Wednesday, 3 November 2010

MRCP revision battle 41.1: Horner's syndrome

Today is another day of completely random battles... with a mnemonic of a addicts hammock and some fevers of unknown cause hopefully each battle should have something of interest in it...

MRCP revision battle 41.1: Horner's syndrome
MRCP revision battle 41.2: Gynaecomastia
MRCP revision battle 41.3: Gingival Hyperplasia
MRCP revision battle 41.4: Leptospirosis
MRCP revision battle 41.5: Opioid and benzo conversions
MRCP revision battle 41.6: Pyrexia of unknown origin
MRCP revision battle 41.7: Fitness to fly

MRCP revision battle 41.1: Horner's syndrome

Horner's syndrome is the triad of:
  • miosis
  • ptosis
  • anhydrosis

 It is caused by an interruption of the sympathetic pupillomotor fibres

Causes may be:
  • central - which causes anhydrosis of the face, arm and trunk
  • pre-ganglionic = second order - which causes anhydrosis of face
  • post-ganglionic = third order - which causes no anhydrosis

A general way to remember the causes is PC Stem:
  • pancoast tumour
  • cervical rib
  • cluster headache
  • carotid artery dissection
  • stroke
  • syringomyelia
  • trauma
  • thyroidectomy
  • encephalitis
  • multiple sclerosis

 An alternative way to try and learn them by their location is:
  • central: STEMS 
    • stroke
    • tumour
    • encephalitis
    • multiple sclerosis
    • syringomyelia
  • pre-ganglionic: PCT
    • pancoast tumour
    • cervical rib
    • trauma
    • thyroidectomy
  • post ganglionic: 2Cs
    • carotid artery dissection
    • cluster headache

Now for some big breasts...

MRCP revision battle 41.2: Gynaecomastia

Gynaecomastia = enlargement of male breast tissue.

Causes can be divided into:

  • adolescence
  • increasing age - due to low testosterone

Drugs (a mnemonic to remember drugs causing gynaecomastia is a addicts hammock)
  • antipsychotics
  • ACE inhibitors
  • digioxin
  • diazepam
  • isoniazid
  • cimetidine
  • TCA
  • spironolactone
  • heroin
  • amiodarone
  • metronidazole
  • marijuana
  • omeprazole
  • calcium channel blockers
  • ketoconazole

  • klinefelters
  • liver cirrhosis
  • hyperthyroidism

So from enlarged breasts to enlarged gums...

MRCP revision battle 41.3: Gingival Hyperplasia

Gingival hyperplasia is the overgrowth of the ginival (=gum) tissue.

Photos of gingival hyperplasia have appeared in part 2 written exams so a grasp of the main differentials is worthwhile.

Conditions to consider include:
  • poor oral hygiene leading to gingivitis
  • AML
  • vitamin C deficiency
  • pregnancy
  • drug-induced casues:
    • phenytoin
    • ciclosporin
    • calcium channel blockers (nifedipine, verapamil)

Now for a change to a spirochaete...

MRCP revision battle 41.4: Leptospirosis

Leptospirosis, also known as Weil's disease, is a disease caused by infection with the spirochaete leptospira interrogans.

It is classically caught from water contaminated with rat's urine, so suspect it as a diagnosis in those in questions who have recently fallen into rivers/out of rowing boats.

After a 2 to 20 day incubation period the patient develops:
  • fever
  • myalgia
  • cough/haemoptysis
  • headache

The patient then either makes a good recovery or develops:
  • meningitis
  • jaundice
  • renal failure (50%)

Treatment is with penicillin/amoxicillin/doxycycline.

Lets move on to some conversions...

MRCP revision battle 41.5: Opioid and benzo conversions

Occasionally in real-life/MRCP exam you may need to convert between different drugs in the same family, so this revision battle briefly covers 2 popular families: the opioids and the benzos.


First, as an aside: remember opiate refers to a substance derived from opium (from the poppy) while opioids are synthetic/semi-synthetic versions of opiates.

  • PO codeine to PO morphine: divide by ten
  • PO tramadol to PO morphine: divide by five
  • PO morphine to PO oxycodone: divide by two
  • PO morphine to S/C morphine: divide by two
  • PO morphine to S/C diamorphine: divide by three
  • PO morphine to S/C oxycodone: divide by three
  • morphine to fentyl: divide by 100

Other misc notes:
  • codeine relies on conversion to an active form by the P450 enzyme group.  Not all patients are able to do this (roughly 10% of the population struggle), and other drugs (such as SSRIs) may interfere with the effectiveness of conversion so the same amount of codeine may have a very variable analgesic effect on different people.
  • doses of all opioids should be reduced in renal failure except fentanyl
  • if asked to prescribe a breakthrough dose this is usually 1/6th of the total 24hr dose.

Benzos (and derivative)

Rough conversions are:

Chlordiazepoxide 15mg = Temazepam 10mg = Diazepam 5mg = Lorazepam 0.5mg

Decrease by 1/8th every 2 weeks.

Now for a little pyrexia of unknown origin...

MRCP revision battle 41.6: Pyrexia of unknown origin

Petersdorf and Beeson defined pyrexia of unknown origin (PUO) as:
  • fever >38.3C on several occasions
  • longer than 3 weeks
  • with no diagnosis reached after 1 week of inpatient investigation

  • infections:
    • abscesses
    • TB
    • malaria
    • any other varient...
  •  malignancy
    • lymphoma
    • hypernephroma
    • leukaemia
    • atrial myxoma
  • connective tissue disease
    • RA
    • SLE

Daily spikes: abscess; TB; schistosomiasis
Twice daily spikes: leishmaniasis

On to the final battle of the day - fitness to fly...

MRCP revision battle 41.7: Fitness to fly

When a patient can fly pops up intermittently, particularly in part 1 written.  The following periods after various medical events at which it is considered safe to fly are quoted from the excellent website and references can be found there.

  • uncomplicated MI: 7 days
  • complicated MI: 4 weeks
  • CABG: 10 days
  • PCI: 5 days
  • pneumothorax: 2 weeks post resolved CXR
  • pregnancy: contraindicated after 36 weeks gestation in singleton pregnancy or 32 weeks gestation if multiple pregnancy
  • laparoscopy/colonoscopy: 24 hrs
  • abdominal surgery: 10 days
  • cast: 24 to 48 hrs
  • CVA: 10 days
  • sickle cell: needs in flight oxygen