1Spontaneous Intracranial Hypotension Sasitorn Petcharunpaisan, M.D. Department of RadiologyKing Chulalongkorn Memorial HospitalBangkok, Thailand
2EpidemiologyNot rare, an important cause of new daily persistent headaches among young & middle age individualsPrevalence: ~1 per 50,000, previously probably underdiagnosedF:M ~ 2:1, onset in 4th or 5th decadeAssociated with connective tissue disorders (Marfan, Ehler Danlos)JAMA 2006.;295(19):
3Etiology & Pathogenesis Generally caused by spinal CSF leakPrecise cause remains largely unknown, underlying structural weakness of spinal meninges is suspectedHx of trivial traumatic events elicited in 1/3Wide variety of dural defects; simple dural hole, fragile meningeal diverticula, absence of dura cover spinal nerve rootJAMA 2006.;295(19):
4Etiology & Pathogenesis Decreased CSF volume may be final common pathway in pathophysiologyAltered distribution of craniospinal elasticity due to spinal CSF leak may be final common pathwaySo, “spontaneous spinal CSF leak” are preferred termsJAMA 2006.;295(19):
5Intracranial Hypotension MR Signs ofIntracranial HypotensionDiffuse pachymeningeal (dural) enhancementBilateral subdural effusion/hematomasDownward displacement of brainEnlargement of pituitary glandEngorgement of dural venous sinusesProminence of spinal epidural venous plexusVenous sinus thrombosis & isolated cortical vein thrombosisAJNR 2008.; 29:
6Monroe-Kellie RuleSum of volumes of intracranial blood, CSF & cerebral tissue must remain constant in an intact craniumLoss of CSF can be compensated by increased vascular component or by increased intracranial CSF componentJAMA 2006.;295(19):
7Monroe-Kellie RuleAccounting for pachymeningeal enhancement, engorged venous structures, pituitary hyperemia and subdural effusionsSubdural hematoma may caused by tearing of bridging veins or rupture of thin wall vessels in subdural zoneSagging of brain is caused by loss of CSF buoyancyTendency of a body to float or to rise when submerge into fluidJAMA 2006.;295(19):
8Diffuse Pachymeningeal, (Dural) Enhancement Diffuse, uniform thicknessLocated at convexity, along falx cerebri, tentorium & posterior fossa duraDisappears after successful treatmentJAMA 2006.;295(19):AJNR 2008.; 29:853-56
9Bilateral Subdural Effusion/Hematomas Incidence: 10-50%Tend to be thin (2-7 mm), typically occur over supratentorial convexityHave variable MR signal, depending on protein conc. & presence of bloodDisappear after successful treatment
10Downward Displacement of The Brain Low lying cerebellar tonsilsEffacement of prepontine cistern, flattening of pons against clivusEffacement of perichiasmatic cistern with bowing of optic chiasm over pituitary fossa
11Engorgement of Dural Venous Sinuses On T1W the middle 1/3 of dominant transverse sinus, shows convex bordersAll venous sinuses become engorgedThe falx & tentorium show marked enhancementAJNR 2007 ; 28:
12Prominent of Epidural Venous Plexus Occasionally patients may even present with a compressive myelopathy due to a prominent venous epidural plexus.AJNR 2009.; 30:147-51
14Treatment Many cases resolved spontaneously There is no randomized control trial evaluation of the treatment optionConservative approach: bed rest, oral hydration, caffeine intake, use of abdominal binderJAMA 2006.;295(19):
15TreatmentMainstay of treatment is epidural blood patch (EBP) - epidural injection of autologous blood into epidural spaceEffective in relieving symptoms in ~1/3, presumable by dural temponade and sealing the leakIf unsuccessful, it can be repeatedJAMA 2006.;295(19):
16TreatmentIf EBP fail, direct EBP or percutaneous placement of fibrin sealant is recommendedRequires knowledge of exact site of CSF leakSurgical Rx is reserved for Pt who failed nonsurgical RxOften successful when focal CSF leak is identifiedLigation or placement of muscle pledgetJAMA 2006.;295(19):
17Pre- post Tx appearance Left: MRI shows ‘saggin’ brain & large pituitary gland. Right: after Tx & symptom resolution the brain & gland have a normal appearance.
18Pituitary gland changes in Intracranial Hypotension Pre- & post treatment changes. The pituitary gland was initially enlarged & after Tx it becomes normal in size.
20Imaging Modalities for Detection of CSF leakage CT myelographyRadioisotope cisternographyMR myelographyMR imagingIntrathecal Gd-enhanced MR► Most common site of CSF leak reported as the cervicothoracic junction & thoracic area, could be single or multiple sites
21CT Myelography Considered most reliable imaging technique Need thin slice sectionScreening of the whole spine may cause large amount of radiation exposure (>10mSv)Additional scan is frequently required in slow flow fistulaAJNR 2008.; 29:116-21
22Radioisotope Cisternography Directly visualizes radioactivity outside the subarachnoid spaceSensitivity is not highIf there is no active leakage or the site of leakage is smaller than resolution, evidence of leak may not seenIndirect - radiotracer may ascend slowly over the convexity or may quickly disappear and then accumulate in the bladderAJNR 2008.; 29:116-21
23MR Myelography Not invasive, no radiation exposure A study of Yoo et al performed in 15 Pts with SIH, detectable in casesUse 2D or 3D FSE heavily T2WAll Pt improved after conservative treatment (2) or EBP (13)AJNR 2008.; 29:649-54
24Spinal MR ImagingSearch for the point of CSF leak is difficult and often unsuccessfulUsually reveals extradural fluid collection, spinal meningeal enhancement, and dilatation of epidural venous plexusLocation of extraarachnoid or extradural fluid collection rarely reflect leakage siteMay help Dx in Pt with normal cranial MRIAJNR 2008.; 29:649-54
25ComplicationsPatient with known intracranial hypotension who rapidly deteriorated shows cerebellar, brainstem & cord infarctions.AJNR 2009, doi: /ajnr.A1749
26Intracranial hypotension due to Post op spinal CSF leak Patient had a tumor resection from the thoracic vertebrae & developed intracranial hypotension found to be due to paraspinal thoracic pseudomeningocele.
27Intracranial hypotension complicated by cortical vein thrmbosis Iatrogenic- post LP- intracranial hypotension with cortical vein thrombosis (arrow).
28ReferencesSpontaneous spinal cerebrospinal fluid leaks and intracranial hypotension. JAMA 2006; 295(19):Diffuse pachymeningeal hyperintensity and subdural effusion/hematoma by FLAIR MRI in patients with spontaneous intracranial hypotension. AJNR 2008; 29:The venous distention sign: a diagnostic sign of intracranial hypotension. AJNR 2008; 28:Intradural spinal vein enlargement in intracranial hypotension. AJNR 2005; 26:34-38Diagnostic criteria for spontaneous spinal CSF leaks and intracranial hypotension. AJNR 2008; 29:853-56Detection of CSF leak in spinal CSF leak syndrome using MR myelography: correlation with radioisotope cisternography. AJNR 2008; 29:649-54Gadolinium-enhanced MR cisternography to evaluate dural leaks in intracranial hypotension syndrome. AJNR 2008; 29:116-21Diagnostic value of spinal MRI in spontaneous intracranial hypotension syndrome. AJNR 2009; 30:147-51False localizing sign of C1-2 CSF leak in spontaneous intracranial hypotension. J Neurosurg 2004; 100:639-44