Misc (WM)

Question 1

Where is the “micturition centre”?

Answer 1

Rostral Pons

Question 2

What are the three peaks of Xanthochromia on pt photospectrometry and the pattern that are possible?

Answer 2

(Rarest Methaemoglobin )
Main two:
Oxyhaemoglobin
Bilirubin (in vivo conversion only)

Light exposure can lead to lysis of RBC to yield oxyhb
Oxyhaemoglobin present first, bilirubin later

Oxyhaemoglobin only - early tap, or traumatic with light exposure

Oxyhaemoglobin at 2-12 hours
Bilirubin is converted from this

Oxyhaemoglobin in large quanitities can mask bilirubin

Question 3

What are the components of PHASES?

Answer 3

Population
Hypertension
Age
Size
Earlier SAH
Site

Question 4

What are the 5 year rupture risks in ISUIA in ant and post circulation by size?

Answer 4

Catergories awith approx scores
<7mm: 0% ant, 2.5 % post
7-12mm: 2.5% ant, 14.5% post [remember this line and you can work back and forward]
13-24mm: 14.5% ant, 18% post
>25mm : 40% ant, 50% post

Question 5

What electrolyte abnormalities most commonly cause seizures?

Answer 5

Low or High Na
Low or High Ca
Low Mg

Question 6

Describe the theories of syrinx formation

Answer 6

1. Craniospinal dissociation = “suck and slosh” theory of Bernard Williams. Manoeuvres that raise csf pressure cause hydrodissection through the spinal cord
2. Heiss-oldfield theory. Occlusion at the foramen magnum causes CSF pulsations during cardiac systole to be transmitted through the Virchow-Robin spaces
3. Hydrodynamic (“water-hammer”) theory of Gardner: systolic pulsations are transmitted with each heartbeat from the intracranial cavity to the central canal.

Question 7

What’s average CSF production?

Answer 7

450ml/day

at any one time there’s 150ml of which 25mls is intraventricular

Question 8

What are radiological features of NPH?

Answer 8

Increased evans index (>0.3) - widest point of vents divided by skull inner table at same level
Widening of temporal horns of lateral ventricle
Acute callosal angle (100 degrees lower limit of normal)
Upward bowing corpus callosum

Disproportionate subarachnoid changes:
Dilated sylvian fissures
Tight high convexity
Cingulate sulcus sign (posterior half of cingulate sulcus is narrower than anterior)
Focal dilatation of sulci over medial surface or convexity (sometimes called transport sulci)

Question 9

What is sensitivity for LP vs lumbar drainage for shunt responsiveness in NPH?

Answer 9

LP 25%

Lumbar Drain 50-100%

Question 10

What are the three features of a typical IIH patient?

Answer 10

Obese
Female
Reproductive Age

Question 11

What are secondary IIH causes?

Answer 11

Multiple include:
Cerebral venous sinus thrombosis
Venous obstruction or right heart failure
Medications (tetracycline, amiodarone)
Endocrine causes (addisons)

Question 12

What are options in IIH if vision threatened?

Answer 12

Lumbar drain
VPS shunt
Optic nerve sheath fenestration
Venous stenting

Question 13

What are normal CSF cell counts/mm3

Answer 13

0 PMN
0 RBC
0-5 Monocytes

Question 14

What’s acceptable RBC: WCC ratio?

Answer 14

1:500 mirroring whole blood

Question 15

Describe BASICS findings

Answer 15

At 22 months
2% revision for infection bactiseal (6% standard and silver)
Overall revision rate is approx 25% irrespective

Question 16

What criteria for conversions EVD to VPS in infection?

Answer 16

Absence fever
Improved microscopy (WCC<10 + nil on culture)
10 days on abx minimum (7-14 days in Oxford case histories)

Question 17

What valves could you use for LP shunt?

Answer 17

Medtronic Strata NSC (non siphon control)

Question 18

What are radiological signs of low ICP?

Answer 18

Pachymeningeal enhancement
Venous engorgement
Effacement of suprasellar cistern
Prominent pituitary gland
Tectal beaking
Tonsillar herniation

Question 19

What changes in SNAP (sensory nerve action potential) and CMAP (compound motor action potential) do you see in 
carpal tunnel (mild, moderate, severe)?

Answer 19

Mild
SNAP - prolonged latency, normal amplitude
CMAP - normal

Moderate
SNAP - prolonged latency, decreased amplitude
CMAP - prolonged latency, normal amplitude

Severe
SNAP - absent
CMAP - prolonged latency, decreased amplitude
+ abnormal needle EMG (insertional activity, polyphasic waves, widening of EMG)

Question 20

What’s normal CMAP amplitude and distal motor latency at carpal tunnel?

Answer 20

CMAP>4 mV
CML<4 milliseconds

(and conduction velocity is generally 40-50)

Question 21

What are the landmarks for percutaneous trigeminal radio frequency rhizotomy?

Answer 21

2.5cm lateral of angle of mouth

Pass needle medial to coronoid process of mandible aiming towards the plane 2.5cm anterior to EAM and mid pupillary line

Question 22

How do you stimulate and lesion in radio frequency trigeminal ablation?

Answer 22

Start 0.1V amplitude (50-75Hz, 1mS) and increase to check division
Then lesion 60-70 degrees for 90 seconds

Question 23

What work up can you do for cerebral abscess?

Answer 23

Source localisation:
Echo
OPG/Dental
Sinuses/ENT
Skin/ulcers
Immunocompromise:
HIV
Diabetes
Blood counts

Question 24

What are the three points of entrapment of ulnar nerve at elbow?

Answer 24

Proximally - arcade of struthers (medial head of triceps to medial intermuscular septum
At elbow - osborne’s ligament = roof of cubital tunnel = medial epicondyle to olecranon
Distally - between 2 heads of flexor carpi ulnaris

(when operating - 10cm proximally, 5cm distally)

Question 25

How would you distinguish ulnar nerve compression in elbow and wrist?

Answer 25

Dorsal sensation is intact suggests wrist compression

If dorsal sensation impaired that suggests compression in elbow