Nonaneurysmal Subarachnoid Hemorrhage
October 1, 1998 3 minutes read
Nonaneurysmal Subarachnoid Hemorrhage
ABSTRACT & COMMENTARY
Source: Wijdicks EFM, et al. Pretruncal nonaneurysmal subarachnoid hemorrhage. Mayo Clin Proc 1998;73:745-752.
Van gijn and associates first pointed out that a perimesencephalic hemorrhage without extension into the adjacent cisterns on CT scan predicted a normal cerebral angiogram.1 Schievink and Wijdicks2 suggested the name "pretruncal nonaneurysmal subarachnoid hemorrhage" (SAH) for this type of bleeding because subsequent studies, using improved neuroimaging techniques (including MRI), have shown the true anatomic localization of the blood to be prepontine rather than just peri-mesencephalic.
Wijdicks and colleagues identified 36 consecutive patients with angiogram-negative SAH admitted to the Mayo Clinic Rochester from 1992 to 1996. They reviewed the clinical and neuroradiologic features and outcome in 24 patients who had SAH restricted to the cisterns surrounding the brainstem. There were 15 males and nine females. Their ages ranged from 3 to 72 years (median, 45 years). Eighteen of 24 complained of a sudden explosive headache. In six, headache intensity increased over a period of minutes. In all patients, the SAH was grade 1 or 2.3 Two patients had a family history of aneurysmal SAH.
In all patients, CT scans showed focal hyperdensity in the prepontine and interpeduncular cisterns as well as extension into the suprasellar cistern. MRI in 18 patients showed that the center of the bleeding was predominantly prepontine. A pontine abnormality that resembled a capillary telangiectasis was found in only one patient. All patients underwent four vessel cerebral angiography once (and, in most cases, twice). Although no aneurysms were identified, cerebral vasospasm was present in the initial angiograms in four patients.
No episodes of rebleeding or delayed cerebral ischemia occurred during hospitalization. At follow-up 3-6 months after the ictus, no recurrent headaches or neurological morbidity was reported.
COMMENTARY
The cause of perimesencephalic or pretruncal non-aneurysmal SAH remains unknown but, presumably, is a ruptured venous or capillary structure in front of the pons. Despite its characteristic CT and MRI appearance and the uniformly negative cerebral angiographic results, Wijdicks et al still recommend that all pretruncal SAH cases be studied with four vessel angiograms. They point out that a ruptured aneurysm at the tip of the basilar artery could result in a pattern of pretruncal SAH-especially when the initial CT is performed days after the ictus and after washout of diffuse cisternal blood has occurred.
With regard to the need for a second cerebral angiogram in patients with pretruncal SAH, Wijdicks et al do not recommend repeat angiography unless uncertainty exists about the quality of the first angiogram.
This series of 24 patients is the largest one reported from a single institution in the United States and confirms that pretruncal SAH is the most common type of spontaneous SAH of unknown cause. -jjc
References
1. van Gijn J, et al. Perimesencephalic hemorrhage: A nonaneurysmal and benign form of subarachnoid hemorrhage. Neurology 1985;35:493-497.
2. Schievink WF, Wijdicks EFM. Pretruncal subarachnoid hemorrhage: An anatomically correct description of the perimesencephalic subarachnoid hemorrhage. Stroke 1997;28:2572.
3. Report of World Federation of Neurological Surgeons Committee on a Universal Subarachnoid Hemorrhage Grading Scale. J Neurosurg 1988;68:985-986.
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