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IMAGING IN SAH 
DR.SARATHMENON.R, MD(Med),DNB(Med),MNAMS 
DM Resident 
Dept.of .Neurosciences 
Amrita Institute of Medical...
INTRODUCTION 
 Definition 
 Epidemology 
 Grading system 
 Imaging modalities 
 Differentials
IMAGING MODALITIES 
 NCCT/CTA 
 MRI /MRA 
 Angiography 
 Nuclear imaging 
 Neurosonography
SAH 
What is it? 
 Bleeding into the subarachnoid space (space between 
the pia & arachnoid meningeal layers) where bloo...
SAH 
 Incidence = 1/7000 people 
 Higher chance if: 
 Female 
 3rd trimester of pregnancy 
 Middle-aged 
 Abuse of s...
SAH – THE PROBLEM 
 80% in 40-65 year olds 
 15% in 20-40 year olds 
 It can kill quickly 
 25% die within 24 hours 
...
GRADING OF SAH 
 WFNS Grading : 
 Grade GCS Motor Deficit 
 I 15 Absent 
 II 13-14 Absent 
 III 13-14 Present 
 IV 7...
MODIFIED H & H GRADING 
Grade Description Mortalit 
y (%) 
Grade 0 Unruptured aneurysm -- 
Grade I Asymptomatic or minimal...
CT GRADING SYSTEM OF FISHER 
1 No subarachnoid blood detected 
2 Diffuse or vertical layers < 1 mm thick 
3 Localized clot...
INVESTIGATIONS 
 CT scan without contrast 
 Lumbar puncture 
 CTA 
 Cerebral angiogram 
 MRI/MRA 
98% sensitive @ 12 ...
CT SCAN- NCCT 
 Evident in the largest subarachnoid spaces- suprasellar cistern 
and Sylvian fissures. 
 most conspicuou...
 • Scrutinize these areas systematically for SAH 
 – Perimesencephalic cisterns 
 – Sylvian fissures 
 Dilation of tem...
CORTICAL SAH
SAH-CISTERNAL
A nonenhanced computed tomography scan of the 
brain that demonstrates an extensive SAH filling the 
basilar cisterns in a...
SAH & LP 
 CT & LP are critical to diagnosing SAH 
 No need for LP if obvious blood in subarachnoid space 
on CT 
 If N...
SAH & LP 
 When blood enters the CSF (e.g. from SAH or during LP) the 
red cells are broken down & oxyhaemoglobin is rele...
CTA 
subarachnoid hemorrhage and contrast 
medium filling the right sylvian fissure, 
the interhemispheric fissure, and th...
CTA SPOT SIGN
MRI/MRA 
 (FLAIR) is the most sensitive for the detection of SAH 
 FLAIR images, SAH appears as high signal-intensity 
(...
 MRA may be useful for evaluating aneurysms > 5mm 
and other vascular lesions that cause SAH
LEVEL OF CONFIDENCE 
 FLAIR MRI is as sensitive as or more sensitive than 
CT scanning in the evaluation of acute SAH 
 ...
SAH appears hyperintense on the T2-weighted and fluid-attenuated inversion 
recovery (FLAIR) images and isointense to hypo...
Sagittal T1-weighted image shows a right SDH (fig a). Axial fluid 
attenuated inversion recovery image demonstrates SAH (a...
NUCLEAR IMAGING 
 not useful in the initial diagnosis of subarachnoid 
hemorrhage (SAH), role in the diagnosis of related...
ANGIOGRAPHY 
 standard imaging -intracranial aneurysms, arteriovenous 
malformations (AVMs), and fistulae 
 (AP), latera...
LEVEL OF CONFIDENCE 
 high degree of accuracy 
 false-negative rate in the range of 1-2% 
 A repeat cerebral arteriogra...
An angiogram showing a bilobed aneurysm of a 
posteroinferior cerebellar artery immediately before 
rupturing
onset of an aneurysmal rupture, with 
extravasation of contrast material into the 
subarachnoid space from the 
anterosupe...
later-phase angiogram of a rupturing bilobed 
aneurysm of a posteroinferior cerebellar 
artery shows progressive opacifica...
late angiogram demonstrating contrast 
medium filling the posterior fossa 
subarachnoid spaces, including the 
ambient, pr...
NEUROSONOGRAPHY 
 Echoencephalography is useful for diagnosing germinal 
matrix and intraventricular hemorrhage in the ne...
SAH: DIFFERENTIAL DIAGNOSIS 
 Aneurysmal 
 Nonaneurysmal 
 “Pseudo-SAH” 
 Reversible cerebral vasoconstriction syndrom...
ANEURYSMAL SAH 
 • SAH caused by ruptured aneurysm 
 • Worst headache of life 
 • 40-60 years, M:F = 1:2 
 • 50% morta...
ANEURYSMAL SAH 
 • NCCT: 
– May show culprit aneurysm as filling defect within 
hyperdense SAH 
– Effaced cistern, hydroc...
Subarachnoid hemorrhage secondary to rupture of left 
superior cerebellar artery aneurysm
NON-ANEURYSMAL SAH-PERIMESENCEPHALIC 
 Hyperdense prepontine, perimesencephalic CSF 
 Location: "Pretruncal" (anterior t...
NON-ANEURYSMAL (PMSAH)
Small SAH, localized to interpeduncular cistern 
• Presumed venous etiology with low 
recurrence
REVERSIBLE CEREBRAL 
VASOCONSTRICTION SYNDROME (RCVS) 
 • Reversible, multifocal cerebral vasoconstrictions 
 • Clinical...
BEWARE: CORTICAL SAH FROM VENOUS 
SINUS THROMBOSIS 
Small SAH with hyperdense clot of superior sagittal sinus on CT, absen...
PSEUDO-SAH 
Increased density in basal cisterns, frequently related to 
cardiopulmonary arrest 
• Hypodense brain (severe ...
two images suggest subarachnoid hemorrhage along the cisterns 
with effacement of the quadrigeminal cisterns seen in menin...
PSEUDO SAH 
 Other causes: intrathecal contrast, meningitis 
 polycythemia 
 Falx cerebri 
 Tentorium cerebelli 
 Str...
SAH WITH INTRAVENTRICULAR 
HEMORRHAGE
CONCLUSION 
 • LP more sensitive than CT 
 • Negative NCCT but still suspicious of SAH –still 
need LP 
 • MRI is sensi...
THANK YOU
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
Imaging  in  SAH
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Imaging In Sub Arachnoid Hemorrhage (SAH)

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Imaging in SAH

  1. 1. IMAGING IN SAH DR.SARATHMENON.R, MD(Med),DNB(Med),MNAMS DM Resident Dept.of .Neurosciences Amrita Institute of Medical Sciences,Kochi
  2. 2. INTRODUCTION  Definition  Epidemology  Grading system  Imaging modalities  Differentials
  3. 3. IMAGING MODALITIES  NCCT/CTA  MRI /MRA  Angiography  Nuclear imaging  Neurosonography
  4. 4. SAH What is it?  Bleeding into the subarachnoid space (space between the pia & arachnoid meningeal layers) where blood vessels lie & CSF flows Where does the blood come from?  An aneursym on a blood vessel in the subarachnoid space has ruptured (~70%)  Unknown (~15%)  AVM (~10%)  Rare causes (e.g. tumour) (~5%) Where does the blood go?  Anywhere where CSF goes, may get hydrocephalus if into ventricle & causes obstruction of CSF circulation
  5. 5. SAH  Incidence = 1/7000 people  Higher chance if:  Female  3rd trimester of pregnancy  Middle-aged  Abuse of stimulant drugs  Connective tissue disorder  Family history  PCKD
  6. 6. SAH – THE PROBLEM  80% in 40-65 year olds  15% in 20-40 year olds  It can kill quickly  25% die within 24 hours  50% will be dead at 6 months  It causes significant disability  Cognitive impairment  Neurological disability depending on size of bleed & complications encountered
  7. 7. GRADING OF SAH  WFNS Grading :  Grade GCS Motor Deficit  I 15 Absent  II 13-14 Absent  III 13-14 Present  IV 7-12 +/-  V 3-6 +/-
  8. 8. MODIFIED H & H GRADING Grade Description Mortalit y (%) Grade 0 Unruptured aneurysm -- Grade I Asymptomatic or minimal headache with normal neurologic examination 2 Grade II Moderate to severe headache, nuchal rigidity, no neurologic deficit other than cranial nerve palsy 5 Grade III Lethargy, confusion, or mild focal deficit 15 — 20 Grade IV Stupor, moderate to severe hemiparesis, possible early decerebrate rigidity, vegetative disturbances 30 — 40 Grade V Deep coma, decerebrate rigidity, moribund appearance 50 — 80
  9. 9. CT GRADING SYSTEM OF FISHER 1 No subarachnoid blood detected 2 Diffuse or vertical layers < 1 mm thick 3 Localized clot and/or vertical layer > 1 mm 4 Intracerebral or intraventricular clot with diffuse or no SAH
  10. 10. INVESTIGATIONS  CT scan without contrast  Lumbar puncture  CTA  Cerebral angiogram  MRI/MRA 98% sensitive @ 12 hours 80% at day 3 50% at day 7 Also good to see if any associated ICH or hydrocephalus. May help localise the location of the aneurysm if there is more than 1 & may also see AVM
  11. 11. CT SCAN- NCCT  Evident in the largest subarachnoid spaces- suprasellar cistern and Sylvian fissures.  most conspicuous within 2-3 days of onset  Acute SAH is typically 50-60 Hounsfield units (HU).  The protein content of the hemoglobin molecule is predominantly responsible for the attenuating effect of blood; absolute measurement in HU varies with the hematocrit value  localizing the source of bleeding- - interhemispheric fissure,frontal lobe- Aco A - Sylvian fissure- I/L MCA - Posterior fossa- post.circulation aneurysm NCCT- Sensitivity-93-100% in first 24 hrs
  12. 12.  • Scrutinize these areas systematically for SAH  – Perimesencephalic cisterns  – Sylvian fissures  Dilation of temporal horns suggestive of hydrocephalus, which raises a possibility of SAH  CTA: Multislice CTA 90-95% + for aneurysm ~ 2 mm
  13. 13. CORTICAL SAH
  14. 14. SAH-CISTERNAL
  15. 15. A nonenhanced computed tomography scan of the brain that demonstrates an extensive SAH filling the basilar cisterns in a patient with a ruptured intracranial aneurysm
  16. 16. SAH & LP  CT & LP are critical to diagnosing SAH  No need for LP if obvious blood in subarachnoid space on CT  If NCCT –ve, LP needed.  Blood may not be evident on CT, especially if it is performed > few days after bleed  LP should only be performed after 12 hours of headache onset  If NCCT,LP –VE, CTA to r/o saccular aneurysm
  17. 17. SAH & LP  When blood enters the CSF (e.g. from SAH or during LP) the red cells are broken down & oxyhaemoglobin is released  It then takes 12 hours for the oxyhaemoglobin to be converted into bilirubin – conversion is via an enzyme found in the brain.  Bilirubin in the CSF, therefore, tells us that blood must have been in the subarachnoid space for at least 12 hours  Blood which entered the CSF during the LP would not encounter the enzyme & could not produce bilirubin  The CSF will look xanthochromic (yellowish discolouration) if bilirubin is present which they will look for with spectroscopy in the lab
  18. 18. CTA subarachnoid hemorrhage and contrast medium filling the right sylvian fissure, the interhemispheric fissure, and the lateral and third ventricles
  19. 19. CTA SPOT SIGN
  20. 20. MRI/MRA  (FLAIR) is the most sensitive for the detection of SAH  FLAIR images, SAH appears as high signal-intensity (white) in normally low signal-intensity (black) CSF spaces.  In acute SAH, FLAIR and CT scanning have similar findings.  T2- and T2*- low signal-intensity in normally high signal-intensity subarachnoid spaces.  T1-weighted - intermediate-intensity or high-intensity signal in the subarachnoid space
  21. 21.  MRA may be useful for evaluating aneurysms > 5mm and other vascular lesions that cause SAH
  22. 22. LEVEL OF CONFIDENCE  FLAIR MRI is as sensitive as or more sensitive than CT scanning in the evaluation of acute SAH  compared with LP, FLAIR MRI cannot exclude SAH.  MRI -valuable in the subacute phase of SAH, in which the density of hemorrhage on CT scans decreases.  Magnetic field inhomogeneity - artifactual increase in signal intensity in sulci over the cerebral convexities on FLAIR images, which can mimic SAH.  Hyperintensity in the subarachnoid space on FLAIR images seen in meningitis or leptomeningeal carcinomatosis
  23. 23. SAH appears hyperintense on the T2-weighted and fluid-attenuated inversion recovery (FLAIR) images and isointense to hypointense on the T1-weighted (T1W) image. Marked blooming is observed on the gradient-echo (GRE) image. Findings in the right parietal region extend into cortical sulci and suggest hyperacute or acute hemorrhage.
  24. 24. Sagittal T1-weighted image shows a right SDH (fig a). Axial fluid attenuated inversion recovery image demonstrates SAH (arrows) in the right parietal region (fig b).
  25. 25. NUCLEAR IMAGING  not useful in the initial diagnosis of subarachnoid hemorrhage (SAH), role in the diagnosis of related vasospasm  (SPECT) scanning with the radiopharmaceutical technetium-99m (99m Tc) hexamethylpropyleneamine oxime (HMPAO).  semiquantitative and qualitative in that the cerebellum is generally considered as a control value for normal perfusion  Space-occupying lesions such as cerebral hematoma can cause perfusion defects on SPECT perfusion imaging
  26. 26. ANGIOGRAPHY  standard imaging -intracranial aneurysms, arteriovenous malformations (AVMs), and fistulae  (AP), lateral, and one or more oblique views of both carotid and vertebral artery contrast injection studies  submentovertical - the neck of a middle cerebral artery bifurcation aneurysm or anterior communicating artery aneurysm  aneurysm location, shape, neck size, and neck-to-maximal diameter ratio - the aneurysm is better treated with open craniotomy or with an endovascular technique.
  27. 27. LEVEL OF CONFIDENCE  high degree of accuracy  false-negative rate in the range of 1-2%  A repeat cerebral arteriogram at 10-14 - initial angiogram negative  B/l selective external and internal carotid artery angiograms - exclude a dural arteriovenous fistula  B/l vertebral arteriograms of the neck ( selective thyrocervical trunk and/or careful injections of the right superior intercostal artery) demonstrate the arterial and venous circulation of the cervical spinal cord  If thorough arteriographic studies do not demonstrate a specific cause for an SAH, a presumptive diagnosis of idiopathic perimesencephalic hemorrhage is sometimes made
  28. 28. An angiogram showing a bilobed aneurysm of a posteroinferior cerebellar artery immediately before rupturing
  29. 29. onset of an aneurysmal rupture, with extravasation of contrast material into the subarachnoid space from the anterosuperior aspect of a bilobed aneurysm in a posteroinferior cerebellar artery
  30. 30. later-phase angiogram of a rupturing bilobed aneurysm of a posteroinferior cerebellar artery shows progressive opacification of the subarachnoid space in the posterior fossa
  31. 31. late angiogram demonstrating contrast medium filling the posterior fossa subarachnoid spaces, including the ambient, prepontine, and perimedullary cisterns
  32. 32. NEUROSONOGRAPHY  Echoencephalography is useful for diagnosing germinal matrix and intraventricular hemorrhage in the newborn  transcranial Doppler USG - diagnosis and management of vasospasm in patients with SAH.  Serial transcranial Doppler USG - presence of vasospasm and allow for the maximization of medical therapy for vasospasm before the patient becomes symptomatic  Flow measured in the middle cerebral arteries, which have have flow velocities normally in the 30-80 cm/s range. Elevation to 120 cm/s indicates moderate vasospasm, and elevation to 200 cm/s indicates severe vasospasm  sensitivity of transcranial Doppler ultrasonographic imaging for the detection of vasospasm has been reported to be 85-90%
  33. 33. SAH: DIFFERENTIAL DIAGNOSIS  Aneurysmal  Nonaneurysmal  “Pseudo-SAH”  Reversible cerebral vasoconstriction syndrome (RCVS)
  34. 34. ANEURYSMAL SAH  • SAH caused by ruptured aneurysm  • Worst headache of life  • 40-60 years, M:F = 1:2  • 50% mortality, 20% rebleed within 1st 2 weeks  • Outcome inversely proportional to Hunt and Hess (H&H) grade and WFNS grade  • Severity of vasospasm/ischemia correlates with Fisher CT grading (amount)  – 1 = no SAH visible  – 2 = diffuse, thin layer (< 1 mm)  – 3 = localized clot or thick layer (> 1 mm)  – 4 = intraventricular blood
  35. 35. ANEURYSMAL SAH  • NCCT: – May show culprit aneurysm as filling defect within hyperdense SAH – Effaced cistern, hydrocephalus, +/- IPH  • CTA: 90-95% positive if > 2 mm  • MRA TOF: 85-95% sensitive for aneurysm > 3 mm  • DSA: current gold standard  • Highest amount of blood near site of rupture  ACoA aneurysm anterior interhemispheric fissure MCA aneurysm Sylvian  Basilar tip, SCA, PICA, VA prepontine cistern, foramen magnum, 4th ventricle
  36. 36. Subarachnoid hemorrhage secondary to rupture of left superior cerebellar artery aneurysm
  37. 37. NON-ANEURYSMAL SAH-PERIMESENCEPHALIC  Hyperdense prepontine, perimesencephalic CSF  Location: "Pretruncal" (anterior to pous, around  midbrain)  • CTA/MRA/DSA - Angiography negative in 90-95% of pnSAH - 5-10% prevalence of vertebrobasilar aneurysm in pnSAH - DSA  Saccular or blister-like aneurysm identified as cause of pnSAH in 5-10%  Vasospasm, hydrocephalus rare « < aSAH)
  38. 38. NON-ANEURYSMAL (PMSAH)
  39. 39. Small SAH, localized to interpeduncular cistern • Presumed venous etiology with low recurrence
  40. 40. REVERSIBLE CEREBRAL VASOCONSTRICTION SYNDROME (RCVS)  • Reversible, multifocal cerebral vasoconstrictions  • Clinical thunderclap headache +/- neurodeficit  • NCCT often negative: 20% with small cortical SAH +/- IPH  • Vasculitic pattern on CTA, MRA and DSA  – Segmental arterial constriction  – Interval DSA may show rapid improvement with vasodilator Rx
  41. 41. BEWARE: CORTICAL SAH FROM VENOUS SINUS THROMBOSIS Small SAH with hyperdense clot of superior sagittal sinus on CT, absence of flow voids on T2WI and loss of venous signal on MRV image
  42. 42. PSEUDO-SAH Increased density in basal cisterns, frequently related to cardiopulmonary arrest • Hypodense brain (severe edema): cisternal effacement, distension +/- thrombosis of vessels •
  43. 43. two images suggest subarachnoid hemorrhage along the cisterns with effacement of the quadrigeminal cisterns seen in meningitis
  44. 44. PSEUDO SAH  Other causes: intrathecal contrast, meningitis  polycythemia  Falx cerebri  Tentorium cerebelli  Streak artifact –bone from skull base  Motion artifact  hyperintensity of SAH is reported to range between 60 and 70 Hounsfield units, whereas that of PSAH is reported to range between 29 and 33 Hounsfield units
  45. 45. SAH WITH INTRAVENTRICULAR HEMORRHAGE
  46. 46. CONCLUSION  • LP more sensitive than CT  • Negative NCCT but still suspicious of SAH –still need LP  • MRI is sensitive to detect SAH using FLAIR, GRE and SWI  – But problematic in perimesencephalic cistern  Persistent vasospasm – vessels can be permanently narrow  Etiologies of non-traumatic SAH  – 80% ruptured aneurysm  – 10% non-aneurysmal perimesencephalic SAH  – 10% others (brain AVM, spinal AVM, DAVF, venous infarct, tumor)
  47. 47. THANK YOU

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