Orbital suppy and anastomoses
In the “normal” disposition, the middle meningeal artery has potential for extensive collateral supply of the orbit via the meningo-lacrimal or meningo-ophthalmic artery. This is typically a diminutive branch which enters the orbit through the superior orbital fissure. In early life (20-30 mm embryo stage), this derivative of the MMA is in hemodynamic balance with embryonic dorsal and ventral ophthalmic arteries. The dorsal ophthalmic originates from the future adult ILT (adult remnant = recurrent ophthalmic branch of the ILT). The ventral ophthalmic initially arises from the ACA A1 segment, and is eventually replaced by the adult ophthalmic artery. If this adult ophthalmic artery fails to develop for some reason, the MMA is first in line to pick up orbital territory as the meningo-ophthalmic artery (even before dorsal ophthalmic which in adult form is very rare.) In some situations orbital supply is shared between the MMA and ophthalmic artery. In cases of ICA occlusion, ophthalmic artery ICA reconstitution is very common, and proceeds either thru the MMA or the superficial temporal artery.
Lateral ECA injection demonstrates opacification of the internal carotid artery (brown arrow) via the middle meningeal artery (red arrow). Notice a large branch of the MMA entering the orbit and retrogradely opacifying the ICA through collaterals with lacrimal arteries. This route represents one of the most common pathways of ICA reconstitution in setting of proximal ICA occlusion. From S. Geibpraserta, S. Pongpecha, D. Armstrongb and T. Kringsc . Dangerous Extracranial–Intracranial Anastomoses and Supply to the Cranial Nerves: Vessels the Neurointerventionalist Needs to Know. AJNR 2009; 30(8) 1459
The so-called meningo-ophthalmic variant origin of the ophthalmic artery is relatively common when “normal” ophthalmic artery fails to develop, as discussed above. If no ophthalmic artery is seen on an ICA injection, the MMA should be the first place to look for it.
ICA injections (above) demonstrate no ophthalmic artery. Note incidentally MHT supply to the pituitary gland with a characteristic pituitary blush. ECA lateral projection injection of the same case (below) demonstrate a prominent meningo-ophthalmic artery. The internal carotid artery in this case is opacified via reflux of contrast medium from a proximal ECA catheter position.
Same case, TOF MRA: The usual origin left ophthlamic artery is faintly visible. On the right, the ophthalmic arises from the MMA. We have several other cases with MRA and angio imaging of the same variant, with less obvious correlation. One strategy for catching these is to look at ophthalmic artery origin. It is usually seen although bone and flow direction make it relatively poorly visible. Asymmetry in ophthalmic artery visualization may be normal however looking at the MMA could be worthwhile.
Selective injection of the petrosquamosal branch demonstrates a fistula in the sigmoid sinus region opacifying the sinus (blue arrows). The fistula was embolized with glue from the branch with the leftmost red arrow.
Arteries of the Dural Sinuses
Arterial channels are always present in the walls of dural sinuses. These vessels are prominently involved in supply of dural fistulas. Many of these are visualized through the middle meningeal artery as the primary meningeal vessel. For example, in this case of ethmoid dural fistula transvenous embolization, a prominent branch in the wall of the superior sagittal sinus (white arrows) is supplied by the middle meningeal artery (black arrow)
Basal tentorial, petrosquamosal anastomoses in setting of Moya-Moya and synangioses.
Patient with bilateral Moya-Moya, post bilateral dural synangiosis and burr hole (see Intracranial Collateral Pathways for the remainder of this case). Stereo image pair on top, with dural/ arterial vasculature in white, and venous outflow in black, outlining an arterial arcade which runs within the dural sheath of the transverse/sigmoid sinuses, partly made up by the jugular branch of the neuromeningeal trunk of the ascending pharyngeal artery. Anastomoses with middle meningeal (petrosquamosal and basal tentorial) and occiptal branches are clearly demonstrated. These arteries frequently participate in supply of sigmoid sinus dural fistulas.
•Red – ascending pharyngeal artery, neuromeningeal trunk
•Pink – ascending pharyngeal artery, jugular branch
•Blue – middle meningeal artery, basal tentorial branch
•Purple – middle meningeal artery, petrosquamosal branch
•White – anastomotic connections between basal tentorial and petrosquamosal branches
•Green –mastoid branch, occipital artery
•Yellow –cerebellar fossa branch, usually from occipital artery
Surgical Synangiosis is essentially an augmentation of “naturally” or spontaneously occuring synangiosis, developing in response to a relatively long-standing vascular constraint. This process is more robust in younger patients, and so is often encountered in angiographic evaluation of Moya Moya disease. In this 4 year old patient, an impressive autosynangiosis recruiting the middle meningeal artery developed to supply mesial posterior frontal and anterior parietal lobes, in response to progressive narrowing of right ICA and left A1 segments.
Notice also a faint autosynangiosis between ethmoid arteries from the ophthalmic and frontal lobe base.
Additional injections of the same patient, showing severe right supraclinoid carotid stenosis (lateral right ICA) and Moya-Moya changes, as well as right PCOM support of MCA territory seen on left vert injection. The right A1 is closed, with both anterior cerebral territories supplied through a moderately diseased left A1. The situation is therefore most tenuous at the right superior convexity, where the above autosynangiosis has developed.
Persistent Stapedial Artery — images courtesy of Drs. Peter Kim Nelson and Eytan Raz
This is a key variant to understanding embryology of the craniofacial circulation. See some images below. Please see dedicated “Persistent Stapedial Artery Page“
Persistent Stapedial Artery — another example. In the same way the inferior tympanic-carotidotympanic connection results in ascending pharyngeal reconstitution of the petrous carotid artery, a persistent inferior tympanic can maintain an embryonic connection to the middle meningeal artery via the petrous branch of the MMA that makes us the facial nerve arcade. Embryonically, the middle meningeal artery does not belong to the IMAX — it instead arises from the petrous ICA via the primitive hyoid artery. The hyoid connects to the inferior tympanic, which goes thru the stapes crura (called stapedial artery at this point) and then via the facial arcade supplies what is ultimately the MMA. This connection is rudimentary in adulthood for most of us. However, in some cases the ascending pharyngeal-inferior tympanic-petrous-MMA connection persists. Simply put, the MMA is a branch of the ascending pharyngeal. Here is an example of this, on MRA; images courtesy of Dr. Eytan Raz. Blue – inferior tympanic branch; red = stapedial; yellow – petrous/horizontal facial nerve canal branch; white = MMA
Axial views, with right AP in clandestine black; the IAC is orange
Another stereo example, courtesy Dr. Daniel Sahlein
Middle Meningeal artery / falx cerebelli anastomosis: all kinds of anastomoses exist between middle, anterior, and posterior meningeal artery territories. These can often be recruited following craniotomy with destruction of the proximal MMA. In this patient status post pterional craniotomy (white arrows), the parietal branch of the MMA (red) is being reconstituted via a prominent falx cerebelli artery (orage). Notice a groove in which the MMA runs on the unsubtracted image.
Another example, even more prominent, post bilateral pterional craniotomies. The artery of the tentorium cerebelli (red) gives rise to the posterior meningeal artery, whose territory has considerably extended due to bilateral MMA sacrifice, demonstrating an impressive meningeal network (yellow arrows)
Same, in beautiful stereo
Recurrent Meningeal Artery — this disposition is complementary to the meningo-ophthalmic situation. Here, it is the ophthalmic artery that supplies territory of the middle meningeal artery through its recurrent meningeal branch (Letter F in figures above). This branch arises from the proximal ophthalmic artery and projects posteriorly through the superior orbital fissure or through its own foramen. On occasion, it assumes supply of middle meningeal territory, via a meningeal branch of the sphenoid ridge (running along the ridge, as expected) and continuing along the inner table of the frontal bone as one or several frontal branches.
Recurrent Meningeal Artery (purple) arising from the ophthalmic artery (orange) and heading posteriorly into the middle cranial fossa. The artery assumes territory of the meningeal branch for the sphenoid ridge (red, foreshortened in lateral projection) and contiues as several branches of the frontoparietal inner table (yellow).
Recurrent Meningeal Artery (B) giving rise to the artery of sphenoid ridge (C), normally a branch of the middle or accessory meningeal artery.
Recurrent Meningeal Artery 2: On head CT, aberrant MMA origin can be inferred by absence of foramen spinosum (or a much smaller foramen than contralaterally, attesting to asymmetery in MMA size.) The contralateral foramen spinosum is labeled in blue. The recurrent meningeal artery travels along the sphenoid ridge (orange arrows) and then over the convexity (red arrows)
Petrous origin of the Middle Meningeal Artery
The most common petrous site of origin is the “Persistent Stapedial Artery”, whereby the MMA persists as a branch of the embryonic stapedial artery (it is a fascinating artery which courses between the crurae of the stapes bone). In the early embryonic life, the Internal Maxillary Artery arose from the ICA, via the hyoid and stapedial arteries. With continued development, the IMAX territory was annexed by the enlarging external carotid branch, which heretofore has been preoccupied with faciolingual and occpital territories. Occasionally, this aquisition does not take place fully, and the MMA continues to arise from the ICA. In the following case, however, the MMA does not originate from the stapedial branch, but more anteriorly, from the mid-section of the horizontal petrous segment, in the expected location of the vidian artery origin. By what mechanism the MMA becomes connected to the vidial segment I do not understand.The following image shows absent of foramen spinosum on on the right (yellow arrow on left), and origin of the right MMA from the vidian segment (purple arrow)
Angiogram of the same patient shows the MMA (red arrows) with its Vidian origin (purple) in frontal (top left) and stereoscopic lateral projections (bottom)