CNS Practicals

Question 1

Which part of the brain lies in the anterior cranial fossa

Answer 1

Frontal lobe of hemisphere

also the olfactory nerve

Question 2

Which parts of the brain lie in the middle cranial fossa

Answer 2

Temporal lobe of hemisphere

optic nerve, oculomotor nerve, ophthalmic artery

Question 3

Where does the pituitary gland lie

Answer 3

It rests in the hypophyseal fossa found in the middle cranial fossa

Question 4

What lies directly above the body of the sphenoid bone

Answer 4

The hypothalamus

Question 5

What passes through the foramen magnum

Answer 5

The medulla

Question 6

Which structures are found in the posterior cranial fossa

Answer 6

Brain stem
Cerebellum
Foramen Magnum

Question 7

What is the infundibulum

Answer 7

The stalk of the pituitary gland

Question 8

Which part of the ventricular system lies in the cerebral hemisphere

Answer 8

The lateral consisting of the anterior, posterior and lateral horn

Question 9

Which part of the ventricular system lies in the diencephalon

Answer 9

The third ventricle

Question 10

Which part of the ventricular system lies in the midbrain

Answer 10

The aqueduct

Question 11

Which part of the ventricular system lies in the pons and medulla

Answer 11

The fourth ventricle

Question 12

How may the lateral ventricle appear

Answer 12

May be cut through twice in the horizontal or corral plane

Question 13

How may the third ventricle appear

Answer 13

May appear as a hole or slit in coronal and horizontal plane, depending on the angle of the section

Question 14

How may the corpus callous appear

Answer 14

May be cut through twice in horizontal plane

Question 15

What is important to remember about the basal ganglia

Answer 15

That there may be more than one part

Question 16

How may the internal capsule appear

Answer 16

Both anterior and posterior limbs can be seen in the horizontal plane

Question 17

Label the parts of the brain

Answer 17

See diagram!

Question 18

What is the function of the ventral and dorsal horns

Answer 18

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

Question 19

Describe the cervical region of the vertebrae

Answer 19

7 vertebrae
8 spinal nerves
All nerves above the vertebrae except for c8

Question 20

Describe the thoracic region of the spine

Answer 20

12 vertebrae
12 spinal nerves
All spinal nerves below corresponding vertebrae

Question 21

Describe the lumbar region of the spine

Answer 21

5 vertebrae
5 spinal nerves
All spinal nerves below corresponding vertebrae

Question 22

Describe the sacral region of the spine

Answer 22

5 vertebrae
5 spinal nerves
All spinal nerves below corresponding vertebrae

Question 23

Describe the coccyx region of the spine

Answer 23

1 fused (up to 4 if unfused)
1 spinal nerve
Below (or between if unfused)

Question 24

Describe the spine

Answer 24

30 vertebrae

31 bilaterally arranged spinal nerves

Question 25

Describe the basic structure of the spine

Answer 25

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

Question 26

When performing lumbar puncture, where should you insert the needle, to obtain a sample of CSF safely

Answer 26

Below the spinal cord | Usually between l3 and L4 or L4 and L5

Question 27

Where is the CSF produced

Answer 27

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

Question 28

Describe the flow of the CSF

Answer 28

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.

Question 29

What happens upon equilibration of the CSF with brain ECF

Answer 29

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

Question 30

How is CSF taken back into the circulation

Answer 30

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

Question 31

How does the composition of the CSF differ from the plasma

Answer 31

``` 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 ```

Question 32

Describe the production of the CSF

Answer 32

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.

Question 33

How does hydrocephalus present in the child

Answer 33

Irritability Increased head circumference Loss of upward gaze

Question 34

How does hydrocephalus present tin the adult

Answer 34

Increased pressure in head Blackouts headaches drowsy

Question 35

Describe communicating hydrocephalus

Answer 35

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)

Question 36

Describe non-communicating hydrocephalus

Answer 36

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

Question 37

What are the consequences of non-communicating hydrocephalus

Answer 37

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

Question 38

How may hydrocephalus be treated

Answer 38

Remove cause, e.g. papilloma Divert CSF, e.g. shunt (ventriculo-peritoneal shunt) Open alternate pathway, e.g. ventriculostomy

Question 39

Describe the different types of haemorrhages

Answer 39

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.

Question 40

How can you distinguish between subdural and epidural haemorrhages

Answer 40

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.

Question 41

Which structures are usually affected in meningitis

Answer 41

Pia mater and subarachnoid space (pus filling), with some spread to the upper layers of the cortex in severe cases.

Question 42

Analysis of a sample of CSF should distinguish between bacterial and viral meningitis. What would you look for?

Answer 42

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.

Question 43

Which 3 bacteria account for the majority of cases of meningitis

Answer 43

Neisseria meningitidis Haemophilus Influenza Step pneunomiae

Question 44

What are the clinical features of meningitis

Answer 44

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