CNS Injury

Question 1

Early symptoms of concussion

Answer 1

Headache
Dizziness
Lack of awareness of surroundings
Muddled thinking
Nausea/Vomiting

Question 2

Late symptoms of concussion (post concussion syndrome)

Answer 2

Persistent headache
Decreased attention and concentration
Poor memory
Easy fatigability
Irritability
Anxiety or depressed mood 
Sleep disturbance

Question 3

Signs of concussion

Answer 3

Vacant stare
Delayed responses
Inattention
Disorientation
Slurred or incoherent speech 
Incoordination
Inappropriate emotionality 
Memory problems 
Loss of consciousness

Question 4

Which areas of the brain are most affected by traumatic biomechanical injury?

Answer 4

Frontal lobes

Temporal poles

Question 5

Contrecoup contusions

Answer 5

Contusions that occur opposite to the side of the skull which is traumatized; caused by the slow progression of intra-parenchymal hematoma which occurs via local decompression of contralateral vessels followed by rupture when the brain “rebounds” and pressure is equalized

Question 6

Which imaging technique is better for visualizing parenchymal lesions - MRI or CT?

Answer 6

MRI

Question 7

What is the mechanism of diffuse axonal injury?

Answer 7

Rotational trauma causes stretch injury to the axon which disrupts the Na/K pump; this causes axonal swelling and axonal disintegration which is visible as “retraction balls” on light microscopy after 24 hours (invisible on CT, MRI)

Question 8

Grading concussion

Answer 8

Grade 1 - confusion, without amnesia or LOC

Grade 2 - confusion and amnesia

Grade 3 - LOC

Question 9

Second impact syndrome - Mechanism

Answer 9

Loss of autoregulation of the CNS vasculature; cerebral vessels lose their tone and become congested with blood, causing increased intracranial pressure which reduces cerebral perfusion, leading to widespread ischemia and vasogenic edema

Question 10

Layers of the scalp

Answer 10

Skin
Subcutaneous Tissue 
Galia 
Loose connective tissue
Pericranium

Question 11

Types of skull fractures

Answer 11

Linear

Depressed

Basilar

Diastatic - traumatic separations of the skull at suture lines

Growing - result from dural tears with herniation of the arachnoid into the fracture site; pulsating CSF hernia may cause progressive bone loss

Question 12

Battle’s Sign

Answer 12

AKA Mastoid Ecchymosis

Most often associated with basilar fractions of the middle cranial fossa

Question 13

Raccoon eyes

Answer 13

Most often associated with basilar fractions of the anterior cranial fossa

Question 14

Epidural Hematoma - Characteristics

Answer 14

Typically result from contact injury temporal skull fractures which lacerate the middle meningeal artery; patient presents after an impact injury with a lucid interval followed by progressive obtundation caused by herniation of the temporal lobe downward, compressing the brainstem

Appears as a “lens” shaped mass on MRI

Mortality < 1 hour

Question 15

Subdural Hematoma

Answer 15

Typically result from linear acceleration/deceleration injuries (falls); rupture of bridging veins that connect the cortical surface of the brain with the dural sinuses rupture, causing hemorrhage into the subdural space which appears “crescent shaped” on MRI

Question 16

Cerebral contusion

Answer 16

Usually the result of high velocity translational or impact injury; superficial hemorrhage of brain surfaces in contact with the rough bony surface of the anterior cranial fossa (frontal lobe) and sphenoid bone (temporal lobe)

Causes mass effect and herniation with secondary brain injury; mortality <20% with medical management to prevent brain swelling + occasional surgical evacuation of large hematomas

Question 17

Diffuse axonal injury

Answer 17

Results from high velocity rotational acceleration/deceleration injury; shearing of axons results in “retraction balls” on microscopic examination

Often no anatomical correlation of injury on CT; MRI may show hemorrhage in large white matter tracts

Patient is unconscious from moment of injury and typically remains in a chronic vegetative state; 80% mortality

Question 18

Point of decompensation

Answer 18

The volume of an increasing intracranial mass lesion at which point the ability of the CNS to compensate by displacing CSF/venous blood has been overwhelmed; any further increase in the volume of the mass lesion past this point will produce an exponential increase in intracranial pressure

Question 19

Subfalcine herniation

Answer 19

The cingulate gyrus herniates away from the growing mass lesion, pushing beneath the falx cerebri at midline; often occludes the anterior cerebral artery causing stroke in this distribution

Question 20

Uncal herniation

Answer 20

AKA transtentorial herniation; the uncus (medial temporal lobe) herniates downward into the posterior fossa, compressing the midbrain and ipsilateral cerebral peduncle

Question 21

Consequences of uncal herniation

Answer 21

Ipsilateral CN III Palsy
Contralateral hemiparesis/hemiplegia
Duret hemorrhage of brainstem
Kernohan’s notch (rare)

Question 22

Kernohan’s notch

Answer 22

A rare consequence of uncal herniation; displacement of the opposite cerebral peduncle and compression against the tentorium, resulting in hemiparesis that is ipsilateral to the mass lesion and herniated uncus

Question 23

Tonsillar herniation

Answer 23

Cerebellar tonsils herniate downward into foramen magnum, compressing the medulla; often leads to Cushing’s reflex (HTN + Bradycardia + Irregular respiration)

Usually caused by a mass lesion in the posterior fossa

Question 24

Treatment of elevated ICP

Answer 24

ABCs of basic life support - maintain O2 delivery via cerebral perfusion

Endotracheal intubation - protects the airway in unconscious patients

Ventillation to a pCO2 of 35mmHg

Elevation of the head to prevent venous congestion

IV osmotic diuretics - draws water across the BBB

Ventricular catheterization to drain the CSF spaces and treat obstructive hydrocephalus

Drug induced coma with barbituates - reduces metabolic demand