Intracranial Space-Occupying Lesions

Question 1

Define intracranial space-occupying lesions.

Answer 1

1. Intracranial space occupying lesions: lesions within the cranial cavity that expand in volume
   a. Characteristic: raised intracranial pressure  herniation (displacement of brain tissue over the free edges of the rigid dural folds or through the openings of the skull)
   b. Consequence: may lead to displacement, compression, or infiltration of surrounding tissue  obstruction of CSF flow

Question 2

What is intra-axial?

Answer 2

Intra-axial: located within the brain parenchyma + arise from the brain cells

Question 3

What is extra-axial?

Answer 3

Extra-axial: located outside the brain parenchyma + arise from structures lining the brain or surrounding it.

Question 4

What is supra-tentorial?

Answer 4

Supra-tentorial: located superior to the tentorium cerebelli (cerebrum + LV + 3rd ventricle + choroid plexus + pineal gland + hypothalamus + pituitary gland + optic nerve)

Question 5

What is infra-tentorial?

Answer 5

Infra-tentorial: located inferior to the tentorium cerebelli (cerebellum + tectum + 4th ventricle + brainstem)

Question 6

What are the clinical presentations of SOLs?

Answer 6

1. Headaches
2. Seizures: burst of uncontrolled electrical activity between neurons that cause temporary abnormalities in muscle tone or movement, behaviours, sensations, and state of awareness
3. Focal neurological deficits: impairments of nerve, spinal cord, or brain function that affects a specific region of the body (causation is localised to a specific area in the CNS). Ex. weakness in the left arm
4. Speech and visual problems
5. Altered mental state
6. Papilledema – optic disk (optic nerve head) swelling – useful for checking ICP in clinical settings
7. Nausea + vomiting

Question 7

What are the mechanisms of the clinical effects of SOLs?

Answer 7

1. Mass effect OR CSF outflow obstruction  raised ICP  headaches, papilledema, nausea + vomiting, altered mental state (behavioural changes)
2. Irritation of cortex  seizures
3. Compression OR Invasion OR Decreased perfusion (blood flow)  focal neurological defects  including speech and visual problems

Question 8

What are some symptoms of raised intracranial pressure?

Answer 8

o Behavioural changes noted by others
o Headache – worse after lying down or with coughing
o Nausea and vomiting
o Papilledema
o Cushing reflex: physiological nervous system response to acute elevations of ICP

Question 9

What is the Cushing triad?

Answer 9

Widened pulse pressure (increasing systolic, decreasing diastolic) + bradycardia + irregular respirations

Question 10

Outline the different types of herniation syndromes.

Answer 10

 Subfalcine herniation/Cingulate herniation/Midline shift: cingulate gyrus is pushed under the falx cerebri by an expanding mass high in a cerebral hemisphere

 Transtentorial herniation: any parenchymal herniation through the tentorial notch
* Uncal herniation: herniation of the uncus medial + downwards, compressing the oculomotor nerves
* Central herniation: descent of the diencephalon and midbrain
* Upward herniation: upward herniation of the brainstem into the supratentorial compartment

 Cerebellar/Tonsillar herniation: cerebellar tonsils (red arrow) has herniated through the foramen magnum (dotted white line), which compresses the medulla against the clivus/odontoid process