Elsevier

Clinical Neurophysiology

Volume 116, Issue 9, September 2005, Pages 2001-2025
Clinical Neurophysiology

Invited review
Routine and quantitative EEG in mild traumatic brain injury

https://doi.org/10.1016/j.clinph.2005.05.008Get rights and content

Abstract

This article reviews the pathophysiology of mild traumatic brain injury, and the findings from EEG and quantitative EEG (QEEG) testing after such an injury.

Research on the clinical presentation and pathophysiology of mild traumatic brain injury is reviewed with an emphasis on details that may pertain to EEG or QEEG and their interpretation. Research reports on EEG and QEEG in mild traumatic brain injury are reviewed in this setting, and conclusions are drawn about general diagnostic results that can be determined using these tests. QEEG strengths and weaknesses are reviewed in the context of factors used to determine the clinical usefulness of proposed diagnostic tests.

Clinical signs, symptoms, and the pathophysiologic axonal injury and cytotoxicity tend to clear over weeks or months after a mild head injury. Loss of consciousness might be similar to a non-convulsive seizure and accompanied subsequently by postictal-like symptoms. EEG shows slowing of the posterior dominant rhythm and increased diffuse theta slowing, which may revert to normal within hours or may clear more slowly over many weeks. There are no clear EEG or QEEG features unique to mild traumatic brain injury. Late after head injury, the correspondence is poor between electrophysiologic findings and clinical symptoms. Complicating factors are reviewed for the proposed commercial uses of QEEG as a diagnostic test for brain injury after concussion or mild traumatic brain injury.

The pathophysiology, clinical symptoms and electrophysiological features tend to clear over time after mild traumatic brain injury. There are no proven pathognomonic signatures useful for identifying head injury as the cause of signs and symptoms, especially late after the injury.

Introduction

Mild traumatic brain injury (MTBI) is a medical problem commonly encountered today in the general community. Some patients complain of persistent cognitive difficulties after such an injury. Quantitative EEG (QEEG) has been proposed as a clinical diagnostic test to identify, confirm, measure and localize brain injury among those patients.

This report reviews the physiology of MTBI, as well as the literature on traditional EEG abnormalities among patients. QEEG reports are discussed in that context. Techniques reviewed here include both QEEG discriminant analysis and the numerical tables of frequency analysis with normative database comparison.

This report generally avoids covering severe head injury, except where needed to understand better the findings in minor head injury. Nor does this report cover evoked potentials, event-related potentials, or recordings during cognitive activation tasks.

Section snippets

Terminology

Several terms are in common use to describe MTBI. The term concussion is an older terminology that still is often used in discussions with the public. Mild closed head injury (CHI) and mild traumatic head injury are similar terms.

The terms are used somewhat interchangeably here. The preferred scientific term, mild traumatic brain injury (MTBI), will be used usually in this report.

The terminology as used here does not necessarily imply that every head injury is accompanied by brain damage. Some

EEG in mild traumatic brain injury

Many decades of research and clinical experience with routine EEG carry with them important lessons for clinical interpretation of studies on patients after MTBI. These are needed not only for clinical interpretation of the routine EEG, but also for our QEEG discussion below. After all, QEEG is just measurements made on the EEG.

QEEG in mild traumatic brain injury

Before discussing QEEG in MTBI, several background issues need to be reviewed. These include QEEG terminology and general problems encountered with QEEG testing for clinical disorders. In addition, there are general issues to be considered for how one assesses the clinical usefulness of a diagnostic test. With this background we best can discuss the clinical utility of QEEG for MTBI.

Summary

MTBI is encountered commonly today in the general population. Various theories have attempted to explain the loss of consciousness. A massive neuronal discharge might produce a clinical state analogous to a non-convulsive epileptic seizure with post-ictal confusion. Mechanical forces produce two types of cellular damage. Ion leaks through cell membranes produce a temporary biochemical imbalance, which can trigger a spreading depression that could cause early amnesia or cognitive disturbances.

Acknowledgements

This work was supported in part by the UCLA Brain Injury Research Center, by National Institutes of Health grants NS30308, NS27544, NS37363, NS02089, and by the a grant from the American Academy of Neurology Education and Research Foundation.

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