Long term sequelae of traumatic brain injury such as cerebral contusions and diffuse axonal injury (DAI) may include cognitive impairment.
Frontobasal/temporal parenchymal loss or T7* black dots typical for DAI in a patient with a history of trauma must therefore be taken into consideration when assessing MR images for dementia.
Jeffrey R. Petrella, MD, R. Edward Coleman, MD and P. Murali Doraiswamy, MD
State of the Art article in Radiology 7558 776:865-886.
Gangliogliomas are most commonly seen in the temporal lobe of patients than age 85 years. They are mixed solid and cystic lesions that are cortically based, with minimal or no mass effect. Calcification is often present. Gadolinium enhancement is variable. The finding of calcification and cystic changes in a cortically based lesion raises the possibility of this neoplasm. These lesions can be associated with concomitant cortical dysplasia.
Mild cognitive impairment is a relatively recent term used to describe people who have some problems with their memory, but do not actually have dementia, since dementia is defined as having problems in two or more cognitive domains.
Some of these patients will be in the early stages of Alzheimer's disease or another dementia, so it is important to identify them.
Finding MTA is a strong risk-factor for progression to dementia.
When we study the MR images we must systematically score for global atrophy, focal atrophy and for vascular disease (. infarcts, white matter lesions, lacunes).
This standardized assessment of the MR findings in a patient suspected of having a cognitive disorder includes:
SPECT scanning is performed during the ictal period to help delineate the epileptogenic zone. It is particularly helpful in patients with normal MRI findings, as well as in patients with abnormal MRI findings and a nonlocalizing EEG.
The neurovascular bundle can be compressed at several areas along the brachial plexus (Figure 65), resulting in a clinical constellation of symptoms commonly referred to as thoracic outlet syndrome. Particularly, the brachial plexus components can be affected at the interscalene triangle, costoclavicular space, or less commonly, the pectoralis minor space. Clinically, this syndrome can result in ulnar distribution hand weakness, hand/arm/neck pain/parasthesias, and upper extremity muscle atrophy. 77 Symptomatology is often exacerbated/reproducible by arm raise. The syndrome is typically caused by anatomic variants such as a cervical rib, prominent lower cervical transverse processes, posttraumatic fibrous bands, or pectoralis muscle hypertrophy. 78 MRI can be used to identify any of the aforementioned causative factors, and should include provocative testing in order to reproduce symptomatology during the time of the scan. 7,77
Remember : when evaluating diffusion, also look at the ADC. We do not use the term diffusion restriction until the tissue has high signal intensity on DWI and low signal intensity on ADC.
Magnetoencephalography (MEG) detects the magnetic fields produced by the electrical currents of neuronal activity. Unlike the electrical currents of neuronal activity, which are extracellular, magnetic fields are produced by the intracellular currents of apical dendrites, which are recorded from the scalp by MEG. Unlike conventional EEG that detects radially oriented electrical activity that is attenuated in strength and spatially distorted by tissues between the brain and scalp surface, magnetic fields are minimally affected by intervening tissue layers. Furthermore, MEG measures a subset of neuronal activity that is tangential to the scalp.
Another challenge Gilk sees to the widespread dissemination of MRI safety measures is the nature of many radiologists' roles. With technologists on the front lines performing the MRIs and radiologists sitting in reading rooms interpreting images, there can be a level of unfamiliarity among radiologists when it comes the impact of accidents in the MRI suite, and their potential liability relating to such events.