CSF Production, Dynamics and Physiology
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The document discusses the dynamics and physiology of cerebrospinal fluid (CSF), including its production, circulation, absorption, and the consequences of altered CSF hydrodynamics. It outlines historical developments in CSF studies, anatomical components involved, and relevant clinical implications such as intracranial pressure and its management. Variations in CSF dynamics lead to various conditions, emphasizing the importance of accurate diagnosis and treatment in neurosurgery.
CSF Production, Dynamics and Physiology
- 1. CSF Production Dynamics and Physiology Dr Fakir MohanSahu Dept. ofNeurosurgery AIIMS Bhubaneswar 13/04/2021 Dr Fakir Mohan Sahu Dept. of Neurosurgery AIIMS Bhubaneswar
- 2. Learning Objectives • Historical Backgrounds • CSF anatomy and Physiology • CSF Production, Circulation and Absorption • CSF Dynamics, ICP, CPP • Consequences of altered CSF Hydrodynamics • Applied Anatomy
- 3. Historical Background • Hippocrates described fluid in brain • Galen described ventricles • Vesalius showed the anatomy • Megendi performed first cisternal puncture in animals • Quinke performed first LP(1891) • Quekensted did first cisternal puncture in humans(1916) • Dandy was credited first ventricular puncture(1918) • Mixter in 1923 performed the first ETV in a child with congenital hydrocephalus using a urethroscope and probe
- 4. Introduction • CSF clear, Colourless, Odourless fluid present within and around the CNS • Tela choroidea • Choroid plexus • Arachnoid villi(Endothelial cell Vesicular Channels) • Arachnoid granules • CSF Flow(Unidirectional, from arachnoid villi to Dural Venous sinuses, Pressure of 1.5 mmHg higher) • Foramens
- 5. CSF Anatomy and Physiology
- 7. AQP1 Mechanism of choroidal production Tight junction Epithelial cells Active process: Uses ATP movement ofions osmotic gradient secretion ofH2O high expressionof AQP1 on apical membrane
- 8. Factors Decreasing CSF production Endogenous Exogenous CSF Pressure Acetazolamide Choroid plexus ischemia Frusemide Hypoxia Amiloride Acidosis/ Alkalosis Omeprazole Hypoglycemia Glycosides Neural Cholera toxins Johnston, I et al. Child's Nerv Syst. 2000
- 11. Sylvian cistern Chiasmatic/ suprasellar cistern Interpeduncular cistern Ambient cistern Quadrigeminal cistern Crural cistern
- 12. Mechanism of CSF flow The pressure gradient is highest in the lateral ventricles and diminishes successively along the subarachnoid space b, the negative venous pressure (dark blue) produced during inspiration causes pressure decrease in temporary intracranial compartment, resulting in CSF outflow (Dreha-Kulaczewski et al. 2017) Delaidelli, Aet al. Journal of Neuroscience 2017 a. Arterial pulse wave (red) causes temporary pressure increase in intracranial compartment, resulting in CSF outflow (O'Connell,1943)
- 13. Absorptio n Arachnoid villi microscopic one-way valves (modified pia andarachnoid) penetrate meningeal dural layer lining venous sinuses arachnoid villi = granulations = Clumps of arachnoid macroscopic
- 14. Mechanism of absorption Hydrostatic pressure in subarachnoid space (11mmHg) > dural sinuses (5mmHg) Arachnoid villi open : pressure in SAS ~1.5 mm Hg > pressure in dural sinuses Passive process Papaiconomou,C.et al News Physiol Sci 2002
- 15. Possible alternative sites of CSF absorption Arachnoid endothelium & membrane Adventitia of bloodvessels and lymphatics Cranial/ spinal nerveroots sleeves/ lymphatics Capillary endothelium Spinal arachnoid projections Johnston, I et al. Child's Nerv Syst. 2000 Papaiconomou,C.et al News Physiol Sci 2002
- 16. Functions of CSF • Cushion around the CNS • Protection(Coup Counter coup injury concept) • Buoyancy /Floating in CSF(Sp. gravity almost equal 140050gm) Post LP-- excess fluid-- traction in foramens - Headache incre. • Haemostasis/Reservoir/ Control • Nourishes- Lipid, Glucose, Electrolytes • Vehicle to remove metabolic waste (ECF and CSF easily exchange) • Carries hormonal Products of CNS • Immune Function- Immunoglobulin and immune Protection
- 17. The Monroe-Kellie doctrine Sum of volumes of the 3 components is constant an increase in volume of any one component accompanied by a reduction in volume of at least one of the remaining two components ICP : Function of the volume and compliance of each component of the intracranial compartment The magnitude and the rate of change in the volume of each component determines its effect on ICP
- 18. Intra Cranial Pressure (ICP) ≤ 15mmHg inadults Intracranial hypertension (ICH) : pressure≥ 20 mmHg Normally lower in children than adults Homeostatic mechanisms stabilize ICP Intracranial contents include : Brain parenchyma — 80 % Cerebrospinal fluid — 10 % Blood — 10%
- 19. Cerebral Perfusion Pressure (CPP) The pressure needed to overcome ICP in order to deliver O2 & nutrients. Clinical surrogate for the adequacy of cerebral perfusion. MAP is the DRIVING FORCE ---------- ICP is the RESISTENCE CPP = MAP – ICP = 100 mmHg – 15mmHg = 85 mmHg (Normal) CPP < 50 mmHg → cerebral ischemia CPP < 30 mmHg→ brain death
- 20. Features of CSF • Volume -150ml • 550ml/day @ 5.5 ml /min • Pressure – 50-150 cm H2O • No RBCs, No Neutrophils, Few Lymphocytes- < 5 / cumm • Glucose- 2/3rd level of plasma(In LP Study always take the venous sample) • Protein-Immune mediated diseases of CNS
- 23. OP(CM APPEAR CELLS PROTEI GLUCO MISC. H20) ANCE N(MG%) SE FUNGAL MENINGITIS INCREASED OPALASCENT 30-300 (LYMPHO) 100-700 <30 +INDIA INK IN CRYPTO. TB MENINGITIS INCREASED OPALASCENT 50-500LY MPHO 60-700 20-40 ZN STAIN +/AFB CS WITH CLOT + BRAIN INCREAS CLEAR/ INCREAS INCREAS NORMAL LESS ABSCESS TURBID / SENSITIV DECREAS
- 24. Other Biomarkers in CSF CSF HCG- Central choriocarcinoma CEA- breast,lungbladdermetsin CNS Alfafetoprotein – germcelltumors, metastatictesticularandhepatic ca. Spermidine– meningiomas Polyaminein leukemia Desmosterol in gliomas betaglucuronidaseinleptomeningeal involvement
- 25. VENTRICULAR CATHETERIZATION POINTS AND TRAJECTORIES OF ACCESS TO VENTRICLES —Kocherʼs point – 3 cm latto midline and 1cm ant to coronal suture —Keenʼs point 2.5 -3 cm above and 2.5-3cm behind pinna —Dandyʼ s point – 3 cm above inion and 2 cm lateral to midline —Frazierʼs point - 6 cm above inion and 4 cm latto midline —Orbital point – 1-2 cm behind superior orbital rim —Supra orbital – 4 cm above orbital rim in midpupillary line
- 27. Intraoperative CSF Puncture points
- 28. Consequences of altered CSF hydrodynamics Abnormal fluid movement (transependymal/transparenchymal) Effects of raised ICP Circulatory changes (micro and macro) Ischemia Changes in brain morphology/parenchymal damage Changes in CSF circulatory path : obstruction/ shunt/ surgery Effects of loss or misdistribution of CSF Post-shunt or other post-surgical changes Johnston, I et al. Child's Nerv Syst. 2000
- 29. Classification of CSF circulation disorders Johnston, I et al. Child's Nerv Syst. 2000
- 30. Types of HCP
- 31. Causes of HCP Congenital Acquired Aqueductal stenosis (MC) SAH/ IVH Dandy-Walker malformation Infections : TBM Arnold-Chiari malformation Mass lesions /Tumors Agenesis of the foramen of Monro Posterior fossa cyst/ Arachnoid cyst Congenital toxoplasmosis Increased venous sinus pressure Bickers-Adams syndrome Traumatic brain injury Neural tube defects Idiopathic
- 32. Diagnostic techniques USG in infants (due to open fontanel) and in utero CT/MRI scanning : the mainstay of diagnosis CSF Flow study CSF pressure measurement
- 33. CT/MRI features Increased frontal horn radius (Mickey mouse ventricle) Dilatation of the temporal horns (>2mm) Acute ventricular angles
- 34. CT/MRI features Periventricular interstitial edema from the transependymal flow : high T2 signal on MRI or low- density change on CT Intra-ventricular flow void from CSF movement
- 35. CT/MRI Features Inferior displacement of the floor of the 3rd ventricle Outward bowing / ballooning of the lateral walls & recesses of the third ventricle (infundibular, optic and pineal recesses) Ballooning of the suprapineal recess
- 36. CT/MRI Features On mid-sagittal plane : Upward displacement of corpus callosum Thinned out corpus callosum Depression of the posterior fornix Decreased mamillopontine distance ( normal >5.5mm)
- 37. CSF flow study To qualitatively assess and quantify pulsatile CSF flow MC technique : Time-resolved 2D phase contrast MRI with velocity encoding (VENC) CSF flow in the context of imaging : pulsatile to-and-fro flow due to vascular pulsations NOT bulk transport of CSF Typical CSF flow is 5-8 cm/s Hyperdynamic circulation : higher velocities : up to 25 cm/s Clinical applications Aqueduct stenosis Normal pressure hydrocephalus(NPH) Patency of third ventriculostomy Flow at the Cervico-medullary junction (foramen magnum) Chiari I malformation
- 38. CSF flow study Images are typically presented in sets of 3 for each plane and velocity obtained. The set comprises of Re-phased image (magnitude of flow compensated signal) • flow is of highsignal • background isvisible
- 39. CSF flow study Magnitude image (magnitude of difference signal) • flow is of high signal (regardless of direction) • background is suppressed Phase image (phase of difference signal) • signal is dependent on direction: forward flow is of high signal; reverse flow is of low signal • background is mid-grey
- 40. CSF pressure measurement Direct assessmentof elevated ICP Surgical placement of ventricular / intraparenchymal pressure transducer Intraparenchymal transducer : more invasive /real time data/ accurate determination of ICP Helps in management decisions
- 41. CSF Pressure Management The main goal is to minimize or prevent brain damage by decreasing ICP and improving CSFflow. Medical management- Acetazolamide, Diuretics therapy Temporary procedures External ventriculardrainage Spinal tap Surgical management Shunt Endoscopic Third Ventriculostomy (ETV)/other endoscopic procedure Eliminating the cause of obstruction
- 42. Endoscopic Third Ventriculostomy Indications: Aqueductal stenosis Posterior fossa tumors and cysts with hydrocephalus Postinfectious hydrocephalus Tuberculous meningitis with hydrocephalus Hydrocephalus associated with myelomeningocoele and Chiari malformation Hydrocephalus secondary to intracerebral / intraventricular hemorrhage Shunt dysfunction Involves creating an opening in the floor of third ventricle to allow CSF to flow into pre-pontine cistern and subarachnoid space Absolute contraindication : obstruction at the level of the arachnoid villi or the venous flow in the superior sagittal sinus
- 44. Additional Radiological findings The Evans' index Ratio of maximum width of the frontal horns of the lateral ventricles (A) and maximal internal diameter of skull (B) at the same level Employed in axial CT / MRI images Varies with the age and sex Marker of ventricular volume A/B > 0.3 - Hydrocephalus
- 45. Narrow callosal angle: Angle measured on a coronal image perpendicular to the anterior commissure - posterior commissure (AC-PC) plane at the level of the posterior commissure Normal = 100-120° NPH = 50-80°
- 46. Cingulate sulcus sign : Denotes the posterior part of the cingulate sulcus being narrower than the anteriorpart. Divider b/w anterior and posterior parts of the sulcus : line drawn parallel to the floor of 4th ventricle
- 47. Cerebral aqueductflow void Loss of signal in the aqueduct ofSylvius Represents higher-than-normal flow velocity of CSF in the aqueduct
- 48. (Disproportionately DESH enlarged subarachnoid space hydrocephalus) Characterized by: • Ventriculomegaly • Tight high-convexity and medial subarachnoid spaces • Disproportionate enlargement of the Sylvianfissures • Focally dilated or entrapped sulci without adjacent cortical atrophy • Acute callosal angle
- 49. Hydrocephalus ex vacuo Compensatory enlargement of the CSF spaces Seen in : asymptomatic elderly people : aging brain with related volume loss pathological conditions that promote brain shrinkage: degeneration (e.g. Alzheimer disease and due to focal damage (e.g. stroke and traumatic • generalised brain leukodystrophies) • encephalomalacia injuries)
- 50. Benign external hydrocephalus Enlargement of the subarachnoid space frontal or frontoparietal regions Ventriculomegaly : absent or mild. Clinically, infants have macrocephaly but otherwise well-appearing and have normal development. Presentation : progressive increase in the head circumference with normal anterior fontanel. Family history of macrocephaly :Frequent Self-limited Do not require any intervention
- 51. Arrested hydrocephalus Asymptomatic/ occult/ compensated/ long standing overt ventriculomegaly of adulthood/ late onset idiopathic aqueductal stenosis Moderate to severe tri-ventricular enlargement No evidenceof periventricular fluid accumulation on imaging Stable for years Incidental diagnosis Conservative approach with serial imaging May be associated with cognitive decline or sudden decompensation
- 52. Intracranial Hypotension Defined as CSF pressure < 60 mm H2O in patients with clinical presentation compatible with intracranial hypotension Most commonly results from a CSF leak somewhere along the neuraxis Intracranial hypotension can broadly be divided into: primary: referred to as spontaneous intracranial hypotension (SIH) secondary: • iatrogenic (lumbar puncture or surgery) • over-shunting due to diversion devices, • traumatic Presentation : positional headache relieved by lying in recumbent position within 15-30minutes Nausea/vomiting/vertigo/neck pain Traumatic or iatrogenic intracranial hypotension : history of abundant, clear rhinorrhea or otorrhea present. Occasionally, presentation is more sinister, with reported cases of decreased level of consciousness and coma
- 53. Radiographic features Imaging is crucial both for confirming the diagnosis of intracranial hypotension and identifying the location of the leak CT Subdural collection Acquired tonsillar ectopia Dural venous sinus distention
- 54. MR I Pachymeningeal enhancement Venous distensionsign Subdural effusions / hematomas Sagging brainstem / acquired tonsillar ectopia Pituitary enlargement Diffuse cerebral edema Reduced CSFvolume Decreased fluid within the optic nerve sheath
- 55. Intracranial HypotensionManagement strict bed rest and the possible Conservative Avoidance of the upright position : addition of analgesics. Restoring CSF volume : oral or i.v. hydration, high oral caffeine intake, and high saltintake Epidural blood patches : firstline Infusion of 10 to 20 cc of autologous blood into the epidural space May be repeated Adverse effects : back pain, radiculopathy, leg paresthesias, and fever Epidural fibrin glue Surgical repair