Wednesday 6 October 2010

MRCP revision battle 25.1: Neuroleptic Malignant Syndrome

Having been blessed by a set of on-calls with some nice interesting cases I'm full of enthusiasm for today's battles, so lets get on with it!

MRCP revision battle 25.1: Neuroleptic malignant syndrome
MRCP revision battle 25.2: Behcets disease
MRCP revision battle 25.3: Subarachnoid haemorrhage
MRCP revision battle 25.4: Normal pressure hydrocephalus
MRCP revision battle 25.5: Gas gangrene
MRCP revision battle 25.6: Methaemoglobinaemia
MRCP revision battle 25.7: The weeverfish

MRCP revision battle 25.1: Neuroleptic malignant syndrome

A nice straightfoward battle to begin with...

Neuroleptic malignant syndrome is a life-threatening condition associated with use of antipsychotic drugs.

Symptoms and signs include:
  • hyperthermia
  • rigidity/muscle cramps
  • extrapyramidal signs
  • autonomic dysfunction (labile BP, sweating, urinary incontinence
  • confusion

Investigations show:
  • raised CK
  • raised WCC

Treatment is:
  • cooling
  • dantrolene (a muscle relaxant; note dantrolene is also used in malignant hyperthermia, which will be one of tomorrows battles)

Now on to a slightly less straightforward battle, Behcets disease...

MRCP revision battle 25.2: Behcets disease

Behcet's disease is a systemic vasculitis of unknown cause.

The classic triad of Behcet's disease is:
  • oral ulcers
  • genital ulcers
  • anterior uveitus
which I remember as GOA, like the place in India.

Other possible features include:
  • thrombophlebitis
  • DVT
  • erythema nodosum
  • pathergy reaction (=needle prick leads to pustule formation)
  • arthritis
  • aseptic meningitis
  • ataxia
  • diarrhoea

Males are more commonly affected than females.
It is commonest in Turkey and Japan.
30% of patients have a positive family history.

HLA B5 is associated with anterior uveitis and HLA B12 is associated with recurrent ulceration.

Severe disease requires steroids/ciclosporin/azathioprine.

Next up - SAH...

MRCP revision battle 25.3: Subarachnoid haemorrhage

Subarachnoid haemorrhage is bleeding into the space between the subarachnoid membrane and the pia mater.

It accounts for 5-10% of all strokes.

  • ruptured berry aneurysm (80%)
  • malformations (15%)
  • post trauma

Common sites of berry aneurysms are:
  • junction of the posterior communicating artery with the internal carotid
  • junction of the anterior communicating artery with the anterior cerebral artery
  • the bifurcation of the middle cerebral artery

If (like me) your anatomy of the circle of willis is a little rusty the wiki commons image below might help refresh your memory:

15% of berry aneurysms are multiple.

Subarachnoid haemorrhages are associated with:
  • polycystic kidneys
  • coarctation of the aorta
  • Ehlers-Danlos syndrome
  • PAN

Classical presentation is a thunderclap occipital headache "as if kicked in head" with vomiting and neck stiffness.
Around 6% of patients will have had a sentinel headache before.

Investigation is:
  • CT - >90% of bleeds detected
  • LP - done >12hrs after onset looking for xanthochromia

  • neurosurgical referral
  • prompt angiography if surgery likely
  • nimodipine

On to another neuro topic - normal pressure hydrocephalus

MRCP revision battle 25.4: Normal pressure hydrocephalus

Normal pressure hydrocephalus is a triad of:
  1. dementia
  2. gait abnormality
  3. urinary incontinence
(remember as DUG!)

It is caused by a defect in the absorption of CSF.
Causes include: meningitis, head injury, subarachnoid haemorrhage.

Note that there is NO headache and NO papilloedema.

  • CT head (predictably) - enlarged ventricles
  • large volume lumbar puncture - ? high opening pressure, ? improvement of symptoms
  • lumbar infusion test

Treatment is a shunt.

Next up... gas gangrene!

MRCP revision battle 25.5: Gas gangrene

Gas gangrene is a life threatening bacterial infection.

It is characterised by muscle necrosis, gas production and sepsis.

A typical appearance is shown below:

                                       From Wiki Commons, taken by Engelbert Schröpfer, Stephan Rauthe and Thomas Meyer.

Most cases are caused by trauma innoculation with bacteria, for example a farmer standing on a pitchfork.
Very rarely it may occur spontaneously, for example in the context of neutropenia.

The commonest causative organism is clostridium perfringens.

Management is:
  • urgent surgical debridement
  • IV Abx 
  • hyperbaric oxygen if available

Next up - methaemoglobinaemia

MRCP revision battle 25.6: Methaemoglobinaemia

Methaemoglobin (MetHb) is formed when the iron in haemoglobin is oxidised from the ferrous state (Fe2+) to the ferric state (Fe3+) 

Methaemoglobinaemia means raised MetHb levels, and as MetHb has a far higher affinity for oxygen than normal haemoglobin this results in tissue hypoxia as the oxygen being carried in the blood is not given up to the tissues.

Clinical features depend on the % of MetHb:
  • 15-20% - cyanosis
  • 20-45% - impaired consciousness
  • >55% - seizures, arrhythmias, coma
  • >70% - lethal

Pulse oximetry will show low oxygen sats, as will the printout from blood gas analysis - but the PaO2 will be high.

Causes of methaemoglobinaemia:
  • congenital
    • pyruvate kinase deficiency
    • G6PD deficiency
    • abnormal haemoglobin - HbH or HbM
    • diaphorase 1 deficiency
  • acquired - accelerated rate of oxidised formation due to meds
    • antibiotics - sulphonamides, trimethoprim, dapsone
    • drugs used in anaesthetics - lidocaine, procaine
    • others -primaquine

  • 1% solution of methylene blue
  • hyperbaric oxygen
  • exchange transfusion
  • dialysis
  • asorbic acid in patients with G6PD deficiency

So to the final battle of the day - weeverfish!

MRCP revision battle 25.7: The weeverfish

Just very briefly...

The weeverfish (AKA trachinus vipera) is found in shallow waters around the coast of the UK.

It is small and sandy-coloured, with sharp dorsal spines.

If you are unfortunate enough to stand on it you will get intense pain.

Happily the toxin produced by the weeverfish is denatured above 40C - so dunk the foot in hot water and the pain should stop.

On that most random of MRCP revision notes, lets end for the day!