Headache

Headache

1. Cerebral circulation

   • Intracranial pressure
     • IDIOPATHIC INTRACRANIAL HTN
       • Headaches worse on coughing and sneezing. Examination usually normal (apart from papilloedema). Refer to neurologist. Requires CT/MRI to exclude other causes of ↑ICP. Lumbar puncture to measure the opening pressure
     • HYDROCEPHALUS ("water on the brain") = Accumulation of CSF resulting in ↑ICP
       • Non-communicating = between foramen of monro <> foramen of luschka/magendie Communicating = after cisterna magna ie. failure to drain subarachnoid granulations
     • SITES OF HERNIATION
       • Cerebral peduncle connects midbrain to brainstem and carries descending motor tracts
         • Blown pupil = Fixed (no response to light), dilated, down and outwards position. EMERGENCY.
         • DECORTICATE posturing = flexors. Due to damage to UPPER MIDBRAIN. M3 on GCS
           • Determining GCS&nbsp;https://www.bing.com/videos/search?q=assessing+glasgow+coma+score&amp;&amp;view=detail&amp;mid=8A407A43C1C7A47DAE618A407A43C1C7A47DAE61&amp;&amp;FORM=VRDGAR&amp;ru=%2Fvideos%2Fsearch%3Fq%3Dassessing%2Bglasgow%2Bcoma%2Bscore%26FORM%3DHDRSC3
         • Decerebrate = extensors. Due to damage to UPPER PONS. M2 on CGS
       • CUSHING RESPONSE
         • 2) Body attempts to raise MAP (to increase CPP and CBF) by sympathetic activation to ^TPR, MAP & systolic BP
           • 3) Baroreceptor reflex responds to ↑MAP > causes bradycardia by ^vagal parasympathetic tone
             • 4) "CUSHING's TRIAD" = ↓Heart rate + ↑Systolic BP + Disordered breathing pattern (alternating apnoea and sighing)
               • EMERGENCY! Get immediate senior help from anaesthetist, intensivist and neurosurgeon to reduce ICP
         • 1) Trigger = brainstem ischaemia due to ↑ICP
   • Bleeding
   • MAP = 1/3 pulse pressure + diastolic pressure
   • MAP - CVP (pressure gradient that drives the flow of blood around the body) = CO x TPR
   • Starling’s law of the heart: CVP <> SV relationship (greater stretch heart in diastole > greater SV in systole)
   • Cerebral Perfusion Pressure CPP = MAP – ICP
     • Cerebral blood flow is controlled by SYMPATHETIC innervation, NOT baroreceptor reflex. Causes cerebral vasoconstriction in response a sudden increase in MAP - Protects smaller downstream vessels
       • "Outline the role of perivascular nociceptive C‐fibres, parasympathetic fibres and sympathetic fibres in vascular headaches"...
         • Previously thought that 5HT release from sympathetic fibres activated nociceptors on C fibres > vasoconstriction > migraines. Now thought that primary event is decreasing neuronal activity in cerebral cortex.
       • "Functional hyperaemia" - eg. Clenching your left fist involves an increase in neuronal activity in your right motor cortex > increase in local blood flow
   • ICP is intracranial pressure (~7-13 mmHg). Found by inserting pressure transducer into brain parenchyma/catheter into the lateral ventricle
   • Venous Drainage
     • Blood from veins > venous sinuses > internal jugular veins. Made of rigid layers of dura mater lined with endothelium. No valves. Don’t collapse if ↑ICP. Also drain CSF from the subarachnoid space via arachnoid granulations
   • BBB - see Year 1
     • Brain Structure-Function, Blood Supply, Formation
     • Areas that don't have BBB = These areas are more permeable and involving hormone signalling (eg release of melatonin from PINEAL body, OSMORECEPTORS and CHEMORECEPTORS involved in the vomiting reflex)
   • ICP and HEMIANOPIA
     • Shining a light into an eye causes constriction of the ipsilateral pupil (DIRECT reflex) and of the contralateral pupil (CONSENSUAL reflex)
       • https://www.youtube.com/watch?v=IsoHFoY5q7o
     • See LLAMA powerpoint for lesion location!
   • CSF
     • 500ml/day produced by choroid plexus mainly in the lateral ventricles of the brain
       • Choroid plexus in Lateral ventricles > foramen of monroe > 3rd ventrivle > foramen of slyvius > 4th ventricle > Foramen of Luscha/Magendie > Cisterna Magna
     • Maintain constant environment for brain cells. Drains unwanted metabolites into venous blood. Transports hormones across brain hemispheres. Cushions brain and allows it to float. ?Lymphatic role

2. Intracranial / Extracranial infections

3. Brain Tumours

4. Lumbar Puncture

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