Subarachnoid hemorrhage due to middle cerebral artery dissection misdiagnosed as a saccular aneurysm - case report
Jong-Myong Lee, M.D
Department of Neurosurgery
Jeonbuk National University Hospital and Medical School,
Jeon-Ju, Korea
Corresponding author
Name: Jong-Myong Lee, M.D.
Zip code: 560-182
Address: Department of Neurosurgery,
Jeonbuk National University Hospital & Medical School,
San 2-20, Keumamdong, Dukjin-Gu, Jeon-Ju, Republic of Korea
Tel: +82-63-250-1870
FAX: +82-63-277-3273
E-mail: nsjmlee@gmail.com
Running title: SAH due to middle cerebral artery dissection
Abstract
Introduction: We report a case of subarachnoid hemorrhage due to a dissecting middle cerebral artery that was misdiagnosed as a saccular aneurysm.
Presentation of case: A 74-years old female patient presented with headache and neck pain for four days. Brain magnetic resonance imaging revealed subarachnoid hemorrhage in both Sylvian fissures. A ruptured left middle cerebral artery bifurcation saccular aneurysm and an unruptured basilar tip aneurysm were diagnosed.
Discussion: The patient was treated surgically using a transsylvian approach. However, no saccular aneurysm was found during surgery, and the diagnosis was corrected to middle cerebral artery dissection. We treated the dissected segment of the MCA and performed clip reinforcement.
Conclusion: We describe MCA dissection misdiagnosed as a saccular aneurysm without neurologic deficit despite total occlusion of the dissected segment of MCA. If dissection is suspected, MRI and angiography should be performed for diagnosis.
Keywords
Middle cerebral artery, Subarachnoid hemorrhage, Dissection
Abbreviations used in this paper.
SAH: Subarachnoid Hemorrhage
MCA: middle cerebral artery
MCAB: middle cerebral artery bifurcation
MRI: Magnetic Resonance Image
CTA: Computed Tomographic Angiography
ACA: anterior cerebral artery
TCD: transcranial Doppler
DSA: digital subtraction angiography
Introduction
Dissection of the intracranial artery is a relatively rare cause of stroke and subarachnoid hemorrhage (SAH).1 It has been reported more frequently in recent years. Intracranial dissection is recognized as a cause of stroke and subarachnoid hemorrhage because of the developed diagnostic tools and the recognition of dissecting aneurysms.2-4 Middle cerebral artery (MCA) dissections are classically rare and severe, presenting mostly as large MCA infarcts, SAH, or intracerebral hemorrhage.1,2,5-10
We present a case of MCA dissection with subarachnoid hemorrhage without an initial neurological deficit despite total occlusion of the dissected segment, which was misdiagnosed as a saccular aneurysm.
Consent for publication
Written informed consent was obtained from the patient for publication of this case report and accompanying images. This case report was conducted in accordance with the Declaration of Helsinki.
Case presentation
A 74-old female presented with severe headache and neck pain for four days. Initial brain MRI showed subarachnoid hemorrhage in both Sylvian fissures and no newly developed infarction. The Glasgow Coma Scale score was 15/15 and the SAH grade was II according to the Hunt and Hess grading system. The other neurological symptoms were unremarkable. The brain CT and CTA showed ruptured left middle cerebral artery bifurcation (MCAB) saccular aneurysm and unruptured basilar tip saccular aneurysm (Figure 1). Other investigations were normal, including electrolyte level, blood cell count, prothrombin and coagulation tests, and cholesterol levels.
The patient underwent surgery via a transsylvian approach. The intraoperative findings differed from our initial disgnosis: they showed no MCAB saccular aneurysm, MCA dissection, or severe atherosclerotic changes in the involved segment (Figure 2). Intraoperative transcranial Doppler (TCD) revealed that the dissected segment of the MCA had no blood flow. The small distal branch of the dissected segment had scanty blood flow. The dissected segment was wrapped, and clip reinforcement was performed (Figure 2). The postoperative neurologic symptom was transient right-leg weakness (Figure 3). However, the patient has fully recovered. Postoperative follow-up digital subtraction angiography (DSA) revealed no changes in the dissected MCA segment (Figure 4).
Discussion
We report a case of subarachnoid hemorrhage due to dissection of the MCA that was misdiagnosed as a saccular aneurysm. Intracranial artery dissection has become an important cause of stokes.8,10-14 Patients with dissected aneurysms may present with subarachnoid hemorrhage, cerebral infarction, or both.2,5,8,10-18
Dissections of the carotid and vertebral arteries usually arise from intimal tears.1 The intramural hematoma is located within the layers of the tunica media, but it may be eccentric, either toward the intima or adventitia.7 A Subintimal dissection tends to result in stenosis of the arterial lumen, whereas subadventitial dissection may cause aneurysmal artery dilatation.19
The supraclinoid segment of the ICA is the most common intracranial site for aneurysms with occasional extension into the MCA and/or ACA.20
The diagnosis of intracranial dissecting aneurysms is difficult, even with angiography and brain MRI. The angiographic characteristics of dissecting aneurysms include the pearl and string sign, narrowing, fusiform, dilatation, and occlusion, however, these are not specific.4,7,11 The pathognomonic sign for dissecting aneurysms may be double-lumen sign, but this is infrequently found.21-23 The optimal surgical procedure has not yet been established, however, surgical methods such as trapping with or without bypass surgery, ligation, or wrapping for ruptured MCA dissecting aneurysms have been reported.24,25
The incidence of symptomatic dissection aneurysms is thought to be much lower in the carotid system, than in the vertebrobasilar system, particularly, in the MCA.1
After dissection, a variety of lesions can develop including pseudoaneurysms, variable narrowing of the lumen, and occlusion of the vessel.7 Therefore, follow-up angiography is important for the correct diagnosis when a dissecting aneurysm is suspected.
Hemorrhage from a dissecting aneurysm may be unrecognized or misdiagnosed as an unexplained SAH because of the difficulty in the angiographic diagnosis.4,25,26 If angiography reveals luminal narrowing, vascular occlusion, or a non-saccular aneurysm in a patient with SAH, dissecting aneurysm of the carotid system should be considered as a likely cause of hemorrhage and infarction.2,4,25,26
In our case, MCA dissection was misdiagnosed as saccular aneurysm. Despite complete obstruction of the superior branch of the MCA, the patient showed no neurological deficits. Initial brain magnetic resonance image (MRI) revealed no newly developed acute cerebral infarction, and postoperative brain CT showed the same findings. There were two reasons for this finding. First, abrupt occlusion synchronized with progressive severe atherosclerotic occlusive disease. Second, the patient had the capacity to sustain collateral blood flow above the infarction threshold. Therefore, despite total occlusion of the dissected segment, the patient presented with only severe headache without neurological symptoms in the preoperative period. Postoperatively, she had experienced transient right-leg weakness without acute infarctions. The patient was discharged without neurological deficits.
Conclusion
We experienced MCA dissection with no neurological deficit despite total occlusion of the MCA branch, which was misdiagnosed as a saccular aneurysm.
Although we misdiagnosed saccular aneurysmal rupture, several options have been suggested for treating ruptured MCA dissection. If dissection is suspected, MRI and angiography should be performed for diagnosis.