CSF & Hydrocephalus Flashcards
What is the mean CSF pressure (ICP) in an adult?
10mmHg
14cm of CSF
Above what would be considered an abnormally high value of ICP?
> 15mmHg
>20cm CSF
Where is the majority of CSF produced?
Choroid plexus - 75%
At what rate of variation is CSF produced?
Circadian rhythm
Max production at 2am and minimum at 6pm
CSF secretion _________ with old age?
Decreases
What drug reduces the production of CSF by up to 50%?
Acetazolamide
Where is the other 25% of CSF produced from?
From the brain interstitial fluid
Where is CSF absorbed?
Mainly the arachnoid granulations
Olfactory lymphatics
Absorption of CSF is a ______ process which depends of the _ _ _ being greater than the pressure in the ______ ________
Passive
Depends on the ICP
Sagittal sinus
What are the main functions of the CSF?
- Buoyancy - reduces brain weight by 96% (1500g becomes 60g)
- Accommodates physiological changes in vascular volumes i.e. mediator of compliance
- Ionic homeostasis
- Provides micronutrients to cerebral tissue
- Clears some waste products of neuro cell metabolism
Give some examples of micronutrients the CSF supplies the cerebral tissue with:
Vitamin C
Thyroxine
What three symptoms are considered the classic triad of normal pressure hydrocephalus?
- Ataxia - (important early sign)
- Memory decline
- Incontinence
What are some of the features of normal pressure hydrocephalus ataxia?
- Difficulty rising from a chair
- Tendency to fall backwards
- Difficulties initiating gait
- Broad based, shuffling gait - Early stage sign
Describe some of the clinical features of a child born with hydrocephalus:
- unusual shaped head
- thin shiny scalp w/ visible veins
- bulging or tense fontanelle
- downward looking eyes
A baby born with congenital hydrocephalus may present with:
- Poor feeding
- Irritability
- Vomiting
- Sleepiness
- Muscle stiffness and spasms in lower limbs
What are the three main physiological causes of ventriculomegaly?
Raised pressure
Increased Volume
Impaired absorption
List some common congenital causes of paediatric hydrocephalus:
- Chiari malformation
- Spina bifida
- Aqueduct stenosis (X linked)
- Dandy walker complex
- Atresia of foramen of munro
List some acquired causes of paediatric hydrocephalus:
- Haemorrhage
- Infection e.g. meningitis
- Traumatic head injury
- Tumour
What are the main categories of valves used in the management of different hydrocephalus?
- Fixed differential pressure
- Adjustable
- Switchable
- Antisyphon
- Constant flow
What % of valves no longer function after 12 years?
80%
List some common complications of shunts:
Over-drainage: - Acute SDH - Slit ventricles Underdrainage: - Blockage - Displacement Infection:
List some ways the risk of infection in a CNS shunt can be reduced:
- Prophylaxis antibiotics
- Iodine use
- Silver impregnated shunts
List some less common complications of shunts:
Intracerebral haemorrhage Seizures Craniosynostosis Dissemination of tumour cells Umbilical fistula Erosion of abdo viscera Ascites / hydroceles Inguinal hernia Silicone allergies
List some symptoms associated with a blocked shunt:
Headache and vomiting
Sunsetting in children
lack of up gaze in adults
Blurred vision
How is a blocked shunt investigated?
CT shows hydrocephalus
Can tap the shunt to send CSF to microbiology
What is a good alternative to shunts for certain cases of hydrocephalus?
Endoscopic 3rd ventriculostomy
How does a VP shunt work
VP = ventriculoperitoneal
shunts CSF from lateral ventricles to the peritoneum
How does an LP shunt work?
LP = lumboperitoneal shunt
Shunts CSF from the subarachnoid space into the abdominal cavity
What shunts tend to have a very limited life expectancy?
LP shunts
When can ETV be used with good success?
70% success with aqueduct stenosis and tumours
50% success with hindbrain hernias
What cases have a high failure rate when treated with ETV?
Vascular
Congenital
Post meningitis
Neonates
Define normal pressure hydrocephalus;
This is an accumulation of CSF which leads to the enlargement of the ventricles of the brain which shows little to no increase in ICP
What is significant about Normal pressure Hydrocephalus?
It is one of the few potentially reversible / treatable causes of dementia
List the main causes of normal pressure hydrocephalus;
Idiopathic (mainly) Post inflammatory e.g. - SAH - Meningitis - Trauma - Craniotomy
What are some of the clinical features of dementia caused by normal pressure hydrocephalus:
Delay in answering questions Loss of spontaneity May progress to akinetic mutism Fluctuates in severity (alongside the triad)
List some of the differential diagnosis of normal pressure hydrocephalus:
Ataxia:
- cerebella problems
- myelopathy
Dementia:
- Alzheimer’s
- Cerebrovascular
Give some examples of genetic causes of dementia:
Huntington’s
Wilsons
Porphyria’s
List some degenerative causes of dementia:
Alzheimer’s
Fronto temporal
Parkinson’s
List some metabolic causes of dementia:
Hypothyroidism
Thiamine (alcoholism)
List some infectious causes of dementia:
Syphilis
Prions
Encephalitis
What are the main investigations for a normal pressure hydrocephalus:
CT MRI ICP measurement LP tap test Lumbar drainage Infusion studies Tracer diffusion studies
What are the main surgical treatment options for normal pressure hydrocephalus?
LP shunt
VP shunt
ETV
Idiopathic intracranial hypertension is a disorder of ______ movement in the brain
Water movement
List some of the conditions / risks associated with IIH
Female Obesity Sleep apnoea Hypothyroidism Addison's Uraemia SLE Vit A Antibiotics Hormones e.g. OCP Lithium Steroid withdrawal
List the symptoms of an idiopathic intracranial hypertension:
Headaches
Visual field loss
Visual acuity loss (you want to step in before this part)
list the signs of idiopathic intracranial hypertension:
Papilloedema
Constriction of visual fields
Loss of visual acuity (late sign)
What are the most appropriate investigations and results for idiopathic intracranial hypertension?
LP pressure = >25cm CSF
CSF chemistry /cytology = normal
CT & MRI = normal
NO evidence of venous sinus thrombosis
List the main treatment options for idiopathic intracranial hypertension:
WEIGHT LOSS Diuretics Lumbar puncture LP / VP shunt Optic nerve sheath fenestration Venous stents Sub temporal decompression Remove underlying medical disorder e.g. w/heparin
List some of the common complications of an LP shunt:
Blockage Infection Nerve root irritation Low pressure headaches Subdural haemorrhage Arachnoiditis Tonsillar herniation
What is spontaneous intracranial hypotension (SIH)?
Rare condition where the fluid pressure inside the skull is abnormally low which leads to a severe disabling headache
List some of the main symptoms of SIH:
Orthostatic headaches Neck / interscapular / arm pain Diplopia / VF defects Dizziness Thunderclap headache Muffled hearing Galactorrhoea Symptomatic subdural haematomas
What is the ‘classic triad’ of spontaneous intracranial hypotension?
Low CSF
Orthostatic headache
Brain sag with parenchymal enhancement
What are some of the causes of spontaneous intracranial hypotension?
Idiopathic
Collagen disorders
Dural diverticula
Trauma
How is SIH treated / managed?
Conservative - bed rest, fluids, analgesia
Epidural blood patches
Surgical repair
List the most appropriate investigations for SIH:
Head MRI LP CT myelography Spinal MRI Isotope myelography
In SIH what might be seen on a cranial MRI
Meningeal enhancement
Chronic subdural haematomas
Hindbrain herniation
What would be seen on an LP in a patient with SIH?
Low pressure
Pleocytosis
Raised protein
Xanthochromia
What leads to galactorrhoea in patients with SIH?
Low CSF leads to compensatory hyperaemia which can occur in the pituitary leading to galactorrhoea
What is the mean age of presentation in a syringomyelia?
31-50 y/o
Define a syringomyelia:
A chronic condition characterised by a fluid filled cavity / cyst known as a syrinx which forms in the spinal cord.
The syrinx can expand over time causing cord compression
What is the incidence of a syringomyelia occurring above a spinal fracture site?
3-5%
Describe the main morphology of a syringomyelia:
Dilated central canals
Spindle
Holocord (can affect whole cord)
Tethered conus
Which parts of the spinal cord are more commonly affected by a syringomyelia?
Cervical
Upper Thoracic
List some of the classic presenting features of a syringomyelia:
Dissociated sensory loss Cuts and burns on hands Small muscle wasting Claw hands Loss of upper limb reflexes Increased lower limb reflexes
What abnormality is a feature of early stage syringomyelia?
Hyperhidrosis (excess sweating)
–> it indicated hyperactivity of pre-ganglionic neurons
List some of the more rare manifestations / features of syringomyelia:
Segmental myoclonus Paroxysmal arm posturing Isolated Horner's Orofacial pain limb hypertrophy Orthostatic hypotension Reduced intestinal mobility
List some of the common presentations of a hindbrain herniation:
Coughing Sneezing Straining laughing Bending forward Visual disturbances Dizziness / tinnitus / hearing loss Dysarthria / Dysphagia Somatic sensory disturbance
What symptom is common in patients with an abnormality of the craniovertebral junction (CVJ)
Sleep apnoea
A common presentation in hindbrain herniation
What treatment options are there for syringomyelia?
Open up the obstructed CSF channels
Drain syrinx cavity
Lower overall CSF pressure
Conservative management
What is meant by communicating hydrocephalus?
Obstruction to the outflow of CSF outwith the ventricular system e.g. post SAH or bacterial meningitis
What is meant by non-communicating hydrocephalus?
Obstruction is occurring from within the ventricular system
e.g. Arnold Chiari malformation
What is hydrocephalus ex vacuo?
This is when there is a loss of brain parenchyma, leading to ventricular expansion, increasing the CSF volume
What is the normal volume of CSF?
120-150ml
What is the normal protein level in CSF?
<0.4g/L
What is the normal value for lymphocytes in the CNS?
<4cells/ml
What are the three most common forms of herniation?
Subfalcine
Tentorial
Tonsillar
