__Crash Course CNS

Question 1

3rd nerve palsy causes

Vasc, metabolic and surgical

Answer 1

Vasc: stroke, aneurysm
Metabolic: diabetes
Surgical: abscess, malignancy

Question 2

Medical vs surgical 3rd nerve palsy

Answer 2

Medical 3rd nerve spares the pupil (core becomes ischaemic in the center)
Surgical 3rd nerve does not (dilated pupil, compression of outside parasympathetic fibres)

Question 3

Ophthalmoplegia, unable to abduct eye, diplopia

+ Causes

which image is false with the diplopia?

Answer 3

6th nerve palsy

Raised ICP, stroke (pons), compressive lesion, trauma, inflammatory cause

Outer image is false

Question 4

Causes of 6th nerve palsy

Answer 4

Raised ICP, stroke (pons), compressive lesion, trauma, inflammatory cause

Question 5

Causes of Horner’s

Answer 5

stroke, demyelination (MS)
Pancoast’s tumour, carotid dissection
trauma, inflammatory conditions

Question 6

Painful Horner’s differentials

Answer 6

need to rule out carotid dissection or stroke

Question 7

Bell’s palsy and forehead involvement

Answer 7

Bell’s palsy includes the forehead, whole half of face affected

(in stroke, forehead is spared)

Question 8

Facial nerve and innervation of the forehead?

Answer 8

The forehead is represented by both hemispheres

Hence in a stroke - can still raise both eyebrows

in Bell’s palsy - paralysis of half the face, including the forehead

Question 9

Other things to examine in a facial nerve palsy?

Answer 9

In the ears for Ramsey Hunt
Skin rashes (shingles)
Diabetes
6th nerve (anatomically close)

Question 10

What is Bell’s phenomenom?

Answer 10

Eyes roll up and in when eyes closed

Visible in Bell’s (normal phenom but abnormal to see it)

Question 11

Why do you get hyperacusis in Bell’s palsy?

Answer 11

Facial nerve innervates stapedius muscle which is important to dampen down loud sounds

Question 12

Internuclear opthalmoplegia pathways

Answer 12

1. Frontal eye field (in frontal cortex) fires
2. Fibres come down to activate lateral gaze center (PPRF) in pons
3. Activate ipsilateral 6th (also in pons) and contralateral 3rd (in midbrain via median longitudinal fasiculus tract)
4. If this tract is damaged, 3rd does not get the message, hence no medial rectus and affected eye does not adduct

Question 13

RAPD

lesion location and causes

Answer 13

Most likely optic nerve lesion

Causes: optic neuritis (multiple sclerosis) 
Anterior ischaemic (eg. GCA)

Question 14

Head tilt
Diplopia (esp when reading/looking down)
Cannot adduct when eye is depressed

Answer 14

4th nerve palsy (Trochlear)

Superior Oblique - twists eye in
loss means eyeball now tilted

Ask does head tilt make the double vision better?

Question 15

Why ‘down and out’ with a 3rd nerve palsy?

Answer 15

Unopposed action of Superior Oblique (abducts, depresses and int rotates) and lateral rectus (abduction)

Question 16

Clinical signs of cerebellar lesion

Answer 16

DANISH

Dysdiadochokinesia
Ataxia
Nystagmus
Intention tremor
Slurred speech
Hypotonia

Question 17

Eye movements in MS?

Answer 17

Internuclear opthalmoplegia

Nystagmus due to cerebellar lesions

Question 18

Poor prognostic factors for MS (x3)

Answer 18

1. Brainstem/cerebellar disease at onset
2. Onset after 40 years
3. Primary progressive MS (no resolution of sx)

Question 19

Features of an Argyll Robertson Pupil

Answer 19

Bilateral small pupils that do not react to light

Highly specific sign of neurosyphilis but can also be a sign of diabetic retinopathy

Question 20

Features of a Holmes-Adie pupil

Answer 20

Abnormal mydriasis/dilated pupils
Reacts slowly to light but faster to accommodation

Due to infection causing inflammation

Adie syndrome – females, at least one abnormally dilated pupil absent reflexes, impaired sweating

Question 21

Features of a Marcus Gunn Pupil

Answer 21

RAPD

decreased pupillary response to light in the affected eye