CSF Pathology Flashcards
What is the mean CSF pressure?
- 10mmHg.
- 14cm CSF.
Values above what level indicate abnormally high CSF pressure?
> 15mmHg or >20cm CSF.
Rate of CSF formation per minute?
0.35ml/min.
What forms CSF?
- Choroid pelxus (75%).
- Brain ISF (25%).
What drug reduces CSF production by >50%?
Acetazolamide.
CSF undergoes substantial absorption via?
Arachnoid granulations.
CSF absorption depends upon?
ICP being greater than the pressure in sagittal sinus.
Valsalva like manoeuvres have what effect on the brain?
Transient venous engorgement.
Physical functions of CSF?
- Buoyancy (reduces brain weight by 96% - 1500g to 60g).
- Accommodation of physiological changes in vascular volumes in the head (- displaced into spinal canal).
Chemical functions of CSF?
- Provides micronutrients to cerebral tissue (e.g. Vitamin C, thyroxine).
- Clears some waste products of nerve cell metabolism e.g. 5HIAA.
- Ionic homeostasis.
Spinal arachnoid webs may be idiopathic or secondary to what?
Previous inflammatory processes due to infection or intracranial haemorrhage.
Due to the spinal arachnoid web CSF in the spinal canal is unable to disperse normally, leading to what?
Focal hydraulic pressure on the spinal cord.
Give an example of a CNS water pathology where there is an abnormal accumulation of water within parenchyma of CNS.
- Cerebral oedema.
- Benign intracranial hypertension.
- Spinal dural arteriovenous fistula.
- Syringomyelia and cord oedema.
Classification of hydrocephalus?
- Obstructive.
- Communicating.
- Infantile.
- Childhood/adult.
Practically speaking, hydrocephalus should be labelled as communicating only if?
It can safely be decompressed via lumbar puncture.
What physical signs at birth may suggest hydrocephalus?
- Unusually large ehad.
- Thin and shiny scalp with easily visible veins.
- Bulging or tense fontanelle.
- Downward looking eyes.
Congenital hydrocephalus may cause what symptoms?
- Poor feeding.
- Irritability.
- Vomiting.
- Sleepiness.
- Muscle stiffness and spasms in a baby’s lower limbs.
Common congenital causes of paediatric hydrocephalus?
- Chiari malformation or Spina Bifida.
- Aqueductal stenosis.
- Dandy Walker complex.
- Congenital arachnoid cysts.
- Atresia of foramen of Munro.
Aqueductal stenosis has which mode of inheritance?
X-linked.
Common acquired causes of paediatric hydrocephalus?
- Haemorrhage (IHV - intraventricular haemorrhage).
- Infection (post-meningitis).
- Traumatic head injury.
- Tumour.
What function do valves have in the management of hydrocephalus?
- Fixed differential pressure.
- Adjustable.
- Anti-syphon.
- Switch able.
- Constant flow.
What percentage of valves used in the management of hydrocephalus are no longer functioning after 12 years?
80%.
Complications of shunts used in hydrocephalus?
- Overdrainage.
- Underdrainage.
- Infection.
How may the risk of infection be reduced in the use of shunts in hydrocephalus?
- Antibiotics or silver impregnated shunts.
- Iodine +++.
Underdrainage of a shunt used in the management of hydrocephalus may be due to?
- Blockage.
- Displacement/disconnected catheter.
Overdrainage of a shunt used in the management of hydrocephalus may be due to?
- Acute subdural haematoma.
- Slit ventricles.
Uncommon complications of shunts used in the management of hydrocephalus?
- Intracerebral haemorrhage.
- Seizures.
- Craniosynostosis.
- Dissemination of tumour cells.
- Umbilical fistula.
- Erosion into abdominal viscera.
- Ascites, hydrocele, inguinal hernia.
- Silicone allergies.
What is craniosynostosis?
Premature fusing of one or more of the fibrous sutures in an infant’s head.
May be a complication of a shunt.
What symptoms may be indicative of a blocked shunt in children?
- Sunsetting (eyes look down).
What symptoms may be indicative of a blocked shunt in adults?
- Lack of upgaze.
What symptoms may be indicative of a blocked shunt in both adults and children?
- Headache and vomiting.
- ## Blurred vision (papilloedema precedes blindness- may be rapid).
Management of blocked shunt in extremis?
Tap the shunt valve.
- NB there is a risk of infection may CSF can be sent to microbiology.
Management of a blocked shunt?
- CT head to show hydrocephalus.
- Urgent surgery to replace shunt.
Tap the shunt valve if patient in extremis (point of death) but note risk of infection so can send CSF to microbio.
Alternative to shunt in hydrocephalus?
Ventriculostomy.
A ventriculoperitoneal shunt may be used to treat hydrocephalus, but has a revision rate of?
40% in the first year.
How do ventriculoperitoneal shunts work?
Shunt drains spinal fluid from ventricles to the abdomen.
Why do shunts (particularly LP) have limited life expectancy?
Terminal slit valves in peritoneal cavity tend to fail with time.
What is normal pressure hydrocephalus?
Enlarged cerebral ventricles with normal/intermittently raised ICP.
What triad of symptoms is seen in normal pressure hydrocephalus?
- Ataxia.
- Memory decline.
- Incontinence.
Normal pressure hydrocephalus may respond to CSF diversion, with a success rate of?
70% but not permanent.
Who does normal pressure hydrocephalus typically affect?
Older age groups.
Causes of normal pressure hydrocephalus?
- Idiopathic.
- Post-inflammatory: subarachnoid haemorrhage, meningitis, trauma, craniotomy.
Describe symptoms of dementia associated with normal pressure hydrocephalus?
- Delay in answering questions.
- Loss of spontaneity.
- May progress to akinetic mutism.
- Often fluctuating severity.
- Urinary incontinence.
What is akinetic mutism?
Patient no longer speaks or moves.
What signs suggest normal pressure hydrocephalus ataxia?
Ataxia precedes all other symptoms in NPH.
- Difficulty rising from chair.
- Tendency to fall backwards.
- Difficulties initiating gait.
- Broad based, shuffling gait.
Differential diagnosis to normal pressure hydrocephalus?
Ataxia: cerebellar, myelopathy.
Dementia: Alzheimer’s, Cerebrovascular.
Genetic/inherited causes of dementia?
- Huntington’s.
- Wilson’s.
- Porphyria.
Infectious/transmissible causes of dementia?
- Syphilis.
- Prions.
- Encephalitis.
Metabolic/toxic causes of dementia?
- Hypothyroidism.
- Thiamine (alcohol).
Which cerebral tumour usually causes dementia?
Bifrontal.
Degenerative causes of dementia?
- Alzheimer’s.
- Fronto-temporal.
- Parkinson’s.
Trauma causes of dementia?
- Major head injury.
- Punch-drunk syndrome.
What is punch drunk syndrome?
Typically seen in alcoholics and boxers.
Due to repeated cerebral concussions.
Characterised by lower limb weakness, unsteady gait, slow muscle movements, tremor, hesitant speech and “mental dullness”.
What disease processes may cause dementia?
- Cerebrovascular disease.
- Demyelination.
- Normal pressure hydrocephalus.
Investigations used in diagnosing normal pressure hydrocephalus?
- Clinical reasoning and CT.
- MRI.
- Tracer diffusion studies.
- ICP measurement.
- Lumbar puncture “tap-test”.
- Lumbar drainage tests.
- Infusion studies.
Arithmetical calculation of resistance to outflow of CSF is a direct application of which law?
Ohm’s law: V= IR.
Rout = P0 - Pe / rate of infusion.
Rout = resistance to outflow. P0 = mean opening pressure. Pe = mean pressure at equilibrium.
What are the units used in calculating resistance to CSF outflow?
mmHg/ml/minute.
What is the principle of infusion studies?
- Record baseline ICP for a period.
- Challenge absorptive mechanisms with saline infusion.
- After 10 minutes new plateau is reached:
NORMAL: (modest increase in pulse pressure) and plateau mean within 10mm of mercury of opening pressure
IMPAIRED CSF ABSORPTION: both amplitude of pressure wave and mean pressure increases dramatically.
How is CSF diversion performed?
- “Tap test” lumbar puncture or lumbar drain.
- Measure normal pressure hydrocephalus triad pre- and post- CSF drainage.
If there is an improvement then shunt.
Normal pressure hydrocephalus may be treated by CSF diversion via one of three methods, which are?
- Lumboperitoneal shunts.
- Ventriculoperitoneal shunts.
- Endoscopic ventriculostomy.
Benign/idiopathic intracranial hypertension is a disorder of what?
CNS water movement.
who does idiopathic intracranial hypertension typically affect?
Young overweight/obese females.
Conditions associated with idiopathic intracranial hypertension?
- Obesity/weight gain.
- Sleep apnoea.
- Hypothyroidism.
- Addison’s.
- Uraemia.
- SLE
- Vitamin A, Lithium, antibiotics, hormones.
- Steroid withdrawal.
Symptoms of idiopathic intracranial hypertension?
- Headaches.
- Visual loss (intervene when visual fields affected before visual acuity is lost).
Do symptoms of idiopathic intracranial hypertension require treatment?
- Headaches: optional treatment.
- Visual failure: mandatory treatment.
Loss of visual acuity is a late sign of idiopathic intracranial hypertension and usually preceded by?
Constriction of visual fields.
Signs of idiopathic intracranial hypertension?
- Papilloedema.
- Visual field constriction.
- Loss of visual acuity.
Investigation results of idiopathic intracranial hypertension?
- LP pressure: >25cm CSF.
- Normal CSF chemistry and cytology.
- Normal CT and MRI.
- No evidence of venous sinus thrombosis.
Treatment of idiopathic intracranial hypertension?
- Resolution with weight loss in majority of cases.
- Treat underlying medical disorder.
- LP.
- Diuretics.
- Lumbo-/Ventriculo-peritoneal shunt.
- Optic nerve sheath fenestration.
- Sub-temporal decompression.
- Venous stents.
Complications of lumboperitoneal shunts?
- Blockage.
- Infection.
- Nerve root irritation.
- Low pressure headaches.
- Subdural haemorrhage.
- Arachnoiditis.
- Tonsillar herniation.
Tonsillar herniation is one complication of lumboperitoneal shunts, causing headaches due to what?
CSF pressure dissociation.
Symptoms of spontaneous intracranial hypotension?
- Orthostatic headaches.
- Neck/ interscapular / arm pain.
- Diplopia/ visual field defects.
- Dizziness.
- Muffled hearing.
- Galactorrhoea.
- Impaired sphincter control.
- Symptomatic subdural haematoma.
What are the causes of spontaneous intracranial hypotension?
- Idiopathic.
- Collagen disorders.
- Dural diverticula.
- Trauma (often minor).
Management of spontaneous intracranial hypotension?
- Conservative: bed rest, fluids, analgesia.
- Epidural blood patches.
- Surgical repair.
What is an epidural blood patch?
Surgical repair of holes in the dura mater of the spinal cord by using autologous blood patches as seals.
In the investigation of spontaneous intracranial hypotension, what might an MRI head show?
- Meningeal enhancement.
- Chronic subdural haematomas.
- Hindbrain herniation.
In the investigation of spontaneous intracranial hypotension, what might a lumbar puncture show?
- Low pressure.
- Pleocytosis.
- Raised protein.
- Xanthochromia.
What is pleocytosis?
Abnormally large numbers of lymphocytes in cerebrospinal fluid.
What is xanthochromia?
Yellowing of CSF due to presence of bilirubin.
What investigations should be performed in suspected spontaneous intracranial hypotension?
- MRI head.
- LP.
- CT myelography.
- Spinal MRI.
- Isotope myelography.
In spontaneous intracranial hypotension, low CSF pressure causes what?
Compensatory hyperaemia in the meninges.
What accounts for cases of galactorrhoea in spontaneous intracranial hypotension?
Hyperaemia through the pituitary.
What is hyperaemia?
Increased/excessive blood flow to an organ/part of the body.
Mean age at presentation of syringomyelia?
31-35.
Does range from childhood to seventies.
Syringomyelia is extremely common in which population?
Traumatic paraplegia victims.
What is the latent interval of syringomyelia?
A few months to many years.
What are the broad classifications of syringomyelia?
- Craniovertebral junction.
- Spinal canal.
- Idiopathic.
What is syringomyelia?
Fluid filled Cyst/cavity formation in the spinal cord. Expands and lengthens over time and may compress and damage spinal cord.
Syringomyelia may arise from what?
- Spondylotic narrowing of spinal canal.
- Fibrosis at craniovertebral junction.
- Idiopathic.
How does syringomyelia classically present?
NB this is rarely seen now.
- Dissociated sensory loss.
- Clawed hands.
- Cuts and burns on hands.
- Small muscle wasting.
- Loss of upper limb reflexes.
- Increased lower limb reflexes.
Syringomyelia causes what abnormalities in sweating?
- Hyperhydrosis in early stage.
What does hyperhydrosis indicate in Syringomyelia?
Hyperactivity in preganglionic neurons.
Involuntary movements seen in Syringomyelia are a result of what?
Possible excitability of spinal neurons.
What symptoms may a patient occasionally present with?
- Segmental myoclonus.
- Paroxysmal arm posturing.
- Isolated Horner’s.
- Orofacial pain (syringobulbia).
- Limb hypertrophy.
- Orthostatic hypotension.
- Reduced intestinal mobility.
Common presentations of hindbrain hernia (commonly associated with Syringomyelia)?
HEADACHES following:
- coughing, sneezing, straining, laughing, bending forward.
- Visual disturbances.
- Dizziness.
- Deafness/tinnitus.
- Dysarthria/dysphagia.
- Somatic sensory disturbances.
Occasional presentations of hindbrain hernia (commonly associated with Syringomyelia)?
- Papilloedema.
- Trigeminal neuralgia.
- Glossopharyngeal neuralgia.
- Respiratory failure.
- Sleep apnoea.
- Blepharoclonus.
- Abnormal masseter/ corneal reflexes.
- Postural evoked vomiting.
- Chronic fatigue.
- Syncope.
Management of syringomyelia?
- Open up obstructed CSF channels.
- Drain syrinx cavity (if opening up channels fails as myelotomy is required).
- Lower overall CSF pressure: less risky CSF shunts?
- Conservative management.
How may CSF conduits be opened up?
- Craniovertebral decompression.
- Laminectomy and duroplasty.
- Others: e.g. excision of intramedullary tumour and division of arachnoid web.
Often, blood and other products released into CSF pathways during surgery lead to?
Recurrent adhesion formation and persistence of syrinx cavity.
Collapse of the syrinx cavity is related to the extent of what?
Arachnoid adhesions/fibrosis.
Which type of fibrosis may prevent creation of a conduit for CSF flow?
extensive intradural fibrosis.
What are the CSF receptacles into which CSF fluid may be diverted?
- Spinal subarachnoid channels.
- Pleural cavity.
- Peritoneal cavity.
When should conservative management be utilised in cases of syringomyelia?
- Spindles.
- Dilated central canals.
- Clinically stable cavities.
- Extensive fibrosis.
- Medically unfit.
Following craniovertebral decompression for hindbrain hernia, what commonly persists?
Sensory symptoms e.g. Dysaesthetic pains.
What is dysaesthesia pain?
Uncomfortable, abnormal sensation of neuropathic pain.
Commonly associated with MS.
Craniovertebral decompression for treating hindbrain hernia usually relieves what?
- Pressure dissociation headaches.
- 80% rate of syrinx collapse.
- Motor deterioration arrests.
Revision/blockage rate for syringopleural shunts used for post-traumatic syringomyelia?
30-50%.
The degree of difficulty in operating on syringomyelia is proportional to?
The extent of intradural fibrosis.
