Cerebrospinal Fluid and Neuroanatomy Review

• Meninges, Trauma, Ventricles, Choroid, CSF, Hydrocephalus, and Cisterns are the key topics.

Meningeal Layers

• The dura mater adheres closely to the skull, with its inner layer forming sinuses.
• Cerebrospinal fluid (CSF) flows in the subarachnoid space.
• Arachnoid trabeculae provide support within the meninges.
• The pia mater is closely apposed to the brain parenchyma.
• The combination of pia and arachnoid mater is referred to as leptomeninges.
• The skull is closely apposed to the dura, while the spinal column is separated by the epidural space.

Periosteal Dural Infoldings

• The falx cerebri is involved in midline shifts and brain herniation.
• The tentorium cerebelli is associated with transtentorial herniation
• The diaphragma sella covers the hypophyseal fossa.
• Pituitary tumors can compress the hypothalamus due to the location of the diaphragma sella.

Meninges and CSF Flow

• The dura is apposed to the skull.
• Arachnoid trabeculae provides support.
• Arachnoid villi (granulations) facilitate the venous return of CSF into the superior sagittal sinus.
• The subarachnoid space is accessible in the cisterna magnum.
• Dura is away from vertebrae in the spinal column.
• Denticulate ligaments offers support within the spinal cord.
• The subarachnoid space is accessible in the lumbar cistern.

Meningitis

• Meningitis involves inflammation of the brain or spinal cord.
• General signs of meningeal irritation include nuchal rigidity, headache, and fever.
• Long-term effects include cranial nerve palsies (II, VII, VIII), general paresis, sensory loss, and ataxia.
• Kernig's sign is when knee straightening by a practitioner causes hamstring pain
• Brudzinski's sign is when neck flexion by a practitioner causes hip flexion.
• Meningitis can be bacterial, viral, fungal, or environmental in origin.
• CSF samples are collected to identify the source of meningitis.

Head Trauma

• Concussion involves an alteration in consciousness as a result of head trauma
• Contusion refers to brain tissue injury, hemorrhagic lesions, and axonal injury.
• Possible outcomes of head trauma include hydrocephalus and dementia.
• Contusions often occur in the temporal and inferior frontal lobes.

Vascular Injury - Hematoma

• Epidural hematoma is caused by a skull fracture and tearing of meningeal arteries.
• Subdural hematoma involves concussion/contusions and tearing of veins at the dural/meningeal border.
• Subarachnoid hemorrhage typically results from a ruptured aneurysm of arteries into the subarachnoid space.
• Contusion means damage at the brain surface.
• Intra-parenchymal hemorrhage happens within brain tissue.

Subarachnoid Cisterns

• Subarachnoid cisterns include paracallosal, quadrigeminal, lamina terminalis, chiasmatic, ambient, interpeduncular (fossa), prepontine, and premedullary cisterns
• Cisterna magna and lumbar cistern are sampled for CSF.
• Cisterns are useful in detecting sub-arachnoid hemorrhage through imaging.
• Cisterns collect fluid in areas of cranial nerves and arteries.
• Blood in CSF suggests injury

Autopsy & CT Scans

• The images show the different views of hematomas

CT/MRI Scans

• The images show the different scans for hematoma and meningioma

Herniation

• Herniation involves the displacement of brain parenchyma
• Subfalcine herniation means cingulate gyrus under falx cerebri. It increases intracranial pressure
• Transtentorial uncal herniation involves temporal lobe against tentorium and damage to cranial nerve III and the cerebral peduncles
• Results in eye motor palsy and hemiparesis
• Tonsillar herniation involves cerebellum through foramen magnum and pressure on the medulla of the brainstem
  • Leads to cardiac and respiratory distress

Case Study One

• A 52 year old male presents with headaches
• Increasing left sided weakness and lethargy
• MRI reveals right sided tumor
• Glioblastoma multiforme
• Autopsy confirms tumor mass on the right
• Uncal herniation can affect: multiple structures at the tentorial notch

Brain Autopsy

• Lethargy - reticular formation
• Weakness - cerebral peduncle
• Duret hemorrhage, posterior cerebral artery infarction and CN III compression was also observed

Development of Ventricles

• Vesicles are brain regions.
• The three vesicle stage, the one space stage, and the five vesicle stage.
• Telencephalon develops into lateral ventricles
• Diencephalon: third ventricle
• Mesencephalon: cerebral aqueduct
• Metencephalon and myelencephalon: fourth ventricle
• Spinal cord: central canal

Lateral Ventricles/Communicating Spaces

• Lateral ventricles include the anterior horn, inferior horn, atrium, and posterior horn.
• Foramen of Monro connects the lateral and third ventricles
• Cerebral aqueduct of Sylvius connects the third and fourth ventricles
• Foramen of Magendie and foramine of Luschka are parts of the fourth ventricle
• There is also a central canal

Choroid Plexus

• The choroid plexus is responsible for CSF production.
• It is present in lateral ventricle and fourth ventricle
• Ventricular exits include:
• Foramen of Magendie
• Foramina of Luschka

Ventricles/Choroid Locations

• Lateral Ventricles in the cerebrum
• Third Ventricle in the diencephalon
• Cerebral Aqueduct in the midbrain
• Fourth Ventricle above the medulla

• T1 and T2 MRI is used to scan ventricles

CSF Production and Flow

• CSF is produced by choroid capillary tufts (plexus).
  • Located in the lateral and fourth ventricles
  • Aids in buoyancy and shock absorption
• CSF flows through the ventricular system into the central canal and foramina of Magendie/Luschka
• CSF also flows throughout the subarachnoid space and returns through arachnoid granulations (villi) into the superior sagittal sinus.

Ependyma

• The ependyma is the epithelial lining of the ventricular cavity
• Tanycytes have end feet that contact blood vessels and help in the creation of the blood barrier.
• Ependymoma is a childhood tumor with consequences like hydrocephalus and brainstem compression

Hydrocephalus

• A developmental disorder includes aqueductal obstructive stenosis. can case CSF prodution/resorptions, and enlargement of the cranium
• Hydrocephalus ex vacuo causes loss of parenchyma. (Huntington's), and enlargement of the lateral ventricles
• Adult obstructive hydrocephalus causes convulsions and seizures
• Pseudotumor cerebri is a hypertensive disease that affects women. Causes headaches and mausea
• Normal Pressure hydrocephalus causes remitting intercranial pressures, affecting imbalance, incontinence and dementia

Pathologies Affecting Intracranial Pressure + Consequences

• Pathologies include: Hydrocephalus, Hematoma, Tumors, Infection, and Obesity/Diabetes
• Consenquences: Compression of vasculature/hemorrage, and compression of parenchyma/edema
• Presentation: Posterior scalp laceration, lethargy/decreased consciousness levels, absent right corneal reflex, right hemi-plegia, snd sensory loss
• Coup/countercoup cerebral contusion + midline shift can cause pincal calcification
• Falx cerebri/tentorium cerebelli + midline shift can cause subdural/subarachnoid hematoma

Case Study: Follow Up

• Countercoup injury affected frontal/temporal lobes
• Caused lethargy; level of consiousness resolves over time
• Hemiparesis/compression of corticospinal tract resolved over the course of a year
• Corneal reflex dysfunction suggests that the brainstem tentorium was involved

Fluid Exchange: Brain to Blood

• Vascular System (arterial blood circulation) --> Blood Brain Barrier/Blood CSF Barrier --> Interstitial Tissue
• Intracelluar Cytoplasm of neurons and Glia --> cerebral venules/cerebral veins --> CSF in Ventricles/Subarachnoid Space --> Archnoid Villi --> Venous Sinuses (superior saggital sinus+spinal sinuses)

Review questions covering the circulation and function of cerebrospinal fluid (CSF), hydrocephalus, and related neuroanatomy. Topics include CSF return to circulation, symptoms of ependymoma, types of hydrocephalus, aqueductal stenosis, pseudotumor cerebri, meninges, and the function of arachnoid trabeculae.