CNS Practicals Flashcards
Which part of the brain lies in the anterior cranial fossa
Frontal lobe of hemisphere
also the olfactory nerve
Which parts of the brain lie in the middle cranial fossa
Temporal lobe of hemisphere
optic nerve, oculomotor nerve, ophthalmic artery
Where does the pituitary gland lie
It rests in the hypophyseal fossa found in the middle cranial fossa
What lies directly above the body of the sphenoid bone
The hypothalamus
What passes through the foramen magnum
The medulla
Which structures are found in the posterior cranial fossa
Brain stem
Cerebellum
Foramen Magnum
What is the infundibulum
The stalk of the pituitary gland
Which part of the ventricular system lies in the cerebral hemisphere
The lateral consisting of the anterior, posterior and lateral horn
Which part of the ventricular system lies in the diencephalon
The third ventricle
Which part of the ventricular system lies in the midbrain
The aqueduct
Which part of the ventricular system lies in the pons and medulla
The fourth ventricle
How may the lateral ventricle appear
May be cut through twice in the horizontal or corral plane
How may the third ventricle appear
May appear as a hole or slit in coronal and horizontal plane, depending on the angle of the section
How may the corpus callous appear
May be cut through twice in horizontal plane
What is important to remember about the basal ganglia
That there may be more than one part
How may the internal capsule appear
Both anterior and posterior limbs can be seen in the horizontal plane
Label the parts of the brain
See diagram!
What is the function of the ventral and dorsal horns
Ventral horn: contains motor neurone cell bodies
Dorsal horn: Contains interneurones which receive sensory information from the cell bodies
Flow of information: towards spinal cord in dorsal root (afferent) away from spinal cord in ventral root (efferent), mix in spinal nerves
Describe the cervical region of the vertebrae
7 vertebrae
8 spinal nerves
All nerves above the vertebrae except for c8
Describe the thoracic region of the spine
12 vertebrae
12 spinal nerves
All spinal nerves below corresponding vertebrae
Describe the lumbar region of the spine
5 vertebrae
5 spinal nerves
All spinal nerves below corresponding vertebrae
Describe the sacral region of the spine
5 vertebrae
5 spinal nerves
All spinal nerves below corresponding vertebrae
Describe the coccyx region of the spine
1 fused (up to 4 if unfused)
1 spinal nerve
Below (or between if unfused)
Describe the spine
30 vertebrae
31 bilaterally arranged spinal nerves
Describe the basic structure of the spine
Anterior vertebral bodies bear weight anteriorly
Posteriorly, the vertebral arches protect the spinal nerves in the vertebral canal
Gaps between the arches (lateral) the intervertebral foramina allow the spinal nerves to exit
When performing lumbar puncture, where should you insert the needle, to obtain a sample of CSF safely
Below the spinal cord
Usually between l3 and L4 or L4 and L5
Where is the CSF produced
CSF is produced by the choroid plexiglass of the lateral, third and fourth ventricles.
Produced at a rate of approximately 500mL a day in Adults
Total space for CSF is 100-150mL (30mL in ventricles)
Therefore it must be turned over around 3 times a day
Describe the flow of the CSF
The CSF flows from the lateral ventricles into the third ventricle (through the foramen of Monro) and then through the aqueduct of Sylvius into the fourth ventricle.
From there it gains access to the subarachnoid space via three orficies: a medial foramen of Magendie, and two lateral foramina of Luschka.
It reaches the nervous tissue by travelling along blood vessels in the perivascular (Virchow-Robin) space where it equilibrates with brain ECF.
What happens upon equilibration of the CSF with brain ECF
Unwanted metabolites are secreted into the blood.
As the choroid plexus is able to absorb material from the CSF (choline, dopamine, serotonin metabolites, urea, creatine, K+) it can be considered an excretory organ of the brain
How is CSF taken back into the circulation
Arachnoid granulations, which are protrusions of the arachnoid space covered by a thin layer of cells that line the venous sinuses
Perineural lymph vessels of the cranial and spinal nerves
How does the composition of the CSF differ from the plasma
Normally contains fewer cells Contains much less protein Less glucose Reduced conc of potassium and calcium ions Same conc of sodium ions Higher conc of magnesium and chloride ions Same osmolarity Lower pH
Describe the production of the CSF
Produced by the choroid plexiglass
By a combination of capillary fenestration and active transport of solutes
Blood and CSF are in osmotic equilibrium because water follows the gradients created.
Lowe protein but higher ionic conc means that the plasma and CSF have the same osmolality.
How does hydrocephalus present in the child
Irritability
Increased head circumference
Loss of upward gaze
How does hydrocephalus present tin the adult
Increased pressure in head
Blackouts
headaches
drowsy
Describe communicating hydrocephalus
All 4 ventricles affected
Reduced absorption, excessive production or increased viscosity of CSF
Block in CSF absorption or CSF flow over brain surface caused by:
Meningitis
Head injury
Congenital
Haemorrhage (sub-arachnoid)
Describe non-communicating hydrocephalus
NON-COMMUNICATING (not all ventricles enlarged)
Causes: Block in ventricular system caused by:
Aqueduct stenosis
Ventricular tumours
Paraventricular tumours
Can be congenital or acquired obstruction
What are the consequences of non-communicating hydrocephalus
Accumulation of fluid proximal to the block
Ventricles rostral to the blockage dilate and put pressure on the brain tissue
This increases intracranial pressures and in newborns it can prevent the fusion of the sutures of the skull bones
How may hydrocephalus be treated
Remove cause, e.g. papilloma
Divert CSF, e.g. shunt (ventriculo-peritoneal shunt)
Open alternate pathway, e.g. ventriculostomy
Describe the different types of haemorrhages
Epidural/ extradural haemorrhage – usually due to a damaged meningeal artery between the skull and the dura after head trauma.
Subdural haemorrhage – usually due to a damaged vein between the dura and arachnoid membrane.
Both can cause a space-occupying lesion in the confined space of the cranium and hence neurological deficits.
How can you distinguish between subdural and epidural haemorrhages
The first symptoms (which may be headache, drowsiness, vomiting or seizure) are likely to arise promptly after arterial bleeding in an epidural haemorrhage whereas symptoms may be delayed by hours or days after venous bleeding in a subdural haemorrhage.
Can confirm with imaging.
Which structures are usually affected in meningitis
Pia mater and subarachnoid space (pus filling), with some spread to the upper layers of the cortex in severe cases.
Analysis of a sample of CSF should distinguish between bacterial and viral meningitis. What would you look for?
With bacterial infection there will be a high white cell count, with neutrophils predominating.
Protein concentration is increased and glucose concentration is decreased.
Bacteria may be identifiable.
With viral infection any increase in white cells is predominantly lymphocytes.
Protein and glucose level of the CSF are usually normal
Viral identification is unlikely.
Which 3 bacteria account for the majority of cases of meningitis
Neisseria meningitidis
Haemophilus Influenza
Step pneunomiae
What are the clinical features of meningitis
Fever, headache, photophobia, painful eye movements,. impaired consciousness is a late and ominous feature
Neck stiffness, positive Kernig’s sign
Occassionally- petechial skin rash (meningococcal), focal neurological signs, particularly cranial nerve palsies
