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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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)

Tags: Assyrian - Epilepsy - History - Mesopotamia - Possession - Text
Posted by Medicalchemy
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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
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Headache Image - Woman Holding Her Head

Headache Image -

Woman Holding Her Head

Image: from TinyPic.com
Tags: Headache - Holding Head - Woman
Posted by Medicalchemy
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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)

Tags: Accessory Nerve - Foramen Magnum - Meninges - Skull - Spinal Cord - Sympathetic Plexus - Vertebral Artery
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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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