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7.1. Case Study 1
Jason, an undergraduate student at a large state university, is walking back to
his apartment after a late night of studying chemistry in the library when he is
stopped by the local (non-university) police. They tell him they discovered a
deliberately broken window off-campus near the library, and as the only person
they found near the scene of the crime, he is a prime suspect. Jason tries to
explain that he was studying inside the library, not throwing rocks at nearby
buildings. He has no witnesses to his evening activities. He wants to prove his
innocence, so he agrees to go in for questioning. The police explain that they will
give him an fMRI lie-detection test at the station.
On his way to the police station, Jason begins to worry about the fMRI test.
While he is not guilty of vandalism, he did cheat on his chemistry exam last
week. He was alone at the library so late that night because he felt bad about
cheating and did not want to have to do it again. Jason does not know if he can
control his thoughts and emotions enough to just think of his study session that
evening, or if his guilty feelings and thoughts about the exam will affect the
outcome of the lie-detection test.
Jason takes the fMRI exam immediately upon arrival at the station. He is nervous
throughout the scan. When it is over, the officer who administered the test tells
him that it was inconclusive, neither validating his alibi nor proving his guilt. The
police decide to release Jason. They explain that they will save the results and
data from Jason's fMRI in a computerized file that is shared with other police
districts (similar to a brain fingerprint), and they may call him back for additional
questioning in the future.
Two weeks later, Jason gets a call from the officer who administered his fMRI.
Based on the inconclusive results, they want him to come back in for another
round of verbal questioning, without an fMRI machine. Jason is tired of this case
dragging on, and just wants to establish his innocence. He sees an
advertisement for "NoMoreLies, Inc." a company that offers fMRI-based lie-
detection services for any reason. Jason considers taking this private fMRI test.
If this test shows that he is not guilty of the vandalism, it might be enough to
counteract the inconclusive evidence from the police-administered fMRI. The
company encourages Jason to buy a test, and assures him that NoMoreLies, Inc. will
give accurate results and stand behind these results in court.
Jason decides to wait until after his next police interrogation before paying for
another fMRI. When he goes back into the station, they bring out his original
brain scan again. They show him a certain region of his brain (region V) on the
image, and inform him that according to their data, it is smaller than average.
They tell him that based on their research, people with an undersized "region V"
tend to be pre-disposed to violence and criminal activities. Although this has no
bearing on Jason's guilt or innocence regarding the broken window near the
library, they want to, as a precaution, to put Jason under a minimum amount of
surveillance and require him to see a psychiatrist. They seek a court order to do
so.
7.2. Case Study 2
Susan Shin, a 24-year-old healthy graduate student is crossing the street to attend class when a delivery truck runs a red light and hits her. She is thrown several feet, hits her head on the curb, and loses consciousness. EMTs have difficulty obtaining blood pressure and her oxygen saturation is below normal. In the Emergency Department (ED) she is still unconscious and is intubated. She is found to have multiple rib fractures, a collapsed lung, and is markedly hypotensive from internal bleeding. A non-contrast CT scan of her brain shows diffuse subarachnoid blood and contusions of her frontal and temporal lobes. Neck CT shows no fractures.
A chest tube is inserted, helping Susan's lung reinflate. She is attached to a ventilator. She is transfused and rushed to emergency surgery which normalizes her blood pressure. After surgery she enters the ICU. Forty hours later, well after the anesthesia was worn off, she still has not regained consciousness. A neurologist is called.
The neurologist examines Susan, finding her unresponsive to any unpleasant
stimuli. She is breathing faster than the ventilator setting. She has equal,
reactive pupils and her eyes move appropriately when ice water is instilled in
each ear. Tickling her throat causes a cough and gag. She flexes slightly from
painful pressure on her nails.
Imaging is appropriate at this point for diagnostic purposes. Further structural imaging can help identify the cause of Susan's coma. Although a repeat CT scan would probably also have been done to follow up on the blood in the brain, MRI will show more detail of which structures are injured. MRI of the spinal cord would be done to exclude a cord injury from the trauma.
The neurologist recommends MRIs of the brain and its vasculature and of the cervical spine. Overnight the ICU nurse notices some quick jerks of the fingers that could represent seizure, so the resident physician obtains an electroencephalogram (EEG). The study shows diffuse slowing of the brain's normal electrical activity as is often seen in comatose patients, but no evidence of seizures.
The MRI of the brain and cervical spine are performed the next day. The cervical
spine is normal. There are no injuries to the cerebral vasculature. The brain scan
shows improvement in the subarachnoid blood and contusions. However, there is
swelling and evidence of traumatic damage to the white matter connecting the
cortex (outermost layer) and deeper parts of the brain, and brightness of part of
the cortex consistent with ischemic and hypoxic injury. The traumatic white
matter damage is confirmed by an MR SPECT study.
Susan does not have an Advance Directive in the form of a designated health care proxy or a living will. She also has no spouse and no children, so her parents are the next in line as her surrogates to make medical decisions for her. They say that she was a competitive athlete and active in her church and would want "to fight this out."
Susan receives state of the art intensive care. She has not become infected, her
laboratory values reflect normal metabolic function, and she is receiving no
sedating medications. Follow-up neuroimaging at appropriate intervals shows a
complete resolution of the swelling and the blood. However, the traumatic axonal
injury and the hypoxic/ischemic injury persist. A week after injury, Susan still has
all brainstem reflexes, has eye opening and occasional spontaneous eye
movements, and withdraws slightly from pain. She has no language, but
sometimes smiles for no clear reason. The ICU team requests a neurologist's
opinion on her prognosis.
What it means to have positive outcome in this setting is not well defined overall, but one attempt is the Glasgow Outcome Scale, which defines "moderate disability" as independence in daily living with physical or mental limitations preventing return to one's previous level of function. For traumatic and non- traumatic coma, detailed tables based on studies with large sample sizes exist, correlating the different features seen on neurological exams with the percentages of patients who go on to recover neurological function to various extents (ranging from none to resumption of former activities). , These numbers can be cited to families who want to know overall odds and to prepare them for the possibility of severe disability if expected. However, except for some scenarios, the percentages cannot foretell the outcome for any one individual patient.
Susan has two different types of injury, both traumatic and anoxic/ischemic, making her prognosis more difficult and complex, because it is not clear which is more severe or contributing most to her current condition.
She is currently in a vegetative state (VS), "awake but unaware." It is too early to comment on its permanence. Data on the likelihood of recovery from the vegetative state collected by the Multi-Society Task Force described outcomes beginning from one month of ongoing VS, after which the term persistent may apply. This patient could remain vegetative or could go on to recover to a higher level of awareness such as minimal consciousness.
Although they are not required for diagnosis of a vegetative state, electrodiagnostic studies can sometimes aid in prognosis. EEG can exclude seizures or demonstrate other patterns known to be associated with poor outcome. Somatosensory evoked potentials (SSEPs) and Brainstem auditory- evoked responses (BAERs) can test the integrity of different circuits in the cortex and brainstem, respectively.
It is a month later. Susan now makes eye contact with her mother, follows her
face with her eyes, and turns to the sound of a voice. She can hold a ball.
Functional imaging is limited by both technical factors and our current knowledge
of its correct interpretation. A study done at different times on the same patient
could show activation of different areas based on the patient's own fluctuating
awareness that day, so may not accurately identify functional integrity. Even if
intact networks were identified, it would be unclear how robust a subjective
experience of consciousness or self-awareness the radiographically observed
activity actually reflected. The neurologist can inform the family that the patient
has recovered some neurological function, but that she is still severely brain
injured, based on her history and physical examination.
The parents want to know if Susan knows that they are there at her bedside, if she can hear them talking to her, and if she is in pain. The neurologist explains that it is not known how much of what healthy people would recognize as conscious awareness is present in minimally conscious individuals. It is probably not the case that she is living an active mental life inside her severely limited body, the way a person with a neuro-degenerative disease might.
The neurologist further explains that patients who recover from MCS do not recall the period of minimal consciousness. Rather, it is thought, and imaging has supported the idea, that MCS involves a fluctuating limited ability to interact, and that these patients have limited activation of selected areas of cortex permitting some interaction without the full integration required for complete awareness. What exactly is intact is highly individual and dependent on the injury each patient sustains. Large areas of pain networks may be preserved, so it is reasonable to ensure patients' comfort, including pain medication. Several studies have shows preservation of auditory networks and at least one has shown evidence of auditory processing and cognitive command following, so although it is unlikely that the patient has total awareness of her family's presence, her brain could be processing their speech rudimentarily.
The neurologist reassures the Shins that Susan will continue to be examined at regular intervals for evidence of neurological recovery. He also provides them with a realistic explanation of her likely severe degree of permanent disability.
The family accepts the lack of indication for functional imaging in diagnosis. Just
then a nearby research neuroscientist decides that Susan is eligible for her
experimental study of functional imaging using PET scanning in minimally
conscious patients.
The proposed neuroimaging studies will be experimental and descriptive. They are not validated for prognosis in Susan's case. Currently, there are many research studies but no large, validated set of prognostic data using fMRI or PET for patients in MCS, so even if it were performed, the test's results would be of uncertain significance. The results might enter a database which in aggregate data could be used to prospectively or retrospectively correlate eventual outcome with features seen on such imaging, and thus might eventually help scientists form prognostic schemes such as those currently in existence for coma. The benefit will not be for this patient or family, but for others in the future. Eventually, physicians may be able to construct a functional, neuroimaging profile of a particular injured patient that gives good information about likely recovery. However, that is a future direction, not a current reality.
