Question 1#

A 27-year-old man presents to the Emergency Department with 2 day history of severe headache and pyrexia (38.2ºC).

A CT scan is reported as follows:

CT Brain: Petechial haemorrhages in the temporal and inferior frontal lobes. No mass effect. Brain parenchyma otherwise normal.

What is the most likely diagnosis?

A. Brain abscess

Correct Answer D: CT head showing temporal lobe changes - think herpes simplex encephalitis.

Herpes simplex encephalitis:

Herpes simplex (HSV) encephalitis is a common topic in the exam. The virus characteristically affects the temporal lobes - questions may give the result of imaging or describe temporal lobe signs e.g. aphasia.

Features:

• Fever, headache, psychiatric symptoms, seizures, vomiting
• Focal features e.g. aphasia
• Peripheral lesions (e.g. cold sores) have no relation to presence of HSV encephalitis

Pathophysiology:

• HSV-1 responsible for 95% of cases in adults
• Typically affects temporal and inferior frontal lobes

Investigation:

• CSF: lymphocytosis, elevated protein
• PCR for HSV
• CT: medial temporal and inferior frontal changes (e.g. petechial haemorrhages) - normal in onethird of patients
• MRI is better
• EEG pattern: lateralised periodic discharges at 2 Hz

Treatment:

• Intravenous aciclovir The prognosis is dependent on whether aciclovir is commenced early. If treatment is started promptly the mortality is 10-20%. Left untreated the mortality approaches 80%

 

Question 2#

A 29-year-old man presents complaining of visual disturbance. Examination reveals a right superior homonymous quadrantanopia.

Where is the lesion most likely to be? 

A. Optic chiasm

Correct Answer B:

Visual field defects:
The main points for the exam are:

• Left homonymous hemianopia means visual field defect to the left, i.e. Lesion of right optic tract
• Homonymous quadrantanopias: PITS (Parietal-Inferior, Temporal-Superior)
• Incongruous defects = optic tract lesion; congruous defects = optic radiation lesion or occipital cortex

A congruous defect simply means complete or symmetrical visual field loss and conversely an incongruous defect is incomplete or asymmetric. Please see the link for an excellent diagram.

Homonymous hemianopia:

• Incongruous defects: lesion of optic tract
• Congruous defects: lesion of optic radiation or occipital cortex
• Macula sparing: lesion of occipital cortex

Homonymous quadrantanopias*:

• Superior: lesion of temporal lobe
• Inferior: lesion of parietal lobe
• Mnemonic = PITS (Parietal-Inferior, Temporal-Superior)

Bitemporal hemianopia:

• Lesion of optic chiasm
• Upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
• Lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma

*This is very much the 'exam answer'. Actual studies suggest that the majority of quadrantanopias are caused by occipital lobe lesions. Please see the following link for more details: http://www.ncbi.nlm.nih.gov/pubmed/9109741 

Question 3#

A 64-year-old man with a history of Parkinson's disease is reviewed in clinic and a decision has been made to start him on cabergoline.

Which one of the following adverse effects is most strongly associated with this drug?

A. Optic neuritis

Correct Answer C: 

Parkinson's disease: management:

Currently accepted practice in the management of patients with Parkinson's disease (PD) is to delay treatment until the onset of disabling symptoms and then to introduce a dopamine receptor agonist. If the patient is elderly, levodopa is sometimes used as an initial treatment.

Dopamine receptor agonists:

• e.g. Bromocriptine, ropinirole, cabergoline, apomorphine xergot-derived dopamine receptor agonists (bromocriptine, cabergoline, pergolide*) have been associated with pulmonary, retroperitoneal and cardiac fibrosis. The Committee on Safety of Medicines advice that an echocardiogram, ESR, creatinine and chest x-ray should be obtained prior to treatment and patients should be closely monitored
• Patients should be warned about the potential for dopamine receptor agonists to cause impulse control disorders and excessive daytime somnolence
• Nasal congestion and postural hypotension are also seen in some patients 

Levodopa:

• Usually combined with a decarboxylase inhibitor (e.g. Carbidopa or benserazide) to prevent peripheral metabolism of levodopa to dopamine
• Reduced effectiveness with time (usually by 2 years)
• Unwanted effects: dyskinesia (involuntary writhing movements), 'on-off' effect, dry mouth, anorexia, palpitations, postural hypotension, psychosis
• No use in neuroleptic induced parkinsonism

MAO-B (Monoamine Oxidase-B) inhibitors:

• e.g. Selegiline
• Inhibits the breakdown of dopamine secreted by the dopaminergic neurons

Amantadine:

• Mechanism is not fully understood, probably increases dopamine release and inhibits its uptake at dopaminergic synapses

COMT (Catechol-O-Methyl Transferase) inhibitors:

• e.g. Entacapone
• COMT is an enzyme involved in the breakdown of dopamine, and hence may be used as an adjunct to levodopa therapy
• Used in established PD

Antimuscarinics:

• Block cholinergic receptors
• Now used more to treat drug-induced parkinsonism rather than idiopathic Parkinson's disease
• Help tremor and rigidity
• e.g. Procyclidine, benzotropine, trihexyphenidyl (benzhexol)

*pergolide was withdrawn from the US market in March 2007 due to concern regarding increased incidence of valvular dysfunction

Question 4#

A 76-year-old man is admitted with a right hemiparesis. He first noticed weakness on his right side around six hours ago. A CT scan shows an ischaemic stroke and aspirin 300mg is commenced.

Terms of further management in the acute phase, which one of the following values should not be corrected?

A. BP 210/110

Correct Answer A: Hypertension should not be treated in the initial period following a stroke.

Elevated blood pressure should not be treated in the acute phase following a stroke unless complications develop. Other physiological parameters should be kept within normal limits - an aggressive approach with respect to this has been shown to improve outcome.

Stroke: management:

The Royal College of Physicians (RCP) published guidelines on the diagnosis and management of patients following a stroke in 2004. NICE also issued stroke guidelines in 2008, although they modified their guidance with respect to antiplatelet therapy in 2010.

Selected points relating to the management of acute stroke include: 

• Blood glucose, hydration, oxygen saturation and temperature should be maintained within normal limits
• Blood pressure should not be lowered in the acute phase unless there are complications e.g. Hypertensive encephalopathy*
• Aspirin 300mg orally or rectally should be given as soon as possible if a haemorrhagic stroke has been excluded
• With regards to atrial fibrillation, the RCP state: 'anticoagulants should not be started until brain imaging has excluded haemorrhage, and usually not until 14 days have passed from the onset of an ischaemic stroke'
• If the cholesterol is > 3.5 mmol/l patients should be commenced on a statin. Many physicians will delay treatment until after at least 48 hours due to the risk of haemorrhagic transformation 

Thrombolysis: Thrombolysis should only be given if:

• It is administered within 3 hours** of onset of stroke symptoms (unless as part of a clinical trial)
• Haemorrhage has been definitively excluded (i.e. Imaging has been performed) Alteplase is currently recommended by NICE

Secondary prevention:

NICE also published a technology appraisal in 2010 on the use of clopidogrel and dipyridamole Recommendations from NICE include:

• Clopidogrel is now recommended by NICE ahead of combination use of aspirin plus modified release (MR) dipyridamole in people who have had an ischaemic stroke
• Aspirin plus MR dipyridamole is now recommended after an ischaemic stroke only if clopidogrel is contraindicated or not tolerated, but treatment is no longer limited to 2 years' duration
• MR dipyridamole alone is recommended after an ischaemic stroke only if aspirin or clopidogrel are contraindicated or not tolerated, again with no limit on duration of treatment

With regards to carotid artery endarterectomy:

• Recommend if patient has suffered stroke or TIA in the carotid territory and are not severely disabled
• Should only be considered if carotid stenosis > 70% according ECST*** criteria or > 50% according to NASCET**** criteria 

*The 2009 Controlling hypertension and hypotension immediately post-stroke (CHHIPS) trial may change thinking on this but guidelines have yet to change to reflect this

**SIGN recommend a window of 4.5 hours

***European Carotid Surgery Trialists' Collaborative Group

****North American Symptomatic Carotid Endarterectomy Trial

Question 5#

A 23-year-old man is referred to neurology clinic. He describes episodes of leg weakness following bouts of laughing whilst out with friends. The following weekend his friends described a brief collapse following a similar episode.

What is the most likely diagnosis?

A. Stokes-Adams attack

Correct Answer B: Cataplexy describes the sudden and transient loss of muscular tone caused by strong emotion (e.g. laughter, being frightened). Around two-thirds of patients with narcolepsy have cataplexy.

Features range from buckling knees to collapse.