The pharyngo-tympano-stapedial middle meningeal artery (PTS-MMA) variant is extremely rare, and never described in the setting of arterial supply to a falcotentorial dural arteriovenous fistula (dAVF). Embryologically, this variant occurs when there is abnormal regression of the proximal stapedial artery. The PTS-MMA originates from the medial proximal cervical internal carotid artery and follows the course of the inferior and superior tympanic arteries.

We present the case of an adult patient with past medical history significant for coronary artery disease. The patient had severe daily headaches as well as imbalance for 4 months prior to presentation. She underwent non-invasive imaging including CT angiography and MRI, which demonstrated a falcotentorial vascular malformation and associated varix of the precentral cerebellar vein (figure 1A). Subsequent cerebral angiography confirmed a falcotentorial dural arteriovenous fistula with arterial supply from the left middle meningeal artery, right posterior meningeal artery, and minor pial supply from the right fetal posterior cerebral artery. Venous drainage into the superior vermian vein and precentral cerebellar vein (PCV) with reflux into the vein of Galen and posterior segments of the basal vein of Rosenthal confirmed a high-risk type fistula (figure 1C).

Preoperative diagnostic imaging. (A) Axial T2-weighted MRI through the falcotentorial region demonstrating a large midline venous varix (arrowhead) and enlarged, draining precentral cerebellar vein (arrow). (B) Right external carotid artery selective angiogram (lateral view) demonstrating absence of the right middle meningeal artery arising from the expected location of the internal maxillary artery. (C) Left common carotid artery angiogram (lateral view) confirming the presence of a tentorial dural arteriovenous fistula predominantly supplied by the enlarged left middle meningeal artery (thin arrow) draining to the precentral cerebellar vein (thick arrow) and associated varix (arrowhead).

The patient returned for endovascular treatment via the enlarged posterior division of the left middle meningeal artery using Onyx 18 (Medtronic Neurovascular, Irvine, California, USA) using the Scepter Mini (Microvention, Aliso Viejo, California, USA) balloon-assisted Onyx embolization technique. Complete diagnostic cerebral angiograhy was performed. Theselective right external carotid arteriogram was notable for absence of the expected right middle meningeal artery origin from the proximal internal maxillary artery (figure 1B). Endovascular treatment was undertaken using a Benchmark 071 guide catheter (Penumbra, Alameda, California, USA) in the proximal left external carotid artery and a Scepter Mini balloon microcatheter over a Traxcess micro-guidewire (Microvention, Aliso Viejo, California, USA) in the distal left middle meningeal artery. Postembolization angiography demonstrated persistent, but decreased filling of the dAVF from the incompletely embolized left middle meningeal artery into the recipient vein.

The patient was scheduled for a follow-up angiogram in 3 months to assess thrombosis of the fistula in the absence of any blood thinning medication. However, follow-up angiography confirmed a residual arteriovenous fistula with new hypertrophied arterial supply from the right PTS-MMA variant (figure 2A). Its distinct anatomic course through the middle ear is best seen on three-dimensional rotational angiography (figure 2B,C). Additional, previously seen arterial pedicles to the dAVF included the right posterior meningeal artery, and to a lesser extent, the right posterior cerebral artery. Given the inherent risks of endovascular treatment via remaining arterial pedicles or transvenous pathways, the patient was taken to the operating room for a torcular craniotomy with a supracerebellar, infratentorial approach to the dAVF. An arterialized PCV (figure 3A) was visualized at the falcotentorial junction. Application of straight aneurysm clips to the arterialized vein at the site of fistulous connection disconnected the arteriovenous fistula, as shown by a darker color to the PCV distal to the clip (figure 3B,C). Six-month postoperative angiography confirmed resolution of arteriovenous shunting as well as improvement in the patient’s clinical symptoms (figure 4).

Post-treatment angiography at 3 months following subtotal transarterial left middle meningeal artery embolization. (A) Right common carotid late-phase arteriogram (lateral view) and (B-C) right common carotid artery 3D rotational angiography (lateral and lateral oblique views, respectively) demonstrating the newly hypertrophied right middle meningeal artery (arrows) arising from the proximal cervical internal carotid artery coursing through the middle ear and along the inner table of the skull to supply the posterior aspect of the tentorial dural arteriovenous fistula consistent with pharyngo-tympano-stapedial middle meningeal artery (arrows in A; blue overlay in B-C) supply to the posterior aspect of the residual fistula (arrowhead in A).

Intraoperative views during clip ligation of tentorial dural arteriovenous fistula (dAVF). (A) An arterialized precentral cerebellar vein (PCV) is seen at the falcotentorial junction. (B) Clip application disconnected the fistula, as shown by the dark (venous) color of the PCV. (C) Demagnified view after clip ligation of the dAVF.

Postoperative right common carotid selective injection following craniotomy for definitive treatment, resulting in no evidence of residual or recurrent dural arteriovenous fistula.

The middle meningeal artery most often arises from the first portion of the internal maxillary artery and courses through the foramen spinosum to enter the skull and provide arterial supply to the intratympanic seventh cranial nerve, cavernous sinus, and dura. It is involved in a variety of pathologic processes. including subdural hematomas, spontaneous and traumatic dural arteriovenous fistulas, dural arterial supply to arteriovenous malformations, and pseudoaneurysms.1 2 Its anatomic course is clinically significant as there are ‘dangerous connections’ to the eye via meningolacrimal or meningo-ophthlamic anastomoses as well as to the branches of the inferolateral trunk of the internal carotid artery in the region of the cavernous sinus.3 Typically, the middle meningeal artery is safe to embolize beyond these dangerous connections. However, this artery may be more dangerous to catheterize and/or embolize in the setting of variant anatomy. In our case, the tortuous course and small caliber of the PTS-MMA variant arising from the internal carotid artery proved too high risk as compared with surgery in the consideration of definitive treatment of the torcular dAVF.

Variant anatomy of the middle meningeal artery ranges from relatively common to extremely rare. The most common variant anatomy of the middle meningeal artery is the recurrent meningeal artery from the ophthalmic artery. The incidence of this relatively common variant has been reported in 0.5–2% of patients.2 4 The rarest middle meningeal artery origins are from the basilar artery,5 6 and as described in this case report, the proximal cervical internal carotid artery.1 The PTS-MMA variant is associated with partial persistence of the stapedial artery.7 In this embryologic event, the proximal stapedial artery regresses while the distal portion is annexed by the inferior tympanic artery, a branch of the ascending pharyngeal artery, and anastomoses within the middle ear with the superior tympanic artery, resulting in the origin of the middle meningeal artery arising from the cervical internal carotid artery, coursing superiorly into the middle ear, and following the course of the typical petrous middle meningeal artery branch.1 7 8

The complex angioarchitecture of tentorial dAVFs and their treatment have been described in the literature.9 10 The largest series of 31 patients reported by Lawton et al describes the particular difficulty of complete obliteration of the fistula via endovascular methods due to the high risk venous drainage patterns and thereby risk of hemorrhage during treatment.11 One case report has described a variant middle meningeal artery arising from the inferolateral trunk to supply a superior sagittal sinus dAVF in an infant.12 However, variant middle meningeal artery supply to the tentorial dAVF location and implications for its treatment have not been described previously.

The pharyngo-tympano-stapedial middle meningeal artery variant is an embryological result of annexation of the partially persistent distal stapedial artery by the inferior tympanic artery and subsequent anastomosis with the superior tympanic arteries in the middle ear.

Middle meningeal artery variant anatomy adds complexity to the endovascular approach and treatment of dural arteriovenous fistulas.

Consent obtained directly from patient(s)

This study involves human participants but approval by the ethics committee was not obtained for this retrospective review of human participation. UCSF IRB number: 10-00936 Participants gave informed consent to participate in the study before taking part.