Computed Tomography and Magnetic Resonance Imaging Findings of Bilateral Subdural Hematoma and Intracystic Hemorrhage in an Spontaneous Arachnoid Cyst Rupture

Abstract

Turkish Abstract

Introduction

Chronic subdural hematoma (SDH), has generally been believed to develop  in elderly people several weeks after a head trauma ¹. Also,  in young people arachnoid cysts were identified as a cause of SDH after head trauma  and are considered a risk factor for chronic SDH in this population ². Arachnoid cysts with bilateral SDH in the absence of head injury  are rare,  and intracystic hemorrhage associated with  SDH is even rarer ³.

In this report, we present computed tomography (CT)  and magnetic resonance imaging (MRI)  findings of a case  of arachnoid cyst with spontaneous  intracystic hemorrhage and  a bilateral subdural hematoma.

Case Report

A 42-year-old male presented with a 5 day history of headache and nausea. There was no history of preceding head trauma and his medical history was unremarkable. A non-contrast  head  CT showed a hyperdense extra-axial collection consistent with a bilateral subdural hematoma. (Figure 1a).

Figure 1A Figure 1A:Non-contrast axial head CT shows a bilateral subdural hematoma (arrows) that is hyperdense to the adjacent brain parenchyma.

A lobulated mass-like appearance of extra-axial hemorrhage within the anterior aspect of the right  middle cranial fossa was also noted (Figure 1b). There was also focal thinning with periosteal scalloping of both the squamous portion of the left temporal bone and of the adjacent greater wing of sphenoid bone (Figure 1c).

Figure 1C CT bone window image at the same level as Fig. 1B demonstrates scalloping of the inner table of the calvarium (Arrows).

On T2-weighted MR imaging (Figure 2a) the subdural collec­tion had a  hyperintense signal to adjacent brain pa­renchyma while on T1-weighted MR imaging (Figure 2b) the collection demonstrated increased signal intensity. These findings were consistent with late subacute hem­orrhage. Also on T2-weighted MR imaging hypointense bands consistent with hemosiderin deposits were also detected at the center of  hemorrhagic cyst in the middle cranial fossa (Figure 2c,d).The hemorrhagic cyst was mildly hyperintense to adjacent brain parenchyma and bilateral subdural hematoma was hyperintense to adjacent brain parencyma on T1 weighted  image.(Figure 2e)

Figure 2A Axial T2-weighted MR image shows bilateral subdural hematoma that is hyperintense to adjacent brain parenchyma

Figure 2B Axial T1-weighted MR image shows bilateral subdural hematoma that is hyperintense to adjacent brain parenchyma

Figure 2C Axial T2 weighted image demonstrates hemosiderin band at the center of hemorrhagic cyst.(Long arrows) Also a contralateral thin subdural haematoma is seen.(Short arrows)

Figure 2D Axial T2 weighted image demonstrates hemosiderin band at the center of hemorrhagic cyst.(Long arrows) Also a contralateral thin subdural haematoma is seen.(Short arrows)

Figure 2E Coronal T2 weighted image shows a hemorrhagic cyst which is mildly hyperintense to adjacent brain parenchyma located at enlarged right middle cranial fossa.(Long arrows).Also bilateral subdural hematoma that is hyperintense to adjacent brain parenchyma is seen.

With radiological findings, a diagnosis of intracystic hemorrhage and bilateral subdural hematoma secondary to arachnoid csyt rupture was made and a frontotemporal craniotomy with subdural hema­toma evacuation and arachnoid cyst fenestration was performed.

Discussion

Arachnoid cysts constitute approximately 1% of all intracranial space-occupying lesions ⁴. The middle cranial fossa, cerebral convexity, perisellar, retrocerebellar, cerebellopontine angle, and quadri­geminal plate cisterns are the most common locations ⁵.  It is believed  that these cysts form from an aberration in arachnoid development which results in splitting or duplication of the membrane, from a defect in condensation of the mesenchyme, or from abnormalities of cerebrospinal fluid (CSF)  flow ^5,6.

Arachnoid cysts are non-enhancing,  well-circumscribed extra-axial lesions with the same attenuation (on CT) or signal (on all MRI pulse sequences) as that of CSF  on both CT and MRI scans ⁵. They do not communicate with the ventricular system and have no identifiable internal architecture. Bony erosion and remodeling, features suggestive of a longstanding process, are commonly associated with arachnoid cysts. These findings are seen in nearly half of the cases and are thought to be secondary to chronic fluid accumulation with transmitted pulsations ^5,7.

Although,  most arachnoid cysts are asymptomatic, symptoms may due to  an increase of intracystic fluid or more rarely hemorrhage into the cyst itself and/or adjacent subdural space. Such hemorrhagic events may be commonly  post-traumatic or rarely spontaneous. Rupture of the outer arachnoid cyst wall and surrounding fragile veins leads  blood  accumulation within the cyst and/or subdural compartment ⁸. Intracystic hemorrhage can also be due to interruption of the highly vascular arachnoid cyst membrane or of the bridging veins traversing the cyst cavity.  Fluid production by flat arachnoid cells lining the cyst walls may explain spontaneous cyst enlargement and hemorrhage if sufficient intracystic pressure is attained to breech the wall and disrupt the vasculature ⁸.

Iaconetta et al.,  reviewed the literature that reported the very rare combination of intracystic bleeding with contralateral or bilateral subdural or extradural hematoma.They  documented  37 such cases  in the literature. In 21 cases (56.7%), there was ipsilateral subdural hematoma. Also, fourteen patients had a history of a previous head injury, whereas others did not ⁹.

Mori et al.,  reviewed  twelve cases of subdural hematoma with arachnoid cyst which were surgically treated in their instution. Arachnoid cysts were located in the middle fossa (eight cases), convexity (two cases), and posterior fossa (two cases) in their patients. Ten  of the 12 patients had a prior head trauma while two patients had spontaneous arachnoid cyst rupture leading to  subdural hematoma. Five patients had right-sided, five patients had left-sided and two patients had bilateral subdural hematomas. Six of 12 patients  had no radiologically demonstrated intracystic hematomas. All the radiologically demonstrated intracystic hematomas were demontrated on MRI. The most common clinical symptom was headache. Hematoma evacuation through burr holes improved the symptoms in all patients with arachnoid cyst ².

Patel et al.,  presented CT and MRI features of a case with a spontaneous subdural hematoma and intracystic hemorrhage in an arachnoid cyst. They well demonstrated enhanced dural membrane, not enhanced  arachnoid cyst and  the arachnoid membrane which separates hemorrhage in the subdural compartment  from hemorrhage inside the arachnoid cyst on contrast enhanced T1-weighted MR images ⁵.

Our patient also had a bilateral subdural hematoma which was associated with spontaneous arachnoid cyst hemorrhage. He had no head trauma or surgery history prior to presentation. He had a radiologically demonstrated intracystic hematoma  on both CT and  MRI. The low detection rates of intracytic hematoma on CT, can be attributed to the later phases of hematoma at the presentation. Also,  hyperdense intracystic hematoma, relatively  large and bilateral subdural hematoma which was seen in our patient may be secondary to an active bleeding.

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