New BB PBL

Question 1

Fundus of the eye

Answer 1

Interior surface of the eye opposite the lens that includes the retina, optic disc, macula and fovea

Question 2

Why do you get optic disc swelling in raised ICP?

Answer 2

Optic nerve sheath continuous with subarachnoid space
Increased ICP transmitted
Optic nerve stops abruptly at the eye
Can lead to compression of the nerve and bulging and protrusion of the optic disc

Question 3

Why does the tumour lead to increased ICP?

Answer 3

Tumour compresses ventricles
Displaces CSF into subarachnoid space
Compression of the skull

Question 4

Location of cochlear nerve

Answer 4

Medulla

Question 5

DIPG

Answer 5

Tumour of astrocytes
Most common in children aged 7-9
0% survival rate

Question 6

Why is surgery not used in DIPG?

Answer 6

Impossible to remove tumour without removing normal brain tissue
Brainstem structures vital for life so can cause death if normal structures damaged
Only used in focal tumours

Question 7

Radiotherapy for DIPG

Answer 7

High energy rays to damage or kill cancer cells
Prolongs life for around 3 months
Responses short lived as tumour quickly regrows

Question 8

Factors forming BBB

Answer 8

Astrocyte end feet

Tight junctions between epithelial cells

Question 9

Course of abducens nerve

Answer 9

Arises from abducens nucleus in pons
Exit the brainstem at the pontomedullary junction
Enters subarachnoid space
Travels through cavernous sinus laterally
Enters orbit through SOF
Innervates lateral rectus

Question 10

Course of the facial nerve

Answer 10

Large motor and small sensory (intermediate nerve) roots exit from the pons
Enter internal acoustic meatus
Fuse to form geniculate ganglion
Gives rise to greater petrosal nerve (parasympathetic to glands), nerve to stapedius and chorda tympani (special sensory and parasympathetic to salivary glands)
Exits facial canal via stylomastoid foramen
Gives rise to posteriro auricular nerve and motor branches to digastric and stylohyoid
Passes through parotid gland
5 terminal branches
-temporal
-zygomatic
-buccal
-mandibular
-cervical

Question 11

Course of the trigeminal nerve

Answer 11

3 sensory and one motor nucleus found throughout brainstem
Sensory roots exit the pons and form trigeminal ganglion
Divides into 3 nerves - V1,2,3
Motor root joins V3
V1 –> SOF
V2 –> foramen rotundum
V3 –> foramen ovale

Question 12

Course of the vestibulocochlear nerve

Answer 12

Vestibular portion from vestibular nuclei in pons and medulla
Cochlear portion from nuclei in medulla
Leave at the cerbellopontine angle
Enter internal acoustic meatus
Split to form vestibular and cochlear nerves
Innervate cochlear and vestibular systems of the ear respectively