CNS Injury

Question 1

Define concussion, or mild traumatic brain injury

Answer 1

An alteration in mental status, disturbance of equilibrium, etc. caused by biomechanical forces that may or may not cause loss of consciousness. The hallmarks of concussion are confusion and amnesia.

Question 2

List the symptoms of concussion.

Answer 2

The most common symptoms of concussion include headache, dizziness, poor attention, inability to concentrate, memory problems, fatigue, irritability, depressed mood, intolerance of bright lights or loud noises, and sleep disturbances.

Question 3

What are the peak age groups and mechanisms of concussions?

Answer 3

Peak age group: 24-35 years old. Most common mechanisms: Motor vehicle accident, Recreation, Violence, Falls, Bicycles, Shaken baby syndrome, motor vehicle violence.

Question 4

What are examples of contact phenomena and what injuries commonly result?

Answer 4

Contact phenomena includes strikes from bats, clubs, pool cues, rocks, etc. Injuries include Scalp lacerations, subgaleal hematoma, skull fractures, epidural hematomas.

Question 5

What is a cerebral contusion and what conditions may result from one?

Answer 5

A contusion is a brain bruise. Contusions may cause swelling, brain shift, increased intracranial pressure, and herniation, resulting in secondary brain injury. Low mortality rates.

Question 6

What are the two types of acceleration injuries?

Answer 6

Translational (straight line motion) and Rotational (pivot around a point).

Question 7

What injuries may result from a translational acceleration injury?

Answer 7

A translational injury may result in stretching/tearing of veins between the brain and dura (causing subdural hematomas), contusions, and coup-contracoup injuries. When combined, these have a high mortality rate.

Question 8

What injuries may result from a rotational acceleration injury?

Answer 8

A rotational injury may result in microscopic tearing of nerve cells in the brain (diffuse axonal injury). No recognizable injury without a microscope. Presentation may be anything from concussion to life-long coma. White matter in brain stem, corpus callosum, and cerebral hemispheres (esp. at white matter-grey matter junctions) is most affected. Possible small bleeds in corpus callosum on MRI/CT.

Question 9

What injuries may result from a penetrating injury?

Answer 9

Penetrating injuries may have direct damage or damage due to pressure/fluid waves from high velocity projectiles in GSW.

Question 10

Name two types of secondary brain injuries

Answer 10

Hypoxia, hypotension

Question 11

What are five types of skull fractures?

Answer 11

Linear, depressed, basilar, diastatic, growing

Question 12

What does a linear or diastatic skull fracture indicate?

Answer 12

High velocity impact. Seen on radiological imagining. No independent importance, but suggested need for close examination of underlying brain structures via MRI/CT. Diastatic occur along skull suture lines, same significance.

Question 13

What does a basilar skull fracture indicate?

Answer 13

Common with high-velocity, blunt injuries. May extend through the cribriform plate or petrous bone and result in CSF leaks (otorrhea/rhinorrhea), leading to risk of meningitis.

Question 14

What does a depressed skull fracture indicate?

Answer 14

Depressed skull fractures may force bone fragments into skull interior or the brain itself. Surgical intervention may be required to remove fragments or correct cosmetic defects.

Question 15

What does a growing fracture indicate?

Answer 15

Growing fractures occur during the first 18 months of infancy. The arachnoid herniates through the fracture line and pulsing CSF motion causes progressive bone loss.

Question 16

What is a diffuse axonal injury?

Answer 16

DAI results from high velocity rotational acceleration injury. Shearing of axons, causes “retraction balls” on microscopic exam, typically at white/grey matter junctions due to difference in density. No sign on CT, MRI = tiny bleeds in CC or white matter tracts.

Question 17

What is the process that leads to secondary injury in the brain?

Answer 17

The primary injury occurs at impact, directly damaging neurons, and is largely irreversible. Secondary injury results from inadequate resuscitation, leading to hypoxia, altered blood flow, and release of free radical mediators. Free radical mediators break down the BBB, leading to interstitial/vasogenic edema. Swelling, inc ICP, further hypoxia, dysautoregulation, and herniation result.

Question 18

What is the goal of treatment of head injuries?

Answer 18

Many head injuries cause hypoxia, altered blood flow, and release of free radical mediators which then cause an increase in ICP which leads to reduced perfusion of the brain, causing greater hypoxia in a positive feedback loop. Treatment is focused on breaking this loop.

Question 19

What are the signs and symptoms of increased Intracranial Pressure?

Answer 19

Frequently manifest as abrupt changes in neurological condition, including headache, nausea, vomiting, then progressive lethargy and eventual loss of consciousness.

Question 20

What are four herniation syndromes?

Answer 20

Subfalcine, Central, Uncal, Tonsillar

Question 21

What occurs in a subfalcine herniation?

Answer 21

A subfalcine herniation occurs when the cingulate gyrus herniates under the falx cerebri. The anterior cerebral artery is often kinked and may result in a stroke in its distribution.

Question 22

What occurs in an Uncal (Transtentorial) herniation?

Answer 22

And Uncal herniation occurs when the uncus herniates across the tentorial edge and down into the posterior fossa. It compresses the midbrain and ipsilateral cerebral peduncle. Results in third nerve palsy (test pupillary light reaction) and contralateral hemiparesis or hemiplagia. May also cause Duret hemorrhage in brainstem, disrupting the ascending reticular activating system.

Question 23

What occurs in a central herniation?

Answer 23

Central herniations occur when there is a downward pressure centrally and can result in bilateral uncle herniation. Results in loss of consciousness.

Question 24

What occurs in a Tonsillar herniation?

Answer 24

The cerebellar tonsils herniate down into the foramen magnum (“coning”). The medulla is compressed, may produce abnormal cardiac and respiratory responses, including Cushing’s reflex (Bradycardia, Hypertension, high ICP). Assoc’d with mass lesions in posterior fossa.

Question 25

What may be the result of performing a lumbar puncture in the setting of an intracranial mass?

Answer 25

An LP in such a setting may precipitate a herniation syndrome because of pressure differentials this creates between the cranial and spinal subarachnoid space.

Question 26

What is excitotoxicity and what does it cause?

Answer 26

Excitotoxicity is the the pathological process that damages and kills neurons by over activation of glutamate receptors (NMDA, AMPA). Pathologically high levels of glutamate allow high levels of Ca++ into neurons, which activates a number of enzymes which then damage the cell and eventually the BBB, leading to vasogenic edema.

Question 27

What is the pathological process that causes cytotoxic edema?

Answer 27

Widespread simultaneous neuronal depolarization spikes extracellular [K+]. Astrocytes rely on low ECM K+ to drive Na/K ATPase, creating low IC Na+, which then drives Glutamate&Na+ co-transport, allowing them to clean up the synaptic cleft. High EC K+ stops this process and causes high glutamate levels (excitotoxicity) and swelling of the astrocyte foot processes -> inc capillary resistance -> dec cerebral blood flow.

Question 28

What are the three components of the Glasgow Coma Score?

Answer 28

Eye-opening (E), BEST Motor Response (M), Verbal Response (V)

Question 29

What are the GCS scores for Eye-opening?

Answer 29

Spontaneous - 4, To speech - 3, To pain - 2, None - 1

Question 30

What are the GCS scores for BEST Motor Response?

Answer 30

Obeys commands - 6, Localizes pain - 5, Flexion - 4, Abnormal flexion (decorticate) - 3, Extension (decerebrate) - 2, None - 1

Question 31

What are the GCS scores for Verbal Response?

Answer 31

Oriented - 5, Confused - 4, Inappropriate words - 3, Incomprehensible sounds - 2, None - 1

Question 32

What are the uses of the GCS?

Answer 32

The GCS correlates well with the likelihood that the patient harbors an intracranial mass lesion, and with the likelihood of a good outcome, moderate disability, severe disability, or death. Usually intubate persons 8 or below.

Question 33

What are the five most common symptoms of concussion?

Answer 33

Headache, dizziness, lack of awareness of surroundings, muddled thinking, nausea and vomiting.

Question 34

What are the most common signs of concussion?

Answer 34

Vacant stare, inattentiveness, delayed responses, disorientation, loss of consciousness.

Question 35

What is CPP and how is it calculated?

Answer 35

CPP is Cerebral Perfusion Pressure, and is the difference between Mean Arterial Pressure and IntraCranial Pressure. i.e. MAP - ICP = CPP

Question 36

What is auto regulation?

Answer 36

Autoregulation is the constriction of blood vessel diameter in response to increased arterial pressure to control the cerebral blood supply/CPP.