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Review Article

Primary Care

PRIMARY CARE

A

VO IDIN G

P

ITFALLS

IN

THE

D

IAGNOSIS

OF

S

UBARACHNOID

H

EMORRHAGE

J

ONATHAN

A. E

DLOW

, M.D., AND

L

OUIS

R. C

APLAN

, M.D.

From the Departments of Emergency Medicine (J.A.E.) and Neurology(L.R.C.), Beth Israel Deaconess Medical Center and Harvard Medical School,Boston. Address reprint requests to Dr. Edlow at the Department of Emer-gency Medicine, Finard 202, 330 Brookline Ave., Boston, MA 02215, orat [email protected].

2000, Massachusetts Medical Society.

For it happens in this, as the physicians say it happens in hecticfever, that in the beginning of the malady it is easy to cure butdifficult to detect, but in the course of time, not having been ei-ther detected or treated in the beginning, it becomes easy to de-tect but difficult to cure.

Niccol Machiavelli, The Prince

ATIENTS with headache account for 1 to2 percent of visits to the emergency depart-ment

1-4

and up to 4 percent of visits to physi-cians offices.

5

Most have primary headache disorders,such as migraine and tension-type headaches. Onlya few patients have treatable secondary causes thatthreaten life, limb, brain, or vision,

1,3-5

such as sub-arachnoid hemorrhage (Table 1). Roughly 80 per-cent of patients with nontraumatic subarachnoid hem-orrhage have ruptured saccular aneurysms, whichoccur in 30,000 patients annually in the UnitedStates.

6

Among the remaining 20 percent, about half

have nonaneurysmal perimesencephalic hemorrhag-es.

7,8

The initial diagnostic approach is the same forboth groups.

Among all patients with headache who presentedto emergency departments, retrospective studies

1,3,4

have found that approximately 1 percent had subarach-noid hemorrhage. One prospective study

9

put thatfigure at 4 percent. Two prospective studies found thatif only patients with the worst headache of theirlives and a normal neurologic examination were con-sidered, 12 percent of such patients had subarachnoidhemorrhage.

9,10

This proportion increased to 25 per-cent when patients whose examinations were abnor-mal were included.

10

The initial hemorrhage may be fatal, may result indevastating neurologic outcomes, or may produce rel-atively minor symptoms. Because early definitive sur-

P

gery to repair aneurysms reduces short-term com-

plications (primarily recurrent bleeding and vasos-pasm) and improves outcomes,

11

accurate early diag-nosis is critical. Despite the widespread availability ofneuroimaging equipment, misdiagnosis of subarach-noid hemorrhage remains common,

12,13

and it is animportant cause of litigation related to emergencymedicine.

14

This review is intended to provide primarycare and emergency physicians with a strategy for iden-tifying patients who should be evaluated for sub-arachnoid hemorrhage and establishing the diagnosis.

SCOPE OF THE PROBLEMOF MISDIAGNOSIS

The typical patient with subarachnoid hemorrhage

has a sudden onset of severe headache (frequently de-scribed as being the worst headache of his or her life)that develops during exertion. Transient loss of con-sciousness or buckling of the legs often accompaniesthe headache. Vomiting soon follows. The physicalexamination may show retinal hemorrhages (Fig. 1),nuchal rigidity, restlessness, a diminished level of con-sciousness, and focal neurologic signs (Table 2). Pa-tients with these classic findings present little di-agnostic difficulty. However, in the absence of suchsymptoms and signs, clinicians often miss the diag-nosis, as several studies have demonstrated.

During the 1980s, 23 to 37 percent of all patientsreferred to the University of Iowa with subarachnoidhemorrhage were given an incorrect diagnosis on theirfirst visit to a physician.

15,16

These patients tended tobe less ill than those given a correct diagnosis and tohave normal neurologic examinations.

Among patients treated at four Connecticut neu-rosurgical units in the 1990s, 25 percent of patients

with subarachnoid hemorrhage initially received anincorrect diagnosis; most of them were in good clin-ical condition at presentation.

13

The condition of halfthe 54 patients with an incorrect diagnosis wors-ened, usually as a result of recurrent bleeding, beforedefinitive treatment was begun. Of the 163 patientsgiven a correct diagnosis, the condition of only 2.5percent worsened. Among patients who were in goodclinical condition when first seen, 91 percent of pa-tients with a correct diagnosis had good or excellentoutcomes at six weeks, as compared with 53 percentof patients with an incorrect diagnosis. British inves-tigators also found that half of a series of patients withsubarachnoid hemorrhage initially received an incor-rect diagnosis; 65 percent had recurrent bleeding be-fore a correct diagnosis was given.

12

Table 3 shows the results of these four studies inwhich a substantial proportion of patients were giv-

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January 6, 2000

The New England Journal of Medicine

en an incorrect diagnosis. Frequent misdiagnosis hasalso been documented in the Netherlands,

17

Portu-gal,

18

and Australia.

19

In the International CooperativeStudy on the Timing of Aneurysm Surgery, involv-ing 68 centers in 14 countries, nearly half the eligi-ble patients with aneurysmal subarachnoid hemor-

rhage were excluded because of a delay of more thanthree days before referral.

20

Three facts are clear. First, physicians consistentlymisdiagnose subarachnoid hemorrhage. Second, thepatients with the greatest likelihood of benefitingfrom surgery are the ones who most often receive anincorrect diagnosis. Third, early complications devel-op in patients with an incorrect diagnosis, resulting in

worse outcomes more often in these patients than inthose initially given a correct diagnosis. Misdiagnosisstems from three recurring, correctable patterns ofdiagnostic error: failure to appreciate the spectrum ofclinical presentation, failure to understand the limi-

tations of computed tomography (CT), and failureto perform and correctly interpret the results of lum-bar puncture (Table 4).

THE SPECTRUM OF PRESENTATION

Warning Headache

Between 20 and 50 percent of patients with docu-mented subarachnoid hemorrhage report a distinct,unusually severe headache in the days or weeks be-fore the index episode of bleeding, referred to as a

warning headache.

21-28

These so-called thunderclapheadaches develop in seconds, achieve maximal inten-sity in minutes, and last hours to days. The differen-tial diagnosis includes subarachnoid hemorrhage

29-31

;acute expansion, dissection, or thrombosis of unrup-tured aneurysms

32

; cerebral venous sinus thrombo-sis

33

; brief headaches during exertion and sexual in-tercourse

34

; and benign thunderclap headache.

31

Allpatients with thunderclap headache should be eval-uated for subarachnoid hemorrhage.

Deviations from the Classic Presentation

Roughly half of all patients with subarachnoidhemorrhage have episodes of minor bleeding, often

*These causes are diseases or conditions that aretreatable and that, if untreated, threaten life, limb,brain, or vision.

T

ABLE

1.

C

AUSES

OF

H

EADACHE

T

HAT

R

EQUIRE

S

PECIFIC

T

HERAPY

.*

Subarachnoid hemorrhage

Meningitis

Encephalitis

Cervicocranial-artery dissection

Temporal arteritis

Acute angle-closure glaucoma

Hypertensive emergency

Carbon monoxide poisoning

Pseudotumor cerebri

Cerebral venous and dural sinus thrombosis

Acute stroke (hemorrhagic or ischemic)

Mass lesionTumor

AbscessIntracranial hematoma (parenchymal,

subdural, or epidural)Parameningeal infection

Figure 1.

Subhyaloid Hemorrhage.

The retina of the right eye of a patient with aneurysmal sub-

arachnoid hemorrhage has small, flame-shaped hemorrhages(arrowheads) and a large subhyaloid hemorrhage (arrow) tem-poral to the optic disk. At the inferior margin of the subhyaloid

hemorrhage, the blood forms layers in a gravity-dependent fash-ion. Ocular hemorrhages in patients with subarachnoid hemor-rhage can be flame-shaped, subhyaloid, or vitreous and are

thought to result from an acute increase in intracranial pressurethat causes obstruction of venous outflow from the eye. Thesehemorrhages may be the only clue to the underlying cause in

unconscious patients with subarachnoid hemorrhage. (Provid-ed by Dr. John J. Weiter.)

*Sixth-nerve palsy may also be associated with nonspecific changes relatedto increased intracranial pressure.

T

ABLE

2.

P

HYSICAL

F

INDINGS

IN

P

ATIENTS

WITH

S

UBARACHNOID

H

EMORRHAGE

.

F

INDING

L

IKELY

L

OCATION

OF

A

NEURYSM

Nuchal rigidity Any

Diminished level of consciousness Any (could result from possiblecomplications of aneurysmal rup-ture: hydrocephalus, hematoma,or ischemia)

Papilledema Any

Retinal and subhyaloid hemorrhage Any

Third-nerve palsy Posterior communicating artery

Sixth-nerve palsy Posterior fossa*

Bilateral weakness in legs or abulia Anterior communicating artery

Nystagmus or ataxia Posterior fossa

Aphasia, hemiparesis, or left-sidedvisual neglect

Middle cerebral artery




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31

with atypical features.

35,36

Among 500 patients withsubarachnoid hemorrhage in one series, the conditiondeveloped in 34 percent during nonstrenuous activ-ities and in 12 percent during sleep.

37

The headachemay be in any location, may be localized or gener-

alized, may be mild,

38

may resolve spontaneously, ormay be relieved by nonnarcotic analgesics.

39

Patientswith such less severe headaches are incorrectly givena diagnosis of a more common condition pos-sibly migraine, tension-type, or sinus-related head-aches.

12,13,15-17

Even these less severe types of head-ache tend to develop abruptly and have a distinctivequality. When vomiting is prominent, especially if ac-companied by low-grade fever, viral syndrome, viralmeningitis, influenza, or gastroenteritis is often diag-nosed.

12,13,15-17

Patients with prominent neck painmay be given a diagnosis of cervical sprain or arthri-tis,

12,15,16,40 and those with blood irritating the lum-bar theca may be given a diagnosis of sciatica.

15,38

Pa-tients who are confused, agitated, or restless and whoare unable to give cogent histories may receive pri-mary psychiatric diagnoses.

12,13,15-17,38

According to the International Headache Society,a first episode of severe headache cannot be classifiedas migraine or tension-type headache; diagnostic cri-teria require multiple episodes with specific character-istics (more than 9 episodes for tension-type headacheand more than 4 episodes for migraine without au-ra).

41

Although patients with primary headache dis-

orders must have their first headache at some point,the diagnosis cannot be made definitively at that time.The first or worst headache requires evaluation, as doqualitatively different headaches in patients with es-tablished headache patterns, even if the headache is

not the worst ever.In patients with unruptured aneurysms, seizures,

mass effect, cranial neuropathy, or brain ischemia frompassage of a clot into the territory distal to the aneu-rysm may also develop.

32

Typically, aneurysmal third-nerve palsy dilates the pupil, whereas microvascularinfarction does not, although there are exceptions.

42

Patients with partial lesions that spare the pupil mustbe evaluated for the presence of aneurysms.

Secondary Head Injury, High Blood Pressure,and Abnormal Electrocardiographic Findings

Diagnostic ambiguity arises in patients with sub-arachnoid hemorrhage who lose consciousness, fall,and sustain head injuries.

13,16,43

Blood seen on CTscanning may be incorrectly attributed to trauma,the most common cause of blood in the subarach-noid space. Some patients may have high blood pres-sure, with or without alterations in consciousness.

20

Excessive focus on blood pressure may lead to theincorrect diagnosis of primary hypertensive emer-gency.

13,15,16

Up to 91 percent of patients with sub-arachnoid hemorrhage have cardiac arrhythmias,

44

andelectrocardiographic patterns mimicking myocardial

*Some patients had more than one diagnosis.

The numbers in parentheses denote the percentages of patients with the particular misdiagnoses among all patients with an incorrectdiagnosis.

T

ABLE

3.

F

REQUENCY

OF

M

ISDIAGNOSIS

OF

S

UBARACHNOID

H

EMORRHAGE

.*

V

ARIABLE

N

EIL

-D

WYER

AND

L

ANG

12

M

AYER

ET

AL

.

13

K

ASSELL

ET

AL

.

15

A

DAMS

ET

AL

.

16

A

LL

S

TUDIES

Overall

Patients with incorrect diagnosis no./total no. (%) 69/136 (51) 54/217 (25) 56/150 (37) 41/182 (23) 220/685 (32)Delay in diagnosis days

MedianRange

8141180

37130

3.6050

47127

60180

no. of patients no. (%)

Specific misdiagnoses

No diagnosis or headache of unknown cause 45 7 0 0 52 (24)Migraine, cluster, or tension headache 9 13 17 8 47 (21)Meningitis or encephalitis 4 8 8 3 23 (10)Systemic infection (influenza, gastroenteritis, or viral syndrome) 6 0 7 10 23 (10)Stroke or cerebral ischemia 1 7 7 2 17 (8)Hypertensive crisis 0 4 5 7 16 (7)Cardiac causes (myocardial infarction, arrhythmia, and syncope) 0 0 11 3 14 (6)Sinus-related condition 0 4 6 3 13 (6)Neck problem (disk-related or arthritis) 3 0 4 4 11 (5)Psychiatric diagnosis (including malingering and alcohol

intoxication)1 2 4 3 10 (5)

Trauma-related condition 0 2 0 1 3 (1)Back pain 0 0 1 0 1 (


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January 6, 2000


ischemia or infarction are seen, resulting in the er-roneous diagnosis of a primary cardiac disorder.

15-17

Despite these caveats, most patients with subarach-noid hemorrhage have abrupt onset of severe, uniqueheadache or neck pain. Many will have abnormal find-ings on neurologic examination, if only subtle men-ingismus or ocular findings. An understanding of this

wide spectrum of clinical presentation, coupled witha careful history taking and physical examination thatactively targets these diagnostic clues, is the beststrategy for identifying patients who should be eval-uated for subarachnoid hemorrhage.

LIMITATIONS OF CT SCANNING

The first diagnostic study should be noncontrast CT(Fig. 2).

6-8,11,45 Technique is important. Very thin cuts(3 mm in thickness) through the base of the brainare recommended, because thicker cuts (10 mm) misssmall collections of blood.46 The plane of scanningshould be parallel to the hard palate.46 Blood and ad-

jacent bone, which both appear white, can be dif-ficult to distinguish from one another, especially insmall hemorrhages. Because the increased density ofblood on CT is a function of the hemoglobin con-

TABLE 4. REASONS FOR MISDIAGNOSISOF SUBARACHNOID HEMORRHAGE.

Failure to appreciate the spectrum of presentations of subarachnoidhemorrhage

Failure to evaluate patients with warning headaches (severe, abrupt, un-

usual headaches)Failure to recognize that headache can improve spontaneously or with non-

narcotic analgesic drugsOverreliance on the classic presentation, leading to the following incorrect

diagnoses:Viral syndrome, viral meningitis, or gastroenteritisMigraine or tension-type headacheSinus-related headacheNeck pain (rarely, back pain)Psychiatric disorders

Focus on secondary head injury (resulting from syncope)Focus on electrocardiographic abnormalitiesFocus on high blood pressureLack of knowledge of presentations of unruptured aneurysm

Failure to understand the limitations of computed tomography

Loss of sensitivity with increasing time between onset of headache andscanning

False negative results in cases of small-volume bleeding (spectrum bias)Interpretation factors (e.g., variations in expertise of physician reading the

scan)Technical factors (e.g., variations in thickness of slices taken at the base of

the brain, motion artifact)False negative results for blood with a hematocrit of less than 30 percent

Failure to perform lumbar puncture and correctly interpret cerebro-spinal fluid findings

Failure to perform lumbar puncture in patients with negative, equivocal, orsuboptimal results on computed tomography

Failure to recognize that xanthochromia may be absent very early (2 weeks after hemorrhage)

Failure to realize that visual inspection for the presence of xanthochromiais less sensitive than spectrophotometry

Failure to distinguish properly between traumatic tap and true subarach-noid hemorrhage

Figure 2. Subarachnoid Hemorrhage on CT Scan.

A 34-year-old woman presented to the emergency departmentwith headache. While sitting at her desk three hours earlier, shehad had a syncopal episode, followed immediately by a moder-

ate-intensity, unusual, localized headache in the left frontal and

temporal areas. She was awake and alert and had no meningeal,ophthalmologic, or neurologic signs. The CT scan without con-

trast material showed blood in the subarachnoid space. In Pan-el A, blood fills the basal cisterns and extends into the sylvianfissures bilaterally and the interhemispheric fissure anteriorly.

In Panel B, the blood in the more rostral sylvian fissures is moredifficult to see. Both images show enlarged lateral, third, andfourth ventricles, indicating the presence of communicating hy-

drocephalus.

B

A




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centration,46 blood with a hemoglobin concentra-tion below 10 g per deciliter may appear isodense.47

Artifacts of motion in the scans of restless patients canrender such scans technically suboptimal and obscurethe diagnosis.

The sensitivity of CT decreases over time from

the onset of symptoms; the dynamics of cerebrospinalfluid and spontaneous lysis can result in the rapidclearing of subarachnoid blood.48 In the InternationalCooperative Study of the Timing of Aneurysm Sur-gery, over 3500 patients with aneurysmal subarach-noid hemorrhage underwent scanning with the typeof CT equipment in use between 1980 and 1983.Ninety-two percent of the scans were positive on theday of rupture, but this percentage declined to 86 per-cent one day later, 76 percent two days later, and 58percent five days later.20 In another study, 85 percentof scans were positive five days after rupture and 50percent at one week.49

Four studies have evaluated modern, third-gener-

ation CT scanners.9,48,50,51 Retrospective studies ofpatients admitted to the hospital with subarachnoidhemorrhage indicate that 100 percent of patients whounderwent scanning in the first 12 hours (80 of 80)50

and 93 percent of patients studied within the first 24hours (134 of 144)51 after the onset of headache hadpositive findings on CT scanning. Prospective stud-ies of outpatients found a sensitivity of 98 percent(117 of 119) for scanning performed in the first 12hours48 and 93 percent (14 of 15) for scanning per-formed in the first 24 hours.9

In three of these studies,9,48,50 expert neuroradiol-ogists interpreted the CT scans, but in many hospitalssuch experts are not available. The fourth study,51 in

which the readings of the initial radiologist were used,found a sensitivity of 93 percent for scanning per-formed within 24 hours after the onset of symptoms.Skill in correctly identifying hemorrhage on CT varies

widely among emergency physicians, neurologists, andgeneral radiologists.52 Less experienced physiciansundoubtedly miss subtle abnormalities.

Spectrum bias is another issue; alert patients aremore likely to seek care later and have normal CTscans than those with diminished mental status.20 Inthe International Cooperative Study, 15 percent of638 alert patients had normal scans.53 Patients withsmall hemorrhages, who are the most likely to receivean incorrect clinical diagnosis, are also more likely tohave negative results on CT.48 Although magnetic res-onance technology is continually advancing and candetect aneurysms, standard magnetic resonance imag-ing is inferior to CT for the detection of acute sub-arachnoid hemorrhage.54 Magnetic resonance imag-ing with fluid-attenuated inversion recovery showspromise,55 but CT remains the imaging method ofchoice because of its wider availability, lower cost, andgreater convenience for ill patients and because thereis wider experience with its interpretation.56

LUMBAR PUNCTURE ANDINTERPRETATION OF FINDINGS

Lumbar puncture should be performed in a pa-tient whose clinical presentation suggests subarachnoidhemorrhage and whose CT scan is negative, equivo-cal, or technically inadequate.6-8,45,48 This recommen-

dation, however, is often not followed in practice.9Lumbar puncture as a first strategy, postulated to becost effective in carefully selected patients who havecompletely normal physical examinations,57 may besafe but has not been studied clinically.

Duffy reported that of 55 patients who underwentlumbar puncture as the initial means of diagnosingsubarachnoid hemorrhage, the condition of 7 dete-riorated immediately thereafter.58 Hillman describedfour alert patients with subarachnoid hemorrhage

whose neurologic condition deteriorated after lumbarpuncture.59 In both studies, all the patients whose con-dition deteriorated had either clots on CT or a di-lated pupil. Patients with possible bacterial meningi-

tis should be treated with antibiotics while awaitingimaging.

Even when lumbar punctures are performed, er-rors are sometimes made in interpreting cerebro-spinal fluid findings. The cerebrospinal fluid pressureshould always be measured. High intracranial pres-sure is an important clue in the occasional patient

with cerebral venous sinus thrombosis33 or pseudot-umor cerebri and may help distinguish bleeding dueto traumatic lumbar puncture from true subarach-noid hemorrhage.60

Traumatic taps occur in up to 20 percent of lum-bar punctures61 and must be distinguished from truehemorrhage. Depending on the method of detection,between 0.5 and 6.0 percent of the population hasincidental intracranial aneurysms.11 Misinterpretationof a traumatic tap in a patient with an incidental an-eurysm can precipitate potentially risky diagnostic andtherapeutic interventions, so distinguishing traumatictaps from true hemorrhages is critical. Neither the im-pression of the operator nor the time-honored three-tube method, in which one looks for a diminishingerythrocyte count in three successive tubes of cere-brospinal fluid, is entirely reliable in identifying a trau-matic tap.7,62 A finding of crenated erythrocytes isalso without value.7 Erythrophages are found incon-sistently in the cerebrospinal fluid62,63 and may takedays to develop.7 The use ofD-dimer levels in cere-brospinal fluid to differentiate true hemorrhage fromtraumatic tap has proved inconsistent.9,63,64 If clear flu-id is obtained on a second puncture one interspacehigher than the initial tap, then it is likely that thefirst puncture was traumatic.60

After aneurysmal hemorrhage, erythrocytes rapid-ly disseminate throughout the subarachnoid space,

where they persist for days or weeks and then are grad-ually lysed.56,60 Released hemoglobin is metabolizedto the pigmented molecules oxyhemoglobin (reddish




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34 January 6, 2000


pink) and bilirubin (yellow), resulting in xanthochro-mia. Oxyhemoglobin can be detected within hours.The formation of bilirubin, an enzyme-dependentprocess, is diagnostically more reliable but requires upto 12 hours to occur.60,65 Timing is therefore impor-tant in interpreting the results of a lumbar puncture;

cerebrospinal fluid should be centrifuged and exam-ined promptly so that erythrocytes resulting frombleeding during lumbar puncture do not undergo lysisin vitro, producing xanthochromia from oxyhemo-globin.

Most authorities agree that the presence of xantho-chromia is the primary criterion for a diagnosis of sub-arachnoid hemorrhage in patients with negative CTscans.7,8,61 Others contend that the presence of eryth-rocytes, even in the absence of xanthochromia, is moreaccurate.66 These divergent opinions may be explainedby the various methods of detecting xanthochromia.Those who believed that xanthochromia is most im-portant used spectrophotometry, whereas those who

believed that erythrocytes are most important usedvisual inspection, which can miss discoloration in upto 50 percent of specimens.67

In a study by Vermeulen et al., all 111 patients withsubarachnoid hemorrhage who underwent lumbarpuncture between 12 hours and 2 weeks after the on-set of symptoms had xanthochromic cerebrospinalfluid, as determined by spectrophotometry.68 Vermeu-len et al., along with others, recommend waiting 12hours after the onset of headache, so that a traumaticfirst attempt undertaken earlier does not lead to xan-thochromia and diagnostic confusion when a subse-quent puncture is performed.7,8,57,68,69 The disadvan-tages of delaying lumbar puncture for 12 hours are

primarily logistic (e.g., the prolongation of a patientsemergency department stay). In addition, there is thepotential for ultra-early rebleeding that is, with-in the first 12 hours after hemorrhage.70

We do not advocate delayed lumbar puncture inpatients with negative CT scans. Patients with per-sistently bloody cerebrospinal fluid without xantho-chromia (as determined by any method in patientspresenting in the first 12 hours after the onset of head-ache and as determined visually in patients present-ing after 12 hours) should undergo vascular imaging

when the level of clinical suspicion of subarachnoidhemorrhage is high. This approach also applies to pa-tients with xanthochromic cerebrospinal fluid.

If CT or lumbar puncture indicates the presence ofsubarachnoid hemorrhage, consultation with a spe-cialist and vascular imaging are indicated. What if theevaluation is negative? Is vascular imaging indicated insuch patients? Day and Raskin reported on a patient

with explosive headache and negative results on CTand lumbar puncture who, on angiography, had anunruptured internal-carotid-artery aneurysm and va-sospasm.71 The aneurysm was clipped, and the patientrecovered. Raps et al. described seven other patients

with unruptured aneurysms and thunderclap head-

aches.32On the other hand, in a retrospective evaluation

of 71 patients with thunderclap headaches whose re-sults on CT and lumbar puncture were negative, noneof the patients had subarachnoid hemorrhage duringan average follow-up period of 3.3 years.72 Nearly half

were later given a diagnosis of migraine or tensionheadache. Furthermore, in three prospective studiesin which a total of 117 patients with thunderclap head-aches and negative findings on CT and lumbar punc-ture were followed for over one year, none of thepatients had hemorrhage or died suddenly.10,30,73

CONCLUSIONS

The data described above strongly support twoconclusions. First, most warning headaches are, in re-ality, indications of unrecognized subarachnoid hem-orrhages that can be diagnosed by appropriate meth-ods. Second, properly performed and interpreted CTand lumbar puncture in patients with acute, severeheadache will identify the vast majority of patients

with subarachnoid hemorrhage. Symptomatic treat-ment of the headache, discharge, and outpatient fol-low-up are a safe practice in patients whose results

*Patients with this risk factor are at very high risk for an-eurysm; clinicians should consider a consultation with a spe-cialist and noninvasive vascular imaging for such patients, even

when the results of computed tomography and lumbar punc-ture are negative.

TABLE 5. FACTORS INDICATINGA HIGH RISKOF ANEURYSMAL SUBARACHNOID HEMORRHAGE.

Clinical history

Onset of headache: abrupt, maximal at onset, thunderclapheadache

Severity of headache: usually worst of life or very severeQualitative characteristics: first headache ever of this inten-sity, unique or different in patients with prior headaches

Associated signs and symptomsLoss of consciousness*Diplopia*Seizure*Focal neurologic signs*

Epidemiologic factors

Cigarette smokingHypertension

Alcohol consumption (especially after a recent binge)Personal or family history of subarachnoid hemorrhage*Polycystic kidney disease*Heritable connective-tissue diseases

EhlersDanlos syndrome (type IV)Pseudoxanthoma elasticumFibromuscular dysplasia*

OtherSickle cell anemia

Alpha1-antitrypsin deficiency

Physical findings

Retinal or subhyaloid hemorrhage*Nuchal rigidity*

Any unequivocal neurologic finding (focal or generalized)*




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are normal. Important exceptions are patients present-ing more than two weeks after the onset of symptoms,

who often have negative CT findings and may havenormal cerebrospinal fluid. Also, some patients whosediagnostic-test results are ambiguous or who are atunusually high risk for aneurysm (Table 5) should un-

dergo neurologic or neurosurgical consultation andvascular imaging by magnetic resonance, CT, or con-ventional catheter angiography.

REFERENCES

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