Vastly differing pathology here. This is hydroencephalopathy (or enlargement of the ventricals). Terri's CT shows more holoencephalophathy - a profound attrophy of white matter).
Niether does it seem the patient in your post have the severe degree of trans-temporal occiptial lobe white matter atrophy compared to Terri Schiavo. Its important to understand that white matter is the brain's circuitry. A simplistic analogy is that white matter is the highway system that connects the information centers of the brain, allowing information to be processed.
Disorders of the occipital lobe can cause visual hallucinations and illusions. Visual hallucinations (visual images with no external stimuli) can be caused by lesions to the occipital region or temporal lobe seizures. Visual illusions (distorted perceptions) can take the form of objects appearing larger or smaller than they actually are, objects lacking color or objects having abnormal coloring. Lesions in the parietal-temporal-occipital association area can cause word blindness with writing impairments (alexia and agraphia) (Kandel, Schwartz & Jessell, 1991).
A study was done to analyze the effect of white matter lesions in different brain regions on regional cortical glucose metabolism, regional cortical atrophy, and cognitive function in a sample with a broad range of cerebrovascular disease and cognitive function. Patients were recruited to study subcortical ischemic vascular disease (SIVD).
Volumetric measures of MRI segmented white matter signal hyperintensities (WMH) in five different brain regions were related to regional PET glucose metabolism (rCMRglc) in cerebral cortex, MRI measures of regional cortical atrophy, and neuropsychological assessment of executive and memory function.
It was found that WMH was significantly higher in the prefrontal region compared to the other brain regions. In all subjects, higher frontal and parietal WMH were associated with reduced frontal rCMRglc, whereas occipitotemporal WMH was only marginally associated with frontal rCMRglc. These associations were stronger and more widely distributed in nondemented subjects where reduced frontal rCMRglc was correlated with WMH for all regions measured. In contrast, there was no relationship between WMH in any brain region and rCMRglc in either parietal or occipitotemporal regions. WMHs in all brain regions were associated with low executive scores in nondemented subjects.
What was concluded from the study was that the frontal lobes are most severely affected by SIVD. While WMHs were found to be more abundant in the frontal region, regardless of where in the brain WMHs are located, however, they are associated with frontal hypometabolism and executive dysfunction.
Interestingly enough though, an MRI is not absolutely necessary to assess brain death (and so thalmic implant extraction - and risk of death - wouldn't be required). The absence of intracranial blood flow could be documented on CT angiography and confirmed by CT perfusion images. Cerebral angiography could confirmed findings consistent with brain death. CT angiography with CT perfusion could represent a rapid noninvasive method for diagnosis of brain death.
Another excellent post raygun.
But Greer didn't see fit to have it performed, and IMO did not want to further muddy the waters with findings he did not expect.
PET scan technology would be of more use than a simple CT.
3) PET Scanning (Positron Emission Tomography)
The PET scan uses a small amount of a radioactive tracer put into the patient through a intravenous injection. After a period of time the tracer is absorbed into the tissue and this absorption is measured by the scanner. A PET scan usually takes between one to two hours to perform and requires the patient to lie completely still.
"PET scanning is an excellent tool for analyzing brain injuries because it shows where the brain is active. While other tests, like the CT scan, show what brain structures look like, the PET scan shows how the brain is actually functioning. For example, the PET scan show above is of an Alzheimer's brain, which is why large areas are black (which shows inactivity). "