Tuesday 7 June 2011

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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Saturday 30 October 2010

Assyrian Text Describing Epileptic Symptoms (c. 650 BC)


Mesopotamian peoples were particularly prone to seeing the hands of god in everything in life.
Disease was typically seen as both a judgement & a punishment upon the person.
This Assyrian text describes epileptic symptoms (c. 650 BC) with a demonic slant:
If at the time of his possession, while he is sitting down, his left eye moves to the side, a lip puckers, saliva flows from his mouth, and his hand, leg and trunk on the left side jerk like a slaughtered sheep, it is migtu. If at the time of possession his mind is awake, the demon can be driven out; if at the time of his possession his mind is not so aware, the demon cannot be driven out.
Reference:
Roy Porter (1997). The Greatest Benefit To Mankind. A Medical History Of Humanity From Antiquity To The Present. Fontana Press. London

Image: Assyrian Relief from Mary Harrsch on flickr (cc)

Sunday 24 October 2010

Neuroanatomy of Pruritus of Cutaneous Origin



Neuroanatomy of Pruritus of Cutaneous Origin:
  • Pruritogen =>
  • Free Nerve Endings =>
  • Unmyelinated C-nerve fibres =>
  • Dorsal horn of spinal cord =>
  • Contralateral spinothalamic tract =>
  • Posterolateral ventral thalamic nucleus =>
  • Somatosensory cortex (post-central cingulate gyrus)
Image: from Medicalchemy
Tags: Spinothalamic tract - Dorsal horn of spinal cord - Free Nerve Endings - Posterolateral ventral thalamic nucleus - Pruritus - Post-central cingulate gyrus - Unmyelinated C-nerve fibres
Posted by Medicalchemy
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Headache Image - Woman Holding Her Head



Headache Image -
Woman Holding Her Head

Structures Passing Through Foramen Magnum (Mnemonic)


Structures Passing Through Foramen Magnum:
  • Accessory nerves (spinal roots)
  • Meningeal lymphatics
  • Spinal cord
  • Spinal meninges
  • Sympathetic plexus of vertebral ateries
  • Vertebral arteries
  • Vertebral artery spinal branches
Mnemonic - 'Spinal Meninges Make A Special Vertical Sheath':
  • Spinal - Spinal Cord
  • Meninges - Spinal Meninges
  • Make - Meningeal lymphatics
  • A - Accessory nerves (spinal roots)
  • Special - Sympathetic plexus on vertebral arteries
  • Vertical - Vertebral arteries
  • Sheath - Spinal branches of vertebral arteries
Image: from Shannan Muskopf (cc)

Sunday 17 October 2010

Cushing's Triad (RICP Finding)

Cushing's Triad Background:
  • Named after the American neurosurgeon Harvey Williams Cushing (1869-1939).
Components of Cushing's Triad:
  • Bradycardia
  • Respiratory pattern change (irregular respirations)
  • Widening pulse pressure (rising systolic + declining diastolic)
Pathophysiology:
  • Produced by the Cushing reflex.
  • Sign of raised intracranial pressure (RICP).
  • May lead to brain herniation, which can be rapidly fatal.
Clinical Details:
  • Suggests severe pressure within the cranial vault.
Causative Factors:
  • Intracerebral hemorrhage
  • Head trauma
  • Enlarging space-occupying lesion (i.e. brain tumor)

Tags: Bradycardia - Brain herniation - Brain Tumour - Cushing's Reflex - Cushing's Triad - Head Trauma - Intracerebral haemorrhage - RICP
Posted by Medicalchemy
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