SUBARACHNOID HEMORRHAGE

SUBARACHNOID HEMORRHAGE

The presence of blood in the subarachnoid space

- a syndrome with a number of causes but term usually equated with that occurring secondary to aneurysmal rupture (most common non-traumatic cause)

Epidemiology:

Overall incidence 10 per 100,000 persons per year

- accounts for 3-5% of all strokes

- significant cause of morbidity and mortality in previously healthy group of often young people (more potential years life lost than other causes due to earlier mean age of onset, peak 6th decade)

- 1.6x higher risk in women

- higher incidence in Japan, Finland, and black populations

- major risk factors are smoking and potentially hypertension and alcohol abuse

History:

1. Headache (HA)

- usually a severe ("worst in my life!") HA with onset building to peak severity over seconds (or minutes) = thunderclap HA / different from any previous HA

(see separate topic for differential dx)

- pretest probabilty of such a headache representing SAH is only 10% (higher if other features present such as focal findings or loss of consciousness)

- up to half have slower-onset headache building over seconds to few minutes

- some have a sentinel bleed with a less persistent but also sudden severe HA in days / weeks preceding (up to 50%; but also common in innocuous benign thunderclap headaches!)

- often transient weakness or loss of consciousness at onset (due to abrupt rise in ICP)

- others remain obtunded or confused after onset

- if predominant neck pain or stabbing between shoulder blades (coup de poignard) then suspect SAH due to spinal AVM or fistula

2. Seizure

- 10% or less at onset but can present with this +/- post-ictal confusional state

- if severe post-ictal headache with new-onset seizure, suspect SAH and image

- others may not give history of headache if very confused, so need high suspicion

3. Nausea & Vomiting:

- often from onset (unlike migraine patient with severe HA but vomiting comes later)

- may also have photophobia

+/- neck stiffness

4. Focal Deficits

- stroke-like sudden onset of hemiparesis or other deficit may accompany headache or rarely occurs in its absence

5. Head Trauma:

- SAH patients may fall or have an accident as a result of bleeding

- this can be confused with traumatic SAH from a trauma itself (eg. fall, MVC)

- hard to establish whether trauma caused the hemorrhage or vice-versa (pattern on CT useful - more at convexity, superficial sulci, adjacent to fracture or impact point)

- if no clear cause for accident found (eg. drive off road) then suspect spontaneous SAH first

- neck manipulation or trauma can cause vertebral artery dissection with intracranial dissection and SAH (usually occipital headadche for day(s) prior to rupture and more severe HA)

Ask about risk factors:

- Family History (predisposition found in 5-20%; while first-degree relatives of SAH patients have 3- to 7-fold higher risk, but no higher in second-degree relatives)

- Associated disorders include polycystic kidney disease (ADPKD), Ehlers-Danlos IV, Neurofibromatosis type I, +/- Marfan's syndrome (rare causes of aneurysms)

- Smoking

- Hypertension

- Alcohol or illicit drug abuse (esp cocaine)

- Endocarditis (Hx of fever, malaise in days preceding SAH, known valvular disease)

- Hx of head trauma (can develop dural AVF)

Examination:

1. Level of consciouness

- often depressed, either transiently or usually persisently

- important predictor of outcome / severity

- use GCS to grade (see WFNS grading below)

2. Pupils / Eyes:

- monocular blindness can result from large AComm or ophthalmic aneurysm as well as pituitary source of bleeding

- assess for oculomotor palsy (pupil fixed & dilated, ptosis, ophthalmoplegia)

- can be due to early uncal herniation in comatose patient but more often (in awake SAH patient) due to compression of CN III by aneurysm sac (usually PComm, but also basilar tip and others)

- CN VI palsy may be sign of raised ICP (can be bilateral)

- look at fundi for papilledema (NOT seen early) or more commonly (20-40%) intraocular hemorrhage (vitreous, subhyaloid hemorrhage almost pathognomonic and may be best sign if comatose)

* the association of vitreous hemorrhage with SAH is known as Terson's syndrome

NB: combination of visual loss and ocular motor nerve palsies raises suspicion (with severe HA) of pituitary apoplexy

3. Focal Motor Deficits:

- hemiparesis can occur contralateral to side of rupture, usually due to intraparenchymal clot (eg. MCA aneurysm rupturing into Sylvian fissure and peri-insular region)

- may also see aphasia, neglect, or other deficits

- lower CN deficits may suggest arterial dissection (esp vertebral) as do brainstem / cerebellar abnormalities (eg. dysmetria, Horner's syndrome)

4. Meningismus:

- nuchal rigidity important sign in patient with suspected SAH but takes 6-12 hours to develop

- irritation of meninges by blood breakdown products ("chemical meningitis")

- may be absent or hard to detect in deeply comatose patients

5. Systemic Features:

- may see fever (neurogenic often), hypertensive response (to mainatin cerebral perfusion) and arrhythmias (may contribute to early mortality) as well as almost universal EKG changes

- can even present with ST depression or elevation mimicking acute coronary event !

WFNS Grading of SAH:

Grade GCS Motor Deficit

I 15 Absent

II 13-14 Absent

III 13-14 Absent

IV 7-12 +/-

V 3-6 +/-

Diagnosis:

Suspect (and investigate for) in any patient with:

- thunderclap HA

- new or different recent onset HA

- loss of consciousness or new-onset seizure with persistent severe HA afterward

- pupillary-involving CN III palsy of recent onset (suggests compressive lesion)

- subhyaloid hemorrhage in patient with altered LOC

- "stroke" (eg. aphasia or hemiparesis) with severe HA or altered LOC (not expected in usual ischemic stroke)

1. Non-Contrast CT Head

- looking for blood (hyperdense) in subarachnoid space, commonly the basal cisterns

- high sensitivity (95% or more) if performed with 3rd-generation scanner within 12-24 hours of ictus

- sensitivity falls over time (blood distributes and less apparent) to 70% at 3-d, 50% at 1-week

- also gives important information on distribution and extent of hemorrhage (and may help to distinguish aneurysmal from traumatic SAH – in the latter, blood is mainly located over convexity +/- adjacent to fracture or intracerebral contusion; AComm aneurysm rupture can simulate basal frontal trauma, however)

- help assess risk of vasospasm and possible site of aneurysm (in patient with multiple aneurysms)

- look for the perimesencephalic pattern of bleeding (if no aneurysm subsequently found)

i.e. blood does not extend into Sylvian or anterior interhemispheric fissures (just ambient & prepontine cisterns); also no significant intraventricular hemorrhage and no intraparenchymal extension (which only happens with aneurysmal / arterial rupture)

Clues to Aneurysm:

- blood in anterior interhemispheric fissure with AComm aneurysms +/- parenchymal hematoma in inferior frontal lobe (can be mimicked by basal-frontal head trauma)

- lateralized SAH in basal cisterns with ICA / PComm rupture (+/- mesial temporal hematoma)

- lateralized bleeding in Sylvian fissure +/- hematoma adjacent with MCA aneurysms

- most blood ventral to brainstem in cisterns with basilar aneurysm

- bleeding around foramen magnum and along tentorium with PICA aneurysm rupture

- if most blood at convexity rather than basal cisterns, consider distal aneurym (ie mycotic) or traumatic

False-Positives:

- generalized cerebral edema with compression and bright-appearance of CSF spaces (eg cisterns) due to venous congestion (also in brain death)

False-Negatives:

- scan done too late after ictus (see above)

- small amount of blood overlooked by inexperienced reader (eg. pretruncal SAH)

- severe anemia with no hyperdense blood (looks isodense and hard to see)

2. Lumbar Puncture

- mandatory to perform sampling of CSF (where bleeding has occurred) if suspect SAH as CT not 100% sensitive (although LP will have low yield if CT negative and patient seen early in course)

- looking for presence of blood (RBCs) or blood breakdown products (eg. bilirubin) in CSF

- need to differentiate true SAH from common 'traumatic tap' where blood introduced at time of procedure, from passing through venous plexus adjacent to dura

- a decrease in number of RBCs from first to last tube sampled is nonspecific indicator that tap was traumatic and no SAH present (unreliable)

- the presence of xanthochromia (yellow color) indicates blood breakdown products and cannot be seen in fresh bleeding from traumatic tap (hemoglobin lyses to release OxyHb -> bilirubin)

- should be tested looking for appropriate peak on spectrophotometry as simple visual inspection of centrifuged CSF supernatant is only 50% sensitive ('flip a coin' !!)

- can also test for bilirubin in CSF if available

- xanthochromia stays positive for 2 or more weeks after ictus so useful in delayed presentations

NB: Hb breakdown takes 6-12 hrs after ictus, so LP and CSF testing may be falsely negative if done too early (need to wait with patient for few hours if seen early and CT negative)

3. MRI / MRA:

- useful if delayed presentation when CT predicted to be negative / low sensitivity

- can look for siderosis (deposition of Hb breakdown products in subarachnoid space) seen on gradient echo imaging (also do LP and look for CSF xanthochromia - see above)

- FLAIR imaging more sensitive in acute phase (before hemosiderin released)

- may remain positive for 6 weeks after ictus

4. Cerebral Angiogram:

- all four vessels injected looking for source of subarachnoid bleeding (ie. vascular lesion)

- common causes (see below for full list) incl. aneurysms, AVMs, arterial dissection

NB: if all testing for source of significant SAH negative and back pain present, consider spinal imaging looking for spinal AVM or dural fistula

DDx of SAH:

1. Traumatic

- most common cause overall

- different pattern with blood in convexity not in basal cisterns as much

- history important but may be hard to know if trauma occurred due to incipient SAH or traumatic SAH from trauma (eg. MVC)

2. Aneurysmal rupture

- accounts for 80-85% of spontaneous (non-traumatic) SAH

- also includes mycotic aneurysms associated with bacterial endocarditis

3. Perimesencephalic SAH

- see below for details; likely accounts for 10-15%

4. AVM

5. Arterial dissection (with intracranial extension) esp vertebral

6. Pituitary apoplexy

7. Drug abuse (eg. cocaine) +/- associated with aneurysm

8. Coagulopathies

Intracranial Aneurysms:

Many types of aneurysms from classical 'berry' or saccular, to fusiform, and mycotic (infectious) types

Saccular aneuryms

- 1-6% incidence with vascular imaging or at autopsy (many of these are small and incidental)

- more common than aneurysms at other sites with similar arterial size

- thin to absent media with loss or fragmentation of the internal elastic lamina

- not strictly congenital as usually develop ('acquired') over time

- more common in certain familial syndromes such as PKD (polycystic kidney disease), pseudoxanthoma elasticum, Ehlers-Danlos IV, Marfan's and neurofibromatosis

- but only 5% of patients with aneurysms have documented connective-tissue disorder

- however up to 20% of those with aneurysmal SAH have 1st or 2nd degree relative with confirmed aneurysm (1st-degree relatives have 4x risk of SAH vs general population)

- slightly greater risk with atherosclerotic disease, in women and if family history*

- having had SAH in past, increases risk of having another aneurysm and it rupturing (2% per year of new aneurysm formation)

Distribution:

- occur at vascular branching points

- most centered around the circle of Willis (at base of brain, in subarachnoid space)

- 20-30% are multiple, and often mirror (eg. bilateral MCA aneurysms)

- usually rupture at the dome

1. Anterior circulation (85%)

- ACA complex incl. Anterior Communicating (AComm) & pericallosal artery

- MCA bi-/trifurcation

- Internal Carotid Artery (esp at origin of PComm, ophthalmic, anterior choroidal, or terminus)

2. Posterior Circulation (15%)

- mostly at basilar tip, but also PICA

Having had an aneurysm rupture (ie. SAH) increases 'risk' of other unruptured aneurysms in same patient rupturing in future

Imaging aneurysms:

- typically with digital-subtraction (invasive) cerebral angiography (DSA) of all four cerebral vessels, but this has complication rate of 1-2% (may also increase rupture risk)

- missing even one vessel may lead to missing the aneurysm (eg. PICA from vertebral)

- new technology allows non-invasive diagnosis with MRA or CTA

- especially useful in low-risk patients such as family members or when looking for unruptured aneurysms / change in size over time - not want to expose patients to risk of DSA

- CTA may even be superior for surgical planning as allows 3-D visualisation including local bony anatomy (for surgical approach)

Screening for Asymptomatic Aneurysms:

- may be requested esp in family members of patients with aneursymal SAH or known heritable disorder (esp ADPKD)

- strong family history if two or more closely related family members with aneursyms (best to screen first-degree relatives only)

- one study found detection rate in this population was 9% (vs 5% in ADPKD, but certain families have phenotype expressing frequent aneurysms)

Management of Asymptomatic Aneurysms:

- if found incidentally, then have to balance future risk of rupture / complications (over entire lifetime) with risk of treatment (invasive with attendant complications from this)

- if risk of treatment (morbidity 15%, mortality 2%+) outweights lifetime risk of rupture and morbidity of SAH then best to observe

- most aneurysms never rupture and people live entire life not knowing have them (as found in most autopsy studies)

- studies shown that smaller aneurysms (esp < 7 mm) have very low risk of rupture; half risk if no prior Hx of SAH (annual rate 0.5% or less)

- generally felt that larger aneursyms, esp > 10 mm have higher risk (2% or more per year) and treatment should be considered

- if observe only, then follow-up angiography (eg MRA) at regular intervals to document increase in size

Perimesencephalic SAH; aka. pretruncal SAH

- accounts for 10% of SAH cases and 2/3 of those with normal angiogram

- combination of uncomplicated SAH presentation (HA without significantly reduced LOC or focal deficits), typical radiologic pattern (see above) and negative 4-vessel (ie full) cerebral angiography

- benign condition (no subsequent risk of serious rebleeding, vasospasm or missed aneurysm) thought to be due to venous bleeding from plexus anterior to pons / midbrain

- headache is sudden onset but may peak over minutes rather than seconds

- should not have significant reduction in LOC and no seizures

- slight risk of hydrocephalus as only complication

- recent finding that altered venous drainage exists in majority of these patients, supporting this hypothesis

- cannot diagnose in "angio-negative" SAH patients without this radiologic pattern, these patients have increased risk of rebleeding / vasospasm (aneurysm 'missed' or other lesion)

- similarly, typical CT findings do NOT obviate need for angiogram, as basilar aneurysm can produce identical (but far more serious) picture

- may do CT angiography in these patients so as not to expose them to risk of DSA and no need repeat angio if typical presentation and imaging, with one negative angio

Angiogram-Negative SAH:

- if perimesencephalic pattern on initial imaging (see above) then confirms nonaneursymal source (likely venous) and no repeated studies warranted (good prognosis)

- if "aneurysmal" pattern on CT scan then cannot reliably exclude aneurysm or other lesion with single negative angiogram

- these patients can still develop vasospasm and have risk of rebleeding (~ 10%)

- can miss aneurysm due to technical inadequacy (not correct projection, not do all 4 cerebral vessels), but also because of vasospasm, thrombosis or mass effect effacing aneurysm

- must repeat angiogram at 1 week (yield of 20%) and lesions occasionally even found on third or fourth angiogram (after months!)

Management of SAH

ABCs

- intubate and ventilate if hypoxemic or comatose (not protecting airway)

- see BP section below for management of circulation

Admission to close observation unit (such as NICU) with cardiac monitoring

- determine if parenchymal hematoma (incl. acute subdural hematoma) requires evacuation or hydrocephalus requiring external ventricular drainage

- high risk for deterioration (from rebleeding, vasospasm, sudden hydrocephalus etc)

NB: rebleeding risk 4% on first day and 2% per day thereafer for first month, up to 30% in 1st month

- rebleeding usually presents dramatically with obtundation, loss of brainstem reflexes, respiratory arrest and need for intubation (or fresh blood seen in drain bag if ventriculostomy placed !)

- CT scan should be done in any SAH patient who deteriorates (also detect hydrocephalus)

- consider emergency surgery if rebleed, give mannitol, hyperventilate (mortality 50%)

- rebleeding with enlargement of hematoma can also occur and cause worsening

- antifibrinolytic drugs have been tried to reduce rebleed risk and found to work but also increase morbidity by raising risk of cerebral ischemia

- need to be monitored for proper BP control and electrolyte / cardiac / metabolic control

- maintain nutritional support with enteric feeding if cannot take orally (delayed gastric emptying common which may necessitate metoclopramide if residuals) + stool softeners

- monitor respiratory status as risk of aspiration (if decreased LOC initially) or pulmonary edema

- DVT prophylaxis with stockings & pneumatic compression devices

- indwelling urinary catheters required if on mechanical ventilation / decreased LOC

Analgesia:

- oral analgesics if feasible including acetaminophen with codeine or oxycocet

- parenteral codeine or morphine

- may also help settle hypertension

BP in SAH

- when aneurysm unprotected, keep BP near patients normal MAP (if known) or MAP 70-110 mm Hg, treating if higher (eg. labetalol, if bradycardic use hydralazine) - to reduce risk of rebleeding (unproven)

- may allow higher BP once aneurysm secured (and promote hypertension as part of hyperdynamic therapy if vasospasm - see below)

NB: antifibrinolytic therapy should not be used as although it does reduce risk of rebleeding there is equal & reciprocal increase in risk of cerebral ischemia (no overall benefit)

Hydrocephalus:

- higher risk if intraventricular casting or high volume of blood

- early sign on initial CT is dilatation of temporal horns

- monitor closely for abrupt or progressive drowsiness / reduced LOC

NB: sudden dramatic change in neuro status may also be due to rebleeding

- classic finding of tectal compression is "sun-downing" with inability to look up (eyes set down) with mid-sized pupils

- recheck CT scan for increased size of ventricles; low threshold for placement of ventriculostomy

- delayed hydrocephalus can also occur, usually "communicating" type from blood obstructing CSF reabsorption through arachnoid villi (may require long-term ventricular shunting, eg. VP shunt)

Hyponatremia:

Cerebral salt wasting and SIADH both occur commonly after SAH

- mild hyponatremia (Na 125-134) usually well-tolerated and self-limiting

- avoid hypotonic fluids (lower Na) but maintain euvolemia (hypovolemia raises chance of spasm)

- follow I+O closely, monitor weight daily

- can use hypertonic saline if sodium continues to fall

- mineralocorticoids may also be useful incl. fludrocortisone acetate (Fluorinef) to maintain Na - but risk of pulmonary edema and hypertension with hypokalemia (close monitoring required)

- alternatively hydrocortisone has some effect without as many side-effects

Seizures:

- often use anticonvulsant prophylaxis, loading with IV phenytoin then continuing for at least 1 wk (in the absence of any evidence that their use helps)

- risk is 10% or less, mainly in first 1-2 weeks after ictus

- if persistent coma after seizure, consider non-convulsive status and order EEG

Vasospasm:

- major cause of residual neurological deficits in survivors of SAH

- reduced blood flow causes ischemia and focal cerebral infarcts

- not all of patients with angiographic vasospasm develop clinical vasospasm and some patients develop infarcts without large vessel apparent narrowing

- presents as new / emerging focal neurological deficits or change in mental status (drowsier)

- onset from day 3-4, peaking at days 5 to 9, and lasting till day 21

* best predicted by volume of subarachnoid blood on initial CT *

Fisher Scale:

1. No blood

2. Diffuse or thin vertical layer of blood < 1 mm thick (no clots > 3 mm thick)

3. Localized clots > 5 x 3 mm or layering > 1 mm thick

4. Intraventricular or intracerebral blood

- prophylaxis with nimodipine 60 mg po q4hr (can be crushed and put through NG tube) x 21 days

* proven in number of randomized trials and Cochrane meta-analysis (NNT < 20 to prevent poor outcome) *

- monitor with transcranial doppler (looking for elevation of flow velocities in vessels, eg. MCA) but confirm suspicion with angiogram (can also treat with angioplasty if found)

- MRI may show lesions on DW imaging also (even while asymptomatic)

- initiate hyderdynamic therapy to raise MAP 15-20%, keep CVP 8-12 mm Hg if even suspect

- may require Swan-Ganz catheter to titrate fluid therapy; keep urine output > 250 cc/hr

- fluids & volume expanders (incl. mineralocorticoids) till preload maximized (stroke volume peaks)

- keep MAP 25% above baseline or > 120 mm Hg (can use phenylephrine 10-30 ug/min)

- watch for cardiac ischemia and arrhythmias as myocardial demand increases

- if resistant to these measures, angiography with angioplasty should be considered

- papaverine intra-arterial infusion provides only transient increased flow and not used anymore unless very distal spasm or diffuse, not amenable to angioplasty

Failure to reverse the deficits suggestsinfarction has occurred (initial CT might not show fully)

- repeating CT scan later will show extent of infarcts

Global cerebral edema:

- present in 8% of initial CT scans but develops in additional 12% later in course (average of 6 days)

- higher risk if loss of consciousness initially, higher Hunt&Hess grade, greater SAH size, larger aneurysm or use of vasopressors

- likely related to microvascular dysfunction with reduced CPP worsening raised ICP (cycle)

- treated with mannitol

- some role of retraction during surgery in post-retraction edema formation

Cardiac Complications:

- EKG changes are common after SAH (can even mimic acute MI !)

- sympathetic response leads to "neurocardiogenic injury" with myocardial necrosis and release of cardiac enzymes (esp troponin)

- may follow with serial EKGs, cardiac monitoring, and troponin measurements

- if evidence of cardiac dysfunction, use beta-blockers and keep HR < 80

- usually reversible, improving over few days

- a recent study (Tung. Stroke 2004; 35: 548) found 20% of SAH patients had elevated troponin, more common with higher H+H score, lower SBP, higher heart rate and more in females / larger BSA

- echocardiograms in these patients often show LV dysfunction which is reversible ("stunned")

Fever in SAH:

- fever is common after SAH and the neurogenic type must be differentiated from secondary infections which are common (eg. pneumonia, urinary tract infection, ventriculitis) + risk of DVT

- found in at least 1/3 of patients after SAH (1/4 to 1/3 of these are neurogenic)

- more common in poor-grade intubated patients, higher Fisher grade / presence of vasospasm and presence of ventriculostomy

Securing the Aneurysm:

- evidence supports early intervention (first 3 days) for good-grade patients with aneurysmal SAH (while may delay for poor-grade till later or if vasospasm already begun when high risk of complications if operate)

- early treatment allows hyperdynamic therapy without increasing risk of rebleeding

- choices are clipping (or other surgical method) vs coiling (endovascular interventions)

- recent ISAT trial of aneurysms deemed favorable to either method showed slightly better outcomes at 1-year for coiled aneurysms; now coiling accounts for 50% or more of interventions

- some aneurysms not amenable to contemporary endovascular techniques due to wide neck (coils slip out and occlude parent vessel) or difficult to access (distal or tortuous, eg pericallosal)

- some concerns about long-term efficacy (durability) of coiling and incomplete thrombosis

NB: surgery may be required acutely if rebleeding or parenchymal hematoma requiring evacuation

Outcome after SAH

- 10% or more of SAH patients die before reaching the hospital

- most important determinants of outcome in those reaching hospital are SAH grade / GCS

(but must r/o other causes of depressed LOC esp hydrocephalus which is reversible)

- other important variables are age, location of aneurysm (posterior circulation worse) and delay in intervention; also more blood (Fisher grade) on initial CT predicts neurological morbidity

- failure to improve in high-grade patients (WFNS IV or V) despite 1-2 days of medical Rx (mannitol, ventriculostomy) portends extremely poor prognosis; most never awaken and die from complications (consider donation if brain death)

- 50% survive in the long-term while 1/3 of survivors remain dependent

NB: cardiac dysfunction even on echo (with normal coronary vessels) is not contraindication to cardiac transplantation

- long-term cognitive dysfunction common in survivors with affective and memory disorders, change in personality (frontal lobe infarction) and trouble concentrating

- small proportion will have complete recovery with no residual reduction in quality of life (10-15%)

- best outcome in pretruncal SAH with no rebleeding, vasospasm or cognitive difficulties

References:

Schievink WI. Intracranial aneurysms. N Engl J Med 1997; 336: 28-40.

van Gijn J, Rinkel GJE. Subarachnoid hemorrhage: diagnosis, causes, and management. Brain 2001: 124: 249-78.

Wijdicks EFM. The clinical practice of critical care neurology, 2e. 2003; Oxford University Press.

Last update: April 2004

Reviewed by: pending

Neurological Medicine Pocketbook

http://www.uwo.ca/cns/resident

Disclaimer