What is the role of imaging studies in the workup of postconcussion syndrome (PCS)?

Updated: Sep 24, 2018
  • Author: Eric L Legome, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Answer

Neurological examination and CT scan findings are frequently normal in patients with postconcussion syndrome; however, this does not confirm the absence of damage to the brain. Imaging modalities such as MRI, SPECT, and MEG have been shown to be more sensitive than CT at detecting brain injuries associated with PCS. These modalities have demonstrated an association between basal ganglia hypoperfusion and headaches, temporal lobe abnormalities and memory deficits, parietal lobe abnormalities and attention problems, and frontal lobe abnormalities and problems with executive function in patients with PCS. Interestingly, these imaging modalities have not born out associations between posttraumatic brain abnormalities and psychiatric symptoms in PCS.

It has been hypothesized that axonal injury at the time of trauma could underlie PCS. Shear strain on the neurons that leads to diffuse axonal injury can occur without CT abnormalities. However, a recent study of a biomarker for axonal injury, serum cleaved tau (C-tau), showed no correlation between C-tau levels at the time of injury and the later development of PCS. [26] Studies looking at serum levels of S-100B, a protein found most commonly in astrocytes, in patients with minor head injury have found conflicting results regarding a correlation between initial levels of the protein and development of PCS. [27]

In a study by Ramos-Zuniga et al, neuropsychological and spectroscopy testing confirmed the diagnosis of postconcussion syndrome in patients with mild head injury (MHI). According to the authors, spectroscopy revealed neurometabolite disturbances in 54% of cases, particularly N-acetylaspartate (Naa) and the Naa/lactate ratio in the frontal lobe. In addition, the authors noted that 55% of patients experienced physical disturbances such as headache and postural vertigo. [28]

CT scanning is used to determine the presence of intracranial abnormalities and skull fractures. In young patients with no loss of consciousness and a normal neurologic examination, CT scanning is of very low yield and is unlikely to be positive. Patients with PCS usually do not present immediately after the trauma.

If a CT scan has already been obtained, the utility of a repeat scan is minimal in the absence of focal neurologic signs or unless the patient is at risk for delayed hemorrhage (eg, an elderly patient on warfarin.)

If a CT scan has not been obtained and if the patient had a loss of consciousness and a GCS of 15, the likelihood of finding an operable lesion is extremely limited. Unfortunately, these patients with symptoms and a normal examination may still harbor an injury that requires intervention. In general, a single head CT scan is still a reasonable, fast, and effective screening test in the significantly symptomatic patient, although it should be balanced by the risks of radiation, especially in children.

MRI, SPECT, and positron emission tomography (PET) scans are more sensitive than CT scans in detecting abnormalities associated with minor head injury and PCS. [28, 29, 30, 31, 32, 33]

An MRI obtained in the acute period has little clinical significance. If one is obtained, it should be obtained on an outpatient basis in conjunction with follow-up. Although traumatic lesions may be depicted on MRIs in patients with minor head injury and a normal nonenhanced CT scan, they rarely influence the acute clinical course.

Principal component analysis of diffusion tensor images (DTI) has been found to identify white matter injury patterns on DTI that correlate with clinically relevant symptoms in mild traumatic brain injury. [32]

An MRI, SPECT, or PET scan obtained 4-24 months after injury may reveal a variety of abnormalities, though this rarely influences treatment or outcome.

In a study of cerebral blood flow (CBF) measured by MRI in pediatric patients (8-18 yr) 40 days after mild traumatic brain injury, global CBF was higher in the symptomatic group and lower in the asymptomatic group compared with controls. [34]


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