Neuro: Gross Brain And Cranial Environment, Spinal Cord And Vertebral Compartment Flashcards
Cerebrum (cerebral hemi)
Cerebelllum ("little brain")
Brain stem (Midbrain, Pons, Medulla)
Spinal Cord & Roots
Pre-Ganglionic Autonomic Neurons
**These are all part of what system?Central Nervous System
Spinal nerves and rami
Somatic nerves (cutaneous and neuromuscular)
Visceral nerves
Autonomic ganglia and post autonomic neurons
**These are all part of what system?
Peripheral Nervous System
Parts of CNS from top down
Telencephalon (Cerebrum) Diencephalon (Thalamus/hypothalamus) Brainstem -Midbrain -Pons -Medulla Spinal Cord
Cranial nerve to cerebrum; Which lobe, mostly?
Olfactory Tract (CN1); Temporal Lobe
Cranial nerve to thalamus
Optic Tracts (CN2)
Cranial nerve to/from Brainstem:
Midbrain
Occipital and Trochlear (CN 3 - CN 4)
Cranial nerve to/from Brainstem:
Pons
Trigeminal, Abducens, and Facial (CN 5 - CN 7)
Cranial nerve to/from Brainstem:
Medulla
Vestibulocochlear, Glossopharyngeal, Vagus, Spinal Accessory, Hypoglossal (CN 8 - CN 12)
Crown-like section through the diencephalon
Coronal Plane
Empty spaces deep in hemispheres of brain
Ventricular spaces (ventricles) **Empty Vents
What do the brain and spinal cord develop from?
Growth and Folding of the Fluid-filled Neural Tube, creating the CNS. Inside this neural tube is the ventricular system, containing CSF.
Wishbone-shaped structure in each cerebral hemisphere
Lateral Ventricle (contains third and fourth ventricle)
Where do the ventricles of the brain travel upon leaving the cerebrum?
They travel down, dorsal and medial to the spinal cord sections, within the central canal
Directional flow and cycling of CSF from inside the ventricular system to the outside area surrounding the CNS = subarachnoid space
CSF travels from the choroidal plexus to Ventricular system to 3 foramen to Subarachnoid space to Veins and sinuses (where it is reabsorbed)
Where does the central canal dead-end?
Sacral Spinal Cord
Axis of the neural tube
Rostral-caudal axis (head-tail)
Dorsal-ventral axis is always ____ to rostrum-caudal axis
Perpendicular
Which axis is kinked in humans?
Rostral-caudal axis
What surface is along the base of the skull?
Ventral/belly
What surface is along the surface of the skull/calvarium?
Dorsal/back surface
At which junction is the rostral-caudal axis kinked?
Midbrain-diencephalic junction
Directional axes that always stay the same, no matter if it kinks or not.
North = superior South = inferior East = posterior West = anterior (This is for a person facing the left)
Plane that cuts through to create a top and a bottom (superior and inferior)
Horizontal/transverse plane
Plane that cuts through to create a front and a back (anterior and posterior)
Coronal plane (coronal crown)
Plane that cuts through to create a left and a right
Sagittal plane (left-midline-right) (“midline section”)
Plane that cuts through to create a left and right side that is lateral to the midline (creates 2 unequal sides)
Para-sagittal plane
Plane that cuts through to create a left and a right, that makes two equal halfs
Mid-sagittal plane
Overview of brain in cranium (outside to inside)
Scalp Skull Dura -Meningeal layer -Periosteal layer Arachnoid -Subarachnoid space Pia mater
Where is the middle meningeal artery located?
It ascends while it is embedded in the dura mater
What do the outer/periosteal and inner/meningeal layers separate to form?
Dural sinuses (ex: sagittal sinus)
Layer that is flush against the dura, but has trabeculae extending to the pia mater
Arachnoid
Thin, transparent layer that is flush with the surface of the brain and follows the gyro and the sulci
Pia mater
Space where the trabeculae are found; contains CSF and vessels
Subarachnoid space
Type of hemorrhage that occurs typically from the tearing of bridging veins
Subdural hemorrhages; bridging veins travel into the sagittal sinus, making them vulnerable to tearing
Materials located within the subarachnoid space
Arteries and veins that supply/drain the brain and spinal cord
Artery and branches that travel through the dura
Middle meningeal artery
- frontal branch
- parietal branch
After removing the dura, what transparent layer is exposed? What does this layer cover?
Arachnoid layer; covers cerebral veins and arteries
After removing the arachnoid layer, what layer, that goes into the grooves of the brain, is exposed?
Pia mater
Midline (middle) covering (dural partition) of the cerebrum
Falx cerebri
Midline (middle) covering (dural partition) of the cerebelllum
Falx cerebelli
Dural partition that travels across the horizontal axis
Tentorium cerebelli
What part of the brainstem comes through the middle of the tentorial notch?
Midbrain
Structures located within the supratentorial compartment
Superior sagittal sinus Falx cerebri Cerebrum -telencephalon Hypothalamus/Thalamus -diencephalon CN 1 CN 2
Structures located within the infratentorial compartment
Cerebellum
-Motor coordination
Brainstem
-CN 3-12
Structures located within the vertebral compartment
Spinal cord
Dorsal and ventral roots
Motor and somatosensory exams
Reflexes
Structures located within the peripheral level
Nerves
Autonomic
Somatic/visceral nerves
Reflexes
A single type of herniation can result from what?
- A local mass
- Progressive supratentorial mass
- Upward transtentorial herniation
Herniation that goes across the falx cerebri
Subfalcine herniation
Herniation that goes down from the middle of the brain
Central herniation
Herniation that goes down the tentorium
Uncal transtentorial herniation
Herniation that goes from midbrain to the tonsils
Tonsilar herniation
What does a herniation affect first?
Brain tissue is displaced and injured
After affecting the brain tissue, what does a herniation affect?
Dural partitions (these can be seen through radiology)
Type of herniation where the falx cerebri is shifted to one side
Subfalcine herniation
When there is a subfalcine herniation, due to a supratentorial mass, what is it called when the gyro and the sulci get “squashed”?
Gyral/sulcal effacement
Normal intracranial pressure (average values)
Less than 20 cm water
Less than 15 cm Hg
Intracranial pressure is measured by what?
Lumbar puncture (subarachnoid space around the cauda equina)
Contra-indications for lumbar puncture
- Suspected increased supratentorial pressure can cause herniations
- Infection or mass in the path of the manometer needle insertion
Origins causing increased mass/volume, to induce increased intracranial pressure
- Hydrocephalus (too much CSF/fluid volume)
- Brain edema (Extra or Intra cellular)
- Hemorrhage (hematoma)
- Tumor or other masses (ex: abscess)
Symptoms of increased intracranial pressure
- Headache (dura) - moving, coughing, straining
- Vomiting and Nausea (Medulla)
- Impaired consciousness
- Skull - bulging fontanelles in infants; suture separation in children
- Increased systemic blood pressure (compensatory mechanism)
- Bradycardia (Medulla) - slowing of heart rate; can suppress vital signs
- Papilledema - protrusion of optic disc forward; blurring of optic disc
What does an increased intracranial pressure do to the optic disc?
Creates a papilledemic disc = rippling effect (“elevation”) due to congestion and axon swelling
Which cranial nerves (sensory [pain]) innervate the dura, falx, and tentorium?
Trigeminal (CN 5)
Vagus (CN 10)
Symptoms of meningeal irritation syndrome
- Headache/Pain (Dura; nociceptive [pain] fibers) - diffuse or local = pressure, chemical signals, inflammation
- Nuchal rigidity/neck stiffness (cervical spinal reflex circuit) - sensory input activates motorneurons and increases muscle tone in neck
- Impairment/loss of consciousness
Causes/sources of meningeal irritation syndrome
- Inflammation
- Infection: Meningitis (viral, bacterial, fungal)
- Pressure (activation of mechanoreceptors)
- -bleeding (ex: subarachnoid hemorrhage)
- -growing intracranial mass (ex: tumor)
What similarity is there between increased intracranial pressure and meningeal irritation syndrome?
Their symptoms overlap; however, meningeal irritation syndrome can occur without having an increased intracranial pressure
Kernig’s Test and Sign
Test: -Passive flexion of hip -Passive extension of knee Sign: -Pain with knee extension
Brudzinski’s Test and Sign
Test:
-Passive flexion of neck
-Pain in neck
Sign:
-Spontaneous, involuntary hip and knee flexion
-Unconscious compensatory response to reduce dural tension and pain induced by the neck flexion
Most forms of CNS infection have what kind of anatomical distribution?
Diffuse
Types of diffuse neurological signs
- Meningeal irritation signs
- Increased intracranial pressure
Deficits pointing to a focal site of pathology
Focal neurological signs (typically absent in CNS)
Exception of focal signs in the CNS
- Abscesses
- Parasitic cysts
- These can lead to focal or multi-focal lesions and signs
Diagnostic approaches for CNS infections
- History
- Physical Exam (fever, lymph nodes)
- Knowledge of microbiology
- Lab tests
- Neuroimaging (radiology) can sometimes confirm a suspected diagnosis
Immunological disorders of the CNS
Some discussions of auto-immune disorders and pathological inflammation of the CNS; Antibodies that were created to react with tumors or infections cross-link with something good, causing problems
Baseline immune surveillance of the CNS
- Few immune cells (lymphocytes) due to exclusion by blood-brain barriers
- Specific brain cells act as immune cells and can allow blood-borne immune cells to enter
Barriers to infection in the CNS
- Intracranial environment normally sterile due to specific barriers
- Infection generally occurs when barriers are disrupted (traumatic injury, immunodeficiency)
- Some direct and open routes exist
Entry into cranium or vertebral compartment of CNS
Bacteria Viruses Fungal cells Parasites **These all typically enter when normal barriers are breached
Viral entry into CNS via PNS neurons
- Viruses enter neurons through axon terminals in target tissues (skin, neuromuscular junction)
- Transported backwards to cell body (soma) in ganglion, spinal cord, or brain
- “trans-synaptic” spread = Some viruses can be further transported backwards across synapses and thus spread further
What are the 3 potential channels for entry
1) Emissary veins (from scalp, through skull, into superior sagittal sinus)
2) Veins from space to cavernous sinus (and other sinuses)
3) Cribiform plate? (Pathway from olfactory epithelium in nasal mucosa?)
Infection of dura or arachnoid and pia
Meningitis (only reaches meninges)
Infection in parenchyma of brain
Encephalitis (reaches brain)
“cephalitis” = head
What sinus do the emissary veins connect with?
Superior Sagittal Sinus
What are the facial veins connected with?
Brain venous sinuses (Cavernous sinus)
Hemorrhages in the epidural meningeal layer involve bleeding from what arteries? Where does the blood accumulate?
- Meningeal arteries
- Between skull and dura
Hemorrhages in the subdural meningeal layer involve bleeding from what arteries? Where does the blood accumulate?
- Cerebral veins (bridging veins)
- Between dura and arachnoid
Hemorrhages in the subarachnoid meningeal layer involve bleeding from between which two layers? Into which space does the blood flow into?
- Between arachnoid and pia/brain
- Into CSF space
Why are there so many chances for epidural hemorrhages?
The meningeal artery crosses multiple suture lines, allowing for multiple points of potential traumatic injury and epidural hemorrhages
How do the cerebral veins drain?
- Cerebral veins to
- Bridging veins to
- Superior sagittal sinus
What usually cause subdural hemorrhages?
Tears in bridging veins at the dura-arachnoid interface
What typically cause subarachnoid hemorrhages?
- Aneurysms (most common origin)
- AVMs (atriovenous malformation) = tangle of arteries and veins
- Surface vessels
- Diffuse neurological signs (non-focal)
- Meningeal irritation signs (MIS)
- Increased Intracranial Pressure (Inc ICP)
- Detectable by lumbar puncture and neuroimaging
