Neuromagnetic Assessment of Pathophysiologic Brain Activity Induced by Minor Head Trauma
Jeffrey David Lewinea,
John T. Davisa,
John Henry Sloana,
P. W. Kodituwakkua and
William W. Orrison Jr
,a
a From the New Mexico Regional Federal Medical Center, Albuquerque (J.D.L., J.T.D., W.W.O.); the Departments of Radiology (J.D.L., W.W.O.), Psychology (J.D.L.), Neurology (W.W.O.), and Psychiatry (P.W.K), the University of New Mexico School of Medicine, Albuquerque (J.D.L., J.T.D., W.W.O.); and St Joseph's Rehabilitation Center, St Joseph's Medical Center, Albuquerque (J.H.S.).
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FIG 1. Spontaneous MEG data are waveforms showing how magnetic flux changes with time. Data regarding the trauma patients often show generalized slowing of the background activity and focal slow waves. Ten seconds of data are shown from several channels. Two examples of slow waves are marked by the green and red lines. One way to express the data is as a power spectrum, shown on the right. Most slow waves have complicated magnetic field patterns, as shown by the leftmost iso-field contour map. Some slow waves have very dipolar patterns, and the source can be localized and plotted on spatially aligned MR images. The red dot shows the location of the indicated slow wave, with black dots showing slow-wave sources from other points in time
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FIG 2. Summary of initial neuroimaging data from all subjects. Group A represents the normal control subjects, group B is the asymptomatic head trauma subjects, and group C is the symptomatic head trauma patients. The set diagram shows what diagnostic tests, if any, provided abnormal findings for each subject. Of particular note are the low false-positive rates for group A and B subjects (all without symptoms), the high sensitivity of MEG to abnormalities in patients with postconcussive symptoms, and the finding that MEG identified abnormalities in all group C subjects who had MR imaging or EEG abnormalities plus seven additional group C subjects who had normal MR imaging and EEG findings
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FIG 3. A–C, Magnetic source localization images of a 29-year-old man who, 2 months before the examinations, hit his head after falling from a ladder. At the time of the study, attentional problems and neck pain had precluded his return to work. The results of MR imaging and clinical EEG were normal, but MEG showed focal right parietal ALFMA.
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FIG 4. A and B, Magnetic source localization images of a 17-year-old patient who suffered diffuse blows to the head during a fight at school. The patient showed a significant cognitive decline and manifestation of an attentional deficit syndrome subsequent to the trauma. An initial examination was performed 4 months after the trauma occurred (A). The results of MR imaging and EEG were normal. MEG revealed abnormal m-SI values bilaterally at temporal and parietal sites. Multiple dipole clusters of low-frequency activity were found in each hemisphere. Sources spread throughout the right and left parietal and frontal regions, with more activity on the right. At the 9-month follow-up examination (B), the patient continued to show an impaired cognitive profile, and similar MEG results were found. There was some minor lessening of the right hemisphere MEG abnormalities, but the residual ALFMA was still significant and widespread.
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