J Neurosurg 48:642-644, 1978

Basal rupture of saccular aneurysm A pathological case report

C. MILLER FISHER, M.D., AND ROBERT G. OJEMANN, M.D.

Neurological and Neurosurgical Services, Massachusetts General Hospital, and the Department of Neurology and Neurosurgery, Harvard Medical School, Boston, Massachusetts In a case of subarachnoid hemorrhage, the arteries of the circle of Willis were left undisturbed and undissected at postmortem examination. A block of frontal lobe tissue with the attached vessels was serially sectioned disclosing in its entirety a saccular aneurysm that had ruptured at the base rather than the dome. The histology of the hemostatic process was clearly depicted. KEY WORDS

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aneurysm

T is generally accepted that the site of rupture of an aneurysm is at the dome, and proof of rupture elsewhere is rarely forthcoming. Crawford ~ using a dissecting microscope post mortem found that three aneurysms of 163 (2%) had bled from the cervical segment or base. His illustration, however, shows an unusually large hole in the wall of the aneurysm. In the microscopic study of the case r e p o r t e d here of cerebral vasospasm associated with subarachnoid hemorrhage (SAH), the middle cerebral and anterior cerebral arteries were left undisturbed, being neither dissected nor examined. A large block of the frontal lobes with the arteries in place was embedded in paraffin, serially sectioned, and stained with phosphotungstic acidhematoxylin. A ruptured aneurysm measuring 7 mm in length, which lay at the bifurcation of the internal carotid into the middle and anterior cerebral arteries, was examined microscopically in its entirety. It was clearly demonstrated that the site of rupture was not

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at the dome but at the neck of the aneurysm, less than l mm from the parent vessel. The sections also provided an unusual opportunity to visualize the histological appearance of the hemostatic process at the site of rupture, 11 days after a hemorrhage, with the tissues of the aneurysm unmarred by the gross dissection of a prosector. Case Report

This 59-year-old man suddenly developed a severe headache and momentarily dropped to his knees. On examination, the cerebrospinal fluid was bloody. The patient was relatively a s y m p t o m a t i c , but 9 days after the hemorrhage he developed a right hemiplegia and aphasia over a period of about 6 hours. Angiography the next day showed narrowing of the lumen of the left middle cerebral artery to less than 0.5 mm. The patient died 13 days after S A H . H e had received epsilonaminocaproic acid, an antifibrinolytie agent, for 5 days before death. J. Neurosurg. / Volume 48 / April, 1978

Basal rupture of saccular aneurysm

FIG. 1. Diagram of the aneurysm.

Neuropathoiogicai Findings There was infarction bilaterally in the territory of the middle and anterior cerebral arteries. In the region of the dome, the wall of the aneurysm was about 1 m m thick and con-

sisted of c o l l a g e n o u s connective tissue, whereas at the neck, the wall around the whole circumference was approximately onethird as thick (Figs. 1 and 2). It appeared as if the body of the aneurysm under the pulsating blood pressure were being lifted from its base like a tethered parachute. A small fibrin-filled gap in the wall marked the site of rupture which lay superiorly and anteriorly in the attenuated neck of aneurysm about 1 m m from the parent artery (Fig. 3). The orifice was reconstructed, using the serial sections, and it was estimated that it measured about 0.5 X 0.14 m m . Directly external to the aneurysm at the site of rupture was a large mass of fibrin embedded in which were platelet masses and "bleeding globes.'" There was no t h r o m b u s or clot within the lumen of the aneurysm, and the wall at the site of rupture bulged outward slightly. The site of rupture appeared to be sealed by a fibrin mass that was largely external to the aneurysm. A

FIG. 2. Section of the aneurysm (AN) showing the intact wall and cap of connective tissue at the dome. Arrow indicates site of rupture. ACA = anterior communicating artery. PTAH, X 15. J. Neurosurg. / Volume 48 / April, 1978

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FIG. 3. Site of rupture with fibrin-filled gap and adjacent subarachnoid blood. This section lies in frontal plane 250 u posterior to that shown in Fig. 2. ACA = anterior cerebral artery. AN = aneurysm. PTAH. • 15. tiny subarachnoid artery was applied to the wall of the aneurysm at one side of the rupture. Comment

The n e u r o s u r g e o n in occluding an aneurysm of this type would find it difficult to apply a clip proximal to the site of rupture. There is also the danger that rupture of such an aneurysm might occur at the base during surgical manipulation. Spontaneous arrest of bleeding seemed not to be influenced by the basal rupture, and h e m o r r h a g e apparently ceased with the usual promptness. In a similarly studied aneurysm in another case, the orifice of rupture was also small, measuring about 0.75 m m in diameter, quite different from the gaping patulous hole often depicted in aneurysms from which the subarachnoid blood has been dissected. 644

Since it is not unusual to find a cap of connective tissue in the dome of an unruptured saccular aneurysm, rupture at a site other than the d o m e m a y be more c o m m o n than suspected. Reference

1. Crawford T: Some observations on the pathogenesis and natural history of intracranial aneurysms. J Neuroi Neurosurg Psychiatr 22:259-266, 1959

This study was supported in part by NINCDS Grant NS05152. Address reprint requests to: C. Miller Fisher, M.D., Department of Neurology, Massachusetts General Hospital, Fruit Street, Boston, Massachusetts 02114. J. Neurosurg. / Volume 48 / April, 1978

Basal rupture of saccular aneurysm. A pathological case report.

J Neurosurg 48:642-644, 1978 Basal rupture of saccular aneurysm A pathological case report C. MILLER FISHER, M.D., AND ROBERT G. OJEMANN, M.D. Neur...
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