A minor perimesencephalic subarachnoid hemorrhage on CT changes

doi:10.4236/wjns.2011.12004

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World Journal of Neuroscience, 2011, 1, 28-30 WJNS

doi:10.4236/wjns.2011.12004 Published Online August 2011 (http://www.SciRP.org/journal/wjns/).

Published Online August 2011 in SciRes. http://www.scirp.org/journal/WJNS

A minor perimesencephalic subarachnoid hemorrhage on CT

changes

Yeting Zhou1, Daoming Tong2

1Medical Evaluation Unit, Shuyang People’Hospital, Shuyang, China;

2Departments of Neurology, Shuyang People’Hospital, Shuyang, China.

Email: [email protected]

Received 2 July 2011; revised 25 July 2011; accepted 4 August 2011.

ABSTRACT

Despite the increasing number of reports of patients

with perimesencephalic subarachnoid hemorrhage

(PMSAH), a minor or atypical PMSAH on CT changes

has not been reported. We present the first described

case of a minor subarachnoid hemorrhage located in

the right perimesencephalic cistern on CT 4 h after

headache onset. Twenty-six hours after headache on-

set, another CT of the head showed that blood dis-

persion. On the third day in hospital, examination of

cerebrospinal fluid revealed xanthochromia. Minor

PMSAH is rare type of SAH, and can been missed if

there is a delay in CT imaging of the head. Any pa-

tient with a suspected minor PMSAH or equivocal

results on CT should undergo routine lumbar punc-

ture.

Keywords: Headache; Perimesencephalic Subarachnoid

Hemorrhage; CT Imaging; Lumbar Puncture;

Angiography

1. INTRODUCTION

Perimesencephalic subarachnoid hemorrhage (PMSAH)

appears to have an etiology and natural history distinct

from aneurysm rupture [1].

The radiographic pattern of PMSAH is relatively dis-

tinct. It involves hemorrhage centered anterior to the

midbrain or pons (with or without extension of blood

around the brainstem) into the sup rasellar cistern, or into

the proximal Sylvian fissure [2]. Headache from PMSAH

is a common presenting chief complaint. Despite the

increasing number of reports of patients with PMSAH [1,

3,4], a minor or atypical PMSAH has not been reported.

Here, we detail the rare case of CT changes in the brain

of a patient with headac he fr o m minor PMSAH.

2. CASE REPORT

A 36-year-old female was admitted to an affiliated hos-

pital of university because of headache. Five hours be-

fore hospital admission, she suddenly began to have a

headache without nausea or vomiting. Four hours after

the onset of headache, CT of the head revealed a minor

or equivocal subarachnoid hemorrhage (SAH) located in

the right perimesencephalic cistern (Figures 1(a) and (b)).

On physical examination, the blood pressure was 150/

72 mmHg. She was alert and oriented, with mild nuchal

rigidity. The results of the remainder of the physical ex-

amination were normal. Laboratory examinations, in-

cluding complete blood count, serum electrolytes, liver

Figure 1. Four hours after headache onset, CT of the head

revealed a minor or equivocal subarachnoid hemorrhage ((a)

and (b), arrow). Twenty-six hours after headache onset, CT of

the head showed that extravasated blood dispersed quickly ((c)

and (d)).

Y. T. Zhou et al. / World Journal of Neuroscience 1 (2011) 28-30 29

function test, and coagu lation studies were all normal. A

diagnosis of SAH was suspected (Hunt-Hess grade I

grade).

Twenty-six hours after the onset of headache, CT of

the head showed that extravasated blood dispersed

quickly (Figures 1(c) and (d)). On the third day of hos-

pital admission, examination of cerebrospinal fluid (CSF)

revealed xanthochromia, and cytologic examination of

CSF showed metemoglobin; these are characteristic fea-

tures of subarachnoid hemorrhage. On the fifth day of

hospital admission, digital subtraction cerebral angiogra-

phy did not demonstrate an aneurysm stemming from the

basilar, anterior cerebral, middle cerebral or posterior

cerebral arteries. The patient reported no specific risk

factors for arterial dissection (e.g., trauma) and had no

significant medical history of hypertension. We made a

diagnosis of minor PMSAH.

The patient was treated with intravenous anti-fibri-

nolytic agents. Within 3 days her symptoms and signs

had resolved. She was discharged home in excellent con-

dition 2 weeks after hospital admission. No further epi-

sodes occurred during the subsequent 12-month follow-

up.

3. CONCLUSION

PMSAH is diagnosed on the basis of CT or MRI. These

imaging methods demonstrate a localized area of hem-

orrhage centered within the perimesencephalic or pre-

pontine cisterns without intracerebral or intraventricular

extension [1,3]. Very few reports describe CT changes of

minor or atypical PMSAH.

Currently our patient, within 4 h after the onset of a

sudden headache, a minor or equivocal area of hemor-

rhage in the right perimesencephalic cistern was seen on

head CT. This suggested the possibility of minor PMSAH.

Twenty-six hours after headache onset, CT of the head

showed that extravasated blood had dispersed quickly.

On the third day of hospital admission, our patient re-

vealed xanthochromia by lumbar puncture, and cytologic

examination of CSF showed metemoglobin. A minor

PMSAH was demonstrated.

PMSAHs account for ~5% of all cases of subarach-

noid hemorrhage [5]. However, in our case, a typical

PMSAH was not revealed on head CT 26 h after head-

ache onset. Hence, the diagnosis of minor PMSAH

would have been missed if our patient with this condi-

tion had not presented to a hospital or delayed in the

time of CT scan.

CT may be less sensitive in patients with a SAH pre-

senting with “minor leaks” or normal neurological status

[6]. A diagnosis of SAH with a negative CT of the head

accounts for 7% of cases with SAH [7]. Therefore, we

speculated that the true prevalence of PMSAH may be

>5%. This also suggests that some patients with a SAH

with a negative finding on head CT may have a minor

PMSAH. One explanation of this finding is that some

patients have only a small amount of blood on initial CT

imaging and, in some patients, the extravasation might be

too small to be detected [6]. The present study showed

that a low grade on the Hunt-Hess scale, normal d iast olic

blood pressure, and a delay in the time of CT imaging

after hospital admission could be the cause of SAH with

negative findings on head CT [8]. Lumbar puncture

should therefore be carried out in any patient with sus-

pected SAH and negative (or equivocal) results on head

CT [9].

Studies indicate that most of the causes in patients

with PMSAH are non-aneurysmal [3,4], but some can

also be aneurismal [1,3,10]. In our patient, diagnostic

cerebral angiography did not reveal an aneurysm, but

aneurysmal PMSAH was not excluded. Minor PMSAH

is rare. Our case did not reveal typical PMSAH on CT. It

also serves as a reminder of the importance of lumbar

puncture and the variability of angiographic results dis-

played by PMSAH. PMSAH accounts for approximately

one-third of cases of non-aneurysmal SAH [5]. The re-

maining cases of non-aneurysmal SAH are heterogene-

ous, including SAH caused by vascular malformations,

venous bleeding [11], and not confined to cases of idio-

pathic SAH [5], Aneurysm rupture occasionally pro-

duces a PMSAH-like pattern of bleeding [10,12], In a

review of 3 large series concerning the neurological

complications associated with DSA, the complication

rate for patients with SAH was 0.25% [13], so studies

recommemded that CT angiography only is the most

beneficial approach in patients with a perimesencephalic

hemorrhage on CT, and accurately excludes and detects

vertebrobasilar aneurysms [12,14].

In conclusion, minor PMSAH is rare type of SAH,

and can been missed if there is a delay in CT imaging of

the head. Any patient with a suspected minor PMSAH or

equivocal results on CT should undergo routine lumbar

puncture.

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