Anatomy and Imaging

Question 1

Describe imaging 3 main types of MRI and CT brain?

Answer 1

T1
• CSF - dark
• Grey matter/white matter - white
• Anatomy and structure

T2
• CSF - white
• Grey matter/white matter - dark
• Best for inflammation/edema
• All fluid - bright

FLAIR
• Same as T2 except CSF signal suppressed - CSF dark
Best for inflammation/edema close to CSF

CT
• CSF dark
Best imaging for bone

Question 2

Abducens nerve (CN VI) palsy

Answer 2

Abducens nerve palsy (VI)
VI - Abducens - LR6 - can’t abduct
• Motor - lateral rectus - abduction
• Exit at pons
• Non localising sign of increased ICP
Has long path in subarachnoid space

Question 3

CNIII - Oculomotor nerve palsy

Answer 3

•CNIII - Oculomotor - ALL3 - “down and out”
CNIII - all rectus muscles except lateral and superior oblique - ‘Down and out’
• Lifts eyelid (levator subnucleus) - ptosis (droopy eyelid)
• Parasympathetic pupil nucleus - pupil constriction

Cause
• Congenital - developmental anomaly, birth trauma
• Intracranial lesion
• Orbital disease

Ex
• Ptosis
• Eye In down and out
• Pupil - failure of pupil to constrict with life (parasympathetic) (note can have pupil sparing)
• Lesion in cavernous sinus - will be associated with 4th, 6th, trigem

Question 4

CNIV - Trochlear

Answer 4

• Superior oblique
CNIV - Trochlear- SO4 - head positioning, compensate for diplopia
• Longest intracranial course
• Only one exiting from brainstem
• Cause - congenital, acquired
• Which is higher (hypertropic) eye?
• Is hypertropia worse on right or left gaze?
In hypertropia worse in right or left head tilt?

Question 5

Recall upper limb myotomes, what are Erb’s and Klumpke’s palsies?

Answer 5

Erb’s palsy
• Injury to C5 and C6
• Internal rotation of forearm, wrist and finger flexion - “waiter’s tip”
• Can have sensory deficits lateral proximal upper extremity

Klumpke’s palsy
Injury to C8, T1 “claw hand”