mild traumatic brain injury: current diagnosis and management kathleen r. bell, md department of...
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Mild Traumatic Brain Injury: Current Diagnosis and Management
Kathleen R. Bell, MD
Department of Rehabilitation Medicine
University of Washington
May 6, 2004
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Overview
Why do we care about mild TBI? TBI overview and spectrum Mild traumatic brain injury
– Mechanism of injury– Presentation– Dilemmas in diagnosis and definition– Medical issues and management
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Mild Traumatic Brain Injury
Why do we care?
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What is concussion?
Mild Traumatic Brain Injury (MTBI) Defined by symptoms (1 or more)
– Any period of observed or self-reported Transient confusion, disorientation or impaired
consciousness Dysfunction of memory around the time of the injury Loss of consciousness lasting less than 30 minutes
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Observed signs of neurological or neuropsychological problem– Seizures right afterwards– Young children – irritability, lethargy, vomiting– Symptoms like headache, dizziness, irritability,
fatigue or poor concentration soon after injury
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Traumatic Brain Injury
1. Incidence - 500,000 admitted cases per year estimated 1.5 million sustain non-fatal brain injury
never admitted 2. Severity - 80% mild TBI, remaining 20% 3. Gender - male preponderance in more severe TBI,
possible female preponderance in mild TBI 4. Age - young adults 15-24 years (infants, children,
elderly); wider ranger for mild
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How often does it happen?
Centers for Disease Control estimates:– 1.5 million people a year have a TBI– About 75% of these are mild (like concussions)– Don’t really know how many because:
No one keeps track outside of hospitals Lots of concussions aren’t reported to anyone
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Etiology of TBI
1. No study has specifically focussed on mild TBI
2. Leading Cause - MVA approx. 28-50% 3. Falls 20-30% (infants, children, elderly) 4. Assaults 9-10% 5. Sports and recreational - 10-20%
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Costs of TBI
For TBI associated with hospitalization and rehabilitation: $37 billion dollars in direct and indirect costs
For mild TBI: ?
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Mechanisms of Severe TBI Penetrating (hi velocity, more damage) Closed/Moderate-Severe
High velocity translational (inferior frontal and temporal lobes)
High velocity rotational (shearing at grey-white interface)
Blunt Force skull fracture contusion at point of impact contrecoup injury (fall)
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– Space occupying lesions epidural hematomas 6% - good recovery subdural hematomas 24% intracerebral hemorrhage/intraventricular hemorrhage temporal lobe contusion/bleed - transtentorial herniation
– Basilar skull fractures infection, CSF leaks
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Secondary Brain Injury– altered cerebral blood flow– hypotension (relationship to ICP and CPP)– release of neurotoxic compounds
cellular inflammatory response cytokines calcium influx oxygen free radicals
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What Happens in Mild TBI?
Because full recovery often occurs, must be temporary neuronal dysfunction rather than cell death– Ionic shifts– Altered metabolism– Impaired connectivity– Changes in neurotransmission
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Acute Metabolic/Ionic Changes
Disruption of neuronal membranes and axonal stretching– Increase in extracellular potassium– Release of excitatory amino acid (EAA) glutamate
Increases kainate, NMDA, D-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)
– Increases extracellular potassium and so on
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“Spreading depression”
This cascade results in neuronal depression May be the cause of early loss of
consciousness, amnesia, and other cognitive dysvunction
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Manning the pumps
To head off further ionic fluxes:– Activation of membrane pumps
Increase in glucose use– Results in glycolysis
Glyocolysis and poor mitochondrial function– Results in increased lactate production
Results in neuronal dysfunction: acidosis, membrane damage, altered blood brain barrier permeability, and edema
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Further disruptions
Cerebral blood flow usually matches up to glucose metabolism– BUT after a percussion injury to the brain, the
cerebral blood flow drops– Now have a mismatch in supply (blood) and
demand (increased neuronal metabolism)
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Other Ion Malfunctions
Calcium accumulation in the cells because of EAA
Calcium gums up the mitochondria, impairing energy production in the cerebral cortex and the hippocampus
Global decreases in cerebral glucose metabolism lasting 2-4 weeks after injury (present regardless of severity of injury)
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Still more problems
Reduced intracellular magnesium levels (correlated with neurologic deficits)– Results in reduced glyocolytic and oxidative
energy production, disordered membrane function, and decreased protein synthesis
– Higher flux of calcium
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Mechanical axonal disruption
Stretching of axons can occur immediately and axonal disconnection can persist for days or weeks– Blocks neuronal transmission by treakdown of the
microtubules
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Neurotransmitter alterations
Postconcussive alterations in– Glutamatergic (NMDA) systems– Adrenergic systems– Cholinergic systems
Impaired long-term potentiation (NMDA dependent) in hippocampus
Changes in choline acetyltransferase activity and loss of forebrain cholinergic neurons – learning and memory
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Other Mechanisms of Mild TBI
Acceleration-deceleration mechanism– Mild diffuse axonal injury without shear
“strain” to neural tissue - affecting intra-axonal neurofilament organization
– Focal contusions in white matter– Labyrinth injury– Subtle changes in blood-brain barrier inducing
neurotransmitter release
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Diagnostic dilemma
Defining the lower and upper limits of mild TBI
Insensitivity of GCS to mild injury Ineffectiveness of imaging studies for
detecting mild injury Reporting of PTA highly unreliable (even
reporting LOC!)
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Mild Traumatic Brain Injury
ACRM Brain Injury Special Interest Group:– Any period of LOC <30 minutes and GCS of 13-15 after this
period of LOC– Any loss of memory for events immediately before or after
the accident, with PTA of <24 hours– Any alteration in mental state at the time of the accident– Focal neurological deficit(s) that may or may not be
transient
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DSM-IV Post-concussional disorder
1. LOC > 5 minutes 2. PTA > 12 hours 3. New onset of seizures or marked worsening of
pre-existing seizure disorder occurring in the first 6 months
4. Rec: abnormal neuropsychological exam 5. Persisting symptoms
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AAN Practice Parameter Sports Concussion
Grade 1: Transient confusion, no LOC, resolution in <15 minutes
Grade 2: Transient confusion, no LOC, lasts >15 minutes
Grade 3: Any LOC, brief or prolonged
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Sports-Related Concussion
(Cantu) Grade I - no LOC, PTA <30 minutes Grade 2 - LOC <5 min Grade 3 - LOC >5 min, PTA >24 hrs
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Scales of Severity of TBI
I. Confusion Normal consciousness, no amnesia
II. Confusion Normal consciousness, PTA
III. Confusion Normal consciousness, PTA, RGA
IV. Coma (paralytic) Level III: Normal consciousness, PTA, RGA
V. Coma Vegetative state or death
VI. Death
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Glasgow Coma Scale
Eyes Open Spontaneously 4 To verbal command 3 To pain 2 No response 1 Best motor response
To verbal command
Obeys 6
To painful stimulus
Localizes pain 5
Flexion-withdrawal 4 Flexion-abnormal 3 Extension 2 No response 1 Best verbal response
Oriented, converses 5
Disoriented, converses 4 Inappropriate 3 Incomprehensible sounds 2 No response 1
Severe 3-8
Moderate 9-12
Mild 13-15
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What the heck is Post-Concussion Syndrome?
Constellation of symptoms:– Headache, sleep disturbance, dizziness/vertigo,
nausea, fatigue, oversensitivity to noise/light, attention/concentration problems, decreased memory, irritability, anxiety, depression, emotional lability
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Physical complaints
Headache - usually mixed Neck pain - often associated with HA Tinnitus Dizziness - BPPV vs. central vs. possible
other otologic problems Fatigue/drowsiness
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Cognitive Sequelae
Memory difficulties (consolidation and retrieval
Diminished attention and concentration (especially divided and alternating attn)
Slowed information processing Decreased cognitive endurance and
judgment
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Behavioral/affective sequelae
Depression Loss of emotional
control Anxiety Irritability Sleep disturbances
Sexual disturbances Hypochondriacal
concern Hypersensitivity to
noise Photophobia
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Duration of symptoms in Mild TBI
Most report resolution of symptoms within the first 3 months after injury
Perhaps 12% of all have symptoms persisting into one year
Does persistence reflect interplay of organic and psychologic factors?
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Diagnostic dilemma
– No strict rule ins/outs for the diagnosis of mild TBI– Head CT, MRI, SPECT - none are entirely reliable
for diagnosis Presence of lesions on CT/MRI indicate a “complicated”
mild TBI PET scans can measure metabolic derangements but
no difference between those with a LOC and those without
– Abnormalities require about 10 days to resolve
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Diagnostic dilemma
Neuropsychological testing– No consensus on which tests to use– Impairments generally resolve 3-6 months– Must be paired with an interview to avoid “faking”
results– Heavily dependent on the diagnostic
interpretation of the examiner PASAT, Wechsler Memory Scale
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Contribution from Sports Medicine
Observed concussions– Disturbances in mental function measured
immediately after concussion can determine the severity of injury
– Players with a LOC (brief) do not recover to baseline in 15 minute but did within 48 hours (small study 91 participants, Kelly)
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Catastrophic outcomes
1. Really not a mild injury 2. Unrecognized posttraumatic depression 3. Premorbid psychiatric condition is
organized around the mild TBI as a focal event
4. Signs of a “functional” event
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Cerebral reserve
Effects of cumulative brain injuries (dementia pugilistica)
Persons with lower initial “reserve” for other reasons
Premorbid psychiatric coditions
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Doctor/Attorney dilemma
Role of litigation– conflicting studies
comparison of 2 groups, one with and one without litigation: equivalent cognitive performance, similar family reports
Canadian study 2000: amending tort law regarding MVA resulted in significant decrease of claims for mild TBI
“Compensation neurosis”
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Rehabilitation of Mild TBI
Most cases: reassurance Persistent symptoms
– reassurance, education, support, and regular monitoring
– teaching effective coping– cognitive remediation
Medical management: avoid prolonged passive treatments, reconditioning
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“I don’t know what it is, but there’s something out there, Mr. Jones.”
Bob Dylan