Session 14 - Brain Environment and TBI

What are the three distinct meningeal layers?

Dura mater, Arachnoid mater, Pia mater

Describe the dura mater

Outermost layer, thick connective tissue, 2 layers (outer periosteal; inner meningeal), the 2 layers form the walls of the venous sinuses which drain blood from the brain

What is the dural septa?

Reflection of the meningeal layer

What does the falx cerebri do?

Longitudinal layer that separates the cerebral hemispheres

What does the tentorium cerebelli do?

Transverse layer that separates the occipital lobe from cerebellum

What does the falx cerebelli do?

Longitudinal layer partially separating the hemispheres of the cerebellum

Function of the dural septa

Constrain anterior-posterior and medial-lateral brain movement

Describe the arachnoid mater

Avascular meninge that is closely attached to dura (making subdural space a “potential” space), the subarachnoid space is filled with cerebrospinal fluid

What do arachnoid villi do?

Penetrate the dural sinuses to get CSF into venous system

Describe the pia mater

Delicate connective tissue, strongly attached to the contours of the brain; two layers (epipia & intima pia)

What is meningitis?

Inflammation of the arachnoid or pia mater that can affect the CNS

Causes of meningitis

Bacterial and fungal causes (most severe), can travel in the blood from other parts of the body or can originate closer to the brain

What is meningoencephalitis?

Inflammation of both the brain and the meninges

Symptoms of meningoencephalitis

Fever, headache, back pain, increased edema and pressure (seizures, vomiting)

What is a meningioma?

Tumor, typically arising from the arachnoid villi, malignant (rare) tumors don’t penetrate neural tissues; tumors can displace or compress brain tissue causing seizures

Describe cerebrospinal fluid

Ultra filtrate of blood serum that protects and nourishes the CNS

Where is CSF produced?

By the choroid plexus

At what hydrostatic pressure is CSF produced?

15 mm Hg

List the circulation of cerebrospinal fluid

Produced in ventricles → Subarachnoid space → Arachnoid villi → Dural sinuses → Venous system

What is hydrocephalus

Increased accumulation of cerebrospinal fluid; in children it will look like an enlarged skull, in adults there will be increased intracranial pressure

Causes of hydrocephalus

Secondary to spina bifida, tumor, meningitis

What is Normal Pressure Hydrocephalus

Increase in ventricle dilation without increased intracranial pressure; the larger ventricular area exerts force on surrounding neural tissue

Where is Normal Pressure Hydrocephalus commonly seen?

Elderly population, following intracranial hemorrhage, following infection

What are symptoms of Normal Pressure Hydrocephalus?

Urinary incontinence, Cognitive impairments, Gait/Balance difficulties (Parkinsonian like; shuffling gait)

What are shunts used for?

Pressure sensitive tube that runs from a ventricle to various locations to provide alternate route for CSF to escape

What is a Traumatic Brain Injury?

Result of a blow to the head: moving head striking a surface or moving surface striking a head; can cause skull fracture or closed head injuries

What are the different types of skull fractures?

Depressed fracture: an area of the skull is pushed down into neural tissue

Compound fracture: skin is broken and the skull is splintered

What is the Coup-Counter Coup

Concussion MOI where a moving brain initially impacts skull on the side of impact then subsequent rebound causes brain to contact skull on the opposite side; multiplanar movement of the brain in the skull

What is an epidural hematoma?

Collection of arterial blood in space between dura mater and cranium as the result of a torn meningeal artery that impacts intracranial pressure

What is a subdural hematoma?

Collection of venous blood in space between dura and arachnoid mater as the result of a torn cerebral vein that impacts intracranial pressure; typically slow developing

What is a herniation?

A shift in brain tissue from higher pressure are to low pressure area

What is a subfalcial herniation?

Herniation where the cingulate gyrus is pushed under falcx cerebri to opposite hemisphere (alters consciousness)

What is an uncal herniation?

Herniation where medial temporal lobe is pushed into tentorial incisure (CN 3 and midbrain are compressed)

What is a cerebellar herniation?

Herniation where cerebellum is pushed down into foramen magnum (impacting brainstem and cervical spine)

How can you measure intracranial pressure?

Manometer and spinal tap

What does yellow CSF indicate?

Subarachnoid/intracerebral hemorrhage

What does cloudy CSF indicate?

White blood cells present; bacterial meningitis

Describe diffuse axonal injury

Stretch of nerve fibers as a result of rotational forces, puts white matter of cerebrum and brainstem under shear stresses causing damage to axons; leads to persistent higher-level function impairments

Define cerebral contusion

Swelling and capillary hemorrhage (brain bruise)

Define cerebral laceration

Actual tears of neural tissue

What is a concussion?

mild traumatic brain injury, caused by head trauma with symptoms that can last from seconds to weeks

Symptoms of a concussion

Headaches, dizziness, confusion, visual impairment

What can multiple concussions do?

Prolong symptoms and/or increase severity, increase susceptibility to adverse neurometabolic changes, increase susceptibility to ALS or alzheimer’s

What is a coma?

Profound state of unconsciousness where patient cannot be aroused; brainstem and thalamic reticular activating systems are compromised

What is decorticate posturing?

Loss of upper extremity flexor inhibition so upper extremities will flex and adduct and lower extremities will be extended

Location of lesion for decorticate posturing

Above red nucleus in rostral midbrain

What is decerebrate posture

Loss of extensor inhibition so all extremities will be extended, upper extremities will be internally rotated, feet will be plantarflexed

Location of lesion for decerebrate posturing

Below the red nucleus in rostral midbrain

Describe the glasgow coma scale

Acute scale of initial severity (lower value = more severe)

What is the Ranchos Los Amigos Scale of Cognitive Function

Scale of cognitive function used to classify patients emerging throughout a brain injury