2 Gross Neuroanatomy (01.04.17)

Question 1

Clinical context of dural components:
Herniation Syndromes

What are the four types of herniations?

Answer 1

1. Subfalcine Herniation
2. Central Herniation
3. Uncal Transtentorial Herniation (goes over transtentorial notch)
4. Tonsillar Herniation (can compress medulla)

Question 2

With respect to herniations, shifts in dural partitions and brain can be detected by/via ___________.

Answer 2

Radiology

Question 3

The average normal values of intracranial pressure are:

\_\_\_\_\_\_ cm (\_\_\_\_ mm) H2O*
-or-
\_\_\_\_\_\_ cm (\_\_\_\_ mm) Hg*

Answer 3

<20 cm (200mm) H2O

<15 cm (150 mm) Hg

*These values are the UPPER limit of the normal range.

Question 4

Name the two ways intracranial pressure is measured.

Answer 4

1. Lumbar Puncture
   (Subarachnoid space around cauda equina)
2. Neurosurgical Insertion
   (Of intracranial monitors/catheters into brain)

Question 5

Contra-indications for lumbar puncture include increased ___________ pressure, which can cause herniations, and an _____________ or mass in the path from the needle insertion.

Answer 5

1. Supratentorial

2. Infection

Question 6

Pathological origins causing increased mass/volume of the head include: (4 key things)

Answer 6

• hydrocephalus (too much CSF)
• brain edema (swelling)
• hemorrhage (hematoma)
• tumor (other mass, i.e. abscess)

Question 7

Symptoms of increased intracranial pressure include:

Answer 7

• nausea
• headache (from mechanical stress on dura–coughing, etc.)
• vomiting (pressure stimulates the vomiting center in the medulla)
• impaired consciousness
• bulging fontanelles in infants
• slowed heart rate (bradycardia)
• papilledema- protrusion of optic disk forward, elevation and blurring of optic disc upon examination

Question 8

Subarachnoid hemorrhaging is commonly caused by ______________.

Answer 8

Aneurysms

Question 9

Subarachnoid hemorrhaging _________ neurological signs.

Answer 9

Diffuse

Question 10

________________ hemorrhaging causes meningeal irritation, increased intracranial pressure, diffuses neurological signs, and is detectable by lumbar puncture and neuroimaging.

Answer 10

Subarachnoid

Question 11

(LO) Review of major parts and levels of CNS:
brain
spinal cord
ventricles

Answer 11

brain:
Cerebrum (telencephalon, which houses cerebral cortex and subcortical regions, and diencephalon, which houses thalamus and hypoothalamus)
Cerebellum
Brainstem (midbrain (aka mesencephalon), pons, medulla)
Spinal cord and roots
Pre-ganglionic autonomic neurons
(*brain and spinal cord develop from the fluid-filled neural tube)
ventricles: the deepest part of the CNS, house CSF.

Question 12

(LO) Understand the distinction between ventricular space and subarachnoid space.

Answer 12

“Subarachnoid space” is where trabeculae are seen –CSF, vessels. (A hemorrhage here is typically caused by tearing of bridging veins.)
Ventricular space includes fluid-filled core regions that are a part of cycling of CSF from inside the ventricular system to the outside area surrounding the CNS.

Question 13

(LO) Understand anatomical axes and directional terminology.

Answer 13

Rostral-Caudal axis is the axis of the neural tube. (“beak to tail”)
Dorsal-Ventral axis (“belly to back”) is always perpendicular to the rostral-caudal axis.
Humans have a kinked neural tube.
Ventral brain surface is along the base of the skull, dorsal surface is along the calvarium.

Question 14

(LO) Meninges: histological organization

Answer 14

from superficial to deep:
dura mater: outer/periosteal and inner/meningeal layers separate to form dural sinuses.

arachnoid mater: normally flush against dura, but has trabeculae extending to pia mater.

pia mater: thin, transparent layer that is flush with brain surface. Follows gyri and sulci.

(subarachnoid space is where the trabeculae are seen)
Note: middle meningeal artery scending while embedded in dura mater.

Question 15

(LO) Photographic tour of meningeal layers, dural compartments of CNS.

Answer 15

starting at the skull:
Dura mater:
1. Periosteal dura
2. Meningeal dura.
3. Dural border cells
Arachnoid mater:
1. Arachnoid trabeculae in subarachnoid space (SAS). Houses artery or vein supplying or draining brain and spinal cord.

Question 16

(LO) Brain herniations

What are the 4 types?

Answer 16

result from a local mass:

1. Subfalcine herniation (“midline shift”)
2. Central herniation
3. Uncal transtentorial herniation (goes over tentorial notch)
4. Tonsillar herniation (can compress the medulla)

Question 17

(LO) Increased intracranial pressure: neurological and ophthalmic aspects.

Answer 17

Causes:
-hydrocephalus (too much CSF/fluid)
-brain edema (swelling per accumulation of fluid. can be extra- or intra- cellular)
-hemorrhage (hematoma)
-tumor or other mass
Symptoms include:
Neurological: headache, nausea, vomiting (pressure on medulla), impaired consciousness, bulging of skull (infants), increased systemic BP, bradycardia (slowing HR, again, medulla disruption).
Ocular: papilledema- gradual protrusion of optic disc forward, elevation and blurring of optic disc upon examination.

Question 18

(LO) Pain innervation and meningeal irritation syndrome (MIS).

Answer 18

Sensory (Pain) Innervation of dura, falx, tentorium is mostly CN V.
MIS symptoms:
-headache and pain (diffuse or local). Activation of nociceptive (pain) fibers in dura.
-neck stiffness (“nuchal rigidity”)
-impairment or loss of consciousness (if pathology progresses)
-various potential causes, including inflammation, infection (“Meningitis”-viral, bacterial, or fungal), and pressure from casuses such as subarachnoid hemorrhage or tumor.

Question 19

(LO) CNS Infection

Note general principles for the blood-brain barrier function and what may cause these to be breached.

Answer 19

1. Normally, very few lymphocytes within CNS due to exclusion by BB barrier. Some types of brain cells act as immune cells and an allow blood-borne immune cells to enter.
2. Intracranial environment normally sterile, but if barriers are disrupted (traumatic injury, immunodeficiency), then some direct and open routes may exist.
3. Bacteria, viruses, fungal cells, parasites can enter into cranium or vertebral compartment when normal barriers are breached.
4. Viral entry can be directly into PNS via axon terminals in target tissue and once inside, viruses cacn be transported backwards to the cell body (soma) in a ganglion, spinal cord, or brain. (ex: rabies)
   Potential channels include:
   emissary veins, veins from face to cavernous sinus, and cribiform plate.

Question 20

(LO) Types of hemorrhages: anatomical source, presentation, synopsis.

Answer 20

Subdural hem: typically caused by tear in bridging veins at the dura-arachnoid interface.
Subarachnoid hem:
-Most common origin is aneurysms.
-Presents non-focal neurological signs (diffuse)
-Increased ICP (intracranial pressure)
-Detectable by lumbar puncture and neuroimaging.