UIUIN INJURY,
1992, VOL. 6, NO. 6, 479-480
Editorial
Brain Inj Downloaded from informahealthcare.com by University of Otago on 01/04/15 For personal use only.
Neuropsychiatric correlates of theta bursts in patients with closed head
J. D. GRABOW Section of Electroencephalography, Mayo Clinic, Rochcster MN, USA
In their paper titled ‘Neuropsychiatric correlates of theta bursts in patients with closed head injury’, (pp. 499-508), Varney et al. suggest that theta bursts in the electroencephalogram (EEG) are a ‘clinically relevant, abnormal finding in the context of previous closed head injury’. I think we should be cautious about attributing any significance to ‘theta bursts’. Theta activity is defined as EEG frequencies that are from 3 to 7 Hz. It may be generalized or focal and may persist throughout the duration of the EEG tracing or occur in paroxysmal bursts. It would have been helpful for the readers to understand what Varney et al. meant by ‘localized theta bursts’ and ‘paroxysmal theta bursts’ if the authors had shown examples of the EEG data. Persistent diffuse theta activity occurs in many cerebral disorders that affect neurons throughout the brain. These conditions include toxic metabolic disorders, degenerative disorders, hypometabolic states, and central nervous system inflammatory disorders. This EEG activity also occurs after certain medications, including some anticonvulsants, are administered. However, Varney et al. discuss paroxysmal rather than persistent theta activity. In routine awake EEG tracings performed in our laboratory, paroxysmal theta activity is often seen when the patients are drowsy (the patients are sleep-deprived in order to obtain a sleep recording as well as an awake recording). Some patients who are not sleep-deprived may be drowsy because of medications taken to control a seizure disorder or psychiatric illness. The generalized paroxysmal bursts of theta activity are not present during mental alerting procedures performed during the awake recording. Focal theta activity occurs in many different regions. Mu rhythm in the lower frequency range (7-11 Hz) has some overlap with theta activity (3-7 Hz). Mu rhythm occurs in the left or right (or both) central regions and is attenuated by voluntary repetitive movements of a limb. Theta activity may occur in the temporal region in normal teenagers and in approximately 15% of adults who are without neurologcal disorder. This theta activity is a non-specific, minimal abnormality. During drowsiness, patients may have rhythmic mid-temporal theta of drowsiness (RMTD), sometimes called the ‘psychomotor variant’ pattern of Gibbs. This theta activity may occur in the left or right (or both) temporal region. The waveforms often have a notched configuration. R M T D is not associated with seizure disorders. Frequencies in the theta range may occur in the occipital regions as an alpha variant, which is often one-half the frequency of the Address correspondence to: J.D. Grabow, Section of Electroencephalography, Mayo Clinic, 200 First Street, S.W., Rochester MN 55905, USA. 026Y-9052/92 $3 00 0 1992 Taylor & Francis Ltd.
_I. D. Gratrow
Brain Inj Downloaded from informahealthcare.com by University of Otago on 01/04/15 For personal use only.
480
10-13-Hz alpha rhythm. There are some rare patterns of paroxysnial theta activity. One such pattern is subclinical rhythmic clectrographic discharges of adults (SREDA), which may last from 20 to 40 5 . Although SKEDA may be generalized, it is often maximal in the posterior head rcgioriz. These discharges are frequently activated by hyperventilation, and they do not correlate with seizure disorders. Another rare EEG pattern in the theta range is one that Varriey et nl. mention in thcir paper. This pattern was described by Ciginek [1] in 1961 and more recently by Westmoreland and Klas 121. In the latter study this pattern was identified in the EEG recordings from 36 patients seen at the Mayo Clinic during a 20-year period (this corresponds to 1 in 10,000 EEG records). O f thc 36 patients, 78% were referred for seizure disorder; this Lvas not statistically significant in comparison with 64% for an age-iiiatched control population of patients who were referred for seizures but who did not have the rare thetd pattern. I n addition, a larger percentage of the patients who had seizure disorders had independent, potentially epileptiforni activity in other regions not related to bursts of mid-line theta activity. The theta activity was niaxinial in the central-frontal vertex region. occurred in paro,xysnial bursts and, in a few patients, was attenuated with iiiovenient of an extrcnuty. T h e frequency of the rhythm was from 5 to 7 Hz, and the duration was from 4 to 70 s. Varney et a / . do not provide data about how many patients with closed head iriury diic to noto or vehicle accidents were screened to obtain the 25 patients who had paroxysiiial theta activity. The 25 patients in the study of Varney et nl. had an abundance ofwhat i$ referred to as ’partial seizure-like symptoms’. It would have been appropriate to study an age- arid sex-matchcd control group of people with closed head injuries who did not have paroxysinal theta activity to determine whether there was a similar proportion of ‘partial seizure-like symptoms’. Also, one should be careful not to infer that seizure-like syniptoms are symptoms related to tnic epileptic seizures. It is not surprising that the patients obtained some benefit from treatment with carbamazepine or valproic acid, because these anticoiivulsant drugs have psychotropic effects. Furthermore, most of the patients in the study appeared to have psychiatric illness rather than true seizure disorder. I t would have been of interest to provide inforniation about the severity of the head injury. The behavioural problenis were thought to be due to damage or dysfunction of the frontal lobes, although no neuroimaging data were presented to substantiate this. In conclusion, I a m sceptical that ‘theta bursts’ in the EEG are related to closed head injury. References 1 . CIGANEK. L.: Theta-discharges in thc middle-linc-EEG symptom of temporal lobc cpilcpsy. Eh~ror~zceplralqyrphy m d Clitiicd .TPrrrophysio/ogy, 13: 669-673, 1961. 2. WESTMOKELAND, B. F. and KLASS. 13. W.: Midline theta rhythm. Archivrs of Nrnvology, 43: 139-141, 1986.
1992, VOL. 6, NO. 6, 479-480
Editorial
Brain Inj Downloaded from informahealthcare.com by University of Otago on 01/04/15 For personal use only.
Neuropsychiatric correlates of theta bursts in patients with closed head
J. D. GRABOW Section of Electroencephalography, Mayo Clinic, Rochcster MN, USA
In their paper titled ‘Neuropsychiatric correlates of theta bursts in patients with closed head injury’, (pp. 499-508), Varney et al. suggest that theta bursts in the electroencephalogram (EEG) are a ‘clinically relevant, abnormal finding in the context of previous closed head injury’. I think we should be cautious about attributing any significance to ‘theta bursts’. Theta activity is defined as EEG frequencies that are from 3 to 7 Hz. It may be generalized or focal and may persist throughout the duration of the EEG tracing or occur in paroxysmal bursts. It would have been helpful for the readers to understand what Varney et al. meant by ‘localized theta bursts’ and ‘paroxysmal theta bursts’ if the authors had shown examples of the EEG data. Persistent diffuse theta activity occurs in many cerebral disorders that affect neurons throughout the brain. These conditions include toxic metabolic disorders, degenerative disorders, hypometabolic states, and central nervous system inflammatory disorders. This EEG activity also occurs after certain medications, including some anticonvulsants, are administered. However, Varney et al. discuss paroxysmal rather than persistent theta activity. In routine awake EEG tracings performed in our laboratory, paroxysmal theta activity is often seen when the patients are drowsy (the patients are sleep-deprived in order to obtain a sleep recording as well as an awake recording). Some patients who are not sleep-deprived may be drowsy because of medications taken to control a seizure disorder or psychiatric illness. The generalized paroxysmal bursts of theta activity are not present during mental alerting procedures performed during the awake recording. Focal theta activity occurs in many different regions. Mu rhythm in the lower frequency range (7-11 Hz) has some overlap with theta activity (3-7 Hz). Mu rhythm occurs in the left or right (or both) central regions and is attenuated by voluntary repetitive movements of a limb. Theta activity may occur in the temporal region in normal teenagers and in approximately 15% of adults who are without neurologcal disorder. This theta activity is a non-specific, minimal abnormality. During drowsiness, patients may have rhythmic mid-temporal theta of drowsiness (RMTD), sometimes called the ‘psychomotor variant’ pattern of Gibbs. This theta activity may occur in the left or right (or both) temporal region. The waveforms often have a notched configuration. R M T D is not associated with seizure disorders. Frequencies in the theta range may occur in the occipital regions as an alpha variant, which is often one-half the frequency of the Address correspondence to: J.D. Grabow, Section of Electroencephalography, Mayo Clinic, 200 First Street, S.W., Rochester MN 55905, USA. 026Y-9052/92 $3 00 0 1992 Taylor & Francis Ltd.
_I. D. Gratrow
Brain Inj Downloaded from informahealthcare.com by University of Otago on 01/04/15 For personal use only.
480
10-13-Hz alpha rhythm. There are some rare patterns of paroxysnial theta activity. One such pattern is subclinical rhythmic clectrographic discharges of adults (SREDA), which may last from 20 to 40 5 . Although SKEDA may be generalized, it is often maximal in the posterior head rcgioriz. These discharges are frequently activated by hyperventilation, and they do not correlate with seizure disorders. Another rare EEG pattern in the theta range is one that Varriey et nl. mention in thcir paper. This pattern was described by Ciginek [1] in 1961 and more recently by Westmoreland and Klas 121. In the latter study this pattern was identified in the EEG recordings from 36 patients seen at the Mayo Clinic during a 20-year period (this corresponds to 1 in 10,000 EEG records). O f thc 36 patients, 78% were referred for seizure disorder; this Lvas not statistically significant in comparison with 64% for an age-iiiatched control population of patients who were referred for seizures but who did not have the rare thetd pattern. I n addition, a larger percentage of the patients who had seizure disorders had independent, potentially epileptiforni activity in other regions not related to bursts of mid-line theta activity. The theta activity was niaxinial in the central-frontal vertex region. occurred in paro,xysnial bursts and, in a few patients, was attenuated with iiiovenient of an extrcnuty. T h e frequency of the rhythm was from 5 to 7 Hz, and the duration was from 4 to 70 s. Varney et a / . do not provide data about how many patients with closed head iriury diic to noto or vehicle accidents were screened to obtain the 25 patients who had paroxysiiial theta activity. The 25 patients in the study of Varney et nl. had an abundance ofwhat i$ referred to as ’partial seizure-like symptoms’. It would have been appropriate to study an age- arid sex-matchcd control group of people with closed head injuries who did not have paroxysinal theta activity to determine whether there was a similar proportion of ‘partial seizure-like symptoms’. Also, one should be careful not to infer that seizure-like syniptoms are symptoms related to tnic epileptic seizures. It is not surprising that the patients obtained some benefit from treatment with carbamazepine or valproic acid, because these anticoiivulsant drugs have psychotropic effects. Furthermore, most of the patients in the study appeared to have psychiatric illness rather than true seizure disorder. I t would have been of interest to provide inforniation about the severity of the head injury. The behavioural problenis were thought to be due to damage or dysfunction of the frontal lobes, although no neuroimaging data were presented to substantiate this. In conclusion, I a m sceptical that ‘theta bursts’ in the EEG are related to closed head injury. References 1 . CIGANEK. L.: Theta-discharges in thc middle-linc-EEG symptom of temporal lobc cpilcpsy. Eh~ror~zceplralqyrphy m d Clitiicd .TPrrrophysio/ogy, 13: 669-673, 1961. 2. WESTMOKELAND, B. F. and KLASS. 13. W.: Midline theta rhythm. Archivrs of Nrnvology, 43: 139-141, 1986.
