A 79-year-old female with history of hypertension and right-sided subdural hemorrhage status-post right hemicraniectomy and cranioplasty presented to the emergency department with progressive head and focal right arm twitching concerning for a focal seizure. A head CT was obtained and is shown in the figure below:
What type of herniation is demonstrated on the head CT and what are the anticipated neurologic findings on examination?
Correct Answer: B
The head CT above demonstrates an acute on subacute left-sided subdural hemorrhage with left-to-right midline shift and compression of the left lateral ventricle and potential trapping of the right lateral ventricle. The timing of the subdural hemorrhage is based on the density of the blood product. Acute blood appears hyperdense to brain parenchyma. After approximately 3 days the blood product begins to break down and will reach an isodense characteristic compared to brain parenchyma, typically around 10 to 14 days. After 21 days, the blood product becomes hypodense to brain tissue and is similar to cerebrospinal fluid. The herniation demonstrated on this image is subfalcine with left frontal lobe shift under the falx into the right hemisphere. Subfalcine herniation results with cingulate gyrus herniation across the falx and compression of the pericallosal arteries resulting in contralateral (and commonly bilateral) leg weakness. Transtentorial or uncal herniation occurs with the medial temporal lobe and uncus compresses the ipsilateral cerebral peduncle resulting in compression of the ipsilateral third cranial nerve resulting in an enlarged and fixed or sluggishly reactive pupil and contralateral weakness. Tonsillar herniation occurs when there is a pressure within the cerebellum resulting in herniation of the cerebellar tonsil into the foramen magnum and compression of the fourth ventricle resulting in noncommunicating hydrocephalus and obtundation. Fungating herniation occurs when there is a skull defect and herniation of brain tissue outside the cranial vault. All herniation occurs due to a pressure gradient from one compartment (left-right hemisphere, or supra-infratentorial compartment).
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A 22-year-old male has an external ventricular drain placed for intracranial pressure monitoring following a traumatic brain injury. The patient continues to have a poor neurologic examination. There are episodes of time when he has an elevation in his intracranial pressure to 20 mm Hg that will last for 10 to 20 minutes at a time. During this time there are no changes to other vital signs. A tracing of the external ventricular drain (EVD) is shown below.
What is the phenomenon depicted?
Correct Answer: A
The intracranial pressure (ICP) waveform shown is the Lundberg A, which are a sustained elevation in ICP with amplitude of 50 to 100 mm Hg (higher than Lundberg B and C waves). They typically last for 5 to 20 minutes and they are always pathological as they represent reduced cerebral compliance and increase intracranial pressure. Lundberg B waves are short elevation of ICP with amplitude of 5 to 20 mm Hg at a frequency of 0.5 to 2 waves/min, which last for 1 to 5 minutes. They are thought to be normal waves with probably some association with unstable ICP and vasospasm. Lundberg C waves are rapid oscillations of 4 to 8 waves/min with low amplitude of <20 mm Hg. They are normal waves with changes related to cardiac and respiratory cycles. Without changes in other physiologic parameters, it is unlikely the ICP change is due to autonomic storming. Common features include increase in blood pressure, respiratory rate, heart rate, worsening level of consciousness, muscle rigidity, and hyperhidrosis.
An 18-year-old male is brought in to the emergency department after a motor vehicle crash. He was on a motorcycle and was found 30 feet away from his vehicle in unconscious state without a helmet. He has noted trauma to his left forearm, active bleeding from the left posterior portion of his scalp. He was intubated in the field with EMS. On arrival he is tachycardic (heart rate 120s), blood pressure 110/62. He was recently paralyzed for intubation and does not have twitches present on train of four testing. A head CT is completed which demonstrates a large left-sided subdural hematoma with 6 mm midline shift. In the interval, as neurosurgery team is taking the patient to the OR, hyperventilation is started to decrease cerebral edema.
How does hyperventilation decrease intracranial pressure?
Correct Answer: D
The intracranial pressure is influenced by pCO2 . A rise in pCO2 will result in brain blood vessel dilatation and then increase in the cerebral blood volume. In contrast, when the pCO2 drops, the blood vessel diameter decreases and results in decreased cerebral blood volume. Although hypocarbic strategy promotes transient decrease in ICP and considered one of the effective intracranial hypertension temporizing measures, hyperventilation carries a serious risk of significant reduction in cerebral blood flow (CBF) and cerebral ischemia. In addition, studies showed prolonged hypocapnia can lead to rebound ICP. For this reason the Brain Trauma Foundation changed recently their 2017 guidelines about hyperventilation and stated that “prolonged prophylactic hyperventilation with partial pressure of carbon dioxide in arterial blood (PaCO2 ) of 25 mm Hg or less is not recommended” (Level IIB).
The change in cerebral blood flow is independent of the pH as there is no change with metabolic acidosis and alkalosis. There is rapid CO2 equilibration between the arterial blood and CSF, and the change in pH of the CSF acts directly in the vasculature resulting in relaxation or contraction.
A 32-year-old female with chronic alcoholism and cirrhosis was brought to the emergency department following a night of binge drinking. She was found unresponsive at home and EMS was called. On arrival to the emergency department she was intubated for airway protection. She did not require sedation for intubation and is not currently on any sedation. A head CT was completed and demonstrated diffuse cerebral edema with effacement of the sulci and ventricular system. Her lab results were remarkable for an elevation in AST and ALT (2000, 1000 units/L respectively), total bilirubin 5.6 mg/dL, and ammonia 3642 µm/L. Her examination remains poor, with only extensor posturing to motor stimulation. Her pupils are 5 mm and sluggishly reactive to light.
Given the findings on head CT what is the next best step in management?
Fulminant liver failure is frequently associated with worsening cerebral edema and elevation in ICP. The detoxification of high ammonia levels to glutamine in astrocytes results in increased intracellular osmolality and cerebral edema. Given the extremely high mortality rate associated with the development of cerebral edema, it is prudent to aggressively manage this pathology. There is a step-wise approach in the management of intracranial hypertension which starts with head of bed elevation, and securing airways should always take priority and starting the patient on sedation could help controlling ICP. In liver failure patients, midazolam, which through multiple CYP pathways, will accumulate and cause complications. Propofol might be a safer option; however, it is thoroughly studied in this cohort of patients.
The use of hyperosmolar therapy (mannitol and hypertonic saline) for increased ICP in acute liver failure is extrapolated from its use in head trauma. Smaller studies showed that hypertonic saline helps reducing ICP when was used in patients with grade III and IV hepatic encephalopathy and mannitol helps reducing cerebral edema and improves survival in patients with fulminant hepatic failure.
Overall, the common practice is to place an intracranial monitor to best manage these patients. However, given the possibly underlying coagulopathy in these patients, hemorrhages related to ICP monitor placement can be catastrophic and may add to the overall mortality. Smaller studies showed that epidural catheters have lower hemorrhage rates and precision relative to subdural bolts and intraparenchymal catheters.
Regarding other ICP management options, hyperventilation is a temporizing measure which can result in lowered ICP but prolonged hyperventilation carries a serious risk of significant reduction in cerebral blood flow (CBF) and cerebral ischemia.
Although transplantation can be potentially considered, treating intracranial hypertension at this point takes priority.
A 62-year-old male was admitted with diffuse subarachnoid hemorrhage, intraventicular extension of the hemorrhage, and early signs of hydrocephalus. An EVD was placed without complication. The EVD has functioned well and following placement the patient’s examination improved. The figure that follows is the waveform produced.
What occurs during the P3 peak?
An external ventricular drain is a soft catheter than can be placed within the ventricular system of the brain for management of elevated intracranial pressure and both communicating and noncommunicating hydrocephalus by means of allowing for diversion of cerebrospinal fluid and potentially clearing the obstructive fluid like blood and pus. The above wave is a normal waveform that is produced during a normal cardiac cycle. The first peak found in the wave is P1 or percussion wave; it correlates with the arterial pulse transmitted through the choroid plexus into the CSF. The second peak is P2, or tidal wave, which represents cerebral compliance as it correlates with arterial pulse bouncing off the brain parenchyma. The third peak is P3, or dicrotic wave; it correlates with the closure of the aortic valve. In normal ICP, P1 > P2 > P3. If P2 > P1, it is indicated that ICP is likely elevated and the intracranial compliance is likely decreased. The respiratory ICP waveform correlates with the respiratory cycle.
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