Mild Traumatic Brain Injury

Mild traumatic brain injury (“mTBI”) is a common cause of neurocognitive deficits. Until recently, concussions were considered minor events with no persistent damage. In recent years, researchers have recognized that structural injury and activation of pathological protein cascades that lead to functional impairment can occur in concussion. Concussion and mTBI are now considered synonymous terms. 

The Centers for Disease Control and Prevention referred to mTBI as “the silent epidemic” in its 2003 Report to Congress on Mild Traumatic Brain Injury in the United States: Steps to Prevent a Serious Public Health Problem.¹ It notes that about 75% of all of the then estimated 1.5 million traumatic brain injury cases reported in the U.S. each year are mTBI. Today, nearly 1.7 million Americans are seen in hospitals for some form of traumatic brain injury each year.² It is also known that there are hundreds of thousands of unreported sports and recreation-related head injuries each year, making the actual number of TBIs as high as 3.8 million annually.³ This coupled with the estimated 320,000 service men and woman who have returned home since 2001 with a traumatic brain injury^4,5, yields a staggering number of affected individuals with demonstrable neuropsychological deficits who often go unrecognized, untreated, and even misjudged.

Although most patients recover fully from mTBI, up to 33% of patients have persistent neurocognitive problems.⁶ As many as 15% have been reported to have disabling symptoms a year later.⁷ For military or civilian patients with mild or moderate TBI, approximately 25-70% will have some memory loss; impaired judgment, difficulty with concentration and with completing tasks^8-12. All frontal lobe functions can be affected, leading to changes in personality, impulse control, judgment, motivation and communication^13-15. Up to 40% of patients with mild or moderate TBI will have neurological symptoms, such as seizures, changes in sensations, speech impairments, headaches, dizziness, fatigue and loss of balance^5,11,12.

Depression or anxiety occur much more frequently after mTBI^{5,11-13,16,17}. Notably, the symptoms of mTBI often overlap with those of Post-Traumatic Stress Disorder (PTSD), such as headache, dizziness, irritability, memory impairment, delayed problem solving, slowed reaction time, fatigue, visual disturbances, sleep disturbances, sensitivity to light and noise, impulsivity, judgment problems, emotional outbursts, depression, and anxiety^{5,9,12,15,18-20}. An estimated 8-19% of returning Warfighters meet criteria for PTSD,^5,21,22 while approximately 20% of returning Warfighters have screened positive for a probable mTBI. It is not surprising that the RAND study estimated that roughly one third of those screening positive for mTBI also had overlapping PTSD or depression⁴. The differentiation of mTBI and PTSD in returning Warfighters is a critical diagnostic and programmatic need for the DoD^11,23. These two overlapping populations have potentially different treatment requirements and different prognoses²⁴. Neuropsychological testing has been unsuccessful in clearly differentiating these two disorders and facilities are struggling to adequately treat the many affected Warfighters without the benefit of adjunctive and adequate diagnostic tests^11,12,25. For civilians with mTBI there are even fewer resources (see Links).

Sports is a common cause of mTBI (concussions), be it skiing, football, soccer, or wrestling. In one study, 6.3% of college football players had experienced a concussion over the course of a single season^26,27. A significant proportion of those who had a concussion experienced repeated concussion and the research showed a progressive increased risk for re-injury. With one concussion the odds ratio of a repeat concussion was 1.5; with 2 concussions the odds ratio of repeat concussion increased to 2.8; and at 3 concussions, the odds ratio increased to 3.4. With each successive concussion, recovery time became more and more prolonged^26,27. Research indicates that younger athletes are at higher risk of injury – a serious concern for parents of children playing football in high school, middle school, and even elementary school. Patients in my private practice who have received concussions (from football, soccer, cheerleading, or motor vehicle accidents) have experienced marked cognitive impairment – often being unable to compute simple math problems – for several weeks. Sideline assessments are inadequate to demonstrate the presence or absence of mTBI. The recent introduction of computerized assessments has resulted in a tendency to delay return-to-play until a player can be evaluated by a physician²⁸. However, computerized assessments are not reliably predictive of long-term outcome. Computerized assessments have a positive predictive value (a positive test is predictive of protracted recovery with associated high vulnerability to repeat concussion) of about 73% and a negative predictive value (a negative test is predictive of no long-term neuropsychological symptoms) of 74%²⁹. In contrast, a SPECT scan (see below) has a positive predictive value of 90-100% and a negative predictive value of 100% in mTBI following motor vehicle accidents^30,31.

Treating Mild Traumatic Brain Injury

A wide variety of symptoms and difficulties can occur following mTBI. Each symptom or symptom cluster requires a different treatment strategy. Medications often can be helpful to stabilize neurocircuitry or systems that have become impaired as a result of injury. The frontal lobes are often damaged in mTBI and improving frontal lobe function is a critical step in treatment. Research is being vigorously pursued to find effective treatments for TBI. As yet, there is no promising treatment that repairs brain injury.
Identifying Mild Traumatic Brain Injury

Traditional brain imaging modalities such as MRI and CT have provided little assistance in identifying mTBI, let alone differentiating it from PTSD. CT and MRI certainly have their applications in helping to diagnose traumatic brain injuries (especially severe injuries). Typically, CT remains a vital first step in the assessment of any traumatic brain injury due to its superior capacity to visualize hemorrhage and skull fracture. However, SPECT has been repeatedly demonstrated to be superior to CT in localizing functional cerebral damage in traumatic brain injury.^30-42 In fact, in a large series of patients with post-concussive syndrome, SPECT demonstrated a 10-fold superiority to CT in predicting clinical symptoms.³⁶ SPECT has also been repeatedly demonstrated to be superior to MRI in localizing functional cerebral damage in traumatic brain injury.^30-35,37 Indeed, new MRI applications such as diffusion-weighted MRI ^43-46 and flow MRI ^47,48 have utilized SPECT as the “gold standard” against which to measure results.

In evaluating mTBI, Bonne and colleagues call for a multimodal integration of clinical evaluation, neuropsychological assessment, and cerebral perfusion studies.⁴⁹ SPECT brain imaging has proven to be highly sensitive for detecting regional cerebral blood flow disturbances in patients with mTBI^30-42,49-60, despite a critique published over 14 years ago by the American Academy of Neurology which was based on a very small number of early studies.⁶¹ SPECT has been found to have high predictive value at 3, 6 and 12 months post injury of 90%, 100% and 100%, respectively.^30,31 It is clear that patients with persistent clinical symptoms continue to have abnormal follow-up SPECT findings. As with any abnormality, the ability to determine progress over time is crucial in choosing the best treatment option. SPECT has been utilized to track neurological changes during a course of treatment, providing clear evidence of neurophysiological changes^52,56-60. SPECT at 1 and 50 weeks was more predictive of functional impairment and yielded more prognostic information compared with MRI at 1 and 50 weeks in a study of traumatic brain injury.⁵⁶ Laatsch and colleagues demonstrated that SPECT and neuropsychological assessment were strongly correlated.⁵⁷ Neurology as a field tends to dismiss SPECT as a tool for evaluating mTBI, repeatedly citing a critique of early studies – referred to as the TTASAN report⁶¹. Neurology seems to be unaware of the wealth of research literature I have presented here and also disregard the opinions of thought leaders in Nuclear Medicine⁵⁴ and Radiology⁵³. More recent reviews⁶² critical of SPECT have scrupulously ignored the key powerful studies demonstrating the effectiveness of SPECT^30,31,36. Oddly, Neurology also seems to miss the point that SPECT imaging can demonstrate functional changes that occur in response to treatment, making it a potent tool for assessing treatments^{52,57-60,63-69}.

On March 19, 2014, an international team led by Dr. Theodore Henderson published a comprehensive review of the utility of SPECT neuroimaging in the evaluation and treatment of traumatic brain injury (TBI). This review published in PLos ONE, summarized data derived from research studies conducted over 30 years and involving 2,634 patients. This quantitative analysis and review found that the frontal lobe was the most common area of injury occurring in 94% of patients with TBI. The temporal lobe was the second most common area injured (77%). In studies comparing SPECT to more conventional neuroimaging techniques such as computed tomography (CT scan) or magnetic resonance imaging (MRI), SPECT proved far superior in detecting TBI in both the acute and chronic condition. Particularly in the case of mild TBI, also known as concussion, anatomical findings that can be picked up by CT or MRI are rarely present. We will have to watch to see if Neurology finally gets the message.

 

References

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