Diagnosis
Pathophysiology
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Epidural hematoma (EDH)
Laceration of middle meningeal artery by temporal bone fracture (blood accumulates between the dura and skull)
Classic presentation: brief loss of consciousness, followed by a lucid interval, then a rapid decline in level of consciousness; better prognosis than subdural
Subdural hematoma (SDH)
Rupture of bridging veins resulting in the accumulation of blood between dura and arachnoid membrane
More likely to have associated brain parenchymal injury than epidural; acute and chronic forms
Intraparenchymal hematoma
Hemorrhage occurs in area of contused brain parenchyma
More likely to occur in association with hypertensive hemorrhage or arteriovenous malformation than with trauma; bleeding may be delayed
Diffuse axonal injury (DAI)
Rotational acceleration and deceleration results in stretching of axons between the gray and white matter
DAI is typically the underlying injury in shaken baby syndrome
Subarachnoid hemorrhage (SAH)
Trauma is most commonly caused by accumulation of blood in CSF-filled subarachnoid spaces, also caused by aneurysm rupture or arteriovenous malformation
Patient complains of “worst headache of my life”
What Is the Most Likely Diagnosis?
This patient has sustained a severe traumatic brain injury (TBI) as evidenced by a glasgow coma scale (GCS) of 7 (eyes-1, verbal-2, motor-4). He likely has a right-sided EDH which is supported by evidence of a right temporal bone fracture (hemotympanum). He also displays the classic sequence for EDH: consciousness, a brief lucid interval, and then progression to coma. The patient has objective signs of intracranial hypertension and uncal herniation, with a dilated nonresponsive right pupil and left-sided hemiplegia.
History and Physical
What Is the Definition of a TBI?
TBI results in a disruption of brain function. To meet the definition of TBI, the following criteria must be met: a period of loss of consciousness, loss of memory for events immediately before or after the accident, alteration in mental state at the time of the accident, and/or focal neurologic deficit.
How Do You Calculate the Glasgow Coma Scale (GCS)?
The GCS (Table 25.1) is composed of three components: eye opening, verbal response, and motor response. By definition, a neurologically intact person has a GCS score of 15. A GCS score of 3–8 indicates severe TBI, 9–12 indicates moderate injury, and 13–15 indicates mild injury. There is a 28 % probability of mortality associated with scores of 7 or 8.
Watch Out
A patient with a GCS of 8 or less is considered to be in a coma and mandates establishment of an airway.
Table 25.1
Glasgow coma scale (GCS)
Eye opening | Best verbal response | Best motor response | Points |
|---|---|---|---|
Follows commands | 6 | ||
Oriented | Localizes pain | 5 | |
Spontaneous | Confused | Withdraws from pain | 4 |
To voice | Inappropriate words | Decorticates posturing | 3 |
To pain | Incomprehensible | Decerebrates posturing | 2 |
None | None | None | 1 |
Watch Out
The GCS score should be frequently reassessed to determine if the patient’s TBI is worsening.
What Non-Head Trauma Factors Can Affect the GCS?
The GCS can be altered by alcohol and drug intoxication, sedatives, severe hypoxia, shock, and severe hypothermia.
What Are Raccoon Eyes? What Is Battle’s Sign?
Raccoon eyes are bilateral periorbital ecchymosis. Battle’s sign is retroauricular ecchymosis. These signs should raise the suspicion of a basilar skull fracture.
How Does the Physical Exam Help to Localize the Site of Intracranial Bleeding?
Paralysis generally occurs contralateral to the lesion, and abnormal pupillary findings will occur ipsilateral to the lesion. The above patient has a left hemiparesis and a blown pupil on the right, referring to a fixed and dilated pupil resulting from compression of the oculomotor nerve (CN 3) by the uncus of the temporal lobe. This localizes the lesion to the right.
What if the Blown Pupil and the Posturing Are on the Same Side? How Do You Use These Findings to Lateralize the Suspected Lesion?
In about 1 out of 5 cases of uncal herniation, the paralysis occurs ipsilateral to the lesion (Kernohan syndrome). This occurs when the contralateral cerebral peduncle is displaced laterally against the contralateral tentorial incisure resulting in paralysis ipsilateral to the lesion, a false localizing sign. In this case the pupil is the more reliable lateralizing sign. Remember dot marks the spot.
What Is the Implication of Abnormal Arm Flexion/Leg Extension with Pain Stimulation? Arm/Leg Extension?
Abnormal flexion in upper extremity and extension in lower extremity in response to painful stimuli is called decorticate posturing. Abnormal extension in upper and lower extremity in response to painful stimuli is called decerebrate posturing. These are primitive reflexes mediated by the brain stem when higher brain function is absent. While both are grave signs, decorticate posturing carries with it a better prognosis than decerebrate posturing.
How Does the Presentation of Chronic SDH Different from Acute SDH?
Acute SDH typically presents within 72 hours of head injury. Chronic SDH can have a delayed onset even months later. Chronic SDH typically affects the elderly, and presentation is often insidious: gait abnormalities, decreased levels of consciousness, aphasia, cognitive dysfunction, memory loss, and/or personality changes.
Pathophysiology
What Is a Concussion?
This is a term used for mild TBI. A concussion temporarily alters brain function by causing problems with memory, balance, coordination, and/or concentration. It may be associated with symptoms such as headaches, dizziness, confusion, personality changes, and irritability. Loss of consciousness is not required to establish the diagnosis of a concussion.
What Is Uncal Herniation?
Uncal herniation occurs when a space-occupying lesion above the tentorium displaces the uncus of the temporal lobe medially and inferiorly over the tentorial incisure impacting on the ipsilateral oculomotor nerve (CN III) and ipsilateral cerebral peduncle, which contains the ipsilateral corticospinal tract. This results in an ipsilateral blown pupil and contralateral paralysis.
What Is the Pathophysiology of an Epidural Hematoma?
Epidural hematoma is the accumulation of blood between the dura and skull. A temporal bone fracture from a head injury results in laceration of the middle meningeal artery (most common source) resulting in an EDH. EDHs have a biconvex appearance on CT. Because the hematoma is from an arterial source, it may expand rapidly and may require urgent surgical evacuation.
What Is the Implication of a “Lucid” Interval with Head Injury?
Initial loss of consciousness results from disruption of the brainstem arousal centers (RAS). The second loss of consciousness results from the expanding hematoma and mass effect. The interval between the first and second LOC is called the lucid interval, which may last minutes to hours. This is classically seen in EDH.
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