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
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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
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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
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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
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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
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Cerebral Cortex Brodmann Areas Listed

Brodmann Areas Listed:

• Areas 3, 1 & 2 - Primary Somatosensory Cortex (typically referred to as Areas 3, 1, 2 by convention)
• Area 4 - Primary Motor Cortex
• Area 5 - Somatosensory Association Cortex
• Area 6 - Premotor cortex and Supplementary Motor Cortex (Secondary Motor Cortex)(Supplementary motor area)
• Area 7 - Somatosensory Association Cortex
• Area 8 - Includes Frontal eye fields
• Area 9 - Dorsolateral prefrontal cortex
• Area 10 - Anterior prefrontal cortex (most rostral part of superior and middle frontal gyri)
• Area 11 - Orbitofrontal area (orbital and rectus gyri, plus part of the rostral part of the superior frontal gyrus)
• Area 12 - Orbitofrontal area (used to be part of BA11, refers to the area between the superior frontal gyrus and the inferior rostral sulcus)
• Area 13 and Area 14 - Insular cortex
• Area 15* - Anterior Temporal Lobe
• Area 17 - Primary visual cortex (V1)
• Area 18 - Secondary visual cortex (V2)
• Area 19 - Associative visual cortex (V3)
• Area 20 - Inferior temporal gyrus
• Area 21 - Middle temporal gyrus
• Area 22 - Superior temporal gyrus, of which the caudal part is usually considered to contain the Wernicke's area
• Area 23 - Ventral Posterior cingulate cortex
• Area 24 - Ventral Anterior cingulate cortex
• Area 25 - Subgenual cortex
• Area 26 - Ectosplenial area
• Area 27 - Piriform cortex
• Area 28 - Posterior Entorhinal Cortex
• Area 29 - Retrosplenial cingulate cortex
• Area 30 - Part of cingulate cortex
• Area 31 - Dorsal Posterior cingulate cortex
• Area 32 - Dorsal anterior cingulate cortex
• Area 33 - Part of anterior cingulate cortex
• Area 34 - Anterior Entorhinal Cortex (on the Parahippocampal gyrus)
• Area 35 - Perirhinal cortex (on the Parahippocampal gyrus)
• Area 36 - Parahippocampal cortex (on the Parahippocampal gyrus)
• Area 37 - Fusiform gyrus
• Area 38 - Temporopolar area (most rostral part of the superior and middle temporal gyri)
• Area 39 - Angular gyrus, also considered by some to be part of Wernicke's area
• Area 40 - Supramarginal gyrus considered by some to be part of Wernicke's area
• Areas 41 & 42 - Primary & Auditory Association Cortex
• Area 43 - Subcentral area (between insula and post/precentral gyrus)
• Area 44 - Pars opercularis, part of Broca's area
• Area 45 - Pars triangularis Broca's area
• Area 46 - Dorsolateral prefrontal cortex
• Area 47 - Inferior prefrontal gyrus
• Area 48 - Retrosubicular area (a small part of the medial surface of the temporal lobe)
• Area 49 - Parasubicular area in a rodent
• Area 52 - Parainsular area (at the junction of the temporal lobe & the insula)

Image: from Gray's Anatomy
Tags: Brodmann Area - Cerebral Cortex
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Vagus Nerve Stimulation (VNS) Treatment Uses

VNS Clinical Uses:

• Intractable epilepsy
• Treatment resistant depression

Other Uses For VNS Under Investigation:

• Alzheimer's disease
• Anxiety disorders
• Fibromyalgia
• Migraines
• Tinnitus

Reference:

• Groves, Duncan A., Brown, Verity J. (2005). Vagus Nerve Stimulation: A Review of its Applications and Potential Mechanisms That Mediate its Clinical Effects. Neuroscience and Biobehavioral Reviews, 29: 493-500.

Tags: Depression - Epilepsy - Vagus Nerve Stimulation
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CSF Glucose - Low Levels

General Details:

• Also known as hypoglycorrhachia.

Causes of Low CSF Glucose:
Infection:

• Lyme disease
• Pyogenic meningitis
• TB meningitis
• Fungal Meningitis

Viral Infection (occasionally):

• Herpes simplex encephalitis
• Mumps meningoencephalitis
• Zoster encephalitis

Other:

• Meningeal carcinomatosis
• Sarcoidosis
• Subarachnoid haemorrhage

Image: D-glucose structural formula
Image Source: from Wikipedia by Richard Wheeler (Zephyris) (Public Domain)
Tags: Herpes Simplex - Herpes Zoster - Lyme Disease - Meningitis - Sarcoidosis - Subarachnoid Haemorrhage
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CSF Protein Level - Marked Elevation

Causes of Markedly Raised CSF Protein:

• Acoustic neuroma
• Alcoholism
• Amyloidosis
• Diabetes mellitus
• Froin's syndrome
• Guillain-Barre syndrome
• Meningitis - Acute Bacterial
• Meningitis - Carcinomatous

Tags: Acoustic neuroma - Alcoholism - Amyloidosis - Diabetes mellitus - Froin's syndrome - Guillain-Barre syndrome - Meningitis
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