Temporal lobe seizures: lateralization with MR volume measurements of the hippocampal formation

Article Abstract:

Epilepsy is a neurological disorder of the brain in which nerve cells sometimes produce uncontrolled electrical discharges, which can cause convulsions, seizures, and other problems. Temporal lobe epilepsy (TLE) involves abnormalities in the temporal lobe of the brain. Epilepsy can be caused by a number of abnormalities, but many times the cause is unknown. TLE is caused by a tumor or other clearly defined lesion in some cases, but in most cases it is characterized by atrophy (shrinkage) of the hippocampal formation (HF), a brain structure, and the anterior (front) portion of the temporal lobe on the side of the lobe where the abnormal cells are found, but there is no specific mass of abnormal cells. Many epileptics are successfully treated with drugs, but some do not respond to drug therapy and surgery is indicated. Correct lateralization, that is, determining on which side of the lobe the abnormality is located, is necessary before surgery can be done. Magnetic resonance (MR) imaging is very useful in lateralization when the abnormality is a specific mass, but when it is not, how MR can be used for lateralization is less clear. The usefulness of five different MR tests in finding which side of the temporal lobe was causing TLE was evaluated by comparing their results of MR with results of traditional tests. MR was used for measurements of hippocampal formation volume, visual grading of unilateral HF atrophy, measurement of anterior temporal lobe (ATL) volume, ATL atrophy, and abnormalities in temporal lobe signal intensities. HF volume measurements were found to be the most accurate MR findings in lateralization. This method was able to detect 76 percent of the HF atrophies, and when they were identified, they were correctly lateralized 100 percent of the time. This MR diagnostic technique can be done easily and inexpensively and is a useful addition to TLE diagnosis and preparation for surgery. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Surgery, Brain abnormalities, Temporal lobes, Temporal lobe epilepsy

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Anterior temporal lobes and hippocampal formations: normative volumetric measurements from MR images in young adults

Article Abstract:

Magnetic resonance (MR) imaging data for volumetric measurement of the brain is appealing due to its excellent soft-tissue contrast, multiplanar imaging capability, and absence of artifacts from the domed portion of the skull. These attributes of MR imaging have made this a useful diagnostic technique for assessing the anterior temporal lobe of the brain. Studies of the anterior temporal lobe are important since this area of the brain plays a role in language production, memory, and partial complex seizure disorders. However, before relationships between MR imaging-based volumetric measurements of the temporal lobe and pathologic states involving the temporal lobe can be investigated, normative values must be established with the use of logical and reproducible boundaries. This research is intended to establish normative values for MR imaging-based volumetric measurements of the left and right anterior temporal lobes and hippocampal formations consisting of several layers in the brain, adjusted for age, sex, and left- or right-handedness as possibly significant covariates and normalized for variability in cranial size among individuals. These normative data can then be used in the evaluation of patients with a variety of disorders relating to the temporal lobes. The study was primarily designed to provide data for the surgical management of patients with refractory temporal lobe epilepsy. The findings of the research, however, were not conclusive in terms of a cause for refractory temporal lobe epilepsy. It was concluded that further investigation into the causes of refractory temporal lobe epilepsy is needed at this time.

Research, Anatomy, Hippocampus (Brain)

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Brain and cerebrospinal fluid volume: measurement with MR imaging

Article Abstract:

Alzheimer's disease (dementia of the Alzheimer type, or DAT) is the major cause of dementia in the elderly. It is characterized by atrophy of the cerebrum of the brain. A specific diagnosis of DAT can only be made by brain biopsy or autopsy. Diagnosis of DAT in the living patient, particularly in the early stages, is problematic. Efforts have been made to find a more accurate method of diagnosing DAT. The major focus has been on methods of measuring brain volume because loss of brain volume is a strong indicator for DAT. Computed tomography (CT) has been used to measure brain volume. Because of technical limitations, CT has only been useful in measuring brain volume indirectly. It lacks both sensitivity and specificity in its measurements and has been of little use clinically. Recently, research has turned to magnetic resonance imaging (MR) to measure brain volume. This imaging technique lacks some of the technical problems of CT and allows for both a direct measure of brain volume and greater sensitivity in localizing such measurements. MR has the potential to be an important diagnostic tool for diseases such as DAT, epilepsy, and certain psychiatric conditions. Before MR becomes a standard diagnostic tool, some problems must be overcome: standards for volume measurements must be developed; consistency and accuracy in measurements must be shown; and cost-effectiveness must be considered. Regardless of these problems, MR is a promising tool for the diagnosis of DAT and related diseases. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Measurement, Alzheimer's disease, editorial

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