Meningitis and Hydroencephalitis Flashcards
What is the role of CSF?
Establishes a stable fluid environment for neurones
Cushions the brain from impact
Suplies nutrients and vital peptides to the brain and removes unwanted metabolites and neurotransmitters
What is the principle source of CSF?
The choroid plexus
A layer of cuboidal epithelial cells surrounding a core of capillaries and loose connective tissue.
They are found in each ventricle
What pathway does CSF take from the choroid plexus to the blood?
Choroid plexus
3rd ventricle
Cerebral aquaduct (via intraventricular foramen)
4th ventricle
Subarachnoid space (via medial and lateral apertures)
Some descends through the foramen magnus reaching the lumbar cistern
The CFS at the base of the brain ascends through the tentorial notch and bathes the surfaces of the cerebral hemispheres, before retuning to the blood via arachnoid granulations
What is an arachnoid granulation?
Pinhead pouches of arachnoid matter projecting through the dural wall of the major venous sinuses (especially the superior sagital sinus)
CSF is transported across the epithelium in giant vacuoles.
What are the meninges are what layers is it made of?
They surround the CNS and suspend it in a protective hacked of CSF
Dura matter
Leptomeninges (arachnoid matter and pia matter with subarachnoid space in between)
What are the 2 main barriers of the blood brain barrier?
Blood - CSF (ependymal lining of choroid plexus)
Blood - ECF ( the CNS capillary bed)
What contributes to the brains extracellular fluid?
As well as the CSF circulatory system, CSF also passively diffuses trough the ependymal-glial membrane lining of the membrane lining the ventricles. It enters the ECF adding to the ECF produced bt the capilary bed and brain cell metabolism.
What is hydrocephalus and what are the two major classifications?
Accumulation of CSF in the ventricular system
Communicating - Problem outside of the ventricular flow
Non-communicating - problem with ventricular flow
What aetiological factors are associated with hydrocephalus?
Arnold-Chari malformation - the cerebellum is partly extruded into the foramen magnum during foetal development because the posterior cranial fossa is underdeveloped. When untreated the head becomes as large as a football and the cerebral hemisphere can be as thin as paper. The condition is almost always associated with spina bifida
Bickers-Adams syndrome - narrowing of the cerebral aquaduct
Acquired aquaduct stenosis, often as a result of infection or intraventricular haemotoma
Cerebellum displacement into the foramen magnum in adults by a space occupying legion such as a tumour of haemotoma
What treatment is available for hydrocephalus?
Removing causative factor
Surgical insertion of a ventriculoatrial shunt (catheter which drains CST into the right atrium)
Surgical insertion of a lumboperitoneal shunt (catheter drains distal CSF from the lumbar area to the peritoneum
Choroid plexectomy
Furosemide and acetazolamide - inhibits CSF secretion
Isosorbide - promotes CSF reabsorption
What is meningitis and what can cause it?
Inflammation of the meninges
Can be caused by virus or bacteria (less common, more serious)
Viruses - enterovirus which lives in intestines, nose and throat, or the measles and mumps virus
Bacteria - Neisseria meningitidis (meningococcal meningitis) Streptococcous pneumonia (pneumococcal meningitis)
What are the symptoms and treatment for bacterial meningitis?
Meningococcal meningitis
Fever, vomiting, nausea, bright light aversion and confusion
Intravenous ceftriaxone
Pneumococcal meningitis
Hearing loss (spreads to subarachnoid space, then cochlear aqueduct, then inner ear). The endotoxin pneumolysis forms Ca2+ permeable channels in the cell membrane, which is highly toxic intracellularly.
Vancomycin and cephalosporin
What are the paths of infection which can cause meningitis?
Skull injury/fracture
Dissemination of bacteria from infective focus
What meningitis diagnostic techniques are available?
Lumbar puncture to show:
Elevated CSF pressure
Cloudy fluid with pus and reduced sugar concentration
Culture or staining for responsible organism
