Posterior Reversible Encephalopathy Syndrome (PRES)

PRES General Details:

• Posterior reversible encephalopathy syndrome (PRES) or reversible posterior leukoencephalopathy syndrome (RPLS).
• A cliniconeuroradiological entity characterized by a diagnostic cerebral magnetic resonance imaging picture associated with altered mental status, headache, cortical blindness, seizures, & other focal neurological signs.

PRES Aetiology:

• Acute hypertension of pregnancy (ie eclampsia)
• Drugs - ciclosporin & tacrolimus (ie organ transplants)
• Hypertensive encephalopathy
• Hypercalcaemia
• Hypomagnesaemia - may exacerbate condition
• Porphyria
• Sepsis
• Uraemia

PRES Clinical Features:

• Coma
• Confusion
• Convulsions (seizures)
• Cortical blindness (visual loss)
• Headache

PRES Pathophysiology:

• Associated with acute/subacute elevations of BP to levels that overcome cerebral autoregulation (~ 240/130 mmHg).
• This dysregulation may then produce vasogenic oedema which is typically most marked in the white matter of the posterior cerebral hemispheres.

PRES Investigation:

• MRI scans - oedema of the white matter of the occipital lobes (see image).

PRES Management:

• Lower blood pressure.
• Symptomatic treatment of seizures.
• Magnesium sulphate - eclampsia induced PRES.
• Withdrawal of offending drugs & correcting metabolic disturbances.

PRES Prognosis:

• May resolve with appropriate treatment.
• Intracerebral haemorrhage can occur with associated haematological disorders.

Reference:
Garg RK (2001). Posterior leukoencephalopathy syndrome. Postgrad Med J 77(903):24–8

Image: Posterior Reversible Encephalopathy Syndrome (PRES) MRI (Radpod Picture of the Day) (cc)
Tags: Ciclosporin - Ciclosporine - Eclampsia - Hypertension - Posterior Reversible Encephalopathy Syndrome (PRES) - RPLS - Tacrolimus
Posted by Medicalchemy
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Basilar Artery Thrombosis

Basilar Artery Thrombosis General Details:

• Thrombotic basilar artery occlusion.
• Reported in 2 per 1000 autopsy cases.
• Stroke registries ~ 27% of ischemic strokes occurring in the posterior circulation.

Basilar Artery Thrombosis Clinical Features:

• Coma / decreased consciousness
• Headache
• Locked-in syndrome
• Ocular palsies
• Photopsia - occipital lobe ischaemia)
• Pseudobulbar palsy
• Pupillary palsies
• Quadriparesis
• Vertigo
• Visual disturbance
• Visual loss - occipital lobe ischaemia

Basilar Artery Thrombosis Aetiology:

• Atherosclerotic occlusive disease - esp. mid segment of the basilar artery, followed by the vertebrobasilar junction.
• Embolism - more frequent in the distal 1/3rd of the basilar artery & vertebrobasilar junction.
• Arterial dissection - more common in the extracranial vertebral artery; intracranial dissections very uncommon.

Basilar Artery Thrombosis Investigations:

• MRI or CT angiogram - basilar artery occlusion, either in the proximal portion (top of the basilar syndrome, usually with midbrain and thalamic damage) or more extensively.

Basilar Artery Thrombosis Treatment:

• Thrombolysis - early presentations; with intravenous or intra-arterial recombinant thromboplastin activator (rTPA). 
• Thrombolysis can reverse the ischaemic damage noted, which is often fatal if untreated.

Basilar Artery Thrombosis Prognosis:

• Generally poor prognosis.
• However, some patients may have a limited ischaemic injury associated with an acute partial occlusion or a slow progressive occlusion.

Image: Basilar Artery Thrombosis on CT showing dense basilar artery; thrombolysis catheter and angiogram showing filling defect (Radpod Picture of the Day) (cc)
Tags: Arterial Dissection - Basilar Artery Thrombosis - Embolism - rTPA - Thrombolysis - TPA
Posted by Medicalchemy
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