Spontaneous Intracranial Hemorrhage Secondary to Rare Pial Arteriovenous Fistula Rupture

PR, aged early 50s, who was previously healthy, woke up with a sudden, sharp, stabbing, 10/10 pain level, right-sided headache with nausea, vomiting, and photophobia. On presentation to the emergency department, PR described this headache as “the worst headache of my life.” PR did not have a history of headaches or any other substantial medical history.

In the emergency department, PRs vital signs were within normal limits, besides slight hypertension (139/71 mm Hg). Upon examination, PR was noted to be drowsy and was unable to name objects. PR also had left homonymous hemianopsia and extinction to bilateral tactile stimulation.

Head CT without contrast (Figure 1A) revealed a right parieto-occipital parenchymal hemorrhage measuring 5.7 x 3.7 x 5 cm with surrounding edema and a midline shift of 5 mm from right to left. PR was then transferred to an outside hospital. Initial CT angiogram of the head and neck was negative for intracranial thrombosis, aneurysm, or other vascular malformations. A CT venogram was performed, which was negative for cerebral venous sinus thrombosis. A nicardipine drip and hypertonic saline were administered and PR was admitted to the intensive care unit for close monitoring and further workup of the intraparenchymal hemorrhage.

Diagnostic Process

Because initial neuroimaging was negative for an underlying etiology for the hematoma, PR underwent digital subtraction angiography (DSA), which revealed a 7 x 6 mm pial arteriovenous fistula (AVF) (Figure 1B) supplied by the right posterior cerebral artery (lateral occipital branch) and the right middle cerebral artery (posterior temporal branches). The nidus was located on the lateral occipital cortical surface. There was a single draining occipital cortical vein to the superior sagittal sinus. There was no feeding artery or nidal aneurysm. Because of the lesion’s distal location and the small caliber of the feeding branches, PR was not a candidate for embolization by interventional radiology.

Case Resolution

The DSA results led to a diagnosis of large intraparenchymal hemorrhage secondary to an underlying ruptured pial AVF. PR was not a candidate for embolization by means of endovascular intervention because of the location of the AVF. The neurosurgery department at the authors’ institution was consulted, and they recommended neurosurgical resection. PR underwent a right parietal occipital craniotomy. The hematoma was evacuated and a clipping resection of the pial AVF was performed. The procedure was well-tolerated.

Repeat DSA revealed no residual AVF (Figure 2). A biopsy during the craniotomy revealed large vessels (arteries and veins) and increased capillaries with associated brain tissue (Figure 3A and 3B). Throughout the hospital course, PR had chronic bifrontal headaches, which were treated conservatively with acetaminophen, steroids, and valproic acid.

PR was eventually moved from the intensive care unit to the medical floor after multiple serial head CT scans without contrast indicated stable results. Once clinical stability was achieved, PR was discharged from the hospital. PR, who lived far from the hospital, was unable to follow-up after discharge.

Discussion

Pial AVFs are rare cerebrovascular malformations, accounting for only ~1.6% of intracranial vascular malformations.¹ Pial AVFs have a unique angioarchitecture that sets them apart from the more common arteriovenous malformations. The unique pial AVF case we report had distinctive clinical characteristics, such as multiple arterial feeders, hemorrhage site, and neurosurgical resection of the AVF.

The pathophysiology behind the formation of pial AVFs is poorly understood. They lack a true nidus and usually have ≥1 arterial feeders draining into a single dilated vein.² This abnormal connection and shunting causes increased turbulent blood flow, which ultimately leads to an increased risk of hemorrhage.^1,3 The most common presenting symptoms of pial AVFs in adults include headache, hemorrhage, and seizures.³

A literature review focused on pial AVFs was recently conducted by Lim et al³ and demonstrated that children (aged ≤18 years) tend to have the congenital form, whereas adults (aged >18 years) tend to have the acquired form of pial AVFs. The acquired form of pial AVF is usually brought on by trauma or iatrogenic causes, such as brain surgery or vasculopathy.³ In our reported case, the pial AVF was found incidentally when the individual presented with a new intracerebral hemorrhage. PR had never undergone neurosurgical intervention in the past and had no medical conditions. Based on the recent literature review, the majority of pial AVFs have a single arterial feeder (75% of cases).³ PR’s pial AVF was fed by multiple arterial feeders, such as the right posterior cerebral artery, lateral occipital branch, and right middle cerebral artery posterior temporal branches. Another unique aspect of PR’s presentation was that the initial intracerebral hemorrhage was mostly in the occipital region, which accounted for only 10% of cases in a recent review of the literature by Lim et al. The frontal lobe was the most common hemorrhage site indicated in this study.³

Another unique aspect of this case was the treatment method. Because of the lack of nidus in a pial AVF, there is an increased risk of rupture due to the turbulent blood flow.² This pathologic blood flow must be disrupted by resecting the fistula, ligating the feeding arteries, or performing embolization.^1,4,5 Because of the distal location of PR’s fistula, along with the small caliber of the arterial feeding branches, PR was not an ideal candidate for endovascular intervention. Therefore, surgical resection of the pial AVF was performed without any major complications. There is ongoing research into alternative treatment methods, including more noninvasive measures, such as endovascular intervention with coils, or liquid embolization with N-butyl-cyanoacrylate.^1,5

Conclusion

Pial AVFs are rare cerebrovascular malformations.² These malformations are more common in children, but can be found in adults, especially in the setting of an intracranial hemorrhage.^3,4 It is important to use tools such as DSA in people with unexplained lobar hemorrhages. In our case, a DSA was able to identify an underlying pial AVF that required intervention. To determine the best intervention, the hemorrhage location and the pial AVF must be taken into consideration. Pial AVFs can be managed endovascularly through various interventions, such as coiling or liquid embolization.