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Brain Tumor, Preoperative Function Localization, and Source Localization

Chapter

Abstract

This 61-year-old female patient suffers from repeated episodes of word-finding difficulties. These problems persist for several hours and then disappear again. The first diagnosis is that these episodes concern TIAs, originating in the left hemisphere, and the patient is sent home with blood-thinning medication. Two months later, the patient is admitted to the hospital after an epileptic seizure, during which the word-finding difficulties occur again, but this time in conjunction with a right-sided paresis, incontinence for urine, and rhythmic limb movements. An EEG shows a left parietal epileptogenic focus. CT scans only show an old infarction in the right internal capsule, but no other abnormalities, particularly not in the left hemisphere. Another 4 months later, a similar seizure occurs and this time an MRI is made which shows a left parieto-occipital lesion which could be either an old infarct or a glioma. In the next few months, problems with word-finding and clumsiness with the right hand are continuously present, although with variable severity. There are no problems with sensibility, swallowing, or walking. The patient does not report any headache or nausea either. When she suffers from a major seizure again a few months later, she is admitted to hospital and a thorough clinical investigation follows.

Keywords

Independent Component Analysis Head Model Somatosensory Evoke Potential Primary Somatosensory Cortex Equivalent Current Dipole 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Glossary

Analytical solution

Closed form expression for a variable that is solved from an equation.

Aphasia

Acquired language disorder involving difficulties understanding and/or producing language.

Astrocytoma

Brain tumor originating from brain cells called astrocytes.

Axial

Imaging direction resulting in images that view the brain from the top or bottom.

Central sulcus

Fold in the cerebral cortex separating the frontal and the parietal lobe. Primary motor function is located on the gyrus in front of it, primary sensory function on the gyrus behind it.

Conductivity

Material property that determines how hard it is for electricity to travel through it.

Co-registration

To manipulate two image datasets from the same person but obtained in different modalities, such that the coordinate systems align.

Coronal

Imaging direction resulting in images that view the brain from the front or back.

Craniotomy

Surgery in which a bone flap is removed from the skull to be able to access the brain.

Dorsal

Top, contrast to ventral (bottom).

Endometrial

Originating from the inner lining of the uterus.

Glioma

A brain tumor originating from the glial cells that support the nerve cells.

Gyrus

Ridge on the cerebral cortex.

Internal capsule

White matter close to the basal ganglia.

Isotropic

The same in all directions.

Median nerve

Nerve in the upper limb innervating several muscles in the forearm and hand.

Metric

A mathematical distance function, e.g. in 2D-space a metric may be Cartesian distance calculated as \( \sqrt {{{x^2} + {y^2}}} \).

Neuronavigation

Computer-assisted technology allowing navigated movement in the skull during brain surgery.

Paresis

Partial loss of movement, weakness.

Permeability

Material property that determines how much magnetization is obtained when a magnetic field is applied.

Permittivity

Material property that determines how much electricity is transmitted.

Sagittal

Imaging direction resulting in images that view the brain from the left or right.

Sensorimotor

Involving sensory and motor function.

Signal-to-noise ratio

Measure used to quantify how much a signal is corrupted by noise; often calculated as the power of the signal divided by the power of the noise (in decibels).

Stationary

No changes over time.

Sulcus

Fold in the cerebral cortex.

TIA

Transient ischemic attack: a temporary period of insufficient blood supply to a part of the brain.

References

Online Sources of Information

  1. http://psyphz.psych.wisc.edu/~shackman/SourceLocalizationMethodology.htm. Links to the most common methods/software packages for EEG/MEG source localization, reviews and sources of method cross-validation
  2. http://en.wikipedia.org/wiki/Maxwell%27s_equations. Description of Maxwell’s equations

Software

  1. http://fieldtrip.fcdonders.nl/start. FieldTrip is a free Matlab software toolbox for MEG and EEG analysis that includes several methods for ECD and distributed source localization
  2. http://sccn.ucsd.edu/eeglab/. Homepage of EEGLAB freeware
  3. http://www.uzh.ch/keyinst/loreta. Website to download (s)LORETA freeware and find all information on the method

Papers

  1. Ebersole JS, Hawes-Ebersole S (2007) Clinical application of dipole models in the localization of epileptiform activity. J Clin Neurophysiol 24:120–129PubMedCrossRefGoogle Scholar
  2. Michel CM, Murray MM, Lantz G, Gonzalez S, Spinelli L, Grave de Peralta R (2004) EEG source imaging. Clin Neurophysiol 115:2195–2222PubMedCrossRefGoogle Scholar
  3. Weinstein D, Zhukov L, Johnson C (2000) Lead-field bases for electroencephalography source imaging. Ann Biomed Eng 28(9):1059–1065PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Department of NeurologyUniversity Medical Center GroningenGroningenThe Netherlands

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