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This article discusses the myth that SPECT (Single-Photon Emission Computed Tomography) scans provide definitive evidence of mild traumatic brain injury in patients with persisting symptoms (3+ months post-injury) when brain CT and MRI are normal. Brain CT and MRI scans are structural scans, meaning they provide information about the structural integrity of brain tissue. Conversely, a SPECT is designed to assess how the brain functions and does not provide useful information about brain structure. SPECT scans combine information obtained from a CT scan (which uses radiation) with a radioactive substance (known as a tracer) injected into the blood stream. When the radioactive tracer enters the bloodstream, it emits gamma rays. The gamma rays are detected by the scanner and in this way a SPECT scan measures blood flow in the brain.
In examining the claim that SPECT scans can demonstrate evidence of brain injury in patients with persisting symptoms (three months or more) after a single MTBI, one needs to examine what the empirical, peer-reviewed literature shows. Most of the studies show that there is evidence of hypoperfusion (i.e., decreased blood flow) in the frontal and temporal regions. However, when one looks closely at the types of patients included in these studies, the time they were assessed post-injury, and whether patients with confounding problems (e.g., multiple brain injuries, psychiatric history, substance abuse) were excluded, significant limitations exist with regards to the conclusions and generalizations one can make regarding patients with persisting symptoms after a single mild TBI.
Two studies were performed by Abu-Judeh et al. (1999, 2000) with SPECT scan in mild TBI. Unfortunately, the 1999 paper combined patients who were less than three months post-injury (62%) with those who were more than three months post-injury. This is problematic because whereas neurological contributions to symptoms after mild TBI can be more safely made before three months post-injury, the symptoms appear to be maintained by non-neurological factors in the vast majority of cases with chronic persisting symptoms (McCrea, 2008). The 2000 paper contained this same problem and also combined mild TBI patients with moderate TBI patients. Naturally, moderate TBI cases would be expected to have a higher incidence of acute and chronic neurological abnormalities compared to mild TBI patients. Therefore, combining patients with mild and moderate brain injuries makes it impossible to generalize the findings to those with mild TBI who have persisting symptoms three months or more post-injury.
A study by Abdel-Dayem et al. (1998) used SPECT scan in 228 patients with mild to moderate TBI. Furthermore, the authors did not state in the methods section how many mild and moderate TBI patients were in each group. Another problem is that more than half of the patients were scanned within three months post-injury. Nedd et al (1993) used SPECT with mild TBI patients but combined them with moderate TBI and studied them in the acute post-injury phase. Once again, this methodological problem makes it impossible to generalize these findings to mild TBI patients with persisting symptoms three months or more post-injury.
In 2001, Hofman at al. used SPECT scan in mild TBI, but the study was conducted in patients who were only five-days post-injury. It is also noted that the agreement between SPECT and MRI results was poor in that study. For example, areas of abnormality on SPECT scans did not always match areas of abnormality on brain MRI. Audenaert et al. (2003) performed a SPECT scan study with mild TBI patients, but once again, patients were studied in the acute phase (within two days post-injury) and only in eight patients. The SPECT study by Ichese et al. (1994) combined patients with mild and “major” TBI, leading to the same problems noted above. Similarly, the SPECT study by Kinuya et al. (2004) combined patients of mild and moderate TBI severity, with the SPECT scan being obtained eight days post-injury, on average. The study by Jacobs et al (1994) divided the mild and moderate TBI patients into separate groups, but the patients were all imaged with SPECT within four weeks post-injury. A later SPECT scan study by Jacobs et al. (1996) with mild TBI patients was also performed within four weeks post-injury,
Gowda et al. (2006) conducted a prospective study of SPECT scans in mild TBI, following patients with regards to symptoms over a 14-month period. However, the SPECT scan itself was performed at 72-hours post-injury. The SPECT scan study by Korn et al. (2005) was performed in patients within 4-weeks post-injury. The study by Lorberboym et al. (2002) studied mild TBI patients with SPECT an hour after admission to the Emergency Room.
The study by Kant et al. (1997) used SPECT scan in mild TBI patients both less than and more than 3 months post-injury. In addition, the study included subjects with significant psychiatric distress, drug and alcohol abuse history, and multiple traumatic brain injuries. This obviously leads to a significant problem in terms of what information can be inferred from the data regarding the neurological effects of a single mild TBI.
There have been some SPECT studies which only evaluated mild TBI patients more than three months post-injury but these studies are also fraught with difficulties regarding the generalizations that can be made. For example, Umile et al. (1998) used SPECT scan in mild TBI patients who were more than 3 months post-injury. However, it was not a prospective study and only included four patients. Although Lewine et al. (2007) studied mild TBI patients more than 3-months post-injury, they included patients with a history of multiple traumatic brain injuries. Furthermore, exclusion criteria were not described in detail (e.g., were patients with significant psychiatric histories included or excluded?). Bonne et al. (2003) studies patients who were an average 5.2 years post-MTBI who still complained of symptoms. Although the authors screened the subjects for current psychopathology, there was no information provided on whether the subjects had histories of multiple traumatic brain injury. Varney and Bushnell (1998) used SPECT scans in 18 veterans who had permanently lost the sense of smell after TBI (greater than three months post-injury), but mixed mild TBI patients with moderate to severe TBI patients.
With all of the problems noted in the studies above, how can one confidently conclude that SPECT scans are reliable and valid evidence for detecting brain injury in patients with symptoms longer than three months after a single mild TBI when structural neuroimaging is normal? Unfortunately, some people generalize from these studies in ways that are not scientifically appropriate. As Granacher (2008) noted “The use of SPECT or PET, without concurrent clinical correlation with structural neuroimaging (CT or MRI), is not recommended to be offered as evidence of MTBI in litigation.” Wortzel et al. (2008) also noted that “…we suggest that expert testimony regarding SPECT findings should be admissible only as evidence to support clinical history, neuropsychological test results, and structural brain imaging findings and not as stand-alone diagnostic data” (emphasis added). Many people are unaware that the American College of Radiology (ACR; 2006) classified SPECT scans as “least useful” in the acute phase of brain injury compared to other imaging techniques. For chronic closed head injury, SPECT scans were rated as a “4” on a scale of 1 to 9 in terms of usefulness (with one meaning least useful) but only in select cases. In addition, the ACR rated SPECT scans are rated as having a “high” relative radiation level.
Another important point worth noting is that while SPECT scans may indeed show hypoperfusion, this is a non-specific finding, meaning that other factors (e.g., psychiatric disorders, substance abuse) can cause it. This is very important for patients, family members, and health care providers to keep in mind before being evaluated with a SPECT scan, particularly due to exposure to radiation, the cost involved (since virtually all insurance companies will not cover it), and the limited information that will result.
A patient of mine spent over $1000 to fly to another state for a SPECT scan because he and his family were desperate for answers regarding diagnostic clarity. The SPECT scan was performed by a doctor who runs a private clinic. The scan cost the family about $1500 and most families pay abut $3000 according to the brochures for this particular clinic. The SPECT scan revealed numerous abnormalities but the report stated that the findings were non-specific in terms of etiology and not diagnostic of any neurological, psychiatric, or behavioral medicine disorder. This gets to the problem on non-specific findings as noted above. After thousands of dollars spent by the family, the information from the SPECT scan was hardly useful. However, some will ignore all of these inherent difficulties and rely on the results as “proof” of brain damage. This is comforting to some because it provides patients with a seeming answer and the cause of their problems can then be viewed as outside their control. In reality, significant cautions need to be made before offering SPECT scan data as proof of brain injury, absent other indicators. A quick internet search will show how some private practice physicians are marketing SPECT scans as an instrument that can “change your life” and can even be used to help in cases of marital difficulty. Buyer beware.
Future SPECT studies in this area should follow MTBI patients prospectively from the time of injury, avoid mixing them with patients with more severe brain injuries, utilize SPECT at three months or more post-injury, and report the results as a group and for those who are symptomatic and asymptomatic. In addition, proper exclusions should be made (or at least controlled for) to assess the impact of potential confounds such as multiple prior brain injuries, substance abuse, and psychiatric conditions.
REFERENCES
Abdel-Dayem et al. (1998). SPECT Brain Perfusion Abnormalities in Mild or Moderate Traumatic Brain Injury. Clinical Nuclear Medicine, 23, 3090317
Abu-Judeh et al. (1999). SPET brain perfusion imaging in mild traumatic brain injury without loss of consciousness and normal computed tomography, 20, 505-510.
Abu-Judeh at al. (2000). SPECT brain perfusion findings in mild or moderate traumatic brain injury. Nucl Med Rev Cent East Eur. 3, 5-11.
American College of Radiology (2006). ACR Appropriateness Criteria for Head Trauma.
Audenaert et al. (2003). Imaging of mild traumatic brain injury using 57Co and 99mTc HMPAO SPECT as compared to other diagnostic procedures. Med Sci Monit., 9, MT112-7.
Bonne et . al 92003). Cerebral blood flow in chronic symptomatic mild traumatic brain injury. Psychiatry Research, 124, 141-52.
Gowda et al. (2006). Technetium Tc-99m Ethyl Cysteinate Dimer Brain Single-Photon Emission CT in Mild Traumatic Brain Injury: A Prospective Study. American Journal of Neuroradiology, 27, 447-51.
Granacher (2008). Commentary: Applications of functional neuroimaging to civil litigation of mild traumatic brain injury. J Am Acad Psychiatry Law, 36, 323-8.
Hofman et al. (2001). MR Imaging, Single-photon Emission CT, and Neurocognitive Performance after Mild Traumatic Brain Injury. AJNR Am J Neuroradiol 22: 441–449.
Ichise et al. (1994). Technetium-99 m-HMPAO SPECT, CT and MRI in the evaluation of patients with chronic traumatic brain injury: a correlation with neuropsychological performance. J Nucl Med, 35, 217-26.
Jacobs et al. (1994). Prospective evaluation of Technetium-99m-HMPAO SPECT in mild and moderate traumatic brain injury. J Nucl Med, 35, 942-947.
Jacobs et al. (1996). One-year follow-up of technetium-99m-HMPAO SPECT in mild head injury. Journal of Nuclear Medicine, 37, 1605-9.
Kant et al. (1997). Tc-HMPAO SPECT in persistent post-concussion syndrome after mild head injury: comparison with MRI/CT. Brain Injury, 11, 115-24.
Kinuya K, Kakuda K, Nobata K, et al. Role of brain perfusion single –photon emission tomography in traumatic head injury. Nucl Med Commun 2004; 25(4):333-337.
Korn et al. (2005). Focal cortical dysfunction and blood-brain barrier disruption in patients with Postconcussion syndrome. J Clin Neurophysiol., 22, 1-9.
Lewine et al. (2007). Objective documentation of traumatic brain injury subsequent to mild head trauma: multimodal brain imaging with MEG, SPECT, and MRI. Journal of Head Trauma Rehabilitation, 22, 141-55.
Lorberboym et al. (2002). Brain SPECT evaluation of amnestic ED patients after mild head trauma. The American Journal of Emergency Medicine, 20, 310-313.
McCrea, M. (2008). Mild traumatic brain injury and postconcussion syndrome. The new evidence base for diagnosis and treatment. New York: Oxford University Press.
Nedd, K., et al (1993). 99mTc-HMPAO SPECT of the brain in mild to moderate traumatic brain injury patients: compared with CT--a prospective study. Brain Injury, 7, 469-479.
Umile et al. (1998). Functional assessment of mild traumatic brain injury
using SPECT and neuropsychological testing. Brain Injury, 12, 577-94.
Varney and Bushnell (1998). NeuroSPECT findings in patients with posttraumatic anosmia: a quantitative analysis. J Head Trauma Rehabil., 13, 63-72.
Wortzel et al. (2008). Forensic applications of cerebral single photon emission computed tomography in mild traumatic brain injury. J Am Acad Psychiatry Law, 36, 310-12.
Dr. Carone offers lectures on MTBI, “post concussion syndrome,” and symptom validity testing upon request. He can be contacted at info@mtbifacts.com.
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