) than the formal "neuropsych battery", and can be performed using a proctored computer. While designed for sports concussions, it is actually generally applicable to concussions of all causes.

Regarding balance testing, moving platform posturography, ENG and rotatory chair testing all are useful. Posturography is the most sensitive of these three for concussion looking for nonspecific effects. ENG and rotatory chair testing are useful primarily to exclude ear damage.

All of these tests have the problem of detecting invalid tests. Athletes typically are eager to return to play, even though they may be mentally impaired. On the other hand, individuals who are hoping to benefit financially from their injury, such as persons in litigation or seeking disability compensation, may exaggerate their balance or cognitive deficits. Both the IMPACT test and the posturography test have methods of detecting invalid or "aphysiologic" patterns.


In any case, while dizziness and nausea symptoms accompanying the entity called "concussion" in the literature usually resolve over 6 weeks, cognitive symptoms and headaches may persist longer. Hoffer et al (2004) suggested that dizziness symptoms persisted an average of 39 weeks -- about 9 months, and that return to work usually occurred at about 16 weeks. Hoffer was reporting symptoms from military trauma rather than sports. In athletes, concussion symptoms resolve quickly -- within 2 weeks(d'Hemecourt, 2011). Of course, sports concussions usually involve a population of people who are otherwise very healthy.

Occasionally symptoms are permanent. As noted above, in many cases, chronic symptoms are psychological in origin. Balance symptoms after concussion generally (i.e. 50% of the time) resolve by 10 days (Peterson et al, 2003). Nevertheless, there are many persons who have longer lasting symptoms. Our experience has been that balance symptoms post neck injury can take much longer to resolve.

Treatment is mostly "tincture of time".

It is currently thought that there is a period of increased vulnerability to repeated injury following a concussion and that its duration is variable. (Giza et al, 2011) Accordingly, athletes with a concussion should not return to play on the same day.

Doolan et al (2011) put forth their recommendations for "retiring", an athlete from sports activities:

Season ending:

Career ending:

Protocol for returning athlete to sports (also from Doolan, 2011)

Common sense would suggest that it is imprudent to return to a contact sport, if one wishes to minimize risk of thinking disturbance. It would also suggest that sports such as boxing where concussions are routine, are very likely to result in impaired thinking over time. While participating in activities where there is a substantial risk of being hit on the head over and over seems extremely unwise to the author of this page, the proper response of society is debatable. While we do legislate that seat belts should be worn when in a motor vehicle, we do not stop people from engaging in many dangerous activities such as driving cars, mountain climbing, or smoking tobacco. There is an assumption made that adults who participate in dangerous activities have the right to direct their own activities.


No medication has been established to speed recovery.

Medications that may help other aspects include:


Copyright November 2, 2014 , Timothy C. Hain, M.D. All rights reserved. Last saved on November 2, 2014